Welding method and welding structure for one-side welding and double-side forming of butt joint of high-strength steel

Abstract

The invention discloses a high-strength steel butt joint single-face welding and double-face forming welding method and structure, and relates to the technical field of welding. The welding method comprises the following steps that two to-be-welded pipe fittings with the diameter larger than or equal to 100 mm and the wall thickness larger than or equal to 10 mm are selected; the two pipe fittings are in butt joint, a groove is formed in the butt joint position, an opening of the groove faces the outer portions of the pipe fittings, and the bottom of the groove faces the inner portions of the pipe fittings; welding rods with the tensile strength matched with that of the pipe fitting are adopted, the bottom layer is welded through broken arc welding, the filling layer is welded through continuous arc welding, and the covering layer is welded through continuous arc welding in sequence in the direction from the bottom of the groove to the opening, so that a fusion part is formed at the groove, and the fusion part protrudes out of the inner wall face of the pipe fitting. By means of the technology, the full penetration and inner wall protruding forming effect of the base layer is guaranteed, single-face welding and double-face forming are achieved, the welding efficiency is improved, the technical requirement for single-face welding and double-face forming of the high-strength steel thick-wall pipe under the limited space condition is met as a whole, and good engineering applicability and reliability are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to a welding method and welding structure for butt joint single-sided welding and double-sided forming of high-strength steel. BACKGROUND

[0002] At present, in the field of welding of high-strength steel, the traditional welding method often requires double-sided welding to ensure the welding quality and the safety and reliability of the structure.

[0003] However, in actual operation, especially for some space-limited or narrow inner wall pipeline construction scenes, this traditional method faces many challenges. First, double-sided welding requires the workpiece to be flipped or welded twice inside the pipeline, which not only increases the construction difficulty, but also makes it difficult to guarantee the welding quality due to the small operating environment. Second, the double-sided welding process not only consumes time but also increases labor costs, reducing the overall construction efficiency.

[0004] Therefore, how to provide a welding method and welding structure for butt joint single-sided welding and double-sided forming of high-strength steel that can adapt to complex construction conditions and improve welding efficiency is a problem that needs to be solved at present. SUMMARY

[0005] The first aspect of the embodiments of the present application provides a welding method for butt joint single-sided welding and double-sided forming of high-strength steel, comprising the following steps: selecting two pipe fittings to be welded with a diameter ≥ 100 mm and a wall thickness ≥ 10 mm; butting the two pipe fittings and opening a groove at the butt joint, the opening of the groove facing the outside of the pipe fitting, and the bottom of the groove facing the inside of the pipe fitting; using a welding rod with a tensile strength matching the pipe fitting, sequentially welding a backing layer by arc breaking welding, a filler layer by arc continuous welding, and a surface layer by arc continuous welding from the bottom of the groove to the opening direction, to form a molten part at the groove, and the molten part protrudes from the inner wall surface of the pipe fitting.

[0006] In some embodiments, the welding rod is a ZS60A welding rod, and the composition of the welding rod includes: chromium: 0.05%-0.24%; nickel: 3.05%-3.4%; molybdenum: 1.0%-1.45%; carbon: ≤0.07%; silicon: ≤0.35%; sulfur: ≤0.015%; phosphorus: ≤0.02%.

[0007] In some embodiments, the angle α of the groove satisfies: 30° < α < 35°, the root gap S satisfies: 3mm < S < 4mm, and the groove toe T satisfies: 1mm < T < 1.5mm.

[0008] In some embodiments, before welding the backing layer by arc breaking welding, it further includes: performing a positioning weld at the groove, and the welding areas of the positioning weld are arranged at intervals along the circumference of the pipe fitting.

[0009] In some embodiments, the backing layer is welded by arc breaking welding, specifically, the welding frequency of arc breaking welding is the same, the starting point of each time is at 1 / 3 of the fusion hole, and the arc length C after starting arc satisfies: 1mm < C < 1.5mm.

[0010] In some embodiments, the welding rod diameter for welding the filler layer and the cover layer is larger than the welding rod diameter for welding the backing layer; the welding current for welding the cover layer is smaller than the welding current for welding the filler layer.

[0011] In some embodiments, the height h of the molten part protruding from the inner wall of the pipe satisfies: 1mm < h < 3mm.

[0012] In some embodiments, the bevel of the pipe is preheated while the backing layer is welded by arc breaking welding, the filler layer is welded by arc continuous welding, and the cover layer is welded by arc continuous welding in sequence from the bottom of the bevel to the opening direction, so that the temperature of the bevel during the whole welding process is within 80℃ to 120℃.

[0013] In some embodiments, the included angle β between the welding rod and the outer wall of the pipe satisfies: 80° < β < 90°.

[0014] The second aspect of the embodiments of the present application provides a welding structure obtained by a welding method for butt joint single-sided welding double-sided forming of high-strength steel, comprising: two pipes arranged in butt joint, a bevel is arranged at the butt joint position of the two pipes, the opening of the bevel faces the outside of the pipe, and the bottom of the bevel faces the inside of the pipe; the bottom of the bevel to the opening direction adopts a welding rod with a tensile strength matched with the pipe to sequentially weld a backing layer by arc breaking welding, a filler layer by arc continuous welding, and a cover layer by arc continuous welding, so as to form a molten part at the bevel, and the molten part protrudes from the inner wall of the pipe.

[0015] Compared with the prior art, the welding method for butt joint single-sided welding double-sided forming of high-strength steel of the present application realizes stable layer-by-layer forming from the root of the bevel to the outside by precisely controlling the process parameters of the backing layer arc breaking welding, including the welding rod diameter, the current and voltage, the arc breaking frequency, the arc starting position, and the arc length, and optimizing the arc continuous welding parameters of the filler layer and the cover layer. This process not only guarantees full penetration and inner wall protruding forming effect of the backing layer, i.e. realizes single-sided welding double-sided forming, improves the welding efficiency, and overall meets the technical requirements of single-sided welding double-sided forming of high-strength steel thick-walled pipes under space limited conditions, and has good engineering applicability and reliability. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a schematic diagram of pipe butt joint of the embodiments of the present application;

[0017] Figure 2 It is a local schematic diagram of pipe butt joint of the embodiments of the present application;

[0018] Figure 3A partial view of a pipe after welding according to an embodiment of the present application;

[0019] Figure 4 A schematic view of a pipe positioning welding according to an embodiment of the present application;

[0020] Figure 5 A schematic view of the position of a welding rod and a pipe during welding of a pipe according to an embodiment of the present application;

[0021] Figure 6 A flow chart of a welding method for butt joint single-sided welding and double-sided forming of a high-strength steel according to an embodiment of the present application.

[0022] Reference signs:

[0023] 1, pipe; 2, groove; 3, welding rod; 41, backing layer; 42, filler layer; 43, surface layer; 4, molten part; 5, welding area; a, angle of the groove; S, root gap; T, groove stop; β, angle between the welding rod and the outer wall of the pipe; d, diameter of the pipe; e, wall thickness; h, height. DETAILED DESCRIPTION

[0024] In order to better understand the technical solutions provided by the embodiments of the present specification, the technical solutions of the embodiments of the present specification will be described in detail below through the accompanying drawings and specific embodiments. It should be understood that the specific features in the embodiments of the present specification and the embodiments are detailed descriptions of the technical solutions of the embodiments of the present specification, and not limitations of the technical solutions of the present specification. In the case of no conflict, the technical features in the embodiments of the present specification and the embodiments can be combined with each other.

[0025] In this document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises... " does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the stated elements. The term "two or more" includes two or more than two.

[0026] As shown in Figures 1-6 the first aspect of the embodiments of the present application provides a welding method for butt joint single-sided welding and double-sided forming of a high-strength steel, comprising the following steps:

[0027] Step S1: select two pipe fittings 1 to be welded with a diameter ≥100 mm and a wall thickness ≥10 mm;

[0028] In one possible case, two high-strength steel pipe fittings 1 are selected, the diameters d of the two pipe fittings 1 to be welded are greater than or equal to 100 mm, the wall thicknesses e are greater than or equal to 10 mm, the high-strength steel is a metal material system with significantly higher strength than ordinary steel, and specifically the pipe fitting 1 can be a 10CrNi3MoV alloy structural steel according to GB / T 3077-2015 standard, the chemical composition of which satisfies: C 0.07-0.12%, Cr 0.70-1.00%, Ni 2.50-3.00%, Mo 0.20-0.40%, V 0.05-0.10%, and the balance is Fe and unavoidable impurities.

[0029] Step S2: butt joint the two pipe fittings 1 and open a groove 2 at the butt joint, the opening of the groove 2 faces the outside of the pipe fitting 1, and the bottom of the groove 2 faces the inside of the pipe fitting 1;

[0030] In one possible case, the ends of the two pipe fittings 1 are butt jointed to coincide the axes of the two pipe fittings 1, and the ends of the two pipe fittings 1 are left with a gap. The positions of the two pipe fittings 1 are fixed, and a groove 2 is opened at the ends of the butt joint of the two pipe fittings 1 to form a V-shaped groove 2 between the two pipe fittings 1. The opening of the V-shaped groove 2 faces the outside of the pipe fitting 1, i.e. the widest part of the groove 2 is located on the side of the outer wall of the pipe, which facilitates the welding torch or welding rod 3 to enter from the outside and perform welding. The bottom of the groove 2 faces the inside of the pipe fitting 1, i.e. the narrowest part (root area) of the groove 2 points to the direction of the inner cavity of the pipe, which guides the welding pool to extend inward, which is beneficial to achieve good forming of the inner wall. The groove 2 structure is a tapered transition that gradually narrows from the outer surface of the pipe fitting 1 to the inside.

[0031] In order to balance weld accessibility, penetration control, filler metal usage, and heat input management, while ensuring double-sided forming under single-sided welding rod 3, the angle α of the V-shaped groove 2 satisfies: 30° < α < 35°, for example, it can be selected as 31°, 33°, or 34°, etc. Further, the root gap S of the groove 2 can satisfy: 3mm < S < 4mm, for example, it can be 3.2mm, 3.5mm, or 3.8mm. This gap range can ensure that the arc effectively breaks through the root during the backing welding to form sufficient penetration, and can also support the molten metal with the help of the surface tension of the molten pool to prevent collapse or burn-through. In addition, the root face T of the groove 2 satisfies: 1mm < T < 1.5mm, such as 1.1mm, 1.3mm, 1.4mm, etc., to enhance the load-carrying capacity of the joint root and serve as a key dimension to control the degree of penetration.

[0032] Step S3: using a welding rod 3 with a tensile strength matching that of the pipe fitting 1, sequentially welding a backing layer 41 by short-circuiting arc welding, a filling layer 42 by continuous arc welding, and a surface layer 43 by continuous arc welding along the bottom of the groove 2 to the opening direction to form a molten portion 4 at the groove 2, and the height h of the molten portion 4 protruding from the inner wall surface of the pipe fitting 1 can be 1-3 mm, such as 1 mm, 1.5 mm, or 3 mm.

[0033] In a possible case, in step S3 of the present application, a welding rod 3 with a tensile strength matching that of the base material of the pipe fitting 1 is used to sequentially perform layered welding along the bottom of the groove 2 to the opening direction, specifically including welding a backing layer 41 by short-circuiting arc welding, a filling layer 42 by continuous arc welding, and a surface layer 43 by continuous arc welding, finally forming a complete molten weld at the groove 2 area, and the molten portion 4 protrudes from the inner wall surface of the pipe fitting 1 on the inner wall side of the pipe, achieving the technical effects of single-sided welding and double-sided forming.

[0034] The welding rod 3 used can be a ZS60A low-alloy high-strength structural steel welding rod 3, and the specific composition is: chromium content of 0.05%-0.24%, nickel content of 3.05%-3.4%, molybdenum content of 1.0%-1.45%, carbon content less than or equal to 0.07%, silicon content less than or equal to 0.35%, sulfur content less than or equal to 0.015%, and phosphorus content less than or equal to 0.02%.

[0035] First, the backing layer 41 is welded, and a ZS60A welding rod 3 with a diameter of 3.2 mm can be selected, and the welding current can be controlled between 95 A and 110 A, and the welding voltage can be 18 V to 20 V, to ensure that the arc is stable and has sufficient penetration capability. The backing layer 41 uses a short-circuiting arc welding process, that is, the formation and cooling process of the molten pool is controlled by periodically igniting and extinguishing the arc. During the entire backing welding process, a consistent short-circuiting frequency is maintained, so that the welding time of each cycle is uniform, thereby ensuring that the heat input and solidification process of the molten pool are stable and controllable. Each time the arc is re-ignited, the arc should be accurately ignited at the 1 / 3 position of the previous molten hole area to achieve good interlayer fusion and transition, avoid the presence of unfused or slag inclusion defects, and promote the smooth extension of the molten pool metal. After ignition, short arc operation is maintained, and the arc length C can be controlled between 1 mm and 1.5 mm, that is, the distance between the end of the welding rod 3 and the molten pool is maintained within this range. This short arc length can ensure sufficient heat concentration for root penetration, and can effectively prevent arc drift, increased spatter, or uncontrolled molten pool collapse. The molten welding rod 3 extends into the pipe fitting 1 and solidifies to form a continuous, dense, and uniform molten portion 4 protruding from the inner wall surface, and the height h of the molten portion 4 protruding from the inner wall surface of the pipe fitting 1 can be 1-3 mm, achieving double-sided forming.

[0036] After completing the root pass 41, proceed with the filler pass 42 welding. Replace with ZS60A welding rod 3 (4.0mm diameter) and use continuous arc welding for multiple filler passes. Set the welding current to 120A to 140A and the welding voltage to 19V to 21V, ensuring continuous arc burning without periodic extinguishing. Fill the groove 2 section pass by pass using a crescent-shaped or small-amplitude sawtooth oscillation method, with each pass width not exceeding three times the diameter of welding rod 3. After each pass, thoroughly remove slag and grind any excessive weld excess to ensure clean interlayers and good fusion. Continuous arc welding offers advantages such as high deposition efficiency and fast welding speed, enabling efficient large-area filler welding. Simultaneously, multi-layer surfacing refines the grain structure and improves weld uniformity.

[0037] Finally, the cover layer 43 is welded, still using ZS60A welding rod 3 with a diameter of 4.0mm, employing a continuous arc welding process. The welding current is further reduced to 115A to 130A, and the welding voltage is maintained at 19V to 21V to reduce heat input and prevent undercut, craters, or excessive weld reinforcement on the outer surface. Narrow-bead welding is used during the welding process to control the weld width, ensuring a smooth transition at the interface between the weld and the base material, resulting in a flat and aesthetically pleasing surface. The final weld reinforcement is controlled within the range of 0–2mm, free from surface defects such as porosity, cracks, slag inclusions, and undercut, meeting the requirements for appearance quality and non-destructive testing.

[0038] This application presents a welding method for single-sided welding and double-sided forming of high-strength steel butt joints. By precisely controlling the process parameters of the intermittent arc welding of the root pass 41, including the electrode diameter, current, voltage, arc interruption frequency, arc initiation position, and arc length, and combining this with optimized continuous arc welding parameters for the filler layer 42 and the capping layer 43, stable layer-by-layer forming from the root of the bevel 2 to the outside is achieved. This process not only ensures full penetration and inner wall protrusion formation of the root pass 41, thus achieving single-sided welding and double-sided forming and improving welding efficiency, but also meets the technical requirements for single-sided welding and double-sided forming of high-strength steel thick-walled pipes under space-constrained conditions, demonstrating good engineering applicability and reliability.

[0039] like Figures 1-6 As shown, in some embodiments, before welding the root layer 41 by intermittent arc welding, the method further includes: performing tack welding on the bevel 2, wherein multiple welding areas 5 of the tack welding are spaced apart along the circumference of the pipe fitting 1.

[0040] In one possible scenario, to ensure that the two pipe fittings 1 maintain a precise butt joint during the subsequent formal welding process and to prevent misalignment, gap changes, or axial displacement caused by thermal expansion, gravity, or welding stress, a tack welding step is also included before performing the root pass 41 welding using intermittent arc welding.

[0041] Tack welding involves evenly distributing multiple welding points along the circumference of pipe fitting 1 within the bevel area 2. These tack welding areas are spaced apart circumferentially, and can be 3, 4, or the number of welding areas 5 can be adjusted as needed to achieve multi-point uniform fixation of the butt joint of pipe fitting 1. After assembly, the coaxiality, root gap S uniformity, misalignment, and other geometric parameters of the two pipe fittings 1 can be checked and confirmed to meet the installation requirements before tack welding can be performed.

[0042] The welding materials used for tack welding are the same as those used for the final weld, employing the same type of ZS60A welding electrode 3, and the weld quality must meet the same standards as the final weld. Specifically, the tack weld should have good formation, smooth transitions, a flat surface, and be free from any welding defects such as cracks, porosity, slag inclusions, lack of fusion, or undercut. The tack weld will be completely fused into the final weld during the subsequent root pass welding, becoming part of the final joint.

[0043] The length of each tack weld can be controlled between 40mm and 50mm, such as 40mm, 45mm, or 50mm, and the weld thickness can be between 5mm and 6mm, such as 5mm, 5.5mm, or 6mm. This size provides sufficient connection strength to fix the pipe fitting in place while avoiding stress concentration or poor fusion during subsequent welding due to excessive length or thickness. After tack welding, the two ends of the weld protrusion formed on the inner wall of the pipe fitting can be ground into a bevel shape to facilitate a smooth transition at the weld joint, resulting in an aesthetically pleasing appearance without pits.

[0044] like Figures 1-6 As shown, in some embodiments, the diameter of the welding rod 3 for welding the filler layer 42 and the cover layer 43 is larger than the diameter of the welding rod 3 for welding the root pass 41; the welding current for welding the cover layer 43 is smaller than the welding current for welding the filler layer 42.

[0045] In one possible scenario, the diameter of the electrode 3 used for welding the filler layer 42 and the capping layer 43 is larger than the diameter of the electrode 3 used for welding the root pass 41. The root pass 41 requires higher operational precision and fine control of the molten pool; therefore, a smaller electrode 3 with a diameter of 3.2 mm is used to facilitate precise guidance of the arc on the root gap S during intermittent arc welding, achieving stable penetration and preventing burn-through. Conversely, the filler layer 42 and the capping layer 43 are used to efficiently fill the groove 2 section and form a good appearance; therefore, a larger electrode 3 with a diameter of 4.0 mm is selected. This provides higher deposition efficiency at a moderate current, accelerates welding speed, and improves overall construction efficiency. Simultaneously, the molten pool formed by the larger diameter electrode 3 is relatively stable, which is beneficial for interlayer fusion and surface smoothness in multi-pass welding.

[0046] Furthermore, during the welding of the cap coat 43, the welding current is set to be lower than that of the filler coat 42. For example, the filler coat 42 uses a current of 120A to 140A, while the cap coat 43 uses 115A to 130A. This decreasing current setting aims to better control the weld width, reinforcement height, and profile of the cap coat. Since the cap coat 43 directly determines the appearance quality and surface finish of the weld, it typically requires higher operational precision. Using a smaller welding current helps achieve a smoother droplet transfer, reduces large-particle spatter and arc voltage fluctuations, and makes the arc more concentrated and stable, thereby improving the smooth transition between the weld edge and the base material. At the same time, the lower heat input effectively prevents defects such as undercut, craters, overmelting, or wavy irregularities in the cap coat 43. Combined with an appropriate welding speed and a small oscillation technique, an ideal forming effect with a smooth surface, uniform texture, and moderate reinforcement height can be achieved.

[0047] In addition, a smaller current can reduce the volume of the molten pool and improve the welder's control over the flow state of the molten pool, especially in the uphill and overhead welding areas of pipe circumferential welds, which helps to prevent molten metal from falling and ensure consistent welding quality in all positions.

[0048] like Figures 1-6 As shown, in some embodiments, the bevel 2 of the pipe fitting 1 is preheated while the bottom of the bevel 2 is welded to the opening direction by intermittent arc welding to form the root layer 41, by continuous arc welding to form the fill layer 42, and by continuous arc welding to form the cover layer 43, so that the temperature of the bevel 2 is within 80°C to 120°C throughout the welding process.

[0049] In one possible scenario, in order to ensure the metallurgical quality and joint performance of the high-strength steel pipe fitting 1 during the welding process and to avoid defects such as cold cracks and hydrogen-induced cracks caused by the high hardening tendency of the material, while performing the intermittent arc welding root layer 41, the continuous arc welding filler layer 42, and the continuous arc welding capping layer 43 in sequence from the bottom of the bevel 2 to the opening direction, the bevel 2 area of ​​the pipe fitting 1 is also preheated and insulated.

[0050] Before starting the root pass (41) welding, the base metal within a certain range on both sides of the bevel 2 should be uniformly preheated. The preheating area should be at least 75mm on each side of the centerline of the bevel 2 to ensure sufficient heat transfer to the joint area. The preheating temperature should be controlled between 80℃ and 120℃, and this temperature range should be continuously monitored and maintained throughout the multi-layer, multi-pass welding process to ensure that the entire welding process is carried out in a stable thermal environment. The main functions of preheating are: to reduce the cooling rate of the weld joint, reduce the tendency of hardened structures (such as martensite) to form in the heat-affected zone; to promote the escape of diffusible hydrogen in the weld metal, effectively preventing hydrogen-induced delayed cracking; and, at the same time, appropriately increasing the initial temperature of the base metal fitting helps to improve the fluidity of the molten pool and enhance the root fusion quality of the root pass (41).

[0051] During the subsequent welding of the filler layer 42 and the cover layer 43, intermittent heating or flame preheating is used to ensure that the interpass temperature is not lower than 80℃ and not higher than 120℃. This temperature window ensures the thermal stability of continuous welding while preventing excessive temperature from causing grain coarsening or excessive heat input accumulation that could lead to joint performance degradation. By maintaining the temperature of the groove 2 region between 80℃ and 120℃ throughout the welding process, the metallurgical bonding quality between the weld layers is improved, ensuring sufficient interpass fusion and reducing the probability of defects such as slag inclusions and incomplete fusion. At the same time, a stable thermal cycling environment also helps to reduce welding residual stress, improve the uniformity and toughness of the weld microstructure, thereby enhancing the mechanical properties and long-term service reliability of the entire welded joint.

[0052] Furthermore, since this invention relates to the welding of high-strength steel pipe fittings 1, these materials have a high carbon equivalent and a strong tendency to harden. If local melting welding (such as tack welding) is performed at low temperatures or without preheating, microcracks are very likely to occur in the weld and heat-affected zone, especially in butt joints with high restraint. Therefore, in order to ensure the quality and reliability of tack welding, the bevel 2 and its two sides can be preheated in the same way as the formal welding before tack welding. The preheating temperature can be controlled between 80℃ and 120℃.

[0053] like Figure 5 As shown, in some embodiments, the included angle β between the welding rod 3 and the outer wall of the pipe fitting 1 satisfies: 80° < β < 90°.

[0054] In one possible scenario, the angle β between the welding electrode 3 and the outer wall of the pipe fitting 1 satisfies: 80° < β < 90°, such as 81°, 85°, or 88°. This angle helps concentrate the arc energy onto the root gap S of the bevel 2, enhancing the penetration ability to the blunt edge, ensuring the formation of a sufficient molten pool and achieving complete penetration. Simultaneously, it effectively suppresses the tendency of the molten pool metal to sag under gravity.

[0055] The results of non-destructive testing and mechanical property testing are shown in Tables 1 and 2 below. The test results meet the design requirements.

[0056] Table 1: Joint Tensile Test Checklist

[0057]

[0058] Table 2: Joint Bending Test Inspection Table

[0059]

[0060]

[0061] like Figures 1-5As shown, the second aspect of the embodiments of the present application provides a welding structure obtained by a welding method of butt joint single-sided welding and double-sided forming of high-strength steel, which comprises two pipe fittings 1 arranged in butt joint, and a groove 2 is formed at the butt joint position of the two pipe fittings 1, the opening of the groove 2 faces the outside of the pipe fittings 1, and the bottom of the groove 2 faces the inside of the pipe fittings 1; a welding rod 3 with a tensile strength matching that of the pipe fittings 1 is used to sequentially weld a backing layer 41 by arc striking welding, a filler layer 42 by arc striking welding, and a cover layer 43 by arc striking welding from the bottom to the opening of the groove 2, so as to form a molten part 4 at the groove 2, and the molten part 4 protrudes from the inner wall surface of the pipe fittings 1.

[0062] As shown, the second aspect of the embodiments of the present application provides a welding structure obtained by a welding method of butt joint single-sided welding and double-sided forming of high-strength steel, which comprises two pipe fittings 1 arranged in butt joint, and a groove 2 is formed at the butt joint position of the two pipe fittings 1, the opening of the groove 2 faces the outside of the pipe fittings 1, and the bottom of the groove 2 faces the inside of the pipe fittings 1; a welding rod 3 with a tensile strength matching that of the pipe fittings 1 is used to sequentially weld a backing layer 41 by arc striking welding, a filler layer 42 by arc striking welding, and a cover layer 43 by arc striking welding from the bottom to the opening of the groove 2, so as to form a molten part 4 at the groove 2, and the molten part 4 protrudes from the inner wall surface of the pipe fittings 1.

[0063] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0064] The above examples are only used to illustrate the technical solutions of the present application, but not limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

[0065] Although the preferred embodiments of the present specification have been described, those skilled in the art can make further changes and modifications to the embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present specification.

[0066] Obviously, those skilled in the art can make various modifications and variations to the present specification without departing from the spirit and scope of the present specification. Thus, if these modifications and variations of the present specification fall within the scope of the claims of the present specification and their equivalents, the present specification also intends to include these modifications and variations.

Claims

1. A welding method of high-strength steel butt single-sided welding double-sided forming, characterized by, The method comprises the following steps: selecting two pipe fittings to be welded with a diameter of ≥100 mm and a wall thickness of ≥10 mm; butting the two pipe fittings and opening a groove at the butt joint, the opening of the groove facing the outside of the pipe fitting, the bottom of the groove facing the inside of the pipe fitting; using an electrode with a tensile strength matching that of the pipe fitting, sequentially welding a backing layer by interrupted arc welding, a filling layer by continuous arc welding, and a cover layer by continuous arc welding along the direction from the bottom of the groove to the opening to form a molten part at the groove, and the molten part protruding from the inner wall of the pipe fitting.

2. The welding method of claim 1, wherein the electrode is a ZS60A electrode, and the electrode composition comprises: chromium: 0.05%-0.24%; nickel: 3.05%-3.4%; molybdenum: 1.0%-1.45%; carbon: ≤0.07%; silicon: ≤0.35%; sulfur: ≤0.015%; phosphorus: ≤0.02%.

3. The welding method of claim 1, wherein the angle α of the groove satisfies 30°<α<35°, the root gap S satisfies 3mm<S<4mm, and the groove toe T satisfies 1mm<T<1.5mm. Before the backing layer is welded by interrupted arc welding, the method further comprises: position welding at the groove, and the plurality of welding areas of the position welding are arranged at intervals along the circumference of the pipe fitting.

4. The high-strength steel butt single-pass welding double-sided forming welding method according to claim 1, characterized by, The backing layer is welded by interrupted arc welding, and the welding frequency of the interrupted arc welding is the same, the ignition point is at 1 / 3 of the fusion hole each time, and the arc length C after ignition satisfies 1mm<C<1.5mm.

6. The welding method of claim 1, wherein the diameter of the electrode used to weld the filling layer and the cover layer is larger than the diameter of the electrode used to weld the backing layer.

5. The high-strength steel butt single-pass welding double-sided forming welding method according to claim 1, characterized by, The welding current used to weld the cover layer is smaller than the welding current used to weld the filling layer.

7. The welding method of claim 1, wherein the height h of the molten part protruding from the inner wall of the pipe fitting satisfies 1mm<h<3mm.

8. The welding method of claim 1, wherein the groove of the pipe fitting is preheated while the backing layer is welded by interrupted arc welding, the filling layer is welded by continuous arc welding, and the cover layer is welded by continuous arc welding along the direction from the bottom of the groove to the opening, so that the temperature of the groove is within 80°C-120°C during the entire welding process.

9. The welding method of claim 1, wherein the included angle β between the electrode and the outer wall of the pipe fitting satisfies 80°<β<90°. The method comprises the following steps: butting two pipe fittings, and opening a groove at the butt joint of the two pipe fittings, the opening of the groove facing the outside of the pipe fitting, and the bottom of the groove facing the inside of the pipe fitting. ​ ​ ​ ​ ​ 10. A welded structure obtained by a welding method of butt single-pass welding of a high-strength steel according to any one of claims 1 to 9, characterized by, ​ ​ The groove is welded by a welding rod with tensile strength matching the pipe from the bottom of the groove to the opening direction in sequence by means of the arc breaking welding to form a backing layer, the arc continuous welding to form a filling layer and the arc continuous welding to form a cover layer, so as to form a molten part at the groove, and the molten part protrudes from the inner wall surface of the pipe.

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