A method of welding a girth weld of a hydrogen pipeline

Abstract

The present application provides a kind of welding method of hydrogen pipeline girth weld, comprising: the steel pipe for hydrogen transmission is cut into two sub steel pipes, and the pipe opening of each sub steel pipe is processed with single side U-shaped groove;Two sub steel pipes are pipe opening matched using the way of pipeline inner wall point solid;The welding opening of pipeline butt joint to be welded is placed on the welding support frame of 5G position, and the surface of the preset length along the groove side of pipeline inner and outer is cleaned;The groove side of pipeline butt joint is uniformly preheated before welding, while monitoring the preheating temperature to within the preset temperature range;Automatic argon arc welding method is used to form root weld layer;Gas shielded arc welding method is used to form hot weld layer, filling layer and cover welding layer;The girth weld of hydrogen pipeline after welding is nondestructively tested.The technical effect of the present application is to realize the automation of hydrogen transmission steel pipe welding, and to improve the low-temperature impact toughness and overall quality of the welded joint by matching welding materials and optimizing process parameters.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen transmission pipeline welding technology, specifically relating to a welding method for circumferential welds in hydrogen transmission pipelines. Background Technology

[0002] Among various hydrogen transportation methods, pipeline hydrogen transport has extremely high economic value in realizing the development of the hydrogen energy industry and promoting the efficient use of energy, and is an important part of accelerating the realization of the energy transition strategy. In long-distance transportation, welding has become the main process for connecting steel pipes into pipelines. However, due to the geometric discontinuities and residual stress in the welding area (weld seam, heat-affected zone, base material) during the welding process, local stress concentration can easily occur. When the toughness is insufficient, hydrogen embrittlement can easily occur. Therefore, hydrogen pipelines have high requirements for the low-temperature impact toughness of the ring weld joints.

[0003] Research on hydrogen pipelines is still in its early stages, starting relatively late. Practical applications in hydrogen pipeline engineering are limited, and the welding process for hydrogen pipelines is relatively simple, mostly relying on manual argon arc welding for root welding. Existing welding techniques are primarily designed for transporting substances like natural gas and oil. While the low-temperature impact toughness and other mechanical properties of circumferential welds meet the requirements for transporting natural gas, they do not meet the high toughness requirements of circumferential welds for hydrogen pipelines. Furthermore, international surveys of hydrogen pipeline engineering projects reveal that small-diameter steel pipes are commonly used for transportation.

[0004] Therefore, there is an urgent need for a welding method for the circumferential weld seam of hydrogen pipelines, which is suitable for the automatic argon arc welding process of large-diameter, thick-walled steel pipes for hydrogen pipelines and has broad application prospects. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art, and to provide a new technical solution for welding a circumferential weld seam in a hydrogen transport pipeline.

[0006] According to one aspect of the present invention, a welding method for circumferential welds in hydrogen pipelines is provided, which employs an automatic argon arc welding method and a dual-torch gas metal arc welding method, comprising the following steps: Step S1: Cut the steel pipe used for hydrogen transportation into two sub-steel pipes, and perform single-sided U-shaped beveling on the pipe end of each sub-steel pipe; wherein, the pipe diameter is 800-900mm, the yield strength is 450MPa, the tensile strength is greater than or equal to 520MPa, and the wall thickness is 20-30mm. Step S2: The two sections of steel pipe are assembled by tack fixing the inner wall of the pipe to form a pipe butt joint. After the pipe end assembly is completed, the bevel size is inspected using a universal welding inspection ruler. Step S3: Place the weld joint of the pipe butt joint that has passed the bevel size inspection on the welding support frame at position 5G, and clean the surface of the pipe inside and outside along the preset length of the bevel until it has a metallic luster. Step S4: Before welding, preheat both sides of the bevel of the pipe butt joint evenly, and monitor the preheating temperature to ensure it is within the preset temperature range. Step S5: Using an automatic argon arc welding method, root welding is performed in a half-circle upward welding manner. First, the arc is started from the position between 6 o'clock and 5 o'clock and welded upwards to the position between 0 o'clock. Then, the arc is started from the position between 6 o'clock and 7 o'clock and welded upwards to the position between 12 o'clock to form the root weld layer. Step S6: Using the gas metal arc welding method, the double-torch external welding machine is used to perform hot welding, filling and capping in a half-circle downward welding manner to form a hot weld layer, a filler layer and a capping weld layer. Step S7: Perform non-destructive testing on the circumferential weld of the welded hydrogen pipeline.

[0007] Optionally, in step S1, when processing the pipe end of the steel pipe with a single-sided U-shaped bevel, the face angle of the upper bevel is 3-5°, the lower bevel is a 1 / 4 semi-circular arc with a radius of 2.4mm, the straight section length is 1.0-1.4mm, and the blunt edge height is 1.5-2.0mm.

[0008] Optionally, in step S2, a universal welding gauge is used to inspect the bevel dimensions, including: measuring the bevel dimensions of the pipe end assembly using the universal welding gauge, wherein the measurement positions include 0, 3, 6 and 9 points, the gap between the ends is 0-0.5mm, the misalignment is not greater than 1 / 8 of the wall thickness of the steel pipe, and the local maximum value of the misalignment of the butt joint is not more than 3mm within any continuous length of 50mm.

[0009] Optionally, in step S4, the pipe joint bevel is uniformly preheated within a 75mm range on both sides. When monitoring the preheating temperature, four measuring points are uniformly selected on the circumference 25mm away from the bevel to measure the pipe temperature, and the average value of the four measuring points is taken as the preheating temperature.

[0010] Optionally, in step S5, the welding material is ER70S-3 grade solid welding wire with a diameter of 1.0mm. The welding machine is connected to a DC welding power supply with steep drop external characteristics through DC power reverse connection method, and the current is supplied in pulse mode. The droplet transfer method adopts short-circuit transfer.

[0011] Optionally, in step S6, the filler layer has multiple layers, and each filler layer uses two welding torches arranged one after the other, with one welding torch in front for preheating and welding the previous layer, and the other welding torch in the back for welding the next layer. The cover layer is a single layer with two passes, while the hot-welding layer and the filler layer are both single layers with one pass. The welding material used is ER70S-3 grade solid welding wire with a diameter of 1.0mm. The welding machine is connected to a DC pulse welding power supply via DC power reverse connection to supply current in a pulse manner. The droplet transfer method adopts droplet transfer.

[0012] Optionally, in step S7, the non-destructive testing includes RT-ray testing, phased array ultrasonic testing, and time-of-flight ultrasonic diffraction testing.

[0013] Optionally, in step S5, when using an automatic argon arc welding method, the shielding gas is argon, the welding base current is 120-135A, the welding peak current is 240-260A, the arc voltage is 9-12.5V, the shielding gas flow rate is 19-21L / min, the wire feed speed is 90-105in. / min, and the welding speed is 14-16cm / min.

[0014] Optionally, in step S5, when using the gas metal arc welding method, the shielding gas is Ar and CO2, the welding current for the hot-weld layer is 170-215A, the welding current for the filler layer is 185-230A, the welding current for the cover layer is 115-135A, the arc voltage is 23-25V, the oscillation width is 1.5-4.0mm, the edge dwell time is 40-90ms, the shielding gas flow rate is 22-24L / min, the wire feed speed is 170-330in. / min, and the welding speed is 33-48cm / min.

[0015] Optionally, in step S4, the preset temperature range is 80-100℃, and the preheating temperature measurement uses a contact thermometer.

[0016] One technical advantage of this invention is that: In this embodiment, the welding method for the circumferential weld of the hydrogen pipeline introduces argon arc automatic welding for the outer root and dual-torch gas metal arc welding for the welding of large-diameter and thick-walled hydrogen pipeline steel pipes. The application of this hydrogen pipeline steel pipe aims to improve the pressure and transport efficiency of the hydrogen pipeline. Simultaneously, this welding method for the circumferential weld of the hydrogen pipeline automates the welding process. By achieving stable control of the welding process and precise regulation of heat input, the uniformity of the weld structure can be effectively improved, thereby meeting the requirements of the hydrogen pipeline for low-temperature impact toughness of the weld joint. This reduces the possibility of hydrogen embrittlement failure due to insufficient toughness in the weld joint, fundamentally ensuring welding quality.

[0017] In addition, the welding method for the circumferential weld of the hydrogen pipeline can significantly reduce the interference of human factors, improve welding efficiency, greatly enhance the stability of the circumferential weld quality, and reduce reliance on high-level welders and personnel costs. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart illustrating a welding method for a circumferential weld seam in a hydrogen transport pipeline according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a pipe connection joint according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the welding of a pipe butt joint according to an embodiment of the present invention.

[0019] In the diagram: 1. Face angle of the upper slope; 2. Lower slope; 3. Straight section; 4. Blunt edge; 5. Gap between the joints; 6. Wall thickness. Detailed Implementation

[0020] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0021] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0022] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0023] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0024] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0025] According to one aspect of the invention, see Figures 1 to 3 This paper presents a welding method for circumferential welds in hydrogen pipelines, which can solve the problems of low efficiency, large heat input fluctuations, and significant influence from human factors caused by the current widespread use of manual argon arc welding for root welding in hydrogen transportation projects. Furthermore, the existing process fails to fully consider the special physical properties of hydrogen medium.

[0026] To improve the pressure and efficiency of hydrogen transportation, the welding method for the circumferential weld of the hydrogen pipeline in this application uses a large-diameter and thick-walled hydrogen transportation steel pipe and realizes fully automatic argon arc welding of the hydrogen transportation pipeline. It can achieve stable control of the welding process and precise regulation of heat input, thereby improving the uniformity of the weld structure, increasing the toughness of the circumferential weld, meeting the mechanical property requirements of the hydrogen transportation pipeline for the circumferential weld, and improving welding efficiency.

[0027] Specifically, the welding method for the circumferential weld of the hydrogen pipeline adopts an automatic argon arc welding method and a dual-torch gas metal arc welding method, including the following steps: Step S1: Cut the steel pipe used for hydrogen transportation into two sub-steel pipes, and perform single-sided U-shaped beveling on the pipe opening of each sub-steel pipe; wherein, the pipe diameter is 800-900mm, the yield strength is 450MPa, the tensile strength is greater than or equal to 520MPa, and the wall thickness is 20-30mm.

[0028] Step S2: The two sections of steel pipe are assembled by tack fixing the inner wall of the pipe to form a pipe butt joint. After the pipe end assembly is completed, the bevel size is inspected using a universal welding inspection ruler.

[0029] Step S3: Place the weld joint of the pipe butt joint that has passed the bevel size inspection on the welding support frame at position 5G, and clean the surface of the pipe inside and outside along the bevel sides for a preset length until it has a metallic luster.

[0030] Step S4: Before welding, preheat both sides of the bevel of the pipe joint evenly, and monitor the preheating temperature to ensure it is within the preset temperature range.

[0031] Step S5: Using an automatic argon arc welding method, root welding is performed in a half-circle upward welding manner. First, the arc is started from the position between 6 o'clock and 5 o'clock and welded upwards to the position between 0 o'clock. Then, the arc is started from the position between 6 o'clock and 7 o'clock and welded upwards to the position between 12 o'clock to form the root weld layer.

[0032] Step S6: Using the gas metal arc welding method, the hot welding, filling, and capping layers are performed by a double-torch external welding machine in a half-circle downward welding manner to form a hot weld layer, a filling layer, and a capping weld layer.

[0033] Step S7: Perform non-destructive testing on the circumferential weld of the welded hydrogen pipeline.

[0034] In this embodiment, the welding method for the circumferential weld of the hydrogen pipeline introduces argon arc automatic welding for the outer root and dual-torch gas metal arc welding for the welding of large-diameter and thick-walled hydrogen pipeline steel pipes. The application of this hydrogen pipeline steel pipe aims to improve the pressure and transport efficiency of the hydrogen pipeline. Simultaneously, this welding method for the circumferential weld of the hydrogen pipeline automates the welding process. By achieving stable control of the welding process and precise regulation of heat input, the uniformity of the weld structure can be effectively improved, thereby meeting the requirements of the hydrogen pipeline for low-temperature impact toughness of the weld joint. This reduces the possibility of hydrogen embrittlement failure due to insufficient toughness in the weld joint, fundamentally ensuring welding quality.

[0035] In addition, the welding method for the circumferential weld of the hydrogen pipeline can significantly reduce the interference of human factors, improve welding efficiency, greatly enhance the stability of the circumferential weld quality, and reduce reliance on high-level welders and personnel costs.

[0036] For example, the specifications of the steel pipe are: pipe diameter φ of 813mm, wall thickness of 22.5mm; its yield strength is 450MPa, and its tensile strength is 570MPa. The chemical composition and mass percentage of the steel pipe are shown below: The composition of carbon is 0.0495%, Si is 0.189%, Mn is 1.272%, P is 0.0065%, S is 0.0015%, Ni is 0.0238%, Cr is 0.196%, Cu is 0.0200%, Nb is 0.040%, V is 0.0337%, Ti is 0.0119%, Mo is 0.0094%, Al is 0.022%, N is 0.001%, B is 0.0005%, V+Nb+Ti is 0.086%, carbon equivalent (Ceq) is 0.312%, and Pcm is 0.137%.

[0037] In the above embodiments, using the aforementioned steel pipe for hydrogen pipelines can significantly improve the pressure and transport efficiency of the hydrogen pipeline. Furthermore, the welding method for the circumferential weld of the hydrogen pipeline described in this application can meet the low-temperature impact toughness requirements of the weld joint in hydrogen pipelines, thereby reducing the possibility of hydrogen embrittlement failure due to insufficient toughness and fundamentally ensuring weld quality.

[0038] Optionally, in step S1, see Figure 2 When processing the end of the sub-steel pipe with a single-sided U-shaped bevel, the upper bevel angle 1 is 3-5°, the lower bevel 2 is a 1 / 4 semicircle arc with a radius of 2.4mm, the straight section 3 is 1.0-1.4mm long, the blunt edge 4 is 1.5-2.0mm high, and the width of the single-sided upper opening is 4.4mm. For example, the length of the sub-steel pipe is 250mm.

[0039] In the above embodiments, not only is the amount of filler metal used in welding reduced, improving the fatigue resistance and crack resistance of the weld, but it is also easy to automate welding, thus improving the fusion quality of the pipe butt joint.

[0040] Optionally, in step S2, a universal welding gauge is used to inspect the bevel dimensions, including: measuring the bevel dimensions of the pipe end assembly using the universal welding gauge, wherein the measurement positions include points 0, 3, 6, and 9; the gap 5 is 0-0.5 mm; the misalignment is no greater than 1 / 8 of the steel pipe wall thickness; and the maximum local value of the misalignment of the butt joint within any continuous length of 50 mm does not exceed 3 mm. For example, the misalignment is less than or equal to 2.8 mm.

[0041] In the above implementation, the setting of the bevel size inspection is more reasonable, which helps to perform high-quality welding on pipe joints that have passed the bevel size inspection.

[0042] Optionally, in step S4, the pipe joint bevel is uniformly preheated within a 75mm range on both sides. When monitoring the preheating temperature, four measuring points are uniformly selected on the circumference 25mm away from the bevel to measure the pipe temperature, and the average value of the four measuring points is taken as the preheating temperature.

[0043] Optionally, in step S5, the welding material is ER70S-3 grade solid welding wire with a diameter of 1.0mm. The welding machine is connected to a DC welding power supply with steep drop external characteristics through DC power reverse connection method, and the current is supplied in pulse mode. The droplet transfer method adopts short-circuit transfer.

[0044] The above embodiments can effectively ensure the welding quality of the root weld layer.

[0045] Optionally, in step S6, the filler layer has multiple layers, and each filler layer uses two welding torches arranged one after the other, with one welding torch in front for preheating and welding the previous layer, and the other welding torch in the back for welding the next layer. The cover layer is a single layer with two passes, while the hot-welding layer and the filler layer are both single layers with one pass. The welding material used is ER70S-3 grade solid welding wire with a diameter of 1.0mm. The welding machine is connected to a DC pulse welding power supply via DC power reverse connection to supply current in a pulse manner. The droplet transfer method adopts droplet transfer.

[0046] In the above embodiments, the welding quality of the hot-welded layer, the filler layer, and the cover weld layer can be well guaranteed.

[0047] Optionally, in step S7, the non-destructive testing includes radiographic testing, phased-array ultrasonic testing, and time-of-flight diffraction (TOF) ultrasonic testing. This helps to effectively and accurately inspect the circumferential welds of the welded hydrogen pipeline.

[0048] Optionally, in step S5, when using an automatic argon arc welding method, the shielding gas is argon, the welding base current is 120-135A, the welding peak current is 240-260A, the arc voltage is 9-12.5V, the shielding gas flow rate is 19-21L / min, the wire feed speed is 90-105in. / min, and the welding speed is 14-16cm / min.

[0049] In the above embodiments, the parameter design of automatic argon arc welding is more reasonable, which can significantly reduce the possibility of hydrogen embrittlement failure of the welded joint due to insufficient toughness, and fundamentally ensure the welding quality.

[0050] Optionally, in step S5, when using the gas metal arc welding method, the shielding gas is Ar and CO2, the welding current for the hot-weld layer is 170-215A, the welding current for the filler layer is 185-230A, the welding current for the cover layer is 115-135A, the arc voltage is 23-25V, the oscillation width is 1.5-4.0mm, the edge dwell time is 40-90ms, the shielding gas flow rate is 22-24L / min, the wire feed speed is 170-330in. / min, and the welding speed is 33-48cm / min.

[0051] In the above embodiments, the parameter design of gas metal arc welding is relatively reasonable, which can realize stable control of the welding process and precise regulation of heat input, effectively improve the uniformity of weld structure, and thus meet the requirements of hydrogen pipeline for low-temperature impact toughness of welded joints.

[0052] For example, the Ar gas purity in the Ar tank is ≥99.96%, and the water content of the Ar gas is ≤0.005%; the volume ratio of Ar to CO2 in the Ar+CO2 gas tank is 80%Ar+20%CO2, the CO2 gas purity is ≥99.5%, the Ar gas purity is ≥99.96%, and the water content of CO2, Ar, and the mixed gas should all be ≤0.005%.

[0053] In this embodiment of the application, the temperature range between floors is controlled at 80-100℃, and a contact thermometer is used for temperature measurement between floors.

[0054] For example, the time interval between the end of root welding and the start of hot welding is ≤18 minutes.

[0055] In one embodiment, the thickness of each filler layer weld metal layer shall not exceed 3 mm, and the weld reinforcement of the cover weld shall not exceed 2 mm, with a local allowable reinforcement of 3 mm, but its continuous length shall not exceed 50 mm.

[0056] In another embodiment, the qualification standard for RT X-ray inspection and phased array ultrasonic inspection (including TOFD) is Level II or above, and no unfused parts are allowed at the root.

[0057] Optionally, in step S4, the preset temperature range is 80-100℃, and a contact thermometer is used for preheating temperature measurement. This helps to better ensure the preheating quality of both sides of the bevel of the pipe joint.

[0058] In the embodiments of this application, the solid welding wire for automatic argon arc welding comprises the following mass percentages: C 0.07%, Si 0.60%, Mn 1.01%, P 0.014%, S 0.010%, Cr 0.020%, Mo 0.004%, Ni 0.010%, V 0.002%, Cu 0.080%, Ti 0.002%, Al 0.03%, Nb 0.001%, with the balance being Fe.

[0059] Solid welding wire for gas metal arc welding comprises the following mass percentages: C 0.07%, Si 0.65%, Mn 1.06%, P 0.012%, S 0.006%, Cu 0.080%, Ni 0.010%, Mo 0.01%, Cr 0.02%, V <0.0005%, Al 0.003%, Nb <0.001%, Co 0.002%, Zr <0.001%, with the balance being Fe.

[0060] For example, when the impact toughness of the pipe ring welded joint is tested, under low temperature conditions (-10℃), the average value of the impact absorption energy of the weld and the inner and outer surfaces of the heat-affected zone of the three samples is not less than 150J, and the single value is not less than 130J.

[0061] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A welding method for circumferential welds in a hydrogen transport pipeline, characterized in that, It employs an automated argon arc welding method and a dual-torch gas metal arc welding method, including the following steps: Step S1: Cut the steel pipe used for hydrogen transportation into two sub-steel pipes, and perform single-sided U-shaped beveling on the pipe end of each sub-steel pipe; wherein, the pipe diameter is 800-900mm, the yield strength is 450MPa, the tensile strength is greater than or equal to 520MPa, and the wall thickness is 20-30mm. In step S1, when processing the pipe end of the steel pipe with a single-sided U-shaped bevel, the face angle of the upper bevel is 3-5°, the lower bevel is a 1 / 4 semi-circular arc with a radius of 2.4mm, the straight section length is 1.0-1.4mm, and the blunt edge height is 1.5-2.0mm. Step S2: The two sections of steel pipe are assembled by tack fixing the inner wall of the pipe to form a pipe butt joint. After the pipe end assembly is completed, the bevel size is inspected using a universal welding inspection ruler. Step S3: Place the weld joint of the pipe butt joint that has passed the bevel size inspection on the welding support frame at position 5G, and clean the surface of the pipe inside and outside along the preset length of the bevel until it has a metallic luster. Step S4: Before welding, preheat both sides of the bevel of the pipe butt joint evenly, and monitor the preheating temperature to ensure it is within the preset temperature range. Step S5: Using an automatic argon arc welding method, root welding is performed in a half-circle upward welding manner. First, the arc is started from the position between 6 o'clock and 5 o'clock and welded upwards to the position between 0 o'clock. Then, the arc is started from the position between 6 o'clock and 7 o'clock and welded upwards to the position between 12 o'clock to form the root weld layer. In step S5, when using the automatic argon arc welding method, the shielding gas is argon, the welding base current is 120-135A, the welding peak current is 240-260A, the arc voltage is 9-12.5V, the shielding gas flow rate is 19-21L / min, the wire feed speed is 90-105in. / min, and the welding speed is 14-16cm / min; Step S6: Using the gas metal arc welding method, the double-torch external welding machine is used to perform hot welding, filling and capping in a half-circle downward welding manner to form a hot weld layer, a filler layer and a capping weld layer. In step S6, the filler layer has multiple layers, and each filler layer uses two welding torches arranged one in front of the other. One welding torch is in front for preheating and welding the previous layer, and the other welding torch is in the back for welding the next layer. The cover layer is a single layer with two passes, while the hot-welding layer and the filler layer are both single layers with one pass. The welding material used is ER70S-3 grade solid welding wire with a diameter of 1.0mm. The welding machine is connected to a DC pulse welding power supply via DC power reverse polarity to supply current in a pulse manner. The droplet transfer method adopts droplet transfer. In step S6, when using the gas metal arc welding method, the shielding gas is Ar and CO2, the welding current for the hot-weld layer is 170-215A, the welding current for the filler layer is 185-230A, the welding current for the cover layer is 115-135A, the arc voltage is 23-25V, the oscillation width is 1.5-4.0mm, the edge dwell time is 40-90ms, the shielding gas flow rate is 22-24L / min, the wire feed speed is 170-330in. / min, and the welding speed is 33-48cm / min; Step S7: Perform non-destructive testing on the circumferential weld of the welded hydrogen pipeline.

2. The welding method for the circumferential weld of a hydrogen transport pipeline according to claim 1, characterized in that, In step S2, the bevel dimensions are inspected using a universal welding gauge, including: measuring the bevel dimensions of the pipe end assembly using the universal welding gauge, wherein the measurement positions include 0, 3, 6 and 9 points, the gap between the ends is 0-0.5mm, the misalignment is not greater than 1 / 8 of the steel pipe wall thickness, and the local maximum value of the misalignment of the butt joint is not more than 3mm within any continuous length of 50mm.

3. The welding method for the circumferential weld of a hydrogen transport pipeline according to claim 1, characterized in that, In step S4, the pipe joint bevel is uniformly preheated within a 75mm range on both sides. When monitoring the preheating temperature, four measuring points are uniformly selected on the circumference 25mm away from the bevel to measure the pipe temperature, and the average value of the four measuring points is taken as the preheating temperature.

4. The welding method for the circumferential weld of a hydrogen transport pipeline according to claim 1, characterized in that, In step S5, ER70S-3 grade solid welding wire with a diameter of 1.0 mm is selected as the welding material. The welding machine is connected to a DC welding power supply with steep drop external characteristics through DC power reverse connection method, and the current is supplied in pulse mode. The droplet transfer method adopts short circuit transfer.

5. The welding method for the circumferential weld of a hydrogen transport pipeline according to claim 1, characterized in that, In step S7, non-destructive testing includes RT-ray testing, phased array ultrasonic testing, and time-of-flight ultrasonic diffraction testing.

6. The welding method for the circumferential weld of a hydrogen transport pipeline according to claim 1, characterized in that, In step S4, the preset temperature range is 80-100℃, and the preheating temperature measurement uses a contact thermometer.

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