A method and apparatus for multi-wire submerged arc welding of straight-seam steel pipe

Abstract

The application provides a multi-wire submerged arc welding method and device for straight-seam steel pipes, and belongs to the technical field of welding. The method comprises the following steps: adopting a multi-wire submerged arc welding process to perform double-sided submerged arc welding on a straight-seam steel pipe, and when welding an outer weld, an ultrasonic auxiliary device arranged at the back of a molten pool generates ultrasonic waves and inputs the ultrasonic waves into the molten pool through a horn, so that the formation of intergranular ferrite in the weld zone is inhibited, the content of intragranular acicular ferrite is increased, and the toughness and hydrogen brittleness resistance of the weld zone are improved. The device comprises a three-wire submerged arc welding device, an ultrasonic auxiliary device and a telescopic cantilever beam; the ultrasonic auxiliary device is installed at the front end of the telescopic cantilever beam and comprises three ultrasonic transducers arranged side by side; a horn is installed at the output end of the ultrasonic transducer; the ultrasonic transducer generates ultrasonic waves and inputs the ultrasonic waves into the molten pool through the horn. The application solves the problems that the existing ultrasonic auxiliary arc welding cannot control the content of acicular ferrite and the effect of reducing residual stress in the weld zone is not obvious.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular, especially relates to a straight seam steel pipe multi-wire submerged arc welding method and device. BACKGROUND

[0002] Green hydrogen energy is considered as the priority development direction of human future energy industry. However, hydrogen storage and transportation still face many challenges, among which how to ensure the hydrogen brittleness resistance of the straight seam welded pipe for hydrogen transportation is a key technical problem. At present, the welding of the straight seam welded pipe mostly adopts the multi-wire submerged arc welding double-sided welding process. The main problem of this welding process is that the welding heat input is large, which brings problems such as coarse weld structure, wide heat affected zone, large welding residual stress, and grain coarsening in the heat affected zone, especially the more weld zone along the grain ferrite has an adverse effect on the toughness and hydrogen brittleness resistance of the welded joint. Therefore, how to effectively refine the multi-wire submerged arc welding weld structure and reduce the residual tensile stress in the weld zone has been the focus of attention in this field.

[0003] Refining the weld structure and reducing the residual stress in the weld zone by reducing the heat input of multi-wire submerged arc welding is a commonly used technical path. At present, the methods for improving the welding efficiency of multi-wire submerged arc welding are as follows: (1) preheating welding wire method: this technology improves the deposition efficiency by preheating the welding wire, and improves the welding efficiency without changing the welding heat input. For example, the invention patent CN104400197A "integrated intelligent adjustable temperature type multi-wire submerged arc welding device and method" mentions a preheating welding wire method and device; the invention patent CN111922492B "magnetic field assisted integrated hot wire submerged arc welding device" also mentions a similar preheating welding wire multi-wire submerged arc welding method. (2) large dry extension method: this method improves the welding wire resistance heat by increasing the length of the welding wire extending out of the welding torch, which has similar characteristics to the preheating welding wire method. For example, the invention patent CN118176077A "electrode assembly for long dry extension submerged arc welding" mentions a special electrode assembly for long dry extension submerged arc welding. Although the above two methods solve the problem of high efficiency welding, the welding heat input does not decrease significantly, and the multi-wire submerged arc welding weld structure cannot be effectively refined and controlled. The methods that can reduce the heat input of multi-wire submerged arc welding are as follows: cold wire composite method: in multi-wire submerged arc welding of three or more wires, a cold wire is introduced to reduce the welding heat input. For example, the invention patent CN112276301A "integrated cold wire submerged arc welding device" specifically relates to an integrated cold wire submerged arc welding device, which includes two arc striking welding wires and one cold wire. The cold wire is agitated by the high frequency vibration of the ultrasonic vibration device to refine the grain and improve the mechanical properties of the weld; however, this method not only has a complex equipment structure and high requirement for the precision of the groove assembly, but also reduces the welding speed and welding efficiency due to the reduction of the welding arc power.

[0004] Ultrasonic energy field assisted arc welding is considered as an effective method to refine the weld structure. At present, there are generally three ways to introduce ultrasonic waves in arc welding: through the base material, through the welding wire and through the welding torch. For the method of introducing from the base material, invention patent CN201810132620.9 "Ultrasonic vibration assisted welding test device" and invention patent CN201510715844.9 "Ultrasonic arc composite welding method capable of refining weld joint grain", use the ultrasonic horn to impact the base material area to realize high-frequency vibration of the molten pool metal to improve the solidification crystallization; the disadvantage of this method is that the transmission of ultrasonic waves through the base material will cause great attenuation, weakening the effect of ultrasonic waves. For the method of introducing from the welding wire and the welding torch, invention patent CN200710144659.4 "Ultrasonic wave and non-melting electrode arc composite welding method" and invention patent CN201410063336.2 "Ultrasonic arc composite welding device", use the horn to act on the welding wire or the welding torch, and finally use the arc as a carrier to conduct the ultrasonic wave to the welding pool metal; this method is to stir the molten pool by mechanical vibration of the welding wire or the welding torch, and is only suitable for open arc welding, and has the risk of increasing weld slag in submerged arc welding. In addition, invention patent CN110524128A "Ultrasonic assisted arc welding method based on ultrasonic energy field direct injection method", proposes an ultrasonic assisted arc welding method without horn, which transmits ultrasonic waves to the welding joint through coupling agent; the direct injection ultrasonic power is relatively low, the effect of refining the weld structure and reducing the residual stress is not obvious, and the installation conditions are relatively high, which is not suitable for continuous production needs. Due to the above reasons, the existing ultrasonic assisted arc welding method has limitations in regulating the intergranular and intragranular ferrite content in the weld area. SUMMARY

[0005] In view of the technical problems in the prior art that the ultrasonic wave is easy to attenuate and the introduced ultrasonic power is not enough to effectively regulate the ferrite content and reduce the residual stress in the weld area, the present application provides a straight seam steel pipe multi-wire submerged arc welding method and device, based on the double-sided submerged arc welding process, without changing the original welding arc power, by directly introducing ultrasonic energy at the back of the molten pool, promoting the flow of molten pool metal, inhibiting intergranular ferrite, promoting intragranular acicular ferrite formation, breaking coarse columnar crystals, reducing weld hydrogen content, and relaxing the tensile residual stress generated during the cooling process of the weld, especially suitable for straight seam welded pipe multi-wire submerged arc welding for hydrogen transmission.

[0006] The technical means adopted by the present application are as follows:

[0007] A straight seam steel pipe multi-wire submerged arc welding method, specifically comprising: using a multi-wire submerged arc welding process to perform double-sided submerged arc welding on the straight seam steel pipe, and when welding the outer weld, an ultrasonic auxiliary device arranged at the back of the molten pool generates ultrasonic waves and inputs the ultrasonic waves into the molten pool through a horn.

[0008] Further, the method specifically comprises the following steps:

[0009] S1, using a double-sided submerged arc welding process to perform cold forming on the straight seam steel pipe, processing double V-shaped grooves at the butt joints of the straight seam steel pipe, and then using a gas shielded welding method to perform backing pre-welding;

[0010] S2, the inner and outer welds are both welded using a three-wire submerged arc welding process: first, the inner weld is welded using a three-wire submerged arc welding process, and then an ultrasonic auxiliary device is arranged on the side of the inner weld facing the inside of the straight seam steel pipe;

[0011] S3, when the outer weld is welded using a three-wire submerged arc welding process, the three-wire submerged arc welding torch and the ultrasonic auxiliary device are respectively located on the two sides of the inner weld, the ultrasonic auxiliary device has three ultrasonic transducers, and the output ends of the ultrasonic transducers are in contact with the back of the molten pool through a horn;

[0012] S4, simultaneously starting the multi-wire submerged arc welding torch and the ultrasonic auxiliary device, and welding the outer weld using a three-wire submerged arc welding process until the entire straight seam steel pipe is welded.

[0013] Further, in steps S2 to S4, the three welding wires of the three-wire submerged arc welding are arranged along the axial direction of the straight seam steel pipe; in steps S3 and S4, the three ultrasonic transducers of the ultrasonic auxiliary device are arranged along the axial direction of the straight seam steel pipe, and the three ultrasonic transducers and the three welding wires of the three-wire submerged arc welding torch are sorted in the same direction, so that the first ultrasonic transducer is located directly below the first welding wire.

[0014] Further, in step S4, the ultrasonic auxiliary device and the three-wire submerged arc welding torch remain unchanged in position, and the straight seam steel pipe is controlled to move along the axial direction to complete the welding.

[0015] Further, it is suitable for welding of carbon steel pipes with a steel grade of X60 and below.

[0016] The application also provides a straight seam steel pipe multi-wire submerged arc welding device, comprising a three-wire submerged arc welding device, an ultrasonic auxiliary device, and a telescopic cantilever beam.

[0017] The three-wire submerged arc welding device is used for welding the outer weld of the straight seam steel pipe, the three-wire submerged arc welding torch of the three-wire submerged arc welding device has three welding wires arranged side by side, the three welding wires are located above the joint of the straight seam steel pipe, and are arranged along the axial direction of the straight seam steel pipe;

[0018] The ultrasonic auxiliary device is installed at the front end of the telescopic cantilever beam, and comprises three ultrasonic transducers arranged side by side, and a horn is installed at the output end of the ultrasonic transducer; when the three-wire submerged arc welding device is used to weld the outer weld of the straight seam steel pipe, the telescopic cantilever beam is used to drive the ultrasonic auxiliary device to extend into the straight seam steel pipe and adjust the position of the ultrasonic transducer, and the ultrasonic auxiliary device is used to generate ultrasonic waves through the ultrasonic transducer and input the ultrasonic waves into the molten pool through the horn.

[0019] Further, the steel pipe moving platform for supporting and driving the straight seam steel pipe to move along the axial direction is further included.

[0020] Further, the bottom of the ultrasonic transducer is provided with a shock absorbing air cylinder for adjusting the distance between the horn and the inner weld surface, and the bottom of the shock absorbing air cylinder is provided with two supporting rollers in contact with the inner wall of the straight seam steel pipe.

[0021] Further, the distance between the two adjacent ultrasonic transducers is 1.5 times the distance between the two adjacent welding wires.

[0022] Further, the horn is made of high-temperature resistant alloy, and the end is processed into a semispherical shape.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] 1. The straight seam steel pipe multi-wire submerged arc welding method provided by the present application promotes the flow of molten pool metal by introducing ultrasonic waves at the back of the weld, suppresses the formation of intergranular ferrite and promotes the formation of intragranular acicular ferrite, compared with the conventional multi-wire submerged arc welding, the weld structure is significantly refined, and the impact energy and hydrogen brittleness resistance are improved.

[0025] 2. The straight seam steel pipe multi-wire submerged arc welding device provided by the present application directly applies ultrasonic vibration at the back of the weld, which not only has large ultrasonic transmission power, but also can reduce the weld hydrogen content and residual tensile stress peak value while refining the weld structure.

[0026] 3. The multi-wire submerged arc welding method and device provided by the present application have simple equipment structure and convenient operation, and can meet the continuous and large-batch production requirements. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0028] Figure 1 Structure diagram of the multi-wire submerged arc welding device for the straight seam steel pipe according to the present application.

[0029] Figure 2 Structure diagram of the ultrasonic auxiliary device and the three-wire submerged arc welding device according to the present application.

[0030] Figure 3 Structure diagram of the ultrasonic auxiliary device according to the present application.

[0031] Figure 4 Macrostructure diagram of the weld section of the straight seam steel pipe obtained by using the method according to embodiment 1.

[0032] Figure 5 Metallographic diagram of the section of the outer weld of the straight seam steel pipe welded according to embodiment 1 at position I.

[0033] Figure 6 Metallographic diagram of the section of the outer weld of the straight seam steel pipe welded according to embodiment 1 at position II.

[0034] Figure 7 Metallographic diagram of the section of the outer weld of the straight seam steel pipe welded according to embodiment 1 at position III.

[0035] Figure 8 Metallographic diagram of the section of the outer weld of the straight seam steel pipe welded according to comparative example 1 at position I.

[0036] Figure 9 Metallographic diagram of the section of the outer weld of the straight seam steel pipe welded according to comparative example 1 at position II.

[0037] Figure 10 Metallographic diagram of the section of the outer weld of the straight seam steel pipe welded according to comparative example 1 at position III.

[0038] In the figure: 1, three-wire submerged arc welding device; 2, ultrasonic auxiliary device; 3, telescopic cantilever beam; 4, steel pipe moving platform; 5, straight seam steel pipe; 6, supporting roller; 7, welding torch; 8, amplitude bar; 9, ultrasonic transducer; 10, shock absorbing air cylinder. DETAILED DESCRIPTION

[0039] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0040] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all embodiments of the present application. The following description of at least one example embodiment is merely illustrative in nature and is in no way limiting on the application or its applications or uses. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0041] It should be noted that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit exemplary embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms, unless the context clearly indicates otherwise, and it will be further understood that the terms "comprising", "including", and / or "having" when used herein, specify the presence of stated features, steps, operations, devices, components and / or combinations thereof.

[0042] Unless specifically stated otherwise, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments are not meant to limit the scope of the present application. At the same time, it should be clear that the sizes of the various parts shown in the drawings are not drawn in proportion. The techniques, methods and devices known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered as part of the specification under appropriate circumstances. In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, and not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0043] In the description of the present application, it should be understood that the orientation words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" and the like indicate the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate and imply that the indicated device or element must have a particular orientation or be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the scope of protection of the present application: the orientation words "inner, outer" refer to the inner and outer of the contour of each component itself.

[0044] For the purposes of this description, spatially relative terms, such as "above", "below", "up", "down", "between", "within", "left", "right", "front", "back", "upper", "lower", "horizontal", "vertical", "above", "below", "up", "down", "top", "bottom", "side", "end", etc., are intended to describe the orientation of one device or feature relative to another device or feature as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the devices in use or operation in addition to the orientations depicted in the figures. The devices can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. For example, if a device is described as "above" or "up" another device or structure, it can be oriented "below" or "down" the other device or structure. Likewise, if a device is described as "between" two other devices or structures, it can be oriented "between" the other devices or structures in a different manner. The devices can be oriented in any other manner, and the spatially relative descriptions used herein interpreted accordingly.

[0045] In addition, it should be noted that the use of "first", "second", and the like words of distinction do not have a special meaning, and are only used to distinguish corresponding parts, and therefore cannot be understood as limiting the scope of protection of the present application.

[0046] For the hydrogen conveying straight seam welded pipe, the present application provides a multi-wire submerged arc welding method for straight seam steel pipes, which specifically comprises:

[0047] The straight seam steel pipe is welded by double-sided submerged arc welding by using the multi-wire submerged arc welding process, and when welding the outside weld, an ultrasonic auxiliary device arranged at the back of the molten pool generates ultrasonic waves which are input into the molten pool through a horn. The method is suitable for welding carbon steel pipes with a steel grade of X60 and below. The weld structure of the steel pipe with this strength grade is mainly composed of grain boundary ferrite and intragranular acicular ferrite. By using the method of introducing ultrasonic waves proposed in the present application, the welding effect of low heat input can be achieved without reducing the welding power of multi-wire submerged arc welding: the formation of intergranular ferrite in the weld zone is inhibited, the content of intragranular acicular ferrite is increased, thereby improving the toughness and hydrogen embrittlement resistance of the weld zone, and the escape of gas and slag in the molten pool is promoted, and the weld shrinkage stress is reduced.

[0048] Further, the method specifically comprises the following steps:

[0049] S1, a straight seam steel pipe is cold formed by using a double-sided submerged arc welding process (JCOE process), a double V-shaped groove is processed at the butt joint of the straight seam steel pipe, and then a backing pre-welding is performed by using a gas shielded welding method;

[0050] S2, the inner and outer two sides welds all adopt three wire submerged arc welding process: first adopt three wire submerged arc welding process to weld the inner side weld, then set up ultrasonic auxiliary device on the side of the inner side weld facing the inside of the straight seam steel pipe, the application introduces ultrasonic energy field to the inner side weld, compared with other ways of introducing ultrasonic, because the inner side weld is thin, the ultrasonic transmission path is short, and the transmission direction is just from the back of the molten pool to the inside of the molten pool, so the attenuation is small.

[0051] S3, when adopting three wire submerged arc welding process to weld the outer side weld, the three wire submerged arc welding torch and the ultrasonic auxiliary device are located on the two sides of the inner side weld respectively, the ultrasonic auxiliary device has three ultrasonic transducers, the output end of the ultrasonic transducer is in contact with the back of the molten pool through a variable amplitude rod, and the back of the molten pool refers to the surface of the side of the inner side weld facing the inside of the straight seam steel pipe.

[0052] S4, simultaneously start the multi-wire submerged arc welding torch and the ultrasonic auxiliary device, adopt three wire submerged arc welding process to weld the outer side weld, and until the whole straight seam steel pipe is welded.

[0053] Further, in steps S2 to S4, the three wires of the three wire submerged arc welding are arranged along the axis of the straight seam steel pipe.

[0054] Further, in steps S3 and S4, the three ultrasonic transducers of the ultrasonic auxiliary device are arranged along the axis of the straight seam steel pipe, and the three ultrasonic transducers and the three wires of the three wire submerged arc welding torch are sorted in the same direction, so that the first ultrasonic transducer is located directly below the first wire.

[0055] Further, in step S4, the ultrasonic auxiliary device and the three wire submerged arc welding torch keep the same position, and the straight seam steel pipe is moved along the axis to complete the welding.

[0056] The method can achieve the effects of low heat input multi-wire submerged arc welding such as refining the structure, promoting the escape of hydrogen, and reducing welding residual stress without changing the existing multi-wire submerged arc welding parameters, and can adjust the frequency and amplitude of the generated ultrasonic wave according to needs.

[0057] As Figures 1-3As shown, the application also provides a straight seam steel pipe multi-wire submerged arc welding device, which comprises a three-wire submerged arc welding device 1, an ultrasonic auxiliary device 2 and a telescopic cantilever beam 3; the three-wire submerged arc welding device 1 is used for welding the outer weld of the straight seam steel pipe 5, the three-wire submerged arc welding torch 7 of the three-wire submerged arc welding device 1 has three welding wires arranged side by side, the three welding wires are located above the joint of the straight seam steel pipe 5 and are arranged in the axial direction of the straight seam steel pipe 5; the ultrasonic auxiliary device 2 is installed at the front end of the telescopic cantilever beam 3, the ultrasonic auxiliary device 2 comprises three ultrasonic transducers 9 arranged side by side, and an amplitude horn 8 is installed at the output end of the ultrasonic transducer 9; when the three-wire submerged arc welding device 1 is used for welding the outer weld of the straight seam steel pipe 5, the telescopic cantilever beam 3 is used for driving the ultrasonic auxiliary device 2 to extend into the inside of the straight seam steel pipe 5 and adjusting the position of the ultrasonic transducer 9, and the ultrasonic auxiliary device 2 is used for generating ultrasonic waves through the ultrasonic transducer 9 and inputting the ultrasonic waves into the molten pool through the amplitude horn 8.

[0058] Further, it also comprises a steel pipe moving platform 4 for supporting and driving the straight seam steel pipe to move in the axial direction.

[0059] Further, the bottom of the ultrasonic transducer 9 is provided with a shock absorbing air cylinder 10 for adjusting the distance between the amplitude horn 8 and the inner weld surface, and the bottom of the shock absorbing air cylinder 10 is provided with two supporting rollers 6 which are in contact with the inner wall of the straight seam steel pipe 5.

[0060] Further, the distance between the two adjacent ultrasonic transducers 9 is 1.5 times the distance between the two adjacent welding wires.

[0061] Further, when the three-wire submerged arc welding device 1 is used for welding the outer weld of the straight seam steel pipe 5, the three ultrasonic transducers 9 and the three welding wires are sorted in the same direction, and the position of the ultrasonic transducer 9 is adjusted by the telescopic cantilever beam 3, so that the first ultrasonic transducer 9 is located directly below the first welding wire.

[0062] Further, when the three-wire submerged arc welding device 1 is used to weld the outer weld of the straight seam steel pipe 5: the telescopic cantilever beam 3 drives the ultrasonic auxiliary device 2 to extend into the interior of the straight seam steel pipe 5, so that the three-wire submerged arc welding torch 7 and the ultrasonic auxiliary device 2 are respectively located on both sides of the inner weld, the three ultrasonic transducers 9 are arranged along the axial direction of the straight seam steel pipe 5, the distance between the amplitude lever 8 and the surface of the inner weld is adjusted by the buffer cylinder 10, so that the amplitude lever 8 is in contact with the surface of the inner weld, and the ultrasonic waves generated by the ultrasonic transducer 9 can be input into the molten pool through the amplitude lever 8; during the welding process, the steel pipe moving platform 4 drives the straight seam steel pipe 5 to move along the axial direction, the ultrasonic auxiliary device 2 and the three-wire submerged arc welding device 1 remain unchanged, and the supporting roller 6 can roll in the straight seam steel pipe 5.

[0063] Further, the amplitude lever 8 is made of high-temperature-resistant alloy, and the end is processed into a semispherical shape.

[0064] Embodiment 1

[0065] In this embodiment, the straight seam steel pipe multi-wire submerged arc welding method is used to weld the L415 grade carbon steel straight seam steel pipe, which specifically includes the following steps:

[0066] S1, the straight seam steel pipe is cold formed by using the double-sided submerged arc welding process, a double-V-shaped groove is processed at the butt joint of the straight seam steel pipe, and then CO2 gas shielded welding is used for pre-welding, and the process parameters of the gas shielded welding are shown in Table 1;

[0067] Table 1 CO2 gas shielded welding process parameters

[0068]

[0069] S2, the inner and outer welds are welded by using the three-wire submerged arc welding process: the inner weld is welded by using the three-wire submerged arc welding process, and the specific process parameters are shown in Table 2:

[0070] Table 2 Three-wire submerged arc welding process parameters of inner weld

[0071]

[0072] Then, the ultrasonic auxiliary device is arranged on the side of the inner weld facing the interior of the straight seam steel pipe.

[0073] S3, when welding the outer weld by the three-wire submerged arc welding process, the three-wire submerged arc welding torch and the ultrasonic auxiliary device are respectively located at two sides of the inner weld, the ultrasonic auxiliary device has three ultrasonic transducers, output ends of the ultrasonic transducers are in contact with the back of the molten pool through amplitude rods; the three ultrasonic transducers of the ultrasonic auxiliary device are arranged along the axial direction of the straight seam steel pipe, and the three ultrasonic transducers and the three welding wires of the three-wire submerged arc welding torch are sorted in the same direction, so that the first ultrasonic transducer is located directly below the first welding wire.

[0074] S4, the multi-wire submerged arc welding torch and the ultrasonic auxiliary device are started at the same time, the vibration frequency of the ultrasonic transducer ranges from 20 kHz to 60 kHz, the amplitude ranges from 0.1 mm to 0.5 mm, the outer weld is welded by the three-wire submerged arc welding process, and the whole straight seam steel pipe is welded, and specific process parameters are shown in Table 3.

[0075] Table 3 Process parameters of the three-wire submerged arc welding of the outer weld

[0076]

[0077] Comparative Example 1

[0078] The difference between Comparative Example 1 and Example 1 is that the ultrasonic auxiliary device is not arranged when the outer weld is welded, and other steps and process parameters are the same as those of Example 1.

[0079] The macrostructure of the weld cross section of the straight seam steel pipe welded in Example 1 is shown in FIG. 4, three different depth positions (corresponding to the labels I, II and III shown in FIG. 4, respectively) on the outer weld of the welded straight seam steel pipe are taken, and the weld cross sections at the positions I, II and III are respectively subjected to metallographic examination, and the results are shown in FIGS. 5, 6 and 7, respectively. Figure 4 Figure 5 Figure 6 Figure 7

[0080] At the same time, the weld cross sections at the same depth positions as the positions I, II and III on the outer weld of the straight seam steel pipe welded in Comparative Example 1 are respectively subjected to metallographic examination, and the results are shown in FIGS. 8, 9 and 10, respectively. Figure 4 Figure 8 Figure 9 Figure 10

[0081] ​​​​​​​​By comparing the metallographs of the weld cross sections at the same position of Example 1 and Comparative Example 1, it can be seen that: the weld structure obtained without introducing ultrasonic waves in Comparative Example 1 has coarse proeutectoid ferrite, large size and partially parallel distribution of acicular ferrite, which will result in poor low-temperature impact performance; after introducing ultrasonic waves in Example 1, the content of intergranular ferrite in the weld structure is obviously reduced, the distribution of proeutectoid ferrite is less, the content of intragranular acicular ferrite is obviously increased, the size of acicular ferrite is small and the acicular ferrite is cross-distributed, so that the low-temperature impact performance of the straight seam steel pipe completed by welding can be improved.

[0082] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for multi-wire submerged arc welding of straight seam steel pipes, characterized in that, Specifically, it includes: Double-sided submerged arc welding of straight seam steel pipes is carried out using multi-wire submerged arc welding process. When welding the outer weld, ultrasonic waves are generated by an ultrasonic auxiliary device set on the back of the molten pool and input into the molten pool through an amplitude transformer. Specifically, the following steps are included: S1. The straight seam steel pipe is cold-formed using double-sided submerged arc welding. A double V-shaped bevel is processed at the joint of the straight seam steel pipe, and then the root pass is pre-welded using gas shielded welding. S2. Both the inner and outer welds adopt the three-wire submerged arc welding process: first, the inner weld is welded using the three-wire submerged arc welding process, and then an ultrasonic auxiliary device is installed on the side of the inner weld facing the inside of the straight seam steel pipe. S3. When welding the outer weld using the three-wire submerged arc welding process, the three-wire submerged arc welding torch and the ultrasonic auxiliary device are located on both sides of the inner weld. The ultrasonic auxiliary device has three ultrasonic transducers, and the output end of the ultrasonic transducer contacts the back of the molten pool through the amplitude transformer. S4. Simultaneously start the multi-wire submerged arc welding torch and ultrasonic auxiliary device, and use the three-wire submerged arc welding process to weld the outer weld seam until the entire straight seam steel pipe is welded.

2. The method for multi-wire submerged arc welding of straight seam steel pipes according to claim 1, characterized in that, In steps S2 to S4, the three welding wires of the three-wire submerged arc welding are arranged along the axial direction of the straight seam steel pipe; in steps S3 and S4, the three ultrasonic transducers of the ultrasonic auxiliary device are arranged along the axial direction of the straight seam steel pipe, and the three ultrasonic transducers and the three welding wires of the three-wire submerged arc welding torch are arranged in the same direction, so that the first ultrasonic transducer is located directly below the first welding wire.

3. The method for multi-wire submerged arc welding of straight seam steel pipes according to claim 1, characterized in that, In step S4, the ultrasonic auxiliary device and the three-wire submerged arc welding torch remain in the same position, and the straight seam steel pipe is controlled to move axially to complete the welding.

4. The method for multi-wire submerged arc welding of straight seam steel pipes according to claim 1, characterized in that, It is suitable for welding carbon steel pipes with strength grades of X60 and below.

5. A multi-wire submerged arc welding apparatus for straight seam steel pipes using the multi-wire submerged arc welding method according to any one of claims 1-4, characterized in that, Includes a three-wire submerged arc welding device, an ultrasonic auxiliary device, and a telescopic cantilever beam; The three-wire submerged arc welding device is used to weld the outer seam of a straight seam steel pipe. The three-wire submerged arc welding gun of the three-wire submerged arc welding device has three welding wires arranged side by side. The three welding wires are located above the interface of the straight seam steel pipe and are arranged along the axial direction of the straight seam steel pipe. The ultrasonic auxiliary device is installed at the front end of the telescopic cantilever beam. The ultrasonic auxiliary device includes three ultrasonic transducers arranged side by side, and an amplitude transformer is installed at the output end of the ultrasonic transducer. When welding the outer weld of the straight seam steel pipe using the three-wire submerged arc welding device, the telescopic cantilever beam is used to drive the ultrasonic auxiliary device to extend into the straight seam steel pipe and adjust the position of the ultrasonic transducer. The ultrasonic auxiliary device is used to generate ultrasonic waves through the ultrasonic transducer and input them into the molten pool through the amplitude transformer.

6. The multi-wire submerged arc welding device for straight seam steel pipes according to claim 5, characterized in that, It also includes a steel pipe moving platform for supporting and driving the straight seam steel pipe to move axially.

7. The multi-wire submerged arc welding device for straight seam steel pipes according to claim 5, characterized in that, The ultrasonic transducer is equipped with a damping cylinder at its bottom for adjusting the distance between the amplitude transformer and the inner weld surface. The damping cylinder has two support rollers at its bottom, and the support rollers are in contact with the inner wall of the straight seam steel pipe.

8. The multi-wire submerged arc welding device for straight seam steel pipes according to claim 5, characterized in that, The distance between two adjacent ultrasonic transducers is 1.5 times the distance between two adjacent welding wires.

9. The multi-wire submerged arc welding device for straight seam steel pipes according to claim 5, characterized in that, The amplitude transformer is made of high-temperature resistant alloy and its end is machined into a hemispherical shape.

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