A fgb single-sided submerged arc welding method

Abstract

The present application relates to the technical field of welding, and discloses a FGB single-sided submerged arc welding method, which comprises the following steps: firstly, fixing a first welding part and a second welding part to form a welding groove with a root width of 4-10 mm; then, installing a gasket at the bottom of the welding groove to block; subsequently, laying welding iron powder with a thickness equal to the root width in the welding groove; finally, adjusting a welding trolley to center a cable-type welding wire with one end of the welding groove, starting the trolley to move to the other end while synchronously laying flux, and completing submerged arc welding. Through the synergistic effect of the pre-laid iron powder and the cable-type welding wire, the present application greatly increases the metal deposition rate and effectively buffers the downward impact heat of the electric arc. The method not only completely solves the problem that the gasket is easily burnt through in large-gap and variable-gap welding, but also gets rid of the cumbersome limitation of multi-wire equipment, and can complete efficient and high-fault-tolerant single-sided welding and double-sided forming by using a portable single-head equipment, which is extremely practical on site.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a wide-gap FGB single-sided submerged arc welding method. Background Technology

[0002] Small and medium-sized submerged arc welding (SAW) equipment typically uses solid welding wire with a diameter not exceeding 5mm. The welding carriages of this equipment are small and lightweight, making it very convenient for workers to carry and move the equipment. This portable equipment is widely used in shipbuilding and steel structure manufacturing. In recent years, factories have begun to promote the use of single-sided SAW technology assisted by FGB (Fiberglass Backing). This technology includes single-wire welding and multi-wire welding. FGB technology achieves single-sided welding with double-sided forming. Therefore, the overall welding efficiency of the factory has been effectively improved.

[0003] However, existing FGB single-sided welding technology has significant drawbacks. First, the solid welding wire commonly used in factories is limited by packaging constraints. The maximum diameter of the solid welding wire cannot exceed 5mm, otherwise it is difficult for the machine to wind it into a small coil. The thinner wire results in a lower current carrying capacity. The wire melts slowly, thus the welding efficiency of a single wire is relatively low. Second, the arc impact force of solid welding wire is very strong. If the assembly gap of the steel plates is greater than 3mm, the strong arc can easily burn through the bottom lining. However, the actual gaps in shipbuilding are often between 4mm and 10mm. Moreover, the gaps in the same weld seam often vary in width. When facing variable gaps, welders must frequently stop the machine to adjust parameters. If the welder does not adjust the parameters, defects such as incomplete penetration or burn-through will occur in the weld seam. Therefore, existing single-wire technology is difficult to adapt to complex working conditions with large gaps.

[0004] To address the shortcomings of single-wire welding, some factories have adopted multi-wire FGB welding technology. However, multi-wire welding equipment is overly complex. The multi-head welding carriage and multiple spools of welding wire are extremely heavy. Workers find it difficult to move this equipment in cramped cabins, resulting in poor on-site practicality. Furthermore, multi-wire equipment requires adjusting too many parameters, making it difficult for welders to achieve the ideal parameter combination in a short time. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an FGB single-sided submerged arc welding method that is simple to operate, uses lightweight equipment, and can adapt to large gaps.

[0006] To address the aforementioned technical problems, this invention provides an FGB single-sided submerged arc welding method, comprising the following steps: S1: Fix the first weldment and the second weldment onto the clip respectively, and form a welding bevel between the first weldment and the second weldment. The root width of the welding bevel is 4 to 10 mm. S2: Install a gasket at the bottom of the weld bevel, the gasket sealing the bottom of the weld bevel; S3: Welding iron powder is laid in the weld bevel, and the thickness of the welding iron powder is equal to the root width of the weld bevel. S4: First, adjust the position of the welding wire on the welding carriage so that the welding wire is aligned with one end of the welding bevel. Then, control the welding carriage to start, so that while simultaneously laying flux, it moves to the other end of the welding bevel to perform submerged arc welding. The welding wire is a cable-type welding wire.

[0007] In a preferred embodiment of the present invention, in S2, the gasket is provided with multiple strips, and the installation step of the gasket includes: S2.1: First, align the first end of the first gasket with one end of the welding bevel; then, from bottom to top along the direction from the first end to the second end of the gasket, apply uniform pressure to the gasket in sequence so that the gasket contacts and adheres to the bottom surface of the first weldment and the second weldment respectively, thus completing the installation of the first gasket. S2.2: First, make the first end of the next pad contact the second end of the previous pad and fix it to the bottom of the first weldment and the second weldment. At the same time, make the middle part of the pad bend downward relative to its first end. Then, fix the second end of the pad to the bottom of the first weldment and the second weldment. Finally, apply uniform pressure to the pad from bottom to top along the direction from the first end to the second end to complete the installation of the pad. S2.3: Repeat S2.2 until all gaskets are installed.

[0008] As a preferred embodiment of the present invention, in S2, the top of the card is provided with a relief groove, the central axis of the relief groove is aligned with the central axis of the welding bevel, and after the installation of the liner is completed, a U-shaped spring flat iron is provided in the relief groove, the U-shaped spring flat iron abuts against the bottom of the liner and the bottom of the relief groove respectively.

[0009] As a preferred embodiment of the present invention, the welding start end of the welding groove is connected to an arc-starting plate. In S4, before the welding carriage is started, the position of the welding wire on the welding carriage is adjusted so that the welding wire is above the arc-starting plate and the distance between the bottom end of the welding wire and the top surface of the arc-starting plate is 1-2 mm. Then, the welding carriage is controlled to lay flux in the welding area. When the flux covers the welding wire, the welding carriage is controlled to start arc welding.

[0010] As a preferred embodiment of the present invention, in S4, during welding, the welding current is 900-1100A, the welding voltage is 39-41V, the welding speed is 35-50cm / min, and the wire extension length is 30-40mm.

[0011] As a preferred embodiment of the present invention, in S4, when the length of the weld is 200-300mm, the weld surface is observed. If the weld surface reinforcement is 0.5-2mm, the current welding parameters are maintained until the welding is completed. If the weld surface reinforcement is greater than 2mm, the welding current and welding speed are increased until normal weld formation is achieved, and then the current welding parameters are maintained until the welding is completed. If the weld surface reinforcement is less than 0.5mm, the welding current and welding speed are decreased until normal weld formation is achieved, and then the current welding parameters are maintained until the welding is completed.

[0012] As a preferred embodiment of the present invention, in S4, when the welding arc moves to a distance of 500-600mm from the welding start point of the welding groove, it is continuously hammered at a distance of 100-150mm on each side of the welding groove.

[0013] As a preferred embodiment of the present invention, the welding end of the welding groove is provided with an arc extinguishing plate. In S4, after the welding arc completely transitions from the end of the welding groove to the arc extinguishing plate, the welding current and welding voltage of the welding carriage are gradually reduced to 50-60% of the normal welding current, and the welding length of the welding carriage on the arc extinguishing plate is not less than 200mm.

[0014] This invention provides a wide-gap FGB single-sided submerged arc welding method, which, compared with existing technologies, has the following advantages: 1. This invention significantly increases the amount of metal filling per unit time by pre-laying welding powder within the welding groove and using a single cable-type welding wire. Although the cable-type welding wire can carry high current, its physical texture remains flexible, allowing it to be easily wound into small-diameter wire spools. Therefore, workers only need a small, lightweight single-wire welding carriage to complete efficient welding. This completely overcomes the shortcomings of traditional multi-wire FGB welding equipment, which is bulky and difficult to move, making it extremely suitable for flexible construction in the narrow spaces inside ships.

[0015] 2. This invention can accommodate wide assembly gaps of 4-10mm. The iron powder laid inside the bevel not only serves as filler metal but also acts as a heat buffer, absorbing a large amount of heat from the downward arc. Simultaneously, the arc generated by the cable welding wire is wider and gentler than that of the solid welding wire. These two factors work synergistically to significantly reduce the vertical impact of the arc on the bottom, effectively preventing the strong arc from burning through the bottom pad and ensuring the quality of single-sided welding with double-sided forming.

[0016] 3. When dealing with unevenly spaced gaps, this invention eliminates the need for frequent worker intervention. Because wider gaps allow for more iron powder to be incorporated, this automatically balances the excess heat absorbed at wider gaps with the required additional filler metal. This adaptive physical filling mechanism eliminates the need for frequent adjustments to welding parameters, allowing the welding carriage to operate smoothly from start to finish. This significantly simplifies equipment setup, reduces reliance on operator skills, and substantially improves production efficiency. Attached Figure Description

[0017] Figure 1 This is a structural diagram of the first and second welded parts of the present invention fixed on the card code; Figure 2 This is a structural diagram of the present invention after the gasket is installed; Figure 3 This is a structural diagram of the present invention after the welding iron powder has been laid; Figure 4 This is a structural diagram of the cable welding wire of the present invention; Figure 5 This is a schematic diagram of the welding process of the present invention (omitting the flux); Figure 6 This is a longitudinal sectional view of the welding process of the present invention; In the figure, 1 is the first weldment; 2 is the second weldment; 3 is the welding bevel; 4 is the clamp; 41 is the clearance groove; 5 is the gasket; 6 is the welding iron powder; 7 is the welding wire; and 8 is the U-shaped spring flat iron. Detailed Implementation

[0018] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0019] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., used to indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] like Figure 1-6 As shown, a preferred embodiment of the FGB single-sided submerged arc welding method of the present invention includes the following steps: S1: Fix the first weldment 1 and the second weldment 2 onto the clamp 4 respectively. A welding groove 3 is formed between the first weldment 1 and the second weldment 2. The root width L of the welding groove 3 is 4 to 10 mm. In this embodiment, the groove angle of the welding groove 3 is 40° and the blunt edge of the welding groove 3 is 0 mm. The first weldment 1 and the second weldment 2 are both steel plates with a thickness of 8 to 13 mm. Generally, there are multiple clamps, and the distance between two adjacent clamps is 300 to 400 mm.

[0021] S2: Install a gasket 5 (FGB gasket 5) at the bottom of the weld groove 3. The gasket 5 seals the bottom of the weld groove 3. It is understood that the top of the clip 4 has clearance space for the installation of the gasket 5.

[0022] S3: Welding iron powder 6 (welding-specific iron powder) is laid in the welding groove 3. The welding iron powder 6 must be laid evenly in the welding groove 3. The upper surface of the welding iron powder 6 layer must be uniform and flat. The thickness of the welding iron powder 6 is equal to the root width of the welding groove 3.

[0023] S4: First, adjust the position of the welding wire 7 on the welding carriage so that the welding wire 7 is aligned with one end of the welding groove 3. Then, control the welding carriage to start, so that it moves to the other end of the welding groove 3 for submerged arc welding while simultaneously laying flux. The welding wire 7 is a cable-type welding wire. The cable-type welding wire includes a central welding wire and at least one layer of peripheral welding wires. The central welding wire is straight, and the peripheral welding wires include multiple peripheral welding wires evenly distributed around the central welding wire. The multiple peripheral welding wires are spirally twisted together. When there are multiple peripheral welding wires, the multiple peripheral welding wires are arranged sequentially from the inside to the outside, that is, the first peripheral welding wire group is wrapped on the central welding wire, and the next peripheral welding wire group is wrapped on the previous peripheral welding wire group.

[0024] Cable welding wire can be made by winding 7 or more fine welding wires, and the outer diameter of cable welding wire can be 6 to 12 mm. Cable welding wire has a large outer diameter, but its overall flexibility is good, making it easy to be bent locally and convenient to wind into small diameter discs, which is convenient to carry and transfer. At the same time, due to its large cross-sectional area, it can withstand a larger welding current and has a high welding deposition efficiency.

[0025] Each fine wire in a cable welding wire can independently conduct welding current, and there is a certain gap between each wire. This results in a large diameter welding arc between the cable welding wire tip and the workpiece, with the arc thrust distributed evenly from the center to the periphery. The weak restraint force of the arc leads to a shallow weld depth and a wide weld width, effectively preventing burn-through in large-gap FGB welding and ensuring continuous welding. Simultaneously, the large weld width ensures good fusion quality on both sides of the butt joint of the steel plate. The arc cross-section of the cable welding wire is similar to that of the welding wire itself. As the welding wire is continuously fed, the arc rotates, providing excellent stirring of the weld pool, resulting in more uniform composition, microstructure, and temperature of the weld, and better mechanical properties.

[0026] See welding process Figure 5-6 As shown. The welding arc of the cable welding wire continuously heats and melts the fed cable welding wire, part of the welding bevel, special iron powder, and flux to form a liquid welding pool (including a lower metal pool and an upper liquid slag pool). Excess flux particles cover the liquid pool to prevent arc light, spatter, and smoke leakage, reducing heat and energy loss, and preventing outside air from entering the welding pool, ensuring welding quality. The bottom of the liquid pool is supported by an FGB pad to prevent the liquid metal from flowing downwards and maintain its stable shape. As the welding carriage moves the welding torch forward at a constant speed, the liquid metal pool gradually cools and solidifies under the support of the FGB pad, forming a solid weld. Simultaneously, the liquid slag covering the liquid metal pool also cools and solidifies, forming solid slag that covers the upper surface of the solid weld. During the welding process, as the cable welding wire is continuously fed and melted, the welding arc rotates uniformly, creating a beneficial stirring effect on the weld pool, improving the homogeneity of the liquid metal, and thus enhancing the mechanical properties of the weld metal. As welding continues, the entire weld seam is completed.

[0027] This embodiment has the following advantages: 1. Cable welding wire has a wide upper limit range of diameter (it can exceed 5mm, and can reach 7mm and above). Cable welding wire has low rigidity and is easy to wind into small coils. The maximum welding current that the welding wire can carry is relatively large (the welding current carried by a single cable welding wire can exceed 800A). The mass of welding wire melted per unit time is large, and the welding deposition efficiency is relatively high.

[0028] 2. Cable welding wire has low arc restraint (large cross-sectional area), low arc stiffness, and weak impact force. When performing FGB single-sided submerged arc welding, it is less likely to cause weld burn-through and interrupt the welding process. It is not strict about the assembly gap requirements for steel plate butt joints (it can be greater than 3mm), and has good adaptability to assembly gaps, allowing for large-gap FGB single-sided submerged arc automatic welding. The assembly gap of ship hull plate butt joints is often maintained between 4 and 10mm, therefore, it has high application and promotion value in the field of shipbuilding welding.

[0029] 3. Cable-type welding wire (FGB) equipment is simple, and the welding carriage and welding wire are small in size and weight, making them easy to carry and transfer. This also reduces the workload related to pre-weld preparation and post-weld completion. Since shipbuilding often requires frequent changes of construction sites and has limited space, FGB offers good on-site practicality.

[0030] 4. The equipment for cable welding wire FGB welding is simple, requires fewer parameters to be adjusted, and is easy and quick to find the optimal parameter combination, resulting in high efficiency.

[0031] 5. When the assembly gap of the same steel plate butt joint changes (uneven assembly gap), there is no need to frequently adjust various welding parameters, which will not cause defects such as incomplete penetration or burn-through in the weld. It can achieve the welding of the entire weld with a single set of welding parameters.

[0032] For example, in S2, multiple gaskets are provided, and the gasket installation steps include: S2.1: Before installation, remove the protective paper tape from the adhesive surface of the gasket. With the fiberglass cloth of the gasket facing upwards, align the central axis of the fiberglass cloth with the central axis of the welding bevel. During installation, first align the first end of the first gasket with one end of the welding bevel. Then, from bottom to top along the direction from the first end to the second end of the gasket, apply uniform pressure to the gasket in sequence to ensure that the gasket is fully in contact with and bonded to the bottom surfaces of the first and second weldments. Firmly attach the tin foil with adhesive to the surface of the gasket to the bottom surface of the weldment to complete the installation of the first gasket. S2.2: First, connect the first end of the next gasket to the second end of the previous gasket and fix it to the bottom of the first and second weldments (ensure that the central axis of the gasket is aligned with the central axis of the weld bevel). At the same time, bend the middle part of the gasket downward relative to its first end, with a bending and sinking amount of about 20-25mm (taking a gasket length of 600mm as an example). Then, fix the second end of the gasket to the bottom of the first and second weldments. At this time, both ends of the gasket are bonded and fixed to the bottom surface of the weldment, but the middle part is bent downward and protrudes, and does not contact the bottom surface of the weldment. Finally, apply uniform pressure to the gasket from bottom to top along the direction from the first end to the second end (ensure that the joint position of the gasket and the previous gasket is fully in contact and firmly pressed to prevent burn-through at the gasket joint position), so that the gasket is fully in contact and bonded to the bottom surface of the weldment, and the installation of the gasket is completed.

[0033] S2.3: Repeat S2.2 until all gaskets are installed. The above installation steps ensure that multiple gaskets are securely fixed.

[0034] For example, see Figure 3 In S2, the top of the card 4 is provided with a relief groove 41, the central axis of the relief groove 41 is aligned with the central axis of the welding bevel. After the installation of the liner is completed, a U-shaped spring flat iron is set in the relief groove 41, and the U-shaped spring flat iron abuts against the bottom of the liner and the bottom of the relief groove 41 respectively.

[0035] To prevent the adhesive strength of the gasket from decreasing under the high temperatures of welding, which could lead to gasket detachment, a U-shaped spring flat iron is added during the bonding and fixing process to strengthen the fixation. The U-shaped spring flat iron is naturally slightly open. During use, the U-shaped spring flat iron is first compressed by hand (reducing its opening size) and inserted into the clearance hole of the temporary fixing clip, then released (its opening size tends to return to its original size under the elastic force). The upward spring pressure of the U-shaped spring flat iron prevents the adhesive strength of the gasket from decreasing under the high temperatures of welding, thus ensuring the continuity of the welding process.

[0036] Because the stiffness of the cable welding wire is weak, the friction force for scratch-based arc initiation is insufficient, resulting in a low success rate. To address this issue, in this embodiment, for example, an arc-starting plate is connected to the welding start end of the welding groove. In step S4, before starting the welding carriage, the welding slag and other contaminants at the end of the cable welding wire are cleaned, and the position of the welding wire on the welding carriage is adjusted so that the welding wire is above the arc-starting plate, with the distance between the bottom end of the welding wire and the top surface of the arc-starting plate being 1-2 mm. Then, the welding carriage is controlled (by opening the flux discharge hopper) to lay flux in the welding area. When the flux covers the welding wire (when the flux completely covers the perimeter of the cable welding wire and reaches a certain thickness), the welding carriage is controlled (by pressing the welding start button) to begin arc welding. In other words, this method changes the traditional scratch-based arc initiation to a micro-touch arc initiation, thus adapting to the physical characteristics of the weak stiffness of the cable welding wire.

[0037] For example, in S4, during welding, the welding current is 900–1100A, the welding voltage is 39–41V, the welding speed is 35–50cm / min, and the wire extension length is 30–40mm. First, the ultra-high current of 900–1100A combined with the 30–40mm wire extension greatly accelerates the melting speed of the wire, allowing even a lightweight single-head welding machine to achieve the high-efficiency output of a heavy multi-wire machine. Second, the high voltage of 39–41V widens and softens the originally sharp arc, and the soft arc disperses the downward impact force, completely preventing the arc from burning through the bottom fiberglass liner. Finally, combined with a stable speed of 35–50cm / min, these parameters form a large and stable molten iron pool within the bevel. This large molten pool has excellent containment, allowing workers to weld the entire weld seam efficiently and safely with a single set of parameters when facing varying gaps of 4–10mm without stopping the machine for adjustments.

[0038] For example, in S4, when the completed weld length is 200-300mm, clean the flux and slag from the weld surface and observe the weld surface. If the weld surface reinforcement is 0.5-2mm and the weld edge transitions smoothly with the base steel plate, it is considered a normal weld formation. At this time, the back weld is also normally formed, so maintain the current welding parameters until the welding is completed. If the weld surface reinforcement is greater than 2mm, with obvious protrusions, and the weld edge does not transition smoothly with the base steel plate surface, exhibiting obvious steps or slight sharp edges, it can be determined that the back weld is not properly formed. If the weld penetration on the front side is insufficient or the weld size on the back side is too small, increase the welding current and welding speed until the normal weld formation is achieved, and then maintain the current welding parameters until the welding is completed. If the weld surface reinforcement is less than 0.5mm, or if there are depressions or rough and elongated fish-scale patterns on the weld, or if there are undercut or lack of fusion defects between the weld edge and the surface of the steel plate base material, it can be determined that the weld penetration on the back side is too large or the weld size on the back side is too large. In this case, reduce the welding current and welding speed until the normal weld formation is achieved, and then maintain the current welding parameters until the welding is completed.

[0039] Because this method involves high welding heat input, a large weld pool, slow weld pool solidification rate, and a strong tendency for regional segregation in the weld pool, the weld terminal experiences abrupt and complex three-dimensional stress changes, and the heat dissipation conditions at the weld terminal suddenly deteriorate, making the weld terminal prone to hot cracking. To prevent terminal welding cracks, the following methods should be used: Strictly control the impurity content in the welding materials, especially the content of harmful elements such as C, S, and P, to reduce the tendency for regional segregation in the weld pool from the source. Strictly control the source of hydrogen, prevent welding materials and welding auxiliary materials from becoming damp, and ensure that the flux is dried at 350℃ for 1-2 hours before use. In humid weather, the welding area must be dried beforehand.

[0040] Furthermore, for example, in S4, when the welding arc moves to 500-600mm from the welding start point of the welding groove, it is continuously hammered (low energy, high frequency) at 100-150mm on each side of the welding groove. This releases the stress in the area and generates a certain vibration effect on the weld pool, reducing the tendency of segregation and grain growth during the solidification process of the weld pool, and effectively improving the crack resistance of the weld in this area.

[0041] For example, the welding end of the welding bevel is equipped with an arc-extinguishing plate. The arc-extinguishing plate has the same material and thickness as the steel plate being welded, and its length and width are not less than 300mm. The bevel shape of the arc-extinguishing plate is consistent with the butt joint of the steel plate. The arc-extinguishing plate is in close contact with the end of the steel plate being welded, resulting in a firm weld and a flat installation. In S4, after the welding arc has completely transitioned from the end of the welding bevel to the arc-extinguishing plate, the welding current and welding voltage of the welding carriage are gradually reduced to 50-60% of the normal welding current. The welding length of the welding carriage on the arc-extinguishing plate is not less than 200mm. This operation directs the area prone to cracking to the arc-extinguishing plate, and by gradually cooling down and welding over a long distance, the end gradually cools down, thereby avoiding the risk of thermal expansion and contraction tearing the weld.

[0042] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A single-sided submerged arc welding method for FGB, characterized in that: Includes the following steps: S1: Fix the first weldment and the second weldment onto the clip respectively, and form a welding bevel between the first weldment and the second weldment. The root width of the welding bevel is 4 to 10 mm. S2: Install a gasket at the bottom of the weld bevel, the gasket sealing the bottom of the weld bevel; S3: Welding iron powder is laid in the weld bevel, and the thickness of the welding iron powder is equal to the root width of the weld bevel. S4: First, adjust the position of the welding wire on the welding carriage so that the welding wire is aligned with one end of the welding bevel. Then, control the welding carriage to start, so that while simultaneously laying flux, it moves to the other end of the welding bevel to perform submerged arc welding. The welding wire is a cable-type welding wire.

2. The FGB single-sided submerged arc welding method according to claim 1, characterized in that: In S2, the gasket is provided with multiple strips, and the installation steps of the gasket include: S2.1: First, align the first end of the first gasket with one end of the welding bevel; then, from bottom to top along the direction from the first end to the second end of the gasket, apply uniform pressure to the gasket in sequence so that the gasket contacts and adheres to the bottom surface of the first weldment and the second weldment respectively, thus completing the installation of the first gasket. S2.2 First, the first end of the next pad contacts the second end of the previous pad and fixes it to the bottom of the first weldment and the second weldment. At the same time, the middle part of the pad is bent downward relative to its first end. Then, the second end of the pad is fixed to the bottom of the first weldment and the second weldment. Finally, uniform pressure is applied to the pad from bottom to top along the direction from the first end to the second end to complete the installation of the pad. S2.3 Repeat S2.2 until all gaskets are installed.

3. The FGB single-sided submerged arc welding method according to claim 1, characterized in that: In S2, the top of the card is provided with a relief groove, the central axis of the relief groove is aligned with the central axis of the welding bevel. After the installation of the liner is completed, a U-shaped spring flat iron is provided in the relief hole, and the U-shaped spring flat iron abuts against the bottom of the liner and the bottom of the relief hole respectively.

4. The FGB single-sided submerged arc welding method according to claim 1, characterized in that: The welding bevel is connected to an arc-starting plate. In S4, before the welding carriage is started, the position of the welding wire on the welding carriage is adjusted so that the welding wire is above the arc-starting plate and the distance between the bottom end of the welding wire and the top surface of the arc-starting plate is 1-2 mm. Then, the welding carriage is controlled to lay flux in the welding area. When the flux covers the welding wire, the welding carriage is controlled to start arc welding.

5. The FGB single-sided submerged arc welding method according to claim 1, characterized in that: In S4, during welding, the welding current is 900-1100A, the welding voltage is 39-41V, the welding speed is 35-50cm / min, and the wire extension length is 30-40mm.

6. The FGB single-sided submerged arc welding method according to claim 1, characterized in that: In S4, when the completed weld length is 200-300mm, observe the weld surface. If the weld surface reinforcement is 0.5-2mm, maintain the current welding parameters until the welding is completed. If the weld surface reinforcement is greater than 2mm, increase the welding current and welding speed until normal weld formation is achieved, then maintain the current welding parameters until the welding is completed. If the weld surface reinforcement is less than 0.5mm, decrease the welding current and welding speed until normal weld formation is achieved, then maintain the current welding parameters until the welding is completed.

7. The FGB single-sided submerged arc welding method according to claim 1, characterized in that: In S4, when the welding arc moves to 500-600mm from the welding start point of the welding groove, it is continuously hammered at a distance of 100-150mm on each side of the welding groove.

8. The FGB single-sided submerged arc welding method according to claim 1, characterized in that: The welding end of the welding groove is provided with an arc extinguishing plate. In S4, after the welding arc completely transitions from the end of the welding groove to the arc extinguishing plate, the welding current and welding voltage of the welding carriage are gradually reduced to 50-60% of the normal welding current, and the length of welding of the welding carriage on the arc extinguishing plate is not less than 200mm.

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