Welding method of steel pipe for hydrogen transmission based on external fixed magnetic field stirring

Abstract

The invention discloses a welding method for a hydrogen conveying steel pipe based on external fixed magnetic field stirring, and relates to the field of welding. The manufacturing method solves the problems that hydrogen-induced failure is prone to occurring in an existing manufacturing method of the steel pipe for hydrogen conveying, and the service life of a hydrogen conveying pipeline is shortened. The method comprises the steps that firstly, a submerged-arc welding experiment table is built; 2, adding an auxiliary magnetic field; an external fixed magnetic field stirring device is additionally arranged under the test plate, and a stable external fixed magnetic field is generated and acts on a welding pool area; step 3, welding two adjacent test plates; a magnetic field is applied through an external fixed magnetic field stirring device, and the magnetic field application mode comprises the steps of firstly selecting a symmetrically applied fixed magnetic field, and then changing the placement position of an N / S pole of the magnetic field to realize direction control of the external fixed magnetic field; after the welding arc is generated, the mass transfer and heat transfer process is changed through the electromagnetic stirring effect; and the welding of the test board is completed. The method is used for welding the hydrogen conveying steel pipe.

Description

Technical Field

[0001] The invention relates to the field of general welding technology, and in particular to a welding method for a hydrogen transport steel pipe based on external fixed magnetic field stirring, and belongs to the scope of high-quality welding manufacturing of hydrogen transport pipelines. Background Art

[0002] At present, the manufacturing method of steel pipes for hydrogen transmission is to use low-grade X42 and X52 pipeline steel as the pipe body parent material, and adopt double-wire or multi-wire submerged arc welding to manufacture the steel pipe. Although the traditional submerged arc welding method has the advantages of high production efficiency and stable weld quality, it has high welding heat input and slow welding speed, which leads to coarse grains in the weld area during the non-equilibrium transformation process, and is prone to metallurgical curves such as microsegregation and inclusions, which in turn causes increased sensitivity to hydrogen embrittlement and is prone to hydrogen-induced failure, affecting the service life of the hydrogen transmission pipeline.

[0003] In summary, the existing manufacturing method of hydrogen transport steel pipes is prone to hydrogen-induced failure, which reduces the service life of the hydrogen transport pipeline. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the existing manufacturing method of hydrogen transport steel pipes is prone to hydrogen-induced failure and reduces the service life of hydrogen transport pipelines, and further provide a welding method for hydrogen transport steel pipes based on external fixed magnetic field stirring.

[0005] The technical solution of the present invention is:

[0006] A welding method for a hydrogen transport steel pipe based on external fixed magnetic field stirring comprises the following steps:

[0007] Step 1: Build a submerged arc welding test bench;

[0008] Step 2: Add auxiliary magnetic field;

[0009] On the basis of the submerged arc welding equipment, an external fixed magnetic field stirring device is added directly below the test plate to generate a stable external fixed magnetic field to act on the welding pool area;

[0010] Step 3: Start the arc for welding, and apply the magnetic field synchronously;

[0011] Two adjacent test plates are welded; at this time, a magnetic field is applied by an external fixed magnetic field stirring device, and the magnetic field is applied in the following manner: first, a symmetrical fixed magnetic field is applied, and then the positions of the N / S poles of the magnetic field are changed to realize the direction control of the external fixed magnetic field;

[0012] After the welding arc is generated, an external fixed magnetic field acts on the liquid metal in the welding pool, changing its mass transfer and heat transfer process through electromagnetic stirring until the welding of the test plate is completed.

[0013] Furthermore, the construction of the submerged arc welding test bench in step 1 includes the following steps:

[0014] Step 1: Use 3 welding wires installed on a continuous automatic feeding device and the same number of welding power supplies, and the positive electrode of each welding power supply is connected to the welding gun, the negative electrode of each welding power supply is fixed to the welding platform, and each welding wire forms an independent arc;

[0015] Step 1 and 2: The arcs of the three welding wires are coupled to the workpiece and together form a molten pool;

[0016] Step 13: Number the welding wires according to the welding direction, 1 wire, 2 wire, and 3 wire respectively.

[0017] Furthermore, the grades of wire 1, wire 2 and wire 3 in steps 1 to 3 are all H08MnMoTiB.

[0018] Furthermore, in step three, the method of symmetrically applying a fixed magnetic field is as follows: a magnetic field generating device with the same magnetic field strength and direction is placed on the left and right sides of the weld respectively.

[0019] Furthermore, in step 3, the position of the N / S pole of the magnetic field is changed to realize the direction control method of the external fixed magnetic field:

[0020] The N pole of the magnetic field generating device of the external fixed magnetic field stirring device on the left side of the weld is facing the welding end direction;

[0021] The N pole of the magnetic field generating device of the external fixed magnetic field stirring device on the right side of the weld faces the starting direction of welding, and the direction of the entire magnetic field is perpendicular to the direction of the weld.

[0022] Furthermore, the parameters for arc starting and welding in step 3 are:

[0023] The welding current of 1 wire is 900A-1000A, the welding voltage is 32-36V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 0°;

[0024] The welding current of 2 wires is 700A-850A, the welding voltage is 36-40V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 90°;

[0025] The welding current of 3 wires is 650A-750A, the welding voltage is 32-36V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 180°.

[0026] Preferably, the parameters for arc starting and welding in step 3 are:

[0027] The welding current of 1 wire is 950A, the welding voltage is 34V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 0°;

[0028] The welding current of 2 wires is 800A, the welding voltage is 38V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 90°;

[0029] The welding current of 3 wires is 700A, the welding voltage is 40V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 180°.

[0030] Preferably, the welding speeds of wire 1, wire 2 and wire 3 in step three are all 1.2 m / min.

[0031] Furthermore, the welding elongation length of wire 1 in step three is 29 mm; the welding elongation length of wire 2 is 26 mm; and the welding elongation length of wire 3 is 28 mm.

[0032] Preferably, the welding diameters of wires 1, 2 and 3 in step three are all 4 mm.

[0033] Compared with the prior art, the present invention has the following effects:

[0034] 1. The implementation principle of the present invention is as follows: in the early hydrogen charging slow tensile test of the welding part of the hydrogen transport steel pipe, it was found that the higher the low-temperature impact performance of the weld joint structure, the better the effect of the hydrogen charging slow tensile test, and the better the effect of resistance to hydrogen-induced damage and failure. Therefore, the patent of the present invention starts from the perspective of refining the grains and improving the low-temperature impact toughness, and invents a submerged arc welding method for hydrogen transport steel pipes based on external magnetic field stirring. The welding molten pool is stirred by an external magnetic field to promote the flow of the molten pool. At the same time, the energy of the external magnetic field is used to crush the generated columnar crystals, which plays a role in refining the grains, thereby improving its resistance to hydrogen-induced damage and failure.

[0035] 2. The fixed magnetic field causes the arc to blow, while the magnetic field evenly distributed on both sides of the arc will offset the interference of the magnetic blow. The fixed magnetic field applied in the present invention will accelerate the flow speed of the plasma in the arc, thereby compressing the arc, increasing the weld penetration, and improving the weld morphology. By controlling the different intensities of the magnetic field in the high temperature zone and the liquefaction zone of the molten pool, the application position and the welding process are matched to improve the microstructure of the weld, control the grain growth, and improve the hydrogen embrittlement resistance and low temperature toughness of the weld, thereby meeting the high requirements of the hydrogen energy industry for welding technology.

[0036] Among them, the so-called magnetic field intensity is generally classified according to the intensity level: the magnetic field with <50 mT is a weak magnetic field: the arc is slightly compressed, the penetration depth increases by about 5%-10%, the weld width is slightly narrowed, the arc stability is improved, and the spatter is reduced. The magnetic field with 50-150 mT is a medium magnetic field: the Lorentz force dominates the molten pool flow, the penetration depth is significantly increased (15%-30%), the weld width tends to be uniform, the cooling rate of the molten pool is accelerated, and the grains are refined (so we generally choose within the medium magnetic field range). The magnetic field with >150 mT is a strong magnetic field: the excessive compression of the arc leads to too high energy density, the increase rate of the penetration depth slows down or even decreases, the weld width fluctuates severely (±0.5 mm), the spatter rate increases by 2-3 times, and undercut defects are likely to appear at the weld edge. The magnetic field is applied uniformly, so the magnetic field borne by each welding wire is theoretically the same.

[0037] In addition, the application position refers to the distance between the magnetic field application position and the weld and the magnetic field direction. Therefore, the position does not need to be moved and is preset in advance. There are only differences in distance and direction. Generally speaking, it can be divided into longitudinal magnetic field (along the weld direction); transverse magnetic field (perpendicular to the weld direction); vertical magnetic field (perpendicular to the workpiece surface). Different magnetic field distances will change the magnitude of the magnetic field intensity. Therefore, the distance needs to be adjusted to achieve an appropriate magnetic field intensity; different magnetic field directions also have a relatively large impact. For example, the longitudinal magnetic field is better, which can balance the convection of the molten pool and has the best weld width uniformity (≤0.1 mm); also, the process matching refers to the matching of the welding current, voltage, and welding speed with the externally applied magnetic field intensity.

[0038] 3. The present invention realizes the precise control of the mass transfer and heat transfer processes during the crystallization process of the liquid metal in the welding molten pool by introducing an externally applied fixed magnetic field stirring technology and controlling the multi-wire submerged arc welding process parameters (specifically reflected in: after applying the fixed magnetic field, the welding arc and the conductive fluid in the molten pool are affected by the Lorentz force in the magnetic field to form a directional eddy current (the circulation speed reaches 0.8-1.2 m / s). By adjusting the magnetic field intensity (50-200 mT) and direction (longitudinal / transverse / vertical), the flow pattern of the molten pool can be precisely controlled. The longitudinal magnetic field will induce a symmetric double-vortex structure in the molten pool along the weld direction, promote the uniform distribution of solute elements (such as Mn, Si), and inhibit dendritic segregation; the transverse magnetic field will stimulate a transverse shear flow, shorten the solute diffusion path, compress the thickness of the solute boundary layer, and improve the reaction kinetic efficiency of the molten pool; the vertical magnetic field will form a vertical rotation stirring of the molten pool, eliminate local superheat, and refine the proportion of equiaxed crystals. In terms of heat transfer and mass transfer: the magnetic field compresses the arc plasma (the arc diameter is reduced by 30%), and the energy density is increased to 2×10 4 W / cm 2 (conventional process 1.2×10 4 W / cm 2). The magnetic field induces the best match between the temperature gradient and the solidification rate (G / R) of the molten pool, promoting the transformation of columnar crystals to equiaxed crystals), thereby improving its low-temperature impact toughness and hydrogen damage resistance, and significantly extending the service life of the hydrogen transport steel pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic diagram of the fixed magnetic field stirring device of the present invention being installed on the lower end surface of the test plate;

[0040] Figure 2 This is a real picture of the present invention when buried welding is performed. At this time, the number of welding wires is 5.

[0041] Figure 3 is the metallographic image of the weld area, where the left image is the metallographic image when no magnetic field is applied, and the right image is the metallographic image when a magnetic field is applied;

[0042] Figure 4 It is a metallographic diagram of the fusion zone structure, where the left figure is the metallographic diagram when no magnetic field is applied, and the right figure is the metallographic diagram when a magnetic field is applied.

[0043] Figure 5 This is the EBSD picture during the welding process when no magnetic field is applied. It can be seen from the observation that the grains are relatively coarse at this time.

[0044] Figure 6 This is an EBSD picture after the welding method of the present invention is adopted and a fixed magnetic field stirring device is added. At this time, the grains are relatively refined. DETAILED DESCRIPTION

[0045] Specific implementation method 1: Combination Figures 1 to 6 To illustrate this embodiment, the embodiment includes the following steps:

[0046] Step 1: Build a submerged arc welding test bench;

[0047] Step 2: Add auxiliary magnetic field;

[0048] On the basis of the submerged arc welding equipment, an external fixed magnetic field stirring device is added directly below the test plate to generate a stable external fixed magnetic field to act on the welding pool area;

[0049] Step 3: Start the arc for welding, and apply the magnetic field synchronously;

[0050] Two adjacent test plates are welded; at this time, a magnetic field is applied by an external fixed magnetic field stirring device, and the magnetic field is applied in the following manner: first, a symmetrical fixed magnetic field is applied, and then the positions of the N / S poles of the magnetic field are changed to realize the direction control of the external fixed magnetic field;

[0051] After the welding arc is generated, an external fixed magnetic field acts on the liquid metal in the welding pool, changing its mass transfer and heat transfer process through electromagnetic stirring until the welding of the test plate is completed.

[0052] The fixed magnetic field stirring device described in this embodiment includes a plurality of long strip magnets. By changing the number, size, distribution distance and direction of the magnets, the strength of the magnetic field is changed. The best test results are: the distance is 20mm, the size is 50*12*5mm, and the effect of stirring grain growth can be achieved. The strength of the external fixed magnetic field is controlled by changing the number and size of the fixed magnetic field; the magnetic field strength is preferably 0.5T.

[0053] The present invention promotes the charged particles in the welding arc to produce high-speed rotating spiral motion through the action of an external fixed magnetic field, thereby changing the shape and static characteristics of the arc and improving welding stability. The stirring action of the external fixed magnetic field can change the organizational structure of the weld metal, refine the grains, improve the mechanical properties of the weld joint, and reduce the generation of welding defects such as pores and cracks.

[0054] In addition, in step three of the present invention, during the welding process, an external fixed magnetic field stirring device works in coordination with the submerged arc welding equipment.

[0055] Specific implementation method 2: Combination Figure 2 To illustrate this embodiment, the construction of the submerged arc welding test bench in step 1 of this embodiment includes the following steps:

[0056] Step 1: Use 3 welding wires installed on a continuous automatic feeding device and the same number of welding power supplies, and the positive electrode of each welding power supply is connected to the welding gun, the negative electrode of each welding power supply is fixed to the welding platform, and each welding wire forms an independent arc;

[0057] Step 1 and 2: The arcs of the three welding wires are coupled to the workpiece and together form a molten pool;

[0058] Step 13: Number the welding wires according to the welding direction, 1 wire, 2 wire, and 3 wire respectively.

[0059] Such an arrangement makes it easy to optimize the wire spacing and keep the welding wires inside the weld groove. When the welding wires are arranged longitudinally, the electric arcs act together on the molten pool to stir the molten pool, reduce the gas concentration in the molten pool, and reduce the probability of pores. In addition, by adjusting the distance and inclination between the welding wires, the shape and size of the weld can be flexibly adjusted. The other components and connection relationships are the same as those in the first specific implementation method.

[0060] Specific implementation method three: Combination Figure 2 To illustrate this embodiment, the grades of wire 1, wire 2 and wire 3 in steps 1 and 3 of this embodiment are all H08MnMoTiB.

[0061] The other components and connection relationships are the same as those in the first or second embodiment. The specific composition of the welding wire is shown in the following table:

[0062]

[0063] Specific implementation method four: Combination Figure 2 To illustrate this embodiment, in step three of this embodiment, the method of symmetrically applying a fixed magnetic field is selected as follows: a magnetic field generating device with the same magnetic field strength and direction is placed on the left and right sides of the weld respectively.

[0064] In this arrangement, since the molten pool formed between each welding wire of the multi-wire submerged arc welding is used as an electromagnetic source, the electromagnetic interference between each arc is controlled by the position of the conductive copper bar, the arc phase angle and other methods, so that a relative balance is achieved. At this time, if an external magnetic field is introduced, it may interfere with the original stable welding process. Therefore, there is no public report on the application of external fixed magnetic field stirring technology to submerged arc welding of steel pipes for hydrogen transmission. In order to solve this technical problem, this embodiment selects symmetrical application of a fixed magnetic field to avoid destroying the static balance of the original magnetic field. Other components and connection relationships are the same as those of specific embodiments one, two or three.

[0065] Specific implementation method five: Combination Figure 1 to Figure 2 To illustrate this embodiment, in step 3 of this embodiment, the position of the N / S pole of the magnetic field is changed to achieve the direction control method of the external fixed magnetic field:

[0066] The N pole of the magnetic field generating device of the external fixed magnetic field stirring device on the left side of the weld is facing the welding end direction;

[0067] The N pole of the magnetic field generating device of the external fixed magnetic field stirring device on the right side of the weld faces the starting direction of welding, and the direction of the entire magnetic field is perpendicular to the direction of the weld.

[0068] The other components and connection relationships are the same as those of the first, second, third or fourth specific implementation modes.

[0069] Specific implementation method six: Combination Figure 1 to Figure 2 To illustrate this embodiment, the parameters for arc starting and welding in step 3 of this embodiment are:

[0070] The welding current of 1 wire is 900A-1000A, the welding voltage is 32-36V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 0°;

[0071] The welding current of 2 wires is 700A-850A, the welding voltage is 36-40V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 90°;

[0072] The welding current of 3 wires is 650A-750A, the welding voltage is 32-36V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 180°.

[0073] By adjusting these parameters, the welding process is more stable, the weld is better formed, and the hydrogen embrittlement resistance and low temperature toughness of the weld are improved. The other components and connection relationships are the same as any one of the specific embodiments 1 to 5.

[0074] Specific implementation method seven: Combination Figure 1 to Figure 2 To illustrate this embodiment, the parameters for arc starting and welding in step 3 of this embodiment are:

[0075] The welding current of 1 wire is 950A, the welding voltage is 34V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 0°;

[0076] The welding current of 2 wires is 800A, the welding voltage is 38V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 90°;

[0077] The welding current of 3 wires is 700A, the welding voltage is 40V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 180°.

[0078] In this way, the uneven distribution of welding wire parameters makes the most of the characteristics of the first welding wire with large DC penetration and the latter two wires with large AC coverage, that is, the penetration and filling amount are guaranteed, and the weld metal will not be seriously coarsened due to excessive arc heat input. The other components and connection relationships are the same as any one of the specific embodiments one to six.

[0079] Specific implementation method eight: Combination Figures 1 to 3 To illustrate this embodiment, the welding speeds of 1 wire, 2 wires and 3 wires in step 3 of this embodiment are all 1.2 m / min.

[0080] With this arrangement, the welding speed is moderate to ensure welding quality. If the welding speed is too fast, the weld will be poorly formed and the arc will be unstable. If the welding speed is too slow, the heat input will increase, resulting in a decrease in the mechanical properties of the weld. The other components and connection relationships are the same as any one of the specific implementation methods one to seven.

[0081] Specific implementation method nine: Combination Figures 1 to 3To illustrate this embodiment, the welding dry extension length of 1 wire in step 3 of this embodiment is 29mm; the welding dry extension length of 2 wires is 26mm; the welding dry extension length of 3 wires is 28mm. In this way, the proportion of resistance heat is regulated by dry extension, and the welding heat input is regulated. In addition, combined with the distribution position of each welding wire, 2 wires are vertical to the test plate, and the others are slanted. In order to ensure that the ends of the welding wires are in the same plane, the lengths of the welding wires are different. The other components and connection relationships are the same as any one of the specific embodiments 1 to 8.

[0082] Specific implementation method ten: Combination Figures 1 to 3 To illustrate this embodiment, the welding diameters of wires 1, 2 and 3 in step 3 of this embodiment are all 4 mm.

[0083] In this configuration, the diameter of the welding wire determines the value of the carrying current. According to the current requirement of about 800A, a welding wire with a diameter of 4mm must be used, otherwise the welding wire will be overburned and softened. The other components and connection relationships are the same as any one of the specific embodiments 1 to 9.

[0084] The present invention achieves effective control of the weld metal structure by precisely controlling the welding parameters and accurately adjusting the stirring conditions of the applied magnetic field, refines the grains (according to the backscattered electron microscope, the average grain size in this experiment is reduced by about 15%), and improves the mechanical properties of the welded joint. By refining the grains, the segregation phenomenon in the weld metal is reduced, and the plasticity and toughness of the weld metal are improved. The generation of welding defects such as pores and cracks is effectively suppressed, the safety and service life of the welded joint are improved, and its impact resistance is improved.

[0085] Compared with the prior art, the submerged arc welding method for hydrogen transport steel pipes based on external fixed magnetic field stirring proposed in the present invention significantly improves the mechanical properties and reliability of the welded joints. By comparing with traditional submerged arc welding, it can be seen from the microstructure that the weld zone, fusion zone and heat-affected zone are significantly refined; from the EBSD image, the grains are significantly refined and the number of small-angle grain boundaries increases; through hydrogen charging slow tensile test, it is found that the tensile strength of the welded joint with fixed magnetic field is higher.

[0086] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A welding method for a hydrogen transport steel pipe based on external fixed magnetic field stirring, characterized in that: It includes the following steps: Step 1: Build a submerged arc welding test bench; Step 2: Add auxiliary magnetic field; On the basis of the submerged arc welding equipment, an external fixed magnetic field stirring device is added directly below the test plate to generate a stable external fixed magnetic field to act on the welding pool area; Step 3: Start the arc for welding, and apply the magnetic field synchronously; Two adjacent test plates are welded; at this time, a magnetic field is applied by an external fixed magnetic field stirring device, and the magnetic field is applied in the following manner: first, a symmetrical fixed magnetic field is applied, and then the positions of the N / S poles of the magnetic field are changed to realize the direction control of the external fixed magnetic field; After the welding arc is generated, an external fixed magnetic field acts on the liquid metal in the welding pool, changing its mass transfer and heat transfer process through electromagnetic stirring until the welding of the test plate is completed.

2. A welding method for a hydrogen transport steel pipe based on external fixed magnetic field stirring according to claim 1, characterized in that: The construction of the submerged arc welding test bench in step 1 includes the following steps: Step 1: Use 3 welding wires installed on a continuous automatic feeding device and the same number of welding power supplies, and the positive electrode of each welding power supply is connected to the welding gun, the negative electrode of each welding power supply is fixed to the welding platform, and each welding wire forms an independent arc; Step 1 and 2: The arcs of the three welding wires are coupled to the workpiece and together form a molten pool; Step 13: Number the welding wires according to the welding direction, 1 wire, 2 wire, and 3 wire respectively.

3. A welding method for a hydrogen transport steel pipe based on external fixed magnetic field stirring according to claim 2, characterized in that: The grades of wire 1, wire 2 and wire 3 in steps 1 and 3 are all H08MnMoTiB.

4. A method for welding a hydrogen transport steel pipe based on external fixed magnetic field stirring according to claim 3, characterized in that: The method of symmetrically applying a fixed magnetic field in step three is: placing a magnetic field generating device with the same magnetic field strength and direction on the left and right sides of the weld respectively.

5. The method for welding a hydrogen transport steel pipe based on external fixed magnetic field stirring according to claim 3, characterized in that: In step 3, the position of the N / S pole of the magnetic field is changed to realize the direction control method of the external fixed magnetic field: The N pole of the magnetic field generating device of the external fixed magnetic field stirring device on the left side of the weld is facing the welding end direction; The N pole of the magnetic field generating device of the external fixed magnetic field stirring device on the right side of the weld faces the starting direction of welding, and the direction of the entire magnetic field is perpendicular to the direction of the weld.

6. The method for welding a hydrogen transport steel pipe based on external fixed magnetic field stirring according to claim 1, characterized in that: The parameters for arc welding in step 3 are: The welding current of 1 wire is 900A-1000A, the welding voltage is 32-36V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 0°; The welding current of 2 wires is 700A-850A, the welding voltage is 36-40V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 90°; The welding current of 3 wires is 650A-750A, the welding voltage is 32-36V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 180°.

7. A method for welding a hydrogen transport steel pipe based on external fixed magnetic field stirring according to claim 6, characterized in that: The parameters for arc welding in step 3 are: The welding current of 1 wire is 950A, the welding voltage is 34V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 0°; The welding current of 2 wires is 800A, the welding voltage is 38V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 90°; The welding current of 3 wires is 700A, the welding voltage is 40V, the welding speed is 1-1.5m / min, the wire spacing is 10mm, and the phase is 180°.

8. A method for welding a hydrogen transport steel pipe based on external fixed magnetic field stirring according to claim 6 or 7, characterized in that: The welding speeds of wires 1, 2 and 3 in step 3 are all 1.2 m / min.

9. A method for welding a hydrogen transport steel pipe based on external fixed magnetic field stirring according to claim 8, characterized in that: The welding elongation length of wire 1 in step 3 is 29 mm; the welding elongation length of wire 2 is 26 mm; and the welding elongation length of wire 3 is 28 mm.

10. A method for welding a hydrogen transport steel pipe based on external fixed magnetic field stirring according to claim 1 or 9, characterized in that: The welding diameters of wires 1, 2 and 3 in step 3 are all 4 mm.

Images