Double-welding-torch solid welding wire automatic welding method
By performing single-sided composite bevel design and multi-layer multi-pass welding on the X80 steel pipe, combined with appropriate welding parameters and G55A5-level welding wire, the problem of low fracture toughness of the welds of the X80 steel pipe is solved, and efficient welding effect is achieved.
Patent Information
- Application Number
- CN202410068411.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-17
- Publication Date
- 2025-07-18
AI Technical Summary
When X80 steel pipe is automatically welded with double-welded torch solid welding wire, the weld fracture toughness value is low and cannot meet the service requirements of the pipeline.
Specific steel pipe composition design and welding process are adopted, including single-sided composite bevel design, multi-layer multi-pass welding and appropriate welding parameters. G55A5-level gas-protected solid welding wire is used to perform root welding, heat welding, fill welding and cover welding, and the welding heat input is controlled to be within 0.6kJ/mm.
It improves the fracture toughness of the weld, meets the service requirements of X80 steel pipes, reduces the amount of filler and improves welding efficiency.
Smart Images
Figure CN120326091A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of on-site welding of pipeline steel pipes, and particularly relates to an automatic welding method for double-torch solid wire welding. Background Art
[0002] Long-distance pipelines are an important way to transport natural gas from remote mining areas to the final users. At present, the construction tasks of oil and gas pipeline main lines are heavy, and the welding of on-site circumferential welds plays a crucial role in the entire pipeline construction. The stability of the circumferential weld performance is an important guarantee for ensuring the pipeline construction efficiency and operation safety. Fracture toughness (CTOD) is an important technical index of the circumferential weld performance, which determines the crack arrest ability of the circumferential weld and has an important impact on the safe service of the pipeline.
[0003] Gas shielded solid wire automatic welding is a method with high welding speed, good welding quality, high welding efficiency and suitable for all-position welding. This welding method has the characteristics of small influence of human factors, high welding efficiency and low labor intensity. Especially, it has great advantages in the pipeline construction of large-diameter, thick-walled steel pipes and under harsh climate conditions. During the process of conducting the CTOD test on the fracture toughness of the circumferential weld joint of double-torch solid wire automatic welding for X80 steel grade natural gas pipeline projects, it is found that the test results have large discreteness, and a certain number of low values appear in both the weld center and the heat affected zone. Although there are differences among different welding material brands, low values also exist.
[0004] Therefore, at present, when X80 steel pipes are welded by double-torch solid wire automatic welding, the fracture toughness value of the weld is low and cannot meet the service requirements of the pipeline. Summary of the Invention
[0005] The purpose of the present invention is to provide an automatic welding method for double-torch solid wire welding to solve the problem of low fracture toughness value of the weld when X80 steel pipes are welded by double-torch solid wire automatic welding.
[0006] To solve the above technical problems, the technical solution provided by the present invention is as follows:
[0007] The present invention provides an automatic welding method for double-torch solid wire welding, including the following steps:
[0008] Step A: Process the groove at the joint of the two steel pipe sections to be welded. Among them, the angle a of the upper groove surface is 5° ± 1°, the angle b of the lower groove surface is 45° ± 1°, the angle c of the inner groove surface is 37.5° ± 1°, the inner groove height h1 is 1.7 ± 0.2 mm, the root face height h2 is 1.1 ± 0.2 mm, the height h3 from the inflection point to the inner wall is 5.1 ± 0.2 mm, and the root opening L is 0 - 0.5 mm;
[0009] Step B: Clean and preheat both sides of the groove.
[0010] Step C: Perform root welding, hot welding, filling welding, and capping welding on the steel pipe joint in sequence to form a root weld layer, a hot weld layer, a filling layer, and a capping layer in sequence in a direction away from the inner wall of the steel pipe, thus completing the welding between the two sections of steel pipes;
[0011] Among them, the welding process parameters of the hot welding process, the filling welding process, and the capping welding process are as follows: welding current is 160 - 230 A, welding voltage is 20 - 23 V, and welding speed is 30 - 80 cm / min.
[0012] Furthermore,
[0013] In the root welding process, the automatic root welding of the internal welding machine is carried out by using the gas metal arc welding method. The welding consumable is a G55A5 grade gas shielded solid wire. The welding process parameters are as follows: welding current is 180 - 200 A, welding voltage is 21 - 22 V, and welding speed is 65 - 70 cm / min.
[0014] Furthermore,
[0015] In the root welding process, the diameter of the welding wire is 0.9 mm.
[0016] Furthermore,
[0017] In the hot welding process, the filling welding process, and the capping welding process, the automatic hot welding, filling welding, and capping welding of the double - torch external welding machine are carried out by using the gas metal arc welding method. The welding consumable is a G55A5 grade solid wire.
[0018] Furthermore,
[0019] In the hot welding process, the filling welding process, and the capping welding process, the diameter of the welding wire is 1.0 mm.
[0020] Furthermore,
[0021] In the root welding process, the hot welding process, the filling welding process, and the capping welding process, the shielding gas is a mixture of Ar and CO₂. By volume ratio, the mixture is 80% Ar and 20% CO₂, the purity of CO₂ gas ≥ 99.5%, and the purity of Ar gas ≥ 99.96%.
[0022] Furthermore,
[0023] In step B, the preheating temperature is not lower than 100 °C - 150 °C.
[0024] Furthermore,
[0025] The root weld layer, the hot weld layer, and the filling layer are single - layer single - pass, and the capping layer is single - layer double - pass.
[0026] Furthermore,
[0027] The interpass temperature is 80°C - 150°C.
[0028] Furthermore,
[0029] The steel pipe to be welded is an X80 pipeline steel pipe, which has the following components by weight percentage:
[0030] C: 0.03 - 0.07%, Si: 0.10 - 0.30%, Mn: 1.50 - 1.80%, P: ≤0.015%, S: ≤0.005%, Cr: 0.10 - 0.30%, Mo: 0.08 - 0.30%, Ni: 0.10 - 0.30%, Al: 0.01 - 0.05%, Cu: ≤0.30%, Nb: 0.020 - 0.080%, Ti: 0.010 - 0.025%, V: ≤0.06%, B: ≤0.0005%, the balance is Fe and other impurities, and CEPcm ≤ 0.21 is satisfied.
[0031] Combining the above technical solutions, the technical effects that the present invention can achieve are as follows:
[0032] The double-torch solid wire automatic welding method provided by the present invention is a double-torch solid wire automatic welding method for high fracture toughness girth weld joints. The butt joint of the steel pipe is processed with a single-sided composite groove, designed with a larger bottom and a smaller top. The settings of parameters such as the uphill groove face angle and the downhill groove face angle ensure that the welding torch can extend into the groove for multi-layer and multi-pass welding. The filling amount is reduced by more than 50% compared with the general V-groove; the welding heat input is within 0.6 kJ / mm with the process parameters adopted. The small heat input condition can play a role in refining grains, which is very beneficial to improving the fracture toughness, and solves the problem of low fracture toughness value of the weld when the X80 steel pipe is welded by the double-torch solid wire automatic welding. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0034] Figure 1 It is a schematic diagram of the joint of the steel pipe to be welded;
[0035] Figure 2 It is a schematic diagram of the number and sequence of welding passes.
[0036] Icon: a, uphill bevel face angle; b, downhill bevel face angle; c, inner bevel face angle; h1, inner bevel height; h2, root face height; h3, height from inflection point to inner wall; L, root opening gap
[0037] 1. Root pass layer; 2. Hot pass layer; 3. Fill pass layer; 3-1. First layer; 3-2. Second layer; 4-1. Third layer; 4-2. Fourth layer; 5-1. Fifth layer; 6. Cap pass layer; 6-1. First pass; 6-2. Second pass Specific implementation manners
[0038] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the present invention usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations
[0039] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention
[0040] The following will describe in detail some implementation manners of the present invention with reference to the accompanying drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other
[0041] In view of this, the present invention provides an automatic welding method for double-torch solid wire, including the following steps: Step A: Process the bevels at the joints of two steel pipes to be welded. Among them, the uphill bevel face angle a is 5°±1°, the downhill bevel face angle b is 45°±1°, the inner bevel face angle c is 37.5°±1°, the inner bevel height h1 is 1.7±0.2 mm, the root face height h2 is 1.1±0.2 mm, the height h3 from the inflection point to the inner wall is 5.1±0.2 mm, and the root opening gap L is 0-0.5 mm; Step B: Clean and preheat both sides of the bevels; Step C: Perform root welding, hot welding, fill welding and cap welding on the steel pipe joints in sequence to form a root pass layer 1, a hot pass layer 2, a fill pass layer 3 and a cap pass layer 6 in sequence in the direction away from the inner wall of the steel pipe at the steel pipe joints, and complete the welding between the two steel pipes; Among them, the welding process parameters of the hot welding process, the fill welding process and the cap welding process are welding current 160-230 A, welding voltage 20-23 V, and welding speed 30-80 cm / min
[0042] The double-torch solid wire automatic welding method provided by the present invention is a double-torch solid wire automatic welding method for high fracture toughness girth weld joints. The butt joint of the steel pipe is processed with a single-sided composite groove, which is designed with a larger bottom and a smaller top. The settings of parameters such as the angle of the upper groove surface and the angle of the lower groove surface ensure that the welding torch can extend into the groove for multi-layer and multi-pass welding. The filling amount is reduced by more than 50% compared with the general V-groove. The welding heat input is within 0.6 kJ / mm with the adopted process parameters. The small heat input condition can play a role in refining grains, which is very beneficial to improving the fracture toughness, and solves the problem of low fracture toughness value of the weld when the X80 steel pipe is welded by the double-torch solid wire automatic welding method.
[0043] The following Figure 1 - Figure 2 will describe in detail the double-torch solid wire automatic welding method provided in this embodiment.
[0044] In this embodiment, the steel pipe to be welded is an X80 pipeline steel pipe, which has the following components by weight percentage:
[0045] C: 0.03 - 0.07%, Si: 0.10 - 0.30%, Mn: 1.50 - 1.80%, P: ≤0.015%, S: ≤0.005%, Cr: 0.10 - 0.30%, Mo: 0.08 - 0.30%, Ni: 0.10 - 0.30%, Al: 0.01 - 0.05%, Cu: ≤0.30%, Nb: 0.020 - 0.080%, Ti: 0.010 - 0.025%, V: 0.02 - 0.06%, B: ≤0.0005%, and the balance is Fe and inevitable other impurities, and CE Pcm ≤0.21.
[0046] Specifically, the reasons for the above component limitations are as follows: Carbon C, manganese Mn, and nickel Ni are austenite-expanding elements that lower the austenite phase transformation temperature and obtain a fine and highly ductile phase transformation structure. However, both C and Mn are prone to segregation and are likely to form hardened structures in the core during cooling, so they are respectively controlled within the ranges of 0.03 - 0.07% and 1.50 - 1.80%. Copper Cu can improve the corrosion resistance of the metal but is also likely to cause hot cracks, and is controlled to be ≤0.30%, with no lower limit restriction. Ni is beneficial to the low-temperature toughness of the steel and can also improve the hot brittleness caused by Cu, and is controlled within the range of 0.10 - 0.30%. Phosphorus P and sulfur S are inevitable harmful elements in pipeline steel. P is prone to causing cold brittleness, and S is likely to form defects such as sulfide inclusions, so their components are strictly controlled with P ≤ 0.015% and S ≤ 0.005%. Although chromium Cr can improve the corrosion resistance of the steel, it will also deteriorate the weldability, and is controlled within the range of 0.10 - 0.30%. Molybdenum Mo promotes the formation of high-ductility acicular ferrite, and the range of the Mo content is 0.08 - 0.30%. Aluminum Al is a strong deoxidizing element, and excessive amounts will form relatively large oxide inclusions, and its content is controlled within the range of 0.01 - 0.05%. A high silicon Si content will deteriorate the weldability, so its content is limited within the range of 0.10 - 0.30%; Niobium Nb, titanium Ti, and vanadium V: Microalloying elements that are also prone to forming carbides, contribute to grain refinement, and are also nitrogen-fixing elements that reduce the adverse effects of N elements on toughness. Nb can effectively improve the toughness of the weld, reduce the embrittlement and hardening tendencies in the heat-affected zone of welding, and improve the welding process performance. Their contents are respectively controlled as Nb: 0.02 - 0.08%, Ti: 0.010 - 0.025%, and V: ≤0.06%.
[0047] Regarding the groove in this embodiment, specifically:
[0048] In this embodiment, the joints of the two steel pipes to be welded are processed with grooves. In order to reduce the amount of filler metal and improve the welding efficiency, referring to Figure 1 , the groove in this embodiment is a single-sided composite groove, designed with a larger bottom and a smaller top. The uphill groove surface angle a is half of the included angle between the two uphill groove surfaces, the downhill groove surface angle b is half of the included angle between the two downhill groove surfaces, the inner groove surface angle c is half of the included angle between the two inner groove surfaces, the height h3 from the inflection point to the inner wall is the distance between the intersection of the uphill groove surface and the downhill groove surface and the inner wall of the steel pipe, the inner groove height h1 is the distance between the intersection of the root face and the inner groove surface and the inner wall of the steel pipe, and the butt gap L is the gap between the pipe ends (i.e., the distance between the two root faces).
[0049] The uphill groove face angle a is 5° ± 1°, and the downhill groove face angle b is 45° ± 1°, ensuring that the welding torch can extend into the groove for multi-layer and multi-pass welding. The inner groove face angle c is 37.5° ± 1°, the inner groove height h1 is 1.7 ± 0.2 mm, the root face h2 is 1.1 ± 0.2 mm, the height h3 from the inflection point to the inner wall is 5.1 ± 0.2 mm, and the root gap L is 0 - 0.5 mm. The filling amount of this single-sided composite groove is reduced by more than 50% compared with that of a general V-groove.
[0050] Regarding the welding process parameters in this embodiment, specifically:
[0051] Perform root welding, hot welding, filling welding, and capping welding on the steel pipe joint in sequence to form a root weld layer 1, a hot weld layer 2, a filling layer 3, and a capping layer 6 in sequence away from the inner wall of the steel pipe at the steel pipe joint, completing the welding between two sections of steel pipes.
[0052] Specifically, use the Gas Metal Arc Welding method for automatic root welding with an internal welding machine to form the root weld layer 1. The welding consumable is selected as a G55A5-class gas-shielded solid wire with a diameter of 0.9 mm; the welding process parameters are: welding current 180 - 200 A, welding voltage 21 - 22 V, welding speed 65 - 70 cm / min; the shielding gas is a mixture of Ar and CO2 with a mixing volume ratio of 80% Ar + 20% CO2, and the requirements are that the purity of CO2 gas ≥ 99.5% and the purity of Ar gas ≥ 99.96%; use the Gas Metal Arc Welding method for automatic hot welding, filling, and capping with a double-torch external welding machine to form the hot weld layer 2, the filling layer 3, and the capping layer 6. Among them, the hot weld layer 2 is located above the root weld layer 1, the filling layer 3 is located above the hot weld layer 2, and the capping layer 6 is located above the filling layer 3. The welding consumable is selected as a G55A5-class solid wire with a diameter of 1.0 mm; the welding process parameters are: welding current 160 - 230 A, welding voltage 20 - 23 V, welding speed 30 - 80 cm / min, and the shielding gas is the same as that for root welding; the welding heat input is within 0.6 kJ / mm with the adopted process parameters. The small heat input condition can play a role in refining the grains, which is very beneficial to improving the fracture toughness.
[0053] The double-torch solid wire automatic welding method provided by this embodiment includes the following steps:
[0054] (1) Use a steel pipe with characteristic chemical components such as the X80 steel pipe described above. Process a single-sided compound groove for the butt joint. The angle a of the upper groove surface is 5° ± 1°, the angle b of the lower groove surface is 45° ± 1°, the angle c of the inner groove surface is 37.5° ± 1°, the height h1 of the inner groove is 1.7 ± 0.2 mm, the height h2 of the root face is 1.1 ± 0.2 mm, the height h3 from the inflection point to the inner wall is 5.1 ± 0.2 mm, and the alignment gap L is 0 - 0.5 mm.
[0055] (2) Use a groove machine to process the grooves at both ends of the steel pipe according to the above requirements. Before welding, clean the areas within 25 mm on both sides of the groove on the inner and outer surfaces of the pipe until they show metallic luster; use a track locator to assist in installing the welding trolley track to ensure that the welding torch is aligned with the center of the welding groove throughout the circumference of the pipe.
[0056] (3) Uniformly preheat the areas within 100 mm on both sides of the groove. The preheating temperature is not lower than 100℃ - 150℃; before formal welding, evenly monitor 4 points on the circumference 25 mm away from the groove to ensure that the preheating or interlayer (pass) temperature meets the requirements.
[0057] (4) Use the Gas Metal Arc Welding method for automatic root welding with an internal welding machine, and the welding process parameters are as described above; use the Gas Metal Arc Welding method for automatic hot welding, filling, and capping with a double-torch external welding machine, and the welding process parameters are as described above; for the circumferential weld joint, first perform 1 layer of root welding, 1 layer of hot welding, and 5 layers of filling (refer to Figure 2 , the filling layer 3 specifically includes the first layer 3 - 1, the second layer 3 - 2, the third layer 4 - 1, the fourth layer 4 - 2, and the fifth layer 5 - 1), and finally perform 1 layer of capping welding (refer to Figure 2 , one layer of capping welding includes two passes, namely the first pass 6 - 1 and the second pass 6 - 2). Except for the capping layer 6 which is single-layer double-pass, the rest of the weld layers 1 are all single-layer single-pass.
[0058] (5) Control the interlayer temperature within 80℃ - 150℃. During the welding process, evenly monitor 4 points on the circumference 25 mm away from the groove to ensure that the preheating or interlayer (pass) temperature meets the requirements.
[0059] (6) The fracture toughness of the weld center and the heat-affected zone of the welded joint obtained by welding with the above steel pipe and welding materials meets the single value ≥ 0.254 mm under low-temperature conditions (-10℃).
[0060] The following specifically lists an embodiment of this method, which specifically includes the following steps:
[0061] (1) Use a steel pipe with characteristic chemical components such as the X80 steel pipe described above. The specific components of the X80 steel pipe are as follows: C: 0.06%, Si: 0.21%, Mn: 1.69%, P: 0.01%, S: 0.002%, Cr: 0.206%, Mo: 0.149%, Ni: 0.152%, Al: 0.035%, Cu: 0.022%, Nb: 0.056%, Ti: 0.013%, V: 0.005%, B: 0.0002%, and the balance is Fe and other inevitable impurities.
[0062] The diameter of the steel pipe is 1219 mm and the wall thickness is 22 mm; for the butt joint, a single-sided composite groove is machined. The angle a of the upper groove surface is 5°, the angle b of the lower groove surface is 45°, the angle c of the inner groove surface is 37.5°, the height h1 of the inner groove is 1.7 mm, the root face h2 is 1.1 mm, the height h3 from the inflection point to the inner wall is 5.1 mm, and the butt joint gap L is 0.1 mm;
[0063] (2) Before welding, clean the areas within 25 mm on both sides of the groove on the inner and outer surfaces of the pipe until they show metallic luster;
[0064] (3) Before welding, uniformly preheat the areas within 100 mm on both sides of the groove, and the preheating temperature is 100°C - 125°C;
[0065] (4) Use G55A5-class welding consumables for gas metal arc welding root pass. The diameter of the welding consumables is 0.9 mm, and the welding process parameters are as follows: welding current 180 - 200 A, welding voltage 21 - 22 V, welding speed 65 - 70 cm / min;
[0066] (5) 10 minutes after the root pass, use a 1.0 mm G55A5-class solid wire for hot welding. Welding voltage: 20.0 - 22.5 V, welding current: 200 - 230 A, welding speed 60 - 80 cm / min, as Figure 2 shown;
[0067] (6) When the hot weld layer 2 cools to 100°C, use a 1.0 mm G55A5-class solid wire to weld the filling passes 3-1, 3-2, 4-1, 4-2, 5-1 in sequence. The interpass temperature is 100°C, welding voltage: 20.0 - 23.0 V, welding current: 180 - 200 A, welding speed 30 - 60 cm / min, as Figure 2 shown;
[0068] (7) When the first-welded weld bead cools to 100°C, use a 1.0 mm G55A5-class solid wire to weld the capping passes 6-1, 6-2. The interpass temperature is 100°C, welding voltage: 20.0 - 23.0 V, welding current: 180 - 200 A, welding speed 30 - 60 cm / min, as Figure 2as shown
[0069] (8) After conducting mechanical property tests on the girth weld joints welded with the above-mentioned X80 steel pipe and welding consumables, the fracture toughness value at the weld center under low-temperature conditions (-10°C) is above 0.308 mm, and the fracture toughness value in the heat-affected zone is above 0.667.
[0070] Starting from expanding the on-site construction welding process window, the double-torch solid wire automatic welding method provided in this embodiment forms a girth weld joint with high fracture toughness and improves the fracture toughness of the double-torch solid wire automatic weld of the X80 steel pipe through reasonable design of the steel pipe composition, selection of appropriate welding materials, reasonable matching of welding consumables, and welding process selection (including joint form design, process parameters, interpass temperature, etc.), and arranging the number of layers and passes according to the groove form design during multi-layer and multi-pass welding.
[0071] The double-torch solid wire automatic welding method provided in this embodiment defines the chemical composition of the steel pipe used for girth weld construction, uses a gas-shielded solid wire of grade G55A5, designs appropriate number of welding layers and welding process parameters, and improves the fracture toughness of the girth weld.
[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. An automatic welding method for double torch solid wire welding, characterized in that, It includes the following steps: Step A: Process the bevel at the joint of the two steel pipes to be welded. Among them, the angle (a) of the upper bevel surface is 5°±1°, the angle (b) of the lower bevel surface is 45°±1°, the angle (c) of the inner bevel surface is 37.5°±1°, the inner bevel height (h1) is 1.7±0.2 mm, the root face height (h2) is 1.1±0.2 mm, the height (h3) from the inflection point to the inner wall is 5.1±0.2 mm, and the root opening (L) is 0 - 0.5 mm; Step B: Clean and preheat both sides of the bevel; Step C: Carry out root welding, hot welding, filling welding and capping welding on the steel pipe joint in sequence to form a root weld layer (1), a hot weld layer (2), a filling layer (3) and a capping layer (6) in sequence in the direction away from the inner wall of the steel pipe, and complete the welding between the two steel pipes; Among them, the welding process parameters of the hot welding process, filling welding process and capping welding process are: welding current 160 - 230 A, welding voltage 20 - 23 V, welding speed 30 - 80 cm / min.
2. The automatic welding method with double - torch solid wire according to claim 1, characterized in that In the root welding process, the automatic root welding of the internal welding machine is carried out by using the gas - shielded metal arc welding method, the welding consumable is the gas - shielded solid wire of G55A5 grade, and the welding process parameters are: welding current 180 - 200 A, welding voltage 21 - 22 V, welding speed 65 - 70 cm / min.
3. The automatic welding method with double - torch solid wire according to claim 2, characterized in that In the root welding process, the diameter of the welding wire is 0.9 mm.
4. The automatic welding method with double - torch solid wire according to claim 1, characterized in that In the hot welding process, filling welding process and capping welding process, the automatic hot welding, filling welding and capping welding of the double - torch external welding machine are carried out by using the gas - shielded metal arc welding method, and the welding consumable is the solid wire of G55A5 grade.
5. The automatic welding method with double - torch solid wire according to claim 4, characterized in that In the hot welding process, filling welding process and capping welding process, the diameter of the welding wire is 1.0 mm.
6. The automatic welding method with double - torch solid wire according to claim 1, characterized in that In the root welding process, hot welding process, filling welding process and capping welding process, the shielding gas is a mixture of Ar and CO2. By volume ratio, the mixture is 80% Ar and 20% CO2, the purity of CO2 gas is ≥99.5%, and the purity of Ar gas is ≥99.96%.
7. The automatic welding method with double - torch solid wire according to claim 1, characterized in that In step B, the preheating temperature is not lower than 100℃ - 150℃.
8. The automatic welding method with double - torch solid wire according to claim 1, characterized in that The root weld layer (1), hot weld layer (2) and filling layer (3) are single - layer single - pass, and the capping layer (6) is single - layer double - pass.
9. The automatic welding method with double - torch solid wire according to claim 1, characterized in that The inter - pass temperature is 80℃ - 150℃.
10. The automatic welding method of double welding torches with solid wire according to claim 1, characterized in that the steel pipe to be welded is an X80 pipeline steel pipe, which has the following components by weight percentage: C: 0.03 - 0.07%, Si: 0.10 - 0.30%, Mn: 1.50 - 1.80%, P: ≤0.015%, S: ≤0.005%, Cr: 0.10 - 0.30%, Mo: 0.08 - 0.30%, Ni: 0.10 - 0.30%, Al: 0.01 - 0.05%, Cu: ≤0.30%, Nb: 0.020 - 0.080%, Ti: 0.010 - 0.025%, V: ≤0.06%, B: ≤0.0005%, the balance being Fe and other impurities, and satisfying CE Pcm ≤0.21.