Gas shielded welding wire for girth welding of high-strain pipeline as well as manufacturing method and application of gas shielded welding wire

Abstract

The invention belongs to the technical field of pipeline welding, and particularly relates to a gas shielded welding wire for girth welding of a high-strain pipeline and a manufacturing method and application of the gas shielded welding wire. The invention discloses a gas shielded welding solid welding wire for girth welding of a high-strain pipeline. The welding wire comprises the following chemical components in percentage by weight: 0.04 to 0.07 percent of C, 1.20 to 1.80 percent of Mn, 0.35 to 0.75 percent of Si, 0.8 to 1.2 percent of Ni, 0.20 to 0.35 percent of Mo, 0.10 to 0.20 percent of Cu, less than or equal to 0.010 percent of S, less than or equal to 0.012 percent of P, 0.04 to 0.10 percent of Ti, 0.003 to 0.006 percent of B and the balance of Fe. On the basis of a Mn-Ni-Mo-Ti alloy system, various alloy elements are reasonably matched, so that the welding wire has high low-temperature impact toughness, excellent welding performance, corrosion resistance and crack tip opening displacement performance (CTOD) while the welding wire meets the requirement for high strength of weld metal, and the welding wire can be widely applied to the field of welding. The method can be suitable for girth welding of high-strength thick-wall high-strain pipelines with the X80 steel grade and the wall thickness being 30 mm or above, and high-strength matching of girth welding joints of high-strength pipeline steel pipes is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of pipeline welding, and particularly relates to a gas shielded welding wire for girth welding of high-strain pipelines, a manufacturing method and an application thereof. Background Art

[0002] Long-distance pipelines inevitably pass through a large number of complex working condition areas such as seismic fault zones, landslide zones, mined-out areas of mines, subsidence zones, etc. This poses new challenges to the design, materials, and construction of pipelines. The strain-based design method can make full use of the plastic deformation ability of high-grade steel pipelines, making it possible to lay oil and gas pipelines in complex working condition areas such as seismic fault zones, landslide zones, mined-out areas of mines, and subsidence zones. In order to improve the gas transmission efficiency, reduce the steel consumption and the corresponding logistics and construction costs, and ensure the high efficiency and safety of oil and gas transportation, the steel grade and pipe diameter of oil and gas long-distance pipelines are continuously increasing. The steel grade has developed to above X80, the pipe diameter reaches above 1219 mm, and the wall thickness reaches above 30 mm.

[0003] Since the welding process of on-site girth welding of pipelines may cause the deterioration of the performance of the welded joints and generate welding defects such as cracks, pores, slag inclusions, incomplete penetration, lack of fusion, etc., the girth weld is the weak link of pipeline deformation, restricting the deformation ability of the pipeline. With the development and application of high-grade steel for pipeline use, the welding of on-site girth welds of high-grade steel pipelines has increasingly become the key problem restricting their application. Especially for the girth welding of high-strength thick-walled pipelines based on strain design, it is very difficult to meet the requirements that the full-scale tensile / compression test of the pipeline does not fracture or deform at the welded joint and the strain is less than the design requirements. The high matching of yield strength and high toughness of the weld metal are the core considerations for the development of welding materials and processes. Preventing the excessive embrittlement and softening of the heat-affected zone is another major problem in the development of base materials and welding processes. China currently has a mature girth welding process for pipelines of X80 and below based on load stress design, while there is little research on the girth welding process for pipelines above X80 based on strain design.

[0004] The welding wire is an indispensable material for gas shielded welding of pipelines. At present, imported products such as those from American Linconln, Italian FILLEUR, Austrian BOHLER, Swedish ESAB, and German Thyssen are widely used as gas shielded solid welding wires for circumferential welding of high-strength thick-walled pipelines. There are also a small number of domestic welding wires from Atlantic, Jinqiao, Daqiao, Jintai, etc. However, the market share of domestic gas shielded solid welding wires in pipeline construction is relatively low, and there are no engineering application cases in the circumferential welding of pipelines with an X80 steel grade and a wall thickness of more than 30 mm based on strain design. Pipelines based on strain design are mainly used in geographically complex and harsh areas such as earthquake fault zones, landslide zones, and subsidence zones, and have relatively high requirements for the welding materials supporting pipeline circumferential welding. The gas shielded welding wire for circumferential welding of high-strain pipelines not only requires good strength and toughness matching but also excellent welding process performance, while the existing products cannot meet the requirements. Therefore, it has become an important problem that needs to be solved urgently to research and develop a gas shielded welding wire for circumferential welding of high-strength thick-walled high-strain pipelines with high strength matching, high plasticity, strong toughness, and a narrow strength change range. There is an urgent need to develop a gas shielded welding wire for circumferential welding of high-strength thick-walled high-strain pipelines. Summary of the Invention

[0005] In view of the above problems, the object of the present invention is to provide a gas shielded welding wire for circumferential welding of high-strain pipelines, its manufacturing method and application. The gas shielded solid welding wire for circumferential welding of high-strain pipelines in the present invention is a gas shielded welding wire with high strength matching, high plasticity, strong toughness, and a narrow strength change range, which can achieve high strength matching of the circumferential welding joints of high-strength pipeline steel pipes, and is a gas shielded welding wire dedicated to the circumferential welding of high-strength thick-walled high-strain pipelines with an X80 steel grade and a wall thickness of more than 30 mm, meeting the special performance requirements such as high strength, excellent low-temperature toughness, and crack tip opening displacement (CTOD) of the pipeline circumferential welding joints.

[0006] The technical solution of the present invention lies in: a gas shielded solid welding wire for circumferential welding of high-strain pipelines, and the chemical composition of the welding wire is by weight percentage: C: 0.04% - 0.07%, Mn: 1.20% - 1.80%, Si: 0.35% - 0.75%, Ni: 0.8% - 1.2%, Mo: 0.20% - 0.35%, Cu: 0.10% - 0.20%, S≤0.010%, P≤0.012%, Ti: 0.04% - 0.10%, B: 0.003% - 0.006%, and the balance is Fe.

[0007] The basis for the design of the chemical composition of the welding wire in the present invention is described as follows: C is an important factor ensuring strength, but it is also a brittle element in high-strength steel welds, which affects the crack resistance and impact toughness of weld metal. Therefore, the carbon content in the welding wire should be strictly controlled. Considering this, the C content is appropriately reduced, and necessary strength is obtained through elements such as Mn, Mo, and Ni. In this design, the C content is controlled within the range of 0.04 - 0.07%.

[0008] Mn is a strengthening element and also a deoxidizing element. The oxides formed during the deoxidation process can improve the strength, low-temperature impact toughness of weld metal and the welding processability. With the increase of Mn content, it can promote the formation of acicular ferrite, increase the proportion of acicular ferrite structure in the weld, and improve toughness. At the same time, the addition of Mn compensates for the strength decrease caused by the reduction of C. However, excessive Mn will cause a decrease in toughness. In this design, the Mn content is controlled within the range of 1.20 - 1.80%.

[0009] Si is a deoxidizing element, which improves the welding processability and has the effect of increasing the strength of weld deposited metal. When the Si content is low, deoxidation is insufficient, which is likely to cause too high oxygen content in the weld and affect the low-temperature impact toughness of the weld; when an appropriate amount of Si element is added to the welding wire, it can improve its welding processability and the strength of weld metal; but excessive Si element will harden the weld metal, reduce the low-temperature toughness of the weld metal, and at the same time increase welding spatter and the processability of the welding wire decreases. The toughness of the deposited metal depends to a large extent on the Si and Mn contents. Too much or too little Si and Mn contents can both cause a decrease in toughness. Therefore, in order to ensure toughness, it is also necessary to control the ratio of Mn and Si. In this design, the Si content is controlled within the range of 0.35 - 0.75%.

[0010] Ni is an element that improves the strength and low-temperature impact toughness of the weld. Ni can refine the structure and promote the formation of acicular ferrite. The solid solution of Ni can also improve the low-temperature toughness. There is an interaction between the influence of Ni on the impact toughness in weld metal and the Mn content. When the two elements are within the optimal matching range, the corresponding weld metal has excellent strength and toughness matching. According to the above-mentioned addition amount of Mn, in this design, the Ni content is controlled within the range of 0.8 - 1.2%.

[0011] Mo can reduce the phase transformation temperature, delay and prevent the nucleation and growth of pearlite, inhibit the formation of proeutectoid ferrite, promote the transformation of acicular ferrite, increase the proportion of acicular ferrite, and can improve the precipitation strengthening effect of nitrides. However, Mo is also harmful to toughness. So the addition of Mo should be limited within a certain range. The Mo content generally should not exceed 0.35%. In this design, the Mo content is controlled within the range of 0.20 - 0.35%.

[0012] Cu helps to improve the corrosion resistance of the weld metal, but to avoid an increase in the hardness of the weld, the addition amount of Cu is generally taken as 0.05 - 0.20%. In this design, the content of Cu is controlled within the range of 0.10 - 0.20%.

[0013] The welds alloyed with Ti / B can obtain a high content of acicular ferrite structure, thus obtaining good toughness. In this design, the content of Ti added is controlled within the range of 0.04 - 0.10%, and the content of B added is controlled within the range of 0.003 - 0.006%.

[0014] The yield strength R of the clad metal after welding the wire eL ≥575 MPa, the tensile strength R m ≥645 MPa, the elongation A ≥ 24%; at -40 °C, the single value of the impact toughness Akv ≥ 80 J, and the average value ≥ 100 J; at -10 °C, the CTOD characteristic value δm ≥ 0.254 mm; the hardness ≤ 280 HV 10 .

[0015] A method for preparing a gas shielded solid wire for circumferential welding of high-strain pipelines, preparing a gas shielded solid wire for circumferential welding of high-strain pipelines as described above, including the following steps: S1: Processing of wire rod: Put the raw materials for preparing the wire into a vacuum induction furnace for smelting, the smelting temperature of the vacuum induction furnace is 1620 °C - 1650 °C, and then it is made into a wire rod with a diameter of 5.5 mm - 6.5 mm through a temperature-controlled rolling process; S2: Removal of surface scale: Remove the scale generated by annealing the wire rod through mechanical and chemical methods; S3: Wire drawing: First, go through 5 - 6 times of rough drawing, draw the wire rod from a diameter of 5.5 mm - 6.5 mm to 2 mm in sequence, and then carry out fine drawing on the wire rod, drawing it to the required diameter of 0.9 mm - 1.2 mm or other designed dimensions; S4: Surface pickling: Pickle and degrease the surface substances and coatings after wire drawing with H2SO4 acid solution with a mass concentration of 12% - 18% at 80 °C; S5: Electroless copper plating: Evenly coat a layer of copper on the wire after pickling and cleaning in the CuSO4 solution, and the coating thickness is 0.6 μm - 1.8 μm; S6: Water washing and drying: Wash the residual acid in the plating solution and passivation on the surface of the wire through a water washing tank, clean the surface attachments, and dry the wire through a high-frequency heater, the frequency of the high-frequency heater is 40 KHz - 70 KHz, and the drying temperature is 90 °C - 120 °C; S7: Wire winding and packaging: Precisely wind the wire through an automatic winding device and package the wire according to relevant requirements.

[0016] In the step S1, in the controlled rolling process, the heating temperature is 1050°C to 1080°C, the starting rolling temperature is 980°C to 1020°C, the number of rolling passes is 2 to 3 times, the finish rolling temperature is 900°C to 950°C, the wire rod spooling temperature is 850°C to 900°C, and the cooling rate of the wire is controlled to be ≥6.5°C / s; after rolling, it is annealed at 800°C to 900°C and then air-cooled to room temperature.

[0017] In the step S2, by chemical and mechanical methods, the scale generated during the annealing of the wire rod is removed by mechanical and chemical methods. The specific process is as follows: First, pickling is carried out with sulfuric acid with a mass concentration of 60 g / L to remove the scale residue and iron salts on the surface of the wire rod, and the pickling temperature control should be at 60 °C; then, the surface residual acid of the wire rod is rinsed and neutralized with weakly alkaline high-pressure water with a pH value of 7 to 8, and the pressure of the high-pressure water is not less than 3 MPa; then, the wire rod is put into a rusting tank, and water mist is evenly and continuously sprayed on the surface of the wire. The wire rod stays in the water mist for a certain period of time until a layer of yellowish-brown iron hydroxide is formed on the surface of the wire. The water mist flow rate is controlled at 1.5 m 3 / h; finally, lime coating is repeatedly carried out 5 to 8 times in a lime solution tank, and the temperature of the lime solution should be controlled at 80 to 100 °C.

[0018] In the step S5: During the electroless copper plating process, the temperature of the CuSO4 solution is 40°C to 60 °C, and the mass concentration is 40 g / L to 70 g / L.

[0019] An application method of a gas shielded solid wire for high-strain pipeline girth welding uses a gas shielded solid wire for high-strain pipeline girth welding as described above. The wire is used for all-position gas shielded welding of high-strain pipelines with an X80 steel grade and a wall thickness of more than 30 mm.

[0020] The all-position gas shielded welding parameters of the high-strain pipeline are specifically as follows: The welding shielding gas is an argon-rich mixed gas, with a volume ratio of 80% to 95% Ar + 20% to 5% CO2; the welding current is 220 A to 260 A, the welding voltage is 20 V to 26 V, the welding speed is 30 cm / min to 35 cm / min, the gas flow rate is 15 L / min to 25 L / min, and the interpass temperature is controlled at 135°C to 165°C.

[0021] The technical effects of the present invention are as follows: 1. The present invention reduces the carbon equivalent, hardening tendency and crack sensitivity coefficient of the weld metal through low-carbon design, and fully utilizes the microalloying theory. By adding alloying elements such as Mn, Ni, Mo, and Cr to the welding wire, the strength and toughness of the weld metal are improved, and a certain amount of microalloying elements such as Ti and B are added to refine the grains of the weld metal, improve the stability of austenite, improve the weld structure, and improve the strength and toughness of the weld metal. 2. The welding wire of the present invention is suitable for semi-automatic gas shielded welding and all-position automatic welding, has good adaptability, and is particularly suitable for all-position circumferential weld welding of X80 steel grade thick-wall high-strain pipelines. 3. The mechanical properties of the deposited metal of the welding wire of the present invention are: yield strength R eL ≥575 MPa, tensile strength R m ≥645 MPa, elongation A≥24%; at -40 °C, the single value of impact toughness Akv≥80 J, and the average value≥100 J; at -10 °C, the CTOD characteristic value δm≥0.254 mm; hardness≤280 HV 10 . The weld metal has high strength, high and low temperature impact toughness, excellent welding performance and crack tip opening displacement performance (CTOD), and at the same time has excellent process performance. The mechanical properties of its welded joints fully meet the relevant performance index requirements of all-position circumferential welds of X80 high-strain pipelines. Detailed implementation mode Example 1

[0022] A solid cored wire for gas shielded welding for circumferential welding of high-strain pipelines, the chemical composition of the welding wire is by weight percentage: C: 0.04% - 0.07%, Mn: 1.20% - 1.80%, Si: 0.35% - 0.75%, Ni: 0.8% - 1.2%, Mo: 0.20% - 0.35%, Cu: 0.10% - 0.20%, S≤0.010%, P≤0.012%, Ti: 0.04% - 0.10%, B: 0.003% - 0.006%, and the balance is Fe.

[0023] The yield strength R of the clad metal after welding the welding wire eL ≥575 MPa, tensile strength R m ≥645 MPa, elongation A≥24%; at -40 °C, the single value of impact toughness Akv≥80 J, and the average value≥100 J; at -10 °C, the CTOD characteristic value δm≥0.254 mm; hardness≤280 HV 10 .

[0024] The present invention reduces the carbon equivalent, hardening tendency and crack sensitivity coefficient of the weld metal through low-carbon design, and fully utilizes the microalloying theory. By adding alloying elements such as Mn, Ni, Mo, and Cr to the welding wire, the strength and toughness of the weld metal are improved, and a certain amount of microalloying elements such as Ti and B are added to refine the grains of the weld metal, improve the stability of austenite, improve the weld structure, and enhance the strength and toughness of the weld metal. Example 2

[0025] A method for preparing a solid cored wire for gas shielded welding for high-strain pipeline girth welding, preparing a solid cored wire for gas shielded welding for high-strain pipeline girth welding as described above, comprising the following steps: S1: Processing of the welding wire coil rod: Put the raw materials for preparing the welding wire into a vacuum induction furnace for smelting. The smelting temperature of the vacuum induction furnace is 1620°C to 1650°C, and then it is processed through a temperature-controlled rolling process to make a welding wire coil rod with a diameter of 5.5 mm to 6.5 mm; S2: Removal of surface scale: Remove the scale generated by annealing the welding wire coil rod through mechanical and chemical methods; S3: Drawing of the welding wire: First, perform 5 to 6 times of rough drawing, draw the welding wire coil rod from a diameter of 5.5 mm to 6.5 mm to 2 mm in sequence, and then perform fine drawing on the welding wire coil rod until the required diameter of 0.9 mm to 1.2 mm or other designed dimensions; S4: Surface pickling: Pickle and degrease the surface substances and coatings after wire drawing of the welding wire with a sulfuric acid solution with a mass concentration of 12% to 18% at 80°C; S5: Electroless copper plating: Evenly coat a layer of copper on the welding wire cleaned by pickling in a CuSO4 solution, and the coating thickness is 0.6 μm to 1.8 μm; S6: Water washing and drying: Wash the residual acid in the plating solution and passivation on the surface of the welding wire through a water washing tank, clean the surface attachments, and dry the welding wire through a high-frequency heater. The frequency of the high-frequency heater is 40 KHz to 70 KHz, and the drying temperature is 90°C to 120°C; S7: Winding and packaging of the welding wire: Precisely wind the welding wire through an automatic winding device and package the welding wire according to relevant requirements.

[0026] In the step S1, in the temperature-controlled rolling process, the heating temperature is 1050°C to 1080°C, the starting rolling temperature is 980°C to 1020°C, the number of rolling passes is 2 to 3 times, the finishing rolling temperature is 900°C to 950°C, the wire coil rod laying temperature is 850°C to 900°C, and the cooling rate of the welding wire is controlled to be ≥6.5°C / s; After annealing treatment at 800°C to 900°C after rolling, the welding wire is air-cooled to room temperature.

[0027] In the step S2, for the chemical and mechanical methods, the scale generated during the annealing of the wire rod is removed by mechanical and chemical methods. The specific process is as follows: First, pickling is carried out with sulfuric acid at a mass concentration of 60 g / L to remove the scale residues and iron salts on the surface of the wire rod, and the pickling temperature control should be at 60 °C; then, the surface of the wire rod is rinsed and neutralized with weak alkaline high-pressure water with a pH value of 7 - 8, and the pressure of the high-pressure water should not be lower than 3 MPa; then, the wire rod is placed in a rusting tank, and water mist is evenly and continuously sprayed on the surface of the steel wire. The wire rod stays in the water mist for a certain period of time until a layer of brownish-yellow iron hydroxide is formed on the surface of the wire. The water mist flow rate is controlled at 1.5 m 3 / h; finally, lime is applied 5 - 8 times repeatedly in the lime solution tank, and the temperature of the lime solution should be controlled at 80 - 100 °C.

[0028] In the step S5: During the electroless copper plating process, the temperature of the CuSO4 solution is 40 °C - 60 °C, and the mass concentration is 40 g / L - 70 g / L. Example 3

[0029] An application method of a gas shielded solid cored wire for high-strain pipeline girth welding uses a gas shielded solid cored wire for high-strain pipeline girth welding as described above. The wire is used for all-position gas shielded welding of high-strain pipelines with X80 steel grade and wall thickness above 30 mm.

[0030] The all-position gas shielded welding parameters of the high-strain pipeline are specifically as follows: The welding shielding gas is an argon-rich mixed gas, with a volume ratio of 80% - 95% Ar + 20% - 5% CO2; the welding current is 220 A - 260 A, the welding voltage is 20 V - 26 V, the welding speed is 30 cm / min - 35 cm / min, the gas flow rate is 15 L / min - 25 L / min, and the interpass temperature is controlled at 135 °C - 165 °C.

[0031] According to a gas shielded solid cored wire for high-strain pipeline girth welding described in the above Example 1, a manufacturing method of a gas shielded solid cored wire for high-strain pipeline girth welding described in Example 2 is adopted for wire manufacturing. Specifically, as shown in Examples 4 - 7 and Comparative Examples 1 - 4, the chemical compositions (by mass percentage) of the wires in each example are shown in Table 1.

[0032] Table 1 Chemical Compositions (Wt.%) of Wires in Examples 4 - 7 and Comparative Examples 1 - 4

[0033] For the wire electrode deposited metal tests of Examples 4 to 7, the welding current used was 220 A to 260 A, the welding voltage was 20 V to 26 V, the welding speed was 30 cm / min to 35 cm / min, and the shielding gas was an argon-rich mixed gas of 80% to 95% Ar + 20% to 5% CO₂; the gas flow rate was 15 L / min to 25 L / min, and the interpass temperature was 135 °C to 165 °C. The wire electrode process performance of Examples 4 to 7 was good, the welding arc was stable, the spatter was small, it was suitable for all-position welding, the weld bead formation was beautiful, and no welding defects such as porosity, slag inclusion, and lack of fusion occurred in the weld. The mechanical properties of the wire electrode deposited metal welded joints are shown in Table 2.

[0034] Table 2 Mechanical property results of the welded joints of the wire electrodes of Examples 4 to 7 and Comparative Examples 1 to 4

[0035] From the performance test results of the examples and comparative examples in Table 2, it can be seen that for the all-weld tensile of the deposited metal welded joints of the wire electrodes in the examples, the yield strength was above 602 MPa, the elongation was above 24.2%, and the transverse tensile strength of the welded joints was above 695 MPa. The test values of the yield strength, elongation, and tensile strength and other indicators of the welded joints of the wire electrodes in the examples were all higher than those of the wire electrodes in the comparative examples; the wire electrodes in the examples showed excellent low-temperature toughness. At -40 °C, the single value of the impact energy of the welded joints was ≥104 J, and the average value was ≥108 J. The average value of the impact energy of the welded joints of the wire electrodes in the examples was higher than the average value of the impact energy of the wire electrodes in the comparative examples, and the single value fluctuation range was smaller, and the stability was better than that of the wire electrodes in the comparative examples; the wire electrodes in the examples showed excellent fracture toughness. At -10 °C, the CTOD characteristic value δm of the welded joints of the wire electrodes in the examples was ≥0.41 mm, and the CTOD characteristic value δm of the welded joints of the wire electrodes in the examples was higher than that of the wire electrodes in the comparative examples; the maximum hardness measured for the welded joints of the wire electrodes in the examples was 275 HV 10 , meeting the control target requirement that the maximum hardness does not exceed 280 HV 10 The hardness values of the welded joints of the wire electrodes in the comparative examples were all higher than 275 HV 10 , and the maximum hardness values of the welded joints of some of the wire electrodes in the comparative examples had exceeded the control target requirement that the maximum hardness does not exceed 280 HV 10 The comparison of the mechanical property results of the welded joints of the wire electrodes in the above examples and the comparative examples shows that the wire electrodes in the examples have both high strength and plasticity, and also have stable and excellent low-temperature toughness. The hardness of the welded joints is reasonably controlled, and the comprehensive mechanical properties are excellent. They can be applied to the circumferential welding of high-strength thick-wall high-strain pipelines with an X80 steel grade and a wall thickness of more than 30 mm, achieving high-strength matching of the circumferential welded joints of high-strength pipeline steel, and effectively ensuring the safe operation of the pipeline.

[0036] As described above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A solid cored wire for gas shielded welding used for circumferential welding of high strain pipelines, characterized in that: The chemical composition of the welding wire is by weight percentage: C: 0.04 - 0.07%, Mn: 1.20 - 1.80%, Si: 0.35 - 0.75%, Ni: 0.8 - 1.2%, Mo: 0.20 - 0.35%, Cu: 0.10 - 0.20%, S ≤ 0.010%, P ≤ 0.012%, Ti: 0.04% - 0.10%, B: 0.003% - 0.006%, and the balance is Fe.

2. The solid cored wire for gas shielded welding used for high strain pipeline girth welding according to claim 1, wherein: The yield strength R of the clad metal after welding the welding wire eL ≥ 575 MPa, the tensile strength R m ≥ 645 MPa, the elongation A ≥ 24%; at -40 °C, the single value of the impact toughness Akv ≥ 80 J, and the average value ≥ 100 J; at -10 °C, the CTOD characteristic value δm ≥ 0.254 mm; the hardness ≤ 280 HV 10 .

3. A method for preparing a solid cored wire for gas shielded welding used in high-strain pipe girth welding, for preparing a solid cored wire for gas shielded welding used in high-strain pipe girth welding as described in Claim 1, characterized in that: It includes the following steps: S1: Processing of the welding wire rod: Put the raw materials for preparing the welding wire into a vacuum induction furnace for smelting. The smelting temperature of the vacuum induction furnace is 1620°C - 1650°C, and then it is made into a welding wire rod with a diameter of 5.5 mm - 6.5 mm through a temperature-controlled rolling process. S2: Removal of surface scale: Remove the scale generated during the annealing of the welding wire rod by mechanical and chemical methods. S3: Drawing of the welding wire: First, go through 5 - 6 times of rough drawing, draw the welding wire rod from a diameter of 5.5 mm - 6.5 mm to 2 mm in sequence, and then conduct fine drawing on the welding wire rod until the required diameter of 0.9 mm - 1.2 mm or other designed dimensions. S4: Surface pickling: Pickle and degrease the surface substances and coatings of the drawn welding wire with a sulfuric acid solution (H2SO4) with a mass concentration of 12% - 18% at 80°C. S5: Electroless copper plating: Evenly coat a layer of copper on the pickled and cleaned welding wire in a CuSO4 solution, and the coating thickness is 0.6 μm - 1.8 μm. S6: Water washing and drying: Wash the residual acid in the plating solution and passivation on the surface of the welding wire through a water washing tank, clean the surface attachments, and dry the welding wire through a high-frequency heater. The frequency of the high-frequency heater is 40 KHz - 70 KHz, and the drying temperature is 90°C - 120°C. S7: Winding and packaging of the welding wire: Precisely wind the welding wire through an automatic winding device and package the welding wire according to relevant requirements.

4. The preparation method of a solid cored wire for gas shielded welding used in high-strain pipeline girth welding according to claim 3, characterized in that: In the step S1, in the temperature-controlled rolling process, the heating temperature is 1050°C - 1080°C, the rolling start temperature is 980°C - 1020°C, the number of rolling passes is 2 - 3 times, the finish rolling temperature is 900°C - 950°C, the wire rod laying temperature of the welding wire is 850°C - 900°C, and the cooling speed of the welding wire is controlled ≥ 6.5°C / s; after annealing treatment at 800°C - 900°C after rolling, the welding wire is air-cooled to room temperature.

5. The preparation method of a solid cored wire for gas shielded welding used in high strain pipe girth welding according to claim 3, characterized in that: In the step S2, the chemical and mechanical methods are used to remove the scale generated during the annealing of the wire rod for the welding wire by mechanical and chemical methods. The specific process is as follows: First, pickling is carried out with sulfuric acid with a mass concentration of 60 g / L to remove the scale residue and iron salt on the surface of the wire rod, and the temperature control during pickling should be at 60 °C; then, the surface of the wire rod is rinsed and neutralized with weak alkaline high-pressure water with a pH value of 7-8, and the pressure of the high-pressure water should not be lower than 3 MPa; then, the wire rod for the welding wire is placed in a rusting tank, and water mist is evenly and continuously sprayed on the surface of the steel wire. The wire rod stays in the water mist for a certain period of time until a layer of brownish-yellow iron hydroxide is formed on the surface of the welding wire, and the water mist flow rate is controlled at 1.5 m 3 / h; finally, lime is applied repeatedly 5-8 times in the lime solution tank, and the temperature of the lime solution should be controlled at 80-100 °C.

6. The preparation method of a solid cored wire for gas shielded welding used in high strain pipeline girth welding according to claim 3, characterized in that: In the step S5: During the electroless copper plating process, the temperature of the CuSO4 solution is 40°C - 60°C and the mass concentration is 40 g / L - 70 g / L.

7. A method for applying a gas shielded solid cored wire for circumferential welding of high strain pipelines, using a gas shielded solid cored wire for circumferential welding of high strain pipelines as described in claim 1, characterized in that: The welding wire is used for all-position gas shielded welding of high-strain pipelines with an X80 steel grade and a wall thickness of more than 30 mm.

8. The application method of a solid cored wire for gas shielded welding used in high strain pipeline girth welding according to claim 7, characterized in that: The all-position gas shielded welding parameters of the high-strain pipeline are specifically as follows: The welding shielding gas is an argon-rich mixed gas, with a volume ratio of 80% - 95% Ar + 20% - 5% CO2; the welding current is 220 A - 260 A, the welding voltage is 20 V - 26 V, the welding speed is 30 cm / min - 35 cm / min, the gas flow rate is 15 L / min - 25 L / min, and the interpass temperature is controlled at 135°C - 165°C.

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