A longitudinal seam welder for steel pipes

Abstract

The present application relates to the technical field of pipeline welding, and proposes a steel pipe inner longitudinal seam welding machine, which comprises a support frame, a cantilever and a welding gun; the welding gun is fixed on the cantilever, and the relative position of the cantilever and the support frame is adjustable, so that the welding gun moves in the pipeline to be welded; the steel pipe inner longitudinal seam welding machine further comprises a fixing seat and a bending mechanism; the fixing seat is fixed on the cantilever; the bending mechanism is arranged on the fixing seat and is used for bending two opposite side limbs of the pipeline to be welded to form two bending parts; the two bending parts enclose an inner weld; the inner weld is in a strip shape, and the cross-sectional width of the inner weld gradually decreases in a direction away from the center line of the pipeline to be welded until zero. By arranging the bending mechanism, the two opposite side limbs of the pipeline to be welded are reshaped into bending parts, thereby forming a continuous, uniform and parallel-to-axial semi-closed inner weld, so that the welding quality and welding efficiency of the pipeline to be welded are improved.

Description

Technical Field

[0001] This invention relates to the field of pipeline welding technology, and in particular to a longitudinal seam welding machine for steel pipes. Background Technology

[0002] Straight seam welded pipes widely adopt the manufacturing process of "steel plate rolling - side limb alignment - inner longitudinal seam welding". Among them, the inner longitudinal seam, as the first closed weld, directly determines the integrity of the pipe structure, circumferential pressure bearing capacity and service sealing performance.

[0003] However, after the steel plate is rolled into a circle, the weld formed by the natural contact of the two opposite limbs has an outward-expanding trapezoidal cross section with the width increasing outward from the center line. Under the action of gravity, the molten metal in the pool is prone to flow outward, resulting in uneven penetration, incomplete root fusion, severe spatter, and poor consistency of forming quality. At the same time, affected by the deviation of shearing accuracy, inconsistent edge chamfering, release of residual stress in the plate, and leveling error, local misalignment, abrupt gap changes, or even incomplete contact often occur after rolling, inducing typical defects such as porosity, cracks, and incomplete penetration, affecting the welding quality and welding efficiency of the steel pipe. Summary of the Invention

[0004] In view of this, the present invention proposes a steel pipe internal longitudinal seam welding machine, which forms a continuous, uniform internal weld seam parallel to the axial direction of the pipe by reshaping the two opposite limbs of the pipe to be welded, thereby improving the welding quality and welding efficiency of the pipe to be welded.

[0005] The technical solution of this invention is implemented as follows: This invention provides a steel pipe internal longitudinal seam welding machine, including a support frame, a cantilever, and a welding torch; the support frame is used to support the pipe to be welded; the welding torch is fixed on the cantilever, and the relative position of the cantilever and the support frame is adjustable, so that the welding torch can move inside the pipe to be welded; it also includes a fixed seat and a bending mechanism, the fixed seat being fixed on the cantilever; the bending mechanism is disposed on the fixed seat and is used to bend two opposite lateral limbs of the pipe to be welded to form two bent portions, the two bent portions enclosing an inner weld, the inner weld being elongated, and the cross-sectional width of the inner weld gradually decreasing along the direction away from the center line of the pipe to be welded until it becomes zero.

[0006] Based on the above technical solutions, preferably, the bending section includes a forming section and a straight section; one end of the forming section is integrally formed on the pipe to be welded, and the other end extends outward from the pipe to be welded and is integrally formed with the straight section and continuously arranged; the two straight sections abut against each other.

[0007] Based on the above technical solutions, preferably, the bending portion includes an extension section, one end of which is integrally formed on the pipe to be welded, and the other end extends into the pipe to be welded; the distance between the two extension sections gradually decreases along the direction away from the center line of the pipe to be welded until it is zero, and then gradually increases, forming the inner weld and the outer weld respectively.

[0008] Based on the above technical solutions, preferably, the sidewall of the inner weld is arc-shaped.

[0009] Based on the above technical solution, preferably, the fixed seat includes a seat body and a slider; the seat body is fixedly mounted on the cantilever, and a cavity is formed on its bottom side. A working groove, a connecting groove, and a suspension groove are formed on the side wall of the cavity. The working groove, the connecting groove, and the suspension groove are arranged sequentially and continuously along the length direction of the cantilever, and the suspension groove is located above the working groove; the slider is slidably mounted between the working groove, the connecting groove, and the suspension groove, and is fixedly connected to the bending mechanism; when the welding torch is inserted into the pipe to be welded, the bending mechanism abuts against the pipe to be welded, so that the slider is locked and fixed in the working groove; when the welding torch passes through the pipe to be welded and moves in the opposite direction, the bending mechanism abuts against the pipe to be welded, so that the slider moves into the suspension groove.

[0010] Based on the above technical solutions, preferably, a brush is also included, which is fixedly disposed on the bottom side of the bending mechanism.

[0011] Based on the above technical solutions, preferably, the bending mechanism includes a mounting base, a bending block, a connecting frame, and two extrusion rollers; the mounting base is fixedly mounted on the fixed base; the bending block is fixedly mounted on the mounting base; the connecting frame is fixedly mounted on the bending block; both extrusion rollers are rotatably mounted on the connecting frame and located at one end of the bending block, and the end of the bending block away from the extrusion rollers is inclined.

[0012] Based on the above technical solutions, preferably, the bending mechanism further includes two gathering wheels, both of which are rotatably mounted on the connecting frame and are positioned opposite each other on both sides of the bending block.

[0013] Based on the above technical solutions, preferably, the surface of the extrusion wheel is provided with spiral protrusions.

[0014] Based on the above technical solutions, preferably, the depth of the inner weld is not greater than the wall thickness of the pipe to be welded.

[0015] The longitudinal seam welding machine for steel pipes of the present invention has the following advantages over the prior art: (1) By setting up a bending mechanism, the two opposite limbs of the pipe to be welded are reshaped into bending parts, forming a continuous, uniform, and semi-closed inner weld that is parallel to the axial direction of the pipe to be welded, thereby improving the welding quality and welding efficiency of the pipe to be welded.

[0016] (2) By setting outward-turned V-shaped inner weld seams and inward-turned X-shaped double weld seams, the multi-condition adaptation and functional expansion of the pipeline to be welded can be realized, so as to meet the usage needs of different application scenarios.

[0017] (3) By setting the fixed seat to include the seat body and the slider, and setting the brush on the bending mechanism, the positioning, bending, cleaning and welding processes are integrated into a closed loop, realizing the integrated processing of the pipe to be welded and greatly improving its welding efficiency. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a partial front view of a steel pipe longitudinal seam welding machine according to the present invention.

[0020] Figure 2 This is a side view of the forming section in a steel pipe longitudinal seam welding machine according to the present invention.

[0021] Figure 3 This is a side view of the extension section in a steel pipe longitudinal seam welding machine according to the present invention.

[0022] Figure 4 This is a perspective view of the welding torch in a steel pipe longitudinal seam welding machine according to the present invention.

[0023] Figure 5 This is a perspective view of the base of a steel pipe longitudinal seam welding machine according to the present invention.

[0024] Figure 6 This is a cross-sectional view of the fixed seat in a steel pipe longitudinal seam welding machine according to the present invention, showing the bending mechanism in the working slot.

[0025] Figure 7 This is a cross-sectional view of the fixed seat in a steel pipe longitudinal seam welding machine according to the present invention, showing the bending mechanism in the suspended groove.

[0026] Figure 8 This is a side view of the bending mechanism in a steel pipe longitudinal seam welding machine according to the present invention.

[0027] Figure 9 This is a perspective view of the bending block in a steel pipe longitudinal seam welding machine according to the present invention.

[0028] Figure 10 This is a perspective view of the connecting frame in a steel pipe longitudinal seam welding machine according to the present invention.

[0029] Figure 11 This is a cross-sectional view of a bending mechanism in a steel pipe longitudinal seam welding machine according to the present invention.

[0030] The components are as follows: 1. Support frame; 2. Cantilever; 3. Welding torch; 4. Fixed seat; 41. Seat body; 42. Slider; 401. Cavity; 402. Working groove; 403. Connecting groove; 404. Suspension groove; 5. Bending mechanism; 51. Mounting seat; 52. Pressing block; 53. Connecting frame; 54. Extrusion wheel; 55. Gathering wheel; 6. Brush; 7. Pipe to be welded; 71. Bending section; 711. Forming section; 712. Straight section; 713. Extension section; 701. Inner weld; 702. Outer weld. Detailed Implementation

[0031] The technical solutions of this invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] In the manufacturing process of straight seam welded pipe, after the steel plate is rolled into an "O" shaped pipe to be welded 7, its two opposite limbs are aligned to form a longitudinal weld seam parallel to the pipe axis. Only by carrying out high-quality and highly consistent continuous welding operations on this weld seam can the two limbs of the pipe body be firmly closed, thereby ensuring the structural integrity, circumferential pressure bearing capacity and long-term service sealing performance of the finished steel pipe.

[0033] The present invention discloses a steel pipe longitudinal seam welding machine, comprising a support frame 1, a cantilever 2, a welding torch 3, a fixed base 4, and a bending mechanism 5, which aims to improve the weld formation quality, the uniformity of the penetration depth, and the overall welding efficiency.

[0034] like Figure 1 As shown, multiple sets of rotating rollers are symmetrically arranged along the axial direction on the top side of the support frame 1. The rotating rollers are driven by servo motors and have synchronous rotation and phase locking functions. They can not only support the pipe 7 to be welded, but also control the pipe 7 to be welded to rotate around its own axis.

[0035] The cantilever 2 is mounted on one end of the support frame 1. A welding torch 3 is fixed to its front end, and a control device for the welding torch 3 and a welding wire supply device are installed at its rear end. During operation, the pipe 7 to be welded is placed on multiple sets of rotating rollers. First, the rollers rotate in tandem to adjust the weld seam to a position directly below. Then, by adjusting the relative position of the cantilever 2 and the support frame 1, the front end of the welding torch 3 is driven to extend into the pipe 7 to be welded, performing continuous and stable traveling welding along the weld seam trajectory to achieve the closure of the two side limbs of the pipe 7. The support frame 1 and / or the cantilever 2 can be mounted on a moving vehicle or other linear module. The linear displacement of the moving vehicle or linear module is used to move the support frame 1 and / or the cantilever 2, thereby achieving dynamic adjustment of the relative position between the cantilever 2 and the support frame 1.

[0036] However, in actual engineering practice, after the steel plate is rolled into a cylindrical shape, the end faces of its two opposite limbs form a weld that opens outwards in a naturally fitted state. The cross-section of this weld is trapezoidal, and the width of the weld gradually increases outwards from the center line of the pipe to be welded 7. This causes the molten pool metal to easily flow outwards under the action of gravity, which seriously restricts the stability of the inner weld penetration and the forming quality. At the same time, in the steel plate cutting, edge chamfering and leveling processes, due to the influence of shearing accuracy, residual stress release of the plate and repeated positioning errors of the equipment, the end faces of the limbs often have unevenness, burrs or oblique deviations. This causes the weld to have local misalignment, abrupt gap changes or even poor fit after rolling, which induces welding defects such as lack of fusion, porosity, and cracks, reduces the welding qualification rate and increases rework costs.

[0037] Therefore, this application adds a lateral limb reshaping unit consisting of a fixed base 4 and a bending mechanism 5. For example, Figure 4 As shown, the fixed base 4 is fixed to the front end of the cantilever 2, and the bending mechanism 5 is mounted on the fixed base 4. During material preparation, allowance is reserved at the two side limbs of the pipe 7 to be welded. In the pre-welding process, the bending mechanism 5 bends the ends of the two opposite side limbs of the pipe 7 to be welded, reshaping them into bent portions 71 arranged along the axial direction of the pipe 7 to be welded. The inner weld 701 formed by the two bent portions 71 abutting each other is a continuous, uniform, and strictly parallel long strip structure parallel to the axial direction of the pipe 7 to be welded. Its cross-sectional width gradually decreases along the direction away from the center line of the pipe 7 to be welded until it becomes zero, thus forming a semi-closed molten pool opening towards the interior of the pipe 7 to be welded. The uniform structure of this inner weld 701, which is parallel to the axial direction of the pipe 7 to be welded, not only greatly improves the molten pool metal retention capacity and heat conduction symmetry, but also eliminates misalignment and abrupt gap changes, significantly improving welding quality and welding efficiency.

[0038] In some embodiments, the bending mechanism 5 is configured to perform an outward bending, that is, to drive the bending portion 71 to bend outwards towards the outside of the pipe 7 to be welded. This design ensures that the bent portion 71 does not intrude into the effective flow section of the pipe cavity after bending, while making the root profile of the inner weld 701 smoothly transition with the inner wall base material of the pipe 7 to be welded, significantly improving the geometric continuity and hydrodynamic performance of the inner wall, avoiding eddies, stress concentration or blind spots caused by local protrusions, and meeting the application scenarios with stringent requirements for inner wall morphology, such as high-pressure transmission pipes and nuclear power pipes.

[0039] As a preferred embodiment, such as Figure 2 As shown, the bending section 71 includes a forming section 711 and a straight section 712. One end of the forming section 711 is integrally formed on the substrate of the pipe 7 to be welded, and the other end extends outward from the pipe 7. The straight section 712 is integrally formed and continuously disposed at the end of the forming section 711 away from the pipe 7 to be welded. The cross-section of the forming section 711 is arc-shaped, and the cross-section of the straight section 712 is rectangular. The two forming sections 711 enclose an inner weld 701 with an approximately V-shaped cross-section. Its two side walls are continuous arc surfaces, which can significantly increase the contact area and the joint interface length between the molten pool metal and the material of the pipe 7 to be welded, thereby improving the strength of the welded structure. At the same time, the two straight sections 712 are in a tightly fitted state before welding, forming a sealing structure for the inner weld 701, which can effectively prevent molten metal from leaking from the root, splashing, or forming incomplete penetration defects during welding, and greatly improve the stability and controllability of the welding process.

[0040] Furthermore, during the welding process, a special fixture (not shown) can be used. This fixture uses a flexible pressure head to simultaneously clamp the outer surfaces of the two straight sections 712, applying uniform pressure. This rigidly constrains the relative displacement of the two sides during the welding thermal cycle, eliminating weld offset caused by thermal creep and electromagnetic disturbance, and ensuring the accuracy of the weld trajectory and the consistency of the weld width.

[0041] like Figure 2 As shown, to balance structural integrity and appearance quality, the depth of the inner weld 701 is preferably controlled to be no greater than the wall thickness of the pipe 7 to be welded. This depth setting ensures that the bent portion 71 has sufficient structural rigidity to support the welding reaction force, and also ensures that after welding, the portion of the bent portion 71 extending outside the pipe 7 to be welded can be removed by CNC plasma cutting or cold milling equipment, so that the outer wall of the pipe after removal restores its original geometric contour, without steps, depressions, or residual stress concentration, thus meeting the continuity requirements of the outer surface.

[0042] Matching the aforementioned outward-folding bending structure, the bending mechanism 5 includes a mounting base 51, a bending block 52, a connecting frame 53, two extrusion rollers 54, and two gathering rollers 55. For example... Figure 8 — Figure 11As shown, the mounting base 51 is located on the bottom side of the fixed base 4, and the bending block 52 is fixedly located in the middle position on the bottom side of the mounting base 51. The working end of the bending block 52 has a gradually inclined structure (inclination angle α=12°–18°), which is used to apply an initial bending moment to the side limb during the feeding process and induce the initial deformation of the forming section 711.

[0043] The connecting frame 53 is fixedly mounted on the bending block 52 in a semi-enclosed shape. Both extrusion rollers 54 are rotatably mounted on the connecting frame 53 and located on both sides of the rear end of the bending block 52. The periphery of the extrusion rollers 54 faces the bottom area of ​​the deformed side limb. After the side limb completes the initial arc bending, the extrusion rollers 54 apply radial extrusion force to the bottom end of the bent part 71, causing the bottom ends of the two bent parts 71 to fit precisely together, forming a straight section 712.

[0044] like Figure 8 As shown, the top side of the connecting frame 53 and the bottom side of the mounting base 51 abut against the outer wall and inner wall of the pipe, respectively. The bending block 52 passes through the gap between the two sides. The top of the connecting frame 53 is provided with an arc-shaped chamfer on both sides of the bending block 52. This chamfer is used to calibrate the curvature of the forming section 711 so that the two forming sections 711 are symmetrical.

[0045] like Figure 11 As shown, two gathering wheels 55 are symmetrically arranged on both sides of the bending block 52 and are rotatably connected to the connecting frame 53. They can apply a small gathering force to the side limb during the initial bending stage, pre-correct the warping and lateral offset of the side limb, reduce the load on the extrusion wheel 54, extend the wheel life and improve the bending repeatability accuracy.

[0046] like Figure 8 and Figure 10 As shown, each extrusion roller 54 has a spiral protrusion on its circumference, and the spiral directions of the two protrusions are opposite. When the bending mechanism 5 moves axially with the cantilever 2, the protrusion applies a continuous and uniform axial downward pressure to the straight section 712 during the rolling process, which effectively suppresses surface defects such as wrinkles and wavy edges caused by material springback or local instability during the bending process, and ensures the flatness of the straight section 712.

[0047] To enable the bending mechanism 5 to start and stop on demand and decouple it from the process, and to avoid interference with the movement path of the welding torch 3 and the inner wall of the pipe under non-bending conditions, this application implements a structural modular reconstruction of the fixed seat 4 and integrates a brush 6 with a pre-welding cleaning function, forming a compact internal longitudinal seam pretreatment system that integrates "positioning constraint - bending forming - pre-welding cleaning - internal welding execution".

[0048] Specifically, such as Figure 4 — Figure 7 As shown, the fixed base 4 includes a base body 41 and a slider 42; the base body 41 is rigidly fixed to the bottom of the front end of the cantilever 2 by bolts, and a cavity 401 is formed on its bottom side; as shown Figure 5As shown, three functional slots are sequentially arranged on the side wall of the cavity 401: working slot 402, connecting slot 403 and suspended slot 404. The three are arranged continuously from back to front along the axis of the cantilever 2. Among them, the suspended slot 404 is located above the working slot 402, and the two are smoothly connected by the inclined connecting slot 403.

[0049] like Figure 4 As shown, the slider 42 is slidably disposed between the working groove 402, the connecting groove 403 and the suspended groove 404, and is fixedly connected to the mounting base 51 or integrally formed; the brush 6 is a composite structural component that is resistant to high temperature and metal dust abrasion, and is fixedly disposed on the bottom side of the connecting frame 53.

[0050] During the bending preparation and execution phase, after the welding torch 3 extends into the inner cavity of the pipe 7 to be welded from the rear end and completes initial positioning, the control system drives the cantilever 2 forward or drives the pipe 7 to be welded backward, and the front end of the bending block 52 simultaneously contacts the two opposite side limbs; Figure 6 As shown, at this time, the slider 42 is subjected to the reaction force and slides into the working groove 402 along the connecting groove 403, and finally abuts against the rear side wall of the working groove 402 to form a mechanical self-locking rigid clamping; as the cantilever 2 continues to move forward or the pipe 7 to be welded continues to move backward, the bending mechanism 5 bends the two side limbs of the pipe 7 to be welded to form the bent part 71.

[0051] After bending, both the bending mechanism 5 and the welding torch 3 pass through the pipe 7 to be welded and are positioned in front of it. At this point, the control system drives the cantilever 2 to retract in the opposite direction or drives the pipe 7 to advance, as shown below. Figure 7 As shown, the front end of the pipe 7 to be welded pushes the bending mechanism 5, causing the slider 42 connected to the bending mechanism 5 to slide along the connecting groove 403 into the suspended groove 404, thereby separating the bending mechanism 5 from the side limb of the pipe 7 to be welded. The brush 6 is located directly above the inner weld 701. The brush 6 is located behind the welding gun 3. As the cantilever 2 continues to retreat or the pipe 7 to be welded continues to advance, the brush 6 and the welding gun 3 pass through the inner weld 701 in sequence to achieve pre-welding cleaning and welding operations.

[0052] In other embodiments, the bending mechanism 5 is configured to perform an inward bending, that is, driven by the fixed seat 4, the ends of the two opposite limbs are simultaneously subjected to controlled plastic bending into the pipe. This design ensures that the bent portion 71 is embedded inside the pipe 7 to be welded after bending and does not protrude from the outer wall surface of the pipe, thereby maintaining zero geometric abrupt changes in the outer wall while ensuring the integrity of the welded structure. This is suitable for applications requiring seabed laying, pipe towing, or continuous external anti-corrosion coating.

[0053] As a preferred embodiment, such as Figure 3As shown, the bending section 71 consists only of an extension section 713. One end of the extension section 713 is integrally formed with the substrate of the pipe body 7 to be welded and continuously arranged, while the other end extends into the inner cavity of the pipe. The distance between the two extension sections 713 first monotonically decreases to zero along the direction away from the pipe centerline, forming the fusion root of the inner weld 701, and then monotonically increases, forming the pre-set gap channel of the outer weld 702. Thus, an X-shaped double weld structure is simultaneously constructed in a single bending action. The inner weld 701 is located on the inner wall side of the pipe and is used to bear the main weld and internal sealing functions; the outer weld 702 is located on the outer wall side of the pipe and can be directly filled by subsequent external welding processes. This structure is particularly suitable for applications such as marine engineering pipelines and LNG storage and transportation pipelines that require bidirectional pressure bearing, all-position welding, and high fatigue life.

[0054] Furthermore, to enhance the metallurgical bonding quality and interface bearing capacity, it is preferable to make the cross-section of the extension section 713 arc-shaped to increase the contact area and bonding interface length between the molten pool metal and the material of the pipe 7 to be welded, thereby improving the strength of the welded structure.

[0055] The bending mechanism 5, which is adapted to the inward bending structure described above, is specifically reconstructed based on the core modules of the outward bending scheme (mounting base 51, bending block 52, connecting frame 53 and two extrusion wheels 54) (not shown). The bending block 52 has opposite tilting directions at its working ends, and the two extrusion wheels 54 are designed with small specifications. Driven by the fixed base 4, the bending block 52 first induces the side limb to bend inward, and then the extrusion wheels 54 apply radial extrusion force to the middle of the bent side limb to form an arc-shaped extension section 713.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A steel pipe longitudinal seam welding machine, comprising a support frame (1), a cantilever (2) and a welding torch (3); the support frame (1) is used to support the pipe (7) to be welded; the welding torch (3) is fixed on the cantilever (2), and the relative position of the cantilever (2) and the support frame (1) is adjustable so that the welding torch (3) can move inside the pipe (7) to be welded; Its features are: It also includes a fixed seat (4) and a bending mechanism (5). The fixed seat (4) is fixed on the cantilever (2). The bending mechanism (5) is set on the fixed seat (4) and is used to bend the two opposite side limbs of the pipe to be welded (7) to form two bent parts (71). The two bent parts (71) surround to form an inner weld (701). The inner weld (701) is long and the cross-sectional width of the inner weld (701) gradually decreases along the direction away from the center line of the pipe to be welded (7) until it is zero. The fixed base (4) includes a base body (41) and a slider (42); the base body (41) is fixedly mounted on the cantilever (2), and a cavity (401) is opened on its bottom side. A working groove (402), a connecting groove (403) and a suspension groove (404) are opened on the side wall of the cavity (401). The working groove (402), the connecting groove (403) and the suspension groove (404) are arranged sequentially and continuously along the length direction of the cantilever (2), and the suspension groove (404) is located above the working groove (402); the slider (42) is slidably mounted between the working groove (402), the connecting groove (403) and the suspension groove (404), and is fixedly connected to the bending mechanism (5); It also includes a brush (6), which is fixedly disposed on the bottom side of the bending mechanism (5); The bending mechanism (5) includes a mounting base (51), a bending block (52), a connecting frame (53), and two extrusion rollers (54); the mounting base (51) is fixedly mounted on the fixed base (4); the bending block (52) is fixedly mounted on the mounting base (51); the connecting frame (53) is fixedly mounted on the bending block (52); the two extrusion rollers (54) are rotatably mounted on the connecting frame (53) and located at one end of the bending block (52), and the end of the bending block (52) away from the extrusion rollers (54) is inclined.

2. The longitudinal seam welding machine for steel pipes as described in claim 1, characterized in that: The bending section (71) includes a forming section (711) and a straight section (712); one end of the forming section (711) is integrally formed on the pipe to be welded (7), and the other end extends outward from the pipe to be welded (7) and is integrally formed with the straight section (712) and continuously arranged; The two straight segments (712) abut each other.

3. The longitudinal seam welding machine for steel pipes as described in claim 1, characterized in that: The bending portion (71) includes an extension section (713), one end of which is integrally formed on the pipe to be welded (7), and the other end extends into the pipe to be welded (7); The distance between the two extension segments (713) gradually decreases along the direction away from the center line of the pipe to be welded (7) until it becomes zero, and then gradually increases to form the inner weld (701) and the outer weld (702) respectively.

4. A steel pipe internal longitudinal seam welding machine as described in claim 2 or 3, characterized in that: The sidewall of the inner weld (701) is arc-shaped.

5. The longitudinal seam welding machine for steel pipes as described in claim 1, characterized in that: When the welding torch (3) is inserted into the pipe (7) to be welded, the bending mechanism (5) abuts against the pipe (7) to be welded, so that the slider (42) is locked and fixed in the working groove (402); when the welding torch (3) passes through the pipe (7) to be welded and moves in the opposite direction, the bending mechanism (5) abuts against the pipe (7) to be welded, so that the slider (42) moves into the suspended groove (404).

6. The longitudinal seam welding machine for steel pipes as described in claim 1, characterized in that: The bending mechanism (5) also includes two gathering wheels (55), both of which are rotatably mounted on the connecting frame (53) and are positioned opposite each other on both sides of the bending block (52).

7. The longitudinal seam welding machine for steel pipes as described in claim 1, characterized in that: The surface of the extrusion wheel (54) is provided with spiral protrusions.

8. The longitudinal seam welding machine for steel pipes as described in claim 2, characterized in that: The depth of the inner weld (701) is not greater than the wall thickness of the pipe (7) to be welded.

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