A laser welding method suitable for positioning welding of U-rib plate units

Abstract

This invention discloses a laser welding method suitable for tack welding of U-rib plate units, relating to the field of bridge welding technology. The method uses a laser welding machine to perform tack welding on U-rib plate units. The specific steps are as follows: S1: Start the laser welding machine, set the laser welding parameters, and clamp the protective circuit chuck onto the end of the U-rib plate unit's panel; S2: Connect the protective gas cylinder and adjust its operating parameters; adjust the welding torch of the laser welding machine so that the angle between the welding torch plane and the panel of the U-rib plate unit is 27°–33°, and the angle between the laser emitter of the welding torch and the weld extension direction is 40°–50°; S3: Adjust the welding torch so that the welding wire contacts the bevel of the U-rib plate unit. After turning on the welding torch, it moves along the extension direction of the bevel of the U-rib plate unit to form a weld, completing the tack welding. This invention solves the technical problems of poor weld quality, poor welding efficiency, and low penetration depth guarantee rate at the tack weld of U-rib plate units in the prior art.

Description

Technical Field

[0001] This invention relates to the field of bridge welding technology, and in particular to a laser welding method suitable for the positioning welding of U-rib plate units. Background Technology

[0002] Orthotropic steel bridge decks, with their advantages of light weight, high load-bearing capacity, and short construction period, have been widely used in the construction of steel bridges, especially in kilometer-long bridges spanning rivers, seas, and other waterways, where their technological advantages are even more significant. However, due to stress concentration caused by local wheel loads and structural details, orthotropic steel bridge decks are prone to various fatigue cracking problems, among which weld root cracks that easily occur in the welds between the U-ribs and the deck have attracted much attention.

[0003] Traditional U-rib plate unit fabrication uses manual gas-shielded arc welding for tack welding, which has low welding efficiency. Due to the limited skill level of the tack welders, defects such as porosity, slag inclusions, discontinuities, and cracks may occur. If these defects are not checked and removed in time, they can easily lead to cracks sprouting at the root of the U-rib weld when incorporated into the formal weld. Summary of the Invention

[0004] The purpose of this invention is to provide a laser welding method suitable for U-rib plate unit positioning welding, which solves the technical problems of poor weld quality, poor welding efficiency, and low penetration guarantee rate of U-rib plate unit positioning weld in the prior art.

[0005] This application discloses a laser welding method suitable for the positioning welding of U-rib plate units, which uses a laser welding machine to perform positioning welding on the U-rib plate units; The specific steps are as follows: S1: Start the laser welding machine, set the laser welding parameters, clamp the protective circuit clamp to the panel end of the U-rib plate unit, and adjust the welding wire extension length of the welding gun of the laser welding machine to 12-16mm. S2: Connect the protective gas cylinder and adjust the working parameters of the protective gas cylinder; adjust the welding gun of the laser welding machine so that the welding gun is tilted on the U-rib plate unit, the angle between the plane of the welding gun and the panel of the U-rib plate unit is 27° to 33°, and the angle between the laser emitter of the welding gun and the weld extension direction is 40° to 50°. S3: Adjust the welding torch so that the welding wire contacts the bevel of the U-rib plate unit. After turning on the welding torch, move the welding torch along the extension direction of the bevel of the U-rib plate unit to form a weld and complete the positioning welding.

[0006] The welding method of this invention belongs to the field of laser welding and is a semi-automatic continuous filler wire laser welding. Compared with traditional gas shielded arc welding, it has outstanding advantages such as low energy consumption, low noise, minimal smoke and dust, environmental friendliness, minimal post-weld deformation, excellent weld formation, and high welding efficiency. It is suitable for welding U-rib plate units.

[0007] Based on the above technical solution, the embodiments of this application can be further improved as follows: Furthermore, the laser welding parameters in step S1 include: a laser welding peak power of 1600W, a scanning speed of 300mm / s, a scanning width of 5mm, a pulse frequency of 2000Hz, a welding speed of 500-550mm / min, and a welding wire extension of 12-16mm. The beneficial effect of this step is to ensure the quality of the subsequent weld by adjusting the laser welding parameters.

[0008] Furthermore, the welding wire is a solid welding wire or a submerged arc welding wire with a diameter of 1.6 mm.

[0009] Furthermore, the protective gas in step S2 is nitrogen or argon.

[0010] Furthermore, the gas in the protective gas cylinder in step S2 is nitrogen or argon, and the operating parameters of the protective gas cylinder are a gas flow rate of 15-20 L / min or an outlet pressure of 0.3-0.4 MPa. The beneficial effect of this step is that the welding quality can be improved by controlling the flow rate of the protective gas.

[0011] Furthermore, the U-rib plate unit includes a U-rib plate and a panel, the U-rib plate is disposed on the panel, and the bottom of the U-rib plate is provided with a V-shaped bevel.

[0012] Furthermore, the angle between the V-shaped bevel and the upper surface of the panel is 50° to 55°.

[0013] Furthermore, before welding, the bevel surface of the V-shaped groove and the area extending 20-30mm outwards are cleaned.

[0014] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: 1. The positioning welds formed in this application are uniform and aesthetically pleasing, requiring no grinding after welding, and have high welding efficiency.

[0015] 2. The welding method of this application causes minimal deformation, avoiding the wavy bends that may occur in the U-rib after positioning in traditional gas shielded arc welding.

[0016] 3. The laser-guided weld in this application has a small weld leg size, which makes it easy to be remelted by the formal weld, thereby improving the penetration rate of the U-rib at the tack weld.

[0017] 4. The welding method of this application produces almost no smoke or dust during the welding process, has low arc intensity that does not harm the eyes, low welding noise, and is green and environmentally friendly.

[0018] 5. The welding method described in this application is simple to operate and easy for staff to learn quickly. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the layout of a laser welding method for positioning welding of U-rib plate units according to a specific embodiment of the present invention; Figure 2 for Figure 1 A partial schematic diagram; Figure 3 for Figure 2 A schematic diagram of direction AA; The specific labels are as follows: 1-Laser emitter; 2-Welding wire; 3-Welding power source; 4-Wire feeding mechanism; 5-Protective gas cylinder; 6-Fiber optic cable; 7-Protective circuit clamp; 8-U-rib plate unit; 9-Welded seam. Detailed Implementation

[0021] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention. It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0022] In the description of this application, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0023] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] To better understand the above technical solutions, the following will provide a detailed description of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0025] This application discloses the use of a laser welding machine to perform positioning welding on U-rib plate units, with the specific structure as follows: Figure 1-3 As shown. The method of this application for tack welding of U-rib plate units has almost no welding fumes during the welding process, the arc intensity is low and does not hurt the eyes, the welding noise is low and the environmental pollution is small, the deformation after welding is minimal, the appearance is uniform and beautiful, no grinding is required, the welding efficiency is high and the penetration depth of the U-rib tack weld can be effectively guaranteed; at the same time, the environmentally friendly and efficient advantages of the laser focused welding energy generated by this application can gradually replace the traditional gas shielded arc welding for tack welding of U-rib plate units, and can effectively guarantee the penetration depth of the U-rib tack weld.

[0026] Regarding the melting depth ratio, the following is a further explanation: Traditional U-rib tack welding uses gas-shielded welding with a typical weld leg size of 4mm. Limited by the skill level of the tack welders, this often results in the root weld failing to reach the blunt edge. During the final weld, the root pass requires controlled current and voltage parameters (to prevent burn-through). With relatively smaller welding parameters compared to the cover pass, the weld pool in the root pass is unlikely to completely penetrate and remelt the thick tack weld. Consequently, the penetration depth of the U-rib weld at the tack weld rarely meets the 80% U-rib plate thickness requirement, often only achieving 60% to 70%. However, with laser welding, the weld leg size at the U-rib tack weld is only 1.5–2.5mm. This smaller weld leg facilitates melting of the blunt corner. Even if the laser tack weld fails to achieve the final 80% penetration requirement, the smaller weld leg size in the subsequent root pass makes it easier for the weld to remelt, significantly improving the penetration depth guarantee rate of the U-rib at the tack weld.

[0027] Example 1: This application discloses a laser welding method for locating welding of U-rib plate units, which is used to weld U-rib plate units to solve the problems of poor weld quality, poor welding efficiency and low penetration guarantee rate of U-rib locating welds. That is, laser welding machine is used to perform positioning welding on the U-rib plate unit; The specific steps are as follows: S1: Start the laser welding machine and set the laser welding parameters; wherein, the laser welding parameters include: laser welding peak power of 1600W, scanning speed of 300mm / s, scanning width of 5mm, pulse frequency of 2000Hz, and welding speed of 500mm / min; clamp the protective circuit clamp to the panel end of the U-rib plate unit, adjust the welding wire extension length of the welding gun of the laser welding machine to 12mm, wherein the welding wire is a solid welding wire or a submerged arc welding wire; S2: Connect the protective gas cylinder and adjust its operating parameters. The protective gas is nitrogen, and its flow rate is 15 L / min. Adjust the welding torch of the laser welding machine so that it is tilted on the U-rib plate unit, with the angle between the welding torch plane and the panel of the U-rib plate unit being 27°, and the angle between the laser emitter of the welding torch and the weld extension direction being 40°. S3: Adjust the welding torch so that the welding wire contacts the bevel of the U-rib plate unit. After turning on the welding torch, move the welding torch along the extension direction of the bevel of the U-rib plate unit to form a weld and complete the positioning welding. Specifically, at this point, the welding wire extends its head, aligns with the root of the U-rib bevel, and is gently pressed to make it contact the root of the bevel. Then, the welding gun operation button is pressed. After the laser focuses and melts the welding wire and emits white light, the welding gun is pulled back at a uniform speed along the reverse thrust of the continuously fed welding wire. The welding gun must not be swung during the welding process. When stopping each section of tack welding, first apply force to press down the welding wire, then release the welding gun operation button and lift the welding gun.

[0028] The laser positioning weld described in this application has a weld length of 40mm, a positioning weld spacing of 200mm, and a positioning weld leg size of 1.5mm.

[0029] The U-rib plate unit includes a U-rib plate and a panel. The U-rib plate is disposed on the panel, and the bottom of the U-rib plate is provided with a V-shaped bevel, wherein the angle between the V-shaped bevel and the upper surface of the panel is 50°.

[0030] Before welding, the bevel surface of the V-shaped groove and the area extending 20mm outwards are cleaned.

[0031] The welding wire described in this application is a solid welding wire with a diameter of 1.6 mm. The selected solid welding wire model is G49A3C1S6, and its chemical composition by mass percentage is as follows: C=0.06%~0.15%, Si=0.80%~1.15%, Mn=1.40%~1.85%, P≤0.025%, S≤0.025%, Ni≤0.15%, Cr≤0.15%, Mo≤0.15%, V≤0.03%, Cu≤0.50%, and the balance is Fe.

[0032] Example 2: Regarding this embodiment, some parameters from Embodiment 1 are adjusted, and the steps are as follows: S1: Start the laser welding machine and set the laser welding parameters; wherein, the laser welding parameters include: laser welding peak power of 1600W, scanning speed of 300mm / s, scanning width of 5mm, pulse frequency of 2000Hz, and welding speed of 550mm / min; clamp the protective circuit clamp to the panel end of the U-rib plate unit, adjust the welding wire extension length of the welding gun of the laser welding machine to 16mm, wherein the welding wire is a solid welding wire or a submerged arc welding wire; S2: Connect the protective gas cylinder and adjust its operating parameters. The protective gas is argon, and its flow rate is 15 L / min. Adjust the welding torch of the laser welding machine so that it is tilted on the U-rib plate unit, with the angle between the welding torch plane and the panel of the U-rib plate unit being 33°, and the angle between the laser emitter of the welding torch and the weld extension direction being 50°. The protective gas is nitrogen or argon, and its flow rate is 20 L / min. S3: Adjust the welding torch so that the welding wire contacts the bevel of the U-rib plate unit. After turning on the welding torch, move the welding torch along the extension direction of the bevel of the U-rib plate unit to form a weld and complete the positioning welding. Specifically, at this point, the welding wire extends its head, aligns with the root of the U-rib bevel, and is gently pressed to make it contact the root of the bevel. Then, the welding gun operation button is pressed. After the laser focuses and melts the welding wire and emits white light, the welding gun is pulled back at a uniform speed along the reverse thrust of the continuously fed welding wire. The welding gun must not be swung during the welding process. When stopping each section of tack welding, first apply force to press down the welding wire, then release the welding gun operation button and lift the welding gun.

[0033] The laser positioning weld described in this application has a weld length of 60mm, a positioning weld spacing of 400mm, and a positioning weld leg size of 2.5mm.

[0034] The U-rib plate unit includes a U-rib plate and a panel. The U-rib plate is disposed on the panel, and the bottom of the U-rib plate is provided with a V-shaped bevel, wherein the angle between the V-shaped bevel and the upper surface of the panel is 55°.

[0035] Before welding, the bevel surface of the V-shaped groove and the area extending 30mm outwards are cleaned.

[0036] The welding wire is a submerged arc welding wire with a diameter of 1.6 mm. The selected submerged arc welding wire is SU35, and its chemical composition by mass percentage is as follows: C≤0.12%, Si≤0.30%, Mn=1.40%~2.00%, P≤0.025%, S≤0.025%, Ni=0.10%~0.50%, Cr≤0.20%, Cu≤0.35%, with the balance being Fe.

[0037] Example 3: Regarding this embodiment, some parameters from Embodiment 1 are adjusted, and the steps are as follows: S1: Start the laser welding machine and set the laser welding parameters; wherein, the laser welding parameters include: laser welding peak power of 1600W, scanning speed of 300mm / s, scanning width of 5mm, pulse frequency of 2000Hz, and welding speed of 520mm / min; clamp the protective circuit clamp to the panel end of the U-rib plate unit, and adjust the wire extension length of the welding gun of the laser welding machine to 14mm, wherein the welding wire is a solid welding wire or a submerged arc welding wire; regarding the welding speed, this embodiment further explains that when the welding speed is low, it will cause a long dwell time, which will affect the laser lens; when the welding speed is too fast, it may affect the weld formation, thereby affecting the weld quality; S2: Connect the protective gas cylinder and adjust its operating parameters. The protective gas is nitrogen, and its flow rate is 15 L / min or its outlet pressure is 0.3–0.4 MPa. Adjust the welding torch of the laser welding machine so that it is tilted on the U-rib plate unit, with the angle between the welding torch plane and the panel of the U-rib plate unit being 30°, and the angle between the laser emitter of the welding torch and the weld extension direction being 45°. The protective gas is nitrogen or argon, and its flow rate is 18 L / min. S3: Adjust the welding torch so that the welding wire contacts the bevel of the U-rib plate unit. After turning on the welding torch, move the welding torch along the extension direction of the bevel of the U-rib plate unit to form a weld and complete the positioning welding. Specifically, at this point, the welding wire extends its head, aligns with the root of the U-rib bevel, and is gently pressed to make it contact the root of the bevel. Then, the welding gun operation button is pressed. After the laser focuses and melts the welding wire and emits white light, the welding gun is pulled back at a uniform speed along the reverse thrust of the continuously fed welding wire. The welding gun must not be swung during the welding process. When stopping each section of tack welding, first apply force to press down the welding wire, then release the welding gun operation button and lift the welding gun.

[0038] The weld length of the laser positioning weld described in this application is 45mm, the positioning weld spacing is 300mm, and the positioning weld leg size is 2mm.

[0039] The U-rib plate unit includes a U-rib plate and a panel. The U-rib plate is disposed on the panel, and the bottom of the U-rib plate is provided with a V-shaped bevel, wherein the angle between the V-shaped bevel and the upper surface of the panel is 52°.

[0040] Before welding, the bevel surface of the V-shaped groove and the area extending 25mm outwards of the U-rib plate unit are cleaned.

[0041] The welding wire described in this application is a solid welding wire with a diameter of 1.6 mm. The selected solid welding wire model is G49A3C1S6, and its chemical composition by mass percentage is as follows: C=0.06%~0.15%, Si=0.80%~1.15%, Mn=1.40%~1.85%, P≤0.025%, S≤0.025%, Ni≤0.15%, Cr≤0.15%, Mo≤0.15%, V≤0.03%, Cu≤0.50%, and the balance is Fe.

[0042] Taking a U-rib plate unit made of Q345qD material as an example, the U-rib plate thickness is 8mm, the face plate thickness is 16mm; the plate unit width is 2400mm, the length is 5000mm; and the number of U-ribs is 4. The U-rib bevel is a single-sided V-groove. Five products were produced using the method of Example 1, namely A1-A5; five products were produced using the method of Example 2, namely B1-B5; five products were produced using the method of Example 3, namely C1-C5; and three products, D1-D3, were produced using gas shielded arc welding. Experiment 1: Phased array flaw detection: For products A1-A5, B1-B5, and C1-C5, phased array flaw detection was performed on all weld lengths. After flaw detection, a total of 2 welds with a penetration depth of less than 80% were found to fall within the laser tack weld range. The penetration depth qualification rate of the laser tack welds was calculated to be 98.1%, which far exceeds the average penetration depth qualification rate of traditional gas shielded tack welds. For example, the penetration depth qualification rate of the D1-D3 tack welds was only 61.3%.

[0043] For products A1, B1, and C1: Experiment 2: For the lifting and static test, the four-hook lifting method was used for products A1, B1 and C1. The four lifting clamps were clamped at the ends of the two middle U-ribs (so that the locating welds directly bear the lifting force). The specific lifting height was 500mm, and the static time was not less than 2 minutes. After the suspension was completed, the products were slowly placed on the platform. It was observed that there was no cracking at the locating welds of products A1, B1 and C1. Experiment 3: Reverse deformation bending test: After the lifting and static test, products A1, B1, and C1 were placed on the reverse deformation jig for pre-deformation bending. After one bending and unloading, the appearance of all tack welds was inspected. Excluding non-welding operation factors, the weld cracking rate in the reverse deformation bending test was only 1.9%, lower than the average level of 5% for traditional gas shielded arc welding.

[0044] For products A2, B2, and C2: Experiment 4: Fillet weld fracture test: After breaking products A2, B2 and C2, the fracture surface inspection revealed "the presence of pores with a maximum size of 0.78 mm, and no lack of fusion was found", which meets the requirements of section 5.27.5 (fillet weld fracture test (positioning welder)) of AWS D1.5 standard.

[0045] Experiment 5: Tensile strength test: Tensile tests were conducted on products A3-A5, B3-B5, C3-C5, and D1-D3 according to the tensile test method in "Cylindrical Head Studs for Arc Stud Welding" (GB / T 10433-2002). The average tensile strength of products A3-A5, B3-B5, and C3-C5 was 107.08 kN, and the average tensile strength of products D1-D3 was 168.13 kN. Considering the difference in weld leg size between the two welding methods (laser welding weld leg size is smaller), after conversion to equal cross-section, the weld strength of laser welding is approximately 2.5 times that of gas-shielded arc welding (under the same conditions).

[0046] In summary, the embodiments of this application employ laser welding to perform locating welding on the U-rib plate unit. By setting reasonable laser welding process parameters, the obtained locating weld has a uniform and aesthetically pleasing appearance, and the weld strength meets the stress requirements for lifting, pre-pressure, and reverse deformation before the formal weld is welded. Furthermore, the penetration depth qualification rate of the locating weld after the formal weld exceeds 98%, verifying the operability and applicability of the proposed laser locating welding of the U-rib plate unit.

[0047] Numerous specific details are set forth in this specification. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification. In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A laser welding method suitable for positioning welding of U-rib plate units, characterized in that, The U-rib plate unit was positioned and welded using a laser welding machine; The specific steps are as follows: S1: Start the laser welding machine, set the laser welding parameters, clamp the protective circuit clamp to the panel end of the U-rib plate unit, and adjust the welding wire extension length of the welding gun of the laser welding machine to 12-16mm. S2: Connect the protective gas cylinder and adjust the working parameters of the protective gas cylinder; adjust the welding gun of the laser welding machine so that the welding gun is tilted on the U-rib plate unit, the angle between the plane of the welding gun and the panel of the U-rib plate unit is 27° to 33°, and the angle between the laser emitter of the welding gun and the weld extension direction is 40° to 50°. S3: Adjust the welding torch so that the welding wire contacts the bevel of the U-rib plate unit. After turning on the welding torch, move the welding torch along the extension direction of the bevel of the U-rib plate unit to form a weld and complete the positioning welding. The specific content of this step is as follows: At this time, the welding wire extends out of the head, is aligned with the root of the U-rib bevel, and the welding wire is lightly pressed to make it contact the root of the bevel. Then, press the welding torch operation button. After the laser focuses and melts the welding wire and emits white light, pull the welding torch backward at a uniform speed along the reverse thrust of the continuous wire feeding. The welding torch must not be wobbled during the welding process. When stopping each section of positioning welding, first apply force to press down the welding wire, then release the welding torch operation button and lift the welding torch. The weld length of laser tack welding is 40-60mm, the tack welding spacing is 200-400mm, and the tack welding leg size is 1.5-2.5mm. The smaller weld leg makes it easier to melt the blunt corner. Even if the laser tack welding stage fails to achieve the final 80% penetration rate requirement, the subsequent formal root welding stage is easy to remelt by the root weld due to the small size of the laser tack welding leg, which can greatly improve the penetration depth guarantee rate of the U-rib at the tack welding. The U-rib plate unit includes a U-rib plate and a panel, the U-rib plate is disposed on the panel, and the bottom of the U-rib plate is provided with a V-shaped bevel. The angle between the V-shaped bevel and the upper surface of the panel is 50° to 55°. The laser welding parameters in step S1 include: a peak laser welding power of 1600W, a scanning speed of 300mm / s, a scanning width of 5mm, a pulse frequency of 2000Hz, and a welding speed of 500-550mm / min.

2. The laser welding method according to claim 1, characterized in that, The welding wire is a solid welding wire or submerged arc welding wire with a diameter of 1.6 mm.

3. The laser welding method according to claim 1, characterized in that, The gas in the protective gas cylinder in step S2 is nitrogen or argon, and the operating parameters of the protective gas cylinder are a gas flow rate of 15-20 L / min or an outlet pressure of 0.3-0.4 MPa.

4. The laser welding method according to claim 3, characterized in that, Before welding, the bevel surface of the V-shaped groove and the area extending 20-30mm outwards are cleaned.

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