Reinforcing mesh welding method for bridge construction

Abstract

The invention relates to the technical field of welding, in particular to a reinforcing mesh welding method for bridge construction, which comprises the following steps: respectively applying pretension to a plurality of first reinforcing steel bars arranged at set intervals in a first direction, so that the first reinforcing steel bars are kept in a linear state, and two ends of the first reinforcing steel bars are fixed; a plurality of second steel bars in the second direction are placed on the first steel bars one by one to form vertical intersection points; acquiring an actual position of the intersection point in real time through a detection system, and acquiring a gap value between the first reinforcing steel bar and the second reinforcing steel bar in real time at the actual position; based on the deviation value of the actual position and the design position, the welding gun is driven to conduct self-adaptive displacement compensation; and the welding pressure is dynamically adjusted based on the gap value, and welding is completed at the compensated position. According to the reinforcing mesh welding method for bridge construction, by introducing pretension control, real-time detection and self-adaptive compensation mechanisms, the problems of position deviation and gaps caused by bending of reinforcing steel bars at present are solved, and efficient and high-quality reinforcing mesh automatic welding is achieved.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a method for welding steel mesh for bridge construction. Background Technology

[0002] In bridge engineering, steel mesh serves as the core framework of concrete structures, and its welding quality directly affects the structural strength and durability. Traditional on-site steel reinforcement binding methods suffer from high labor costs, low efficiency, and significant material waste. Although promoting prefabricated welded mesh technology can improve laying efficiency, reduce labor costs, and decrease on-site waste, this technology still faces key bottlenecks.

[0003] Specifically, long steel bars naturally bend during transportation and storage, and the actual position of the intersections deviates from the design coordinates during laying, forcing secondary on-site correction and negating the efficiency advantages of factory production. Irregular gaps are formed at the intersections of bent steel bars, and the rate of incomplete welds increases when the gaps are too large in traditional constant pressure welding, requiring manual welding to repair, which increases quality risks and construction delays. Summary of the Invention

[0004] This invention provides a method for welding steel mesh for bridge construction, which can effectively solve the problems pointed out in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: Methods for welding steel mesh for bridge construction include: Pretension is applied to several first steel bars arranged at a set interval in the first direction to keep the first steel bars in a straight line and fix both ends; Several second steel bars arranged at a set interval in the second direction are placed one by one on the first steel bar to form a vertical intersection point; For each of the second reinforcing bars, the actual position of each intersection point is obtained sequentially by the detection system, and the gap value between the first and second reinforcing bars is obtained in real time at the actual position; Based on the deviation between the actual position and the design position, the welding torch performs adaptive displacement compensation during the continuous welding of each intersection point. Welding pressure is dynamically adjusted based on the gap value, and welding is completed at the compensated position.

[0006] Furthermore, the actual positions of each intersection point are sequentially obtained through the detection system, including: Images of the intersection area are acquired using a visual sensor, and the coordinates of the center point of the overlapping area between the first and second reinforcing bars are determined based on an image recognition algorithm, which serves as the actual location of the intersection.

[0007] Furthermore, the gap value between the first and second reinforcing bars is acquired in real time at the actual location, including: A laser beam is emitted vertically above the coordinates of the center point to obtain distance measurement data from the laser beam to the surface of the second reinforcing bar. The gap value is calculated based on the ranging data.

[0008] Furthermore, when the gap value is greater than a set threshold, the following is executed: After adjusting the position of the second reinforcing bar, the gap value was re-tested; If the gap value is less than or equal to the set threshold, welding is performed. If the gap value is still greater than the set threshold after N consecutive adjustments, then the second steel bar is replaced, where N≥3.

[0009] Furthermore, during the repeated welding of the same type of steel mesh, the probability value of the gap value exceeding the set threshold at each intersection point on each of the second steel bars is continuously counted. For each of the second reinforcing bars, the welding positions are sorted from low to high according to the probability value.

[0010] Further, adjusting the position of the second reinforcing bar includes: A vibrator is installed at the fixed end of the first reinforcing bar; The vibrator is controlled to drive the first steel bar to vibrate at a frequency of 20 to 50 Hz. Vibration is transmitted through the contact between the first and second reinforcing bars, causing the second reinforcing bar to shift in the direction of gravity.

[0011] Further, obtaining the actual positions of each intersection point includes: Identify the four corner points of the overlapping area between two steel bars in the image; Connect two pairs of diagonal points to obtain two straight lines; The intersection of the two straight lines is taken as the coordinate of the center point of the overlapping area between the first and second reinforcing bars.

[0012] Furthermore, the welding includes: At the actual location of the intersection, a preload is applied to the overlapping first and second reinforcing bars using the dual electrode head of a resistance welding machine. The preload is adjusted according to the gap value. While maintaining the pre-pressure state, the first current is applied, and the dynamic value of the contact resistance and the fluctuation value of the electrode pressure are monitored in real time. When the dynamic value of the contact resistance is less than the first threshold and the absolute value of the electrode pressure fluctuation value is less than the second threshold, the first stage is completed and the second stage is entered. Switch to a second current higher than the first current, and simultaneously monitor the dynamic resistance attenuation slope. When the dynamic resistance attenuation slope is less than a third threshold, stop the power supply to complete the welding.

[0013] Furthermore, the first current is 40% to 60% of the rated current of the resistance welding machine, and the second current is 70% to 90% of the rated current of the resistance welding machine.

[0014] Furthermore, the rate of decrease of the dynamic value of the contact resistance in the first stage is recorded. If the rate of decrease is less than the fourth threshold, the corresponding solder joint is marked as a potential dummy solder joint.

[0015] The technical solution of this invention can achieve the following technical effects: In this invention, pretension is applied to the first reinforcing bar and both ends are fixed to force it to maintain a straight state, effectively overcoming the natural bending of long reinforcing bars during transportation and storage. The second reinforcing bars are placed and welded one by one. A detection system obtains the actual position and gap value of the intersection points in real time. Based on the deviation value, the welding torch is driven to adaptively compensate for displacement, achieving precise alignment of the intersection points without manual measurement or correction, ensuring the geometric accuracy of the reinforcing mesh. Simultaneously, the welding pressure is dynamically adjusted based on the gap value, solving the welding defects caused by the gap at the intersection of bent reinforcing bars, reducing the rate of incomplete welds, and avoiding the need for manual repair welding.

[0016] The steel mesh welding method for bridge construction of the present invention solves the problems of position deviation and gap caused by steel bar bending by introducing pretension control, real-time detection and adaptive compensation mechanism, and realizes efficient and high-quality automated welding of steel mesh. Attached Figure Description

[0017] 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 recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart of the steel mesh welding method for bridge construction; Figure 2 This is a schematic diagram showing the distribution of the first and second reinforcing bars; Figure 3 This is a plan view of the reinforcing mesh; Figure 4 A schematic diagram showing the offset of the four corner points of the overlapping area of ​​the two reinforcing bars; Figure 5 This is a flowchart of the welding process; Figure label: 1. First reinforcing bar; 2. Second reinforcing bar; 3. Fixed area; 4. Center point. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Welding methods for steel mesh used in bridge construction, such as Figure 1 and 2 As shown, it includes: S1: Apply pretension to several first reinforcing bars 1 arranged at a set interval in the first direction to keep the first reinforcing bars 1 in a straight line and fix both ends, such as Figure 2 As shown, a fixed area 3 is formed at the end; in this embodiment, the pretension must be guaranteed not to exceed 60% of the yield strength of the first steel bar 1 to avoid plastic deformation, and at the same time ensure that the first steel bar 1 sags less than or equal to 20mm under a span of 20m. S2: Place one by one the second steel bars 2 arranged at a set interval in the second direction on the first steel bar 1 to form a vertical intersection point; wherein, the set interval in steps S1 and S2 can be the same, or different interval values ​​can be selected as needed; S3: For each second reinforcing bar 2, the actual position of each intersection point is obtained sequentially through the detection system, and the gap value between the first reinforcing bar 1 and the second reinforcing bar 2 is obtained in real time at the actual position; S4: Based on the deviation between the actual position and the design position, the welding torch performs adaptive displacement compensation during the continuous welding of each intersection point. S5: Based on the gap value, the welding pressure is dynamically adjusted to complete the welding at the compensated position, thereby achieving precise welding of each second steel bar 2.

[0021] In this invention, pretension is applied to the first reinforcing bar 1 and both ends are fixed to force it to maintain a straight state, effectively overcoming the natural bending of long reinforcing bars during transportation and storage. The second reinforcing bars 2 are placed and welded one by one, reducing equipment complexity. The actual position and gap value of the intersection are obtained in real time through the detection system. Based on the deviation value, the welding torch can be driven to adaptively compensate for displacement, achieving precise alignment of the intersection point without manual measurement or correction, ensuring the geometric accuracy of the reinforcing mesh. At the same time, the welding pressure is dynamically adjusted based on the gap value, solving the welding defects caused by the gap at the intersection of bent reinforcing bars, reducing the rate of false welds and avoiding the need for manual repair welding.

[0022] The steel mesh welding method for bridge construction of the present invention solves the problems of position deviation and gap caused by steel bar bending by introducing pretension control, real-time detection and adaptive compensation mechanism, and realizes efficient and high-quality automated welding of steel mesh.

[0023] As a preferred embodiment of the above, the actual positions of each intersection point are obtained sequentially by the detection system, such as... Figure 3 As shown, it includes: acquiring images of the intersection area through a visual sensor, and determining the coordinates of the center point 4 of the overlapping area of ​​the first reinforcing bar 1 and the second reinforcing bar 2 based on an image recognition algorithm, as the actual location of the intersection.

[0024] In bridge steel mesh welding scenarios, industrial-grade CCD or CMOS cameras are preferred for vision sensors, with a resolution of 2 megapixels or higher. To achieve better image acquisition, a ring-shaped LED light source can be added around the overlapping area during implementation to overcome image noise caused by ambient light interference and steel surface defects to a certain extent.

[0025] In this preferred embodiment, the image recognition algorithm includes, but is not limited to, existing technologies such as edge detection and feature point matching, to accurately locate the geometric center coordinates of the overlapping area of ​​the two steel bars, thereby achieving non-contact measurement of the actual location of the intersection. As a preferred embodiment of the above, the gap value between the first reinforcing bar 1 and the second reinforcing bar 2 is obtained in real time at the actual location, including: vertically emitting a laser beam directly above the coordinates of the center point 4, obtaining distance measurement data from the laser beam to the surface of the second reinforcing bar 2; and calculating the gap value based on the distance measurement data.

[0026] During implementation, the first and second reinforcing bars 1 and 2, which are intersecting and bonded, will make point contact. In this preferred embodiment, the laser reflection point on the surface of the second reinforcing bar 2 is considered to be directly above the point contact position. Based on the fixed and height-data-readable first reinforcing bar 1, when there is no gap between the first reinforcing bar 1 and the second reinforcing bar 2, the ranging data will indirectly reflect that the vertical distance between the laser reflection point and the point contact position on the second reinforcing bar 2 is the diameter of the second reinforcing bar 2; when the ranging data indirectly reflects that the distance between the laser reflection point and the point contact position on the second reinforcing bar 2 is greater than the diameter of the second reinforcing bar 2, the gap value can be obtained by calculating the difference between the laser reflection point and the diameter of the second reinforcing bar 2.

[0027] By determining the relatively accurate coordinates of the center point 4 based on the actual posture of the second reinforcing bar 2, and the corresponding gap value, a relatively accurate data reference can be provided for the welding pressure. This is crucial and beneficial for real-time parameter adjustment during the automatic welding process. Of course, during implementation, if the coordinates of the center point 4 deviate too much from the set coordinates, a warning alarm can be triggered. In this embodiment, all welding is performed on the premise that the position of the center point 4 coordinates is controllable.

[0028] As a preferred embodiment of the above, when the gap value is greater than a set threshold, the following is executed: After adjusting the position of the second reinforcing bar 2, the gap value was re-tested; If the gap value is less than or equal to the set threshold, then welding is performed; If the gap value is still greater than the set threshold after N consecutive adjustments, then replace the second steel bar 2, where N≥3.

[0029] In this embodiment, the welding of the second reinforcing bar 2 is performed after all gap values ​​meet the requirements. If any gap value still fails to meet the requirements after adjustment, the second reinforcing bar 2 must be replaced. In this preferred embodiment, random errors can be eliminated by implementing position adjustment; by reasonably determining the N value, systematic defects, such as reinforcing bar bending, can be identified. In this case, replacing the second reinforcing bar 2 can prevent defective products from flowing into the next process.

[0030] As a preferred embodiment, the threshold value corresponding to the gap value can be specifically set to 0.5 to 1.2 mm, and more preferably, it can be set to 0.7 to 0.9 mm.

[0031] As a preferred embodiment of the above, during the repeated welding of the same type of steel mesh, the probability value of the gap value exceeding the set threshold at each intersection of each second steel bar 2 is continuously counted; for the welding of each second steel bar 2, all welding positions are sorted according to the probability value from low to high.

[0032] In this preferred scheme, intelligent sorting of welding positions for individual rebars and optimization of the welding execution sequence using historical out-of-tolerance probability data can improve the welding efficiency and quality stability of individual rebars. Specifically, for multiple welding positions on a single second rebar 2, prioritizing the welding of low-probability points with high structural stability establishes rigid support anchor points, dividing the long rebar into multiple short spans. When welding high-probability points subsequently, local thermal deformation is confined to a small range between adjacent anchor points, preventing continuous transmission and superposition along the length direction, thereby reducing the overall deformation. Simultaneously, the compressive residual stress generated by the cooling and shrinkage of the first welded points can partially offset the initial gap of the high-probability points, forming a mechanical pre-compensation effect.

[0033] As a preferred embodiment of the above, adjusting the position of the second reinforcing bar 2 includes: A vibrator is installed at the fixed end of the first reinforcing bar 1; The vibrator is controlled to drive the first steel bar 1 to vibrate at a frequency of 20 to 50 Hz. Vibration is transmitted through the contact between the first reinforcing bar 1 and the second reinforcing bar 2, causing the second reinforcing bar 2 to be displaced in the direction of gravity.

[0034] In this preferred embodiment, each first reinforcing bar 1 in each steel mesh can be fixed by the same fixed structure, allowing the vibration energy of the vibrator to be transmitted to each first reinforcing bar 1 through the fixed structure. The vibration energy is directionally transmitted through the point contact position, driving the second reinforcing bar 2 to produce a pure translational micro-displacement in the direction of gravity. The amplitude can be specifically controlled to be below 0.5mm, enabling the second reinforcing bar 2 to accurately settle into place without external prying. At the same time, the first reinforcing bar 1 maintains its original position due to the fixed end constraint and high rigidity characteristics, achieving gap closure without disturbing the calibrated coordinate reference. The frictional force at the contact point forms displacement isolation, effectively suppressing the transmission of lateral displacement and ensuring the stability of the second reinforcing bar 2 after position adjustment.

[0035] As a preferred embodiment of the above, such as Figure 4 As shown, the actual positions of each intersection point are obtained, including: Identify the four corner points of the overlapping area between two steel bars in the image, i.e. Figure 4 Points A, B, C, and D shown in the diagram, Connect two pairs of diagonal points to obtain two straight lines, namely line AD and line BC in the figure; The intersection of the two straight lines is taken as the coordinate of the center point of the overlapping area of ​​the first reinforcing bar 1 and the second reinforcing bar 2, that is... Figure 4 Point M shown is the actual location of the intersection.

[0036] In actual production, the deformation of the second reinforcing bar 2 at any welding point is often manifested as a slight shift in position in the image, as shown in the figure, shifting from points A, B, C, D to points A', B', C', D'. By actually obtaining the four points after the shift and correspondingly obtaining the straight lines A'D' and B'C', the actual position point M' of the intersection after deformation can be obtained.

[0037] In this preferred scheme, four deformation-sensitive corner points in the overlapping area of ​​the reinforcing bars are identified, and two virtual reference lines are constructed by connecting the diagonals. The intersection point M is used as the coordinate of the actual intersection point after deformation compensation. When the second reinforcing bar 2 experiences local displacement, the intersection point M' based on the new diagonals can accurately represent the true intersection position, ensuring that the subsequent laser gap measurement reference point always coincides with the mechanical contact point. This eliminates the positioning error caused by reinforcing bar deformation at its source and guarantees the required welding positioning accuracy.

[0038] As a preferred embodiment of the above, such as Figure 5 As shown, welding includes: A1: At the actual location of the intersection, a preload is applied to the overlapping first steel bar 1 and second steel bar 2 by the dual electrode head of the resistance welding machine. The preload is adjusted according to the gap value. A2: While maintaining the pre-pressure state, the first current is applied, and the dynamic value of the contact resistance and the fluctuation value of the electrode pressure are monitored in real time. When the dynamic value of the contact resistance is less than the first threshold and the absolute value of the electrode pressure fluctuation value is less than the second threshold, the first stage is completed and the second stage is entered. A3: Switch to a second current higher than the first current, and simultaneously monitor the dynamic resistance attenuation slope. When the dynamic resistance attenuation slope is less than the third threshold, stop the power supply to complete the welding.

[0039] During implementation, the resistance welding machine applies axial pressure synchronously through the upper and lower electrode heads. Specifically, the pressure range can be adjusted between 3kN and 6kN according to the gap value. When energized, the current forms a closed loop through the two electrodes, generating Joule heat in the overlapping area of ​​the reinforcing bars to achieve local fusion connection.

[0040] In the first stage, the preferred first current is 40% to 60% of the rated current, such as a current range of 8kA to 12kA. This stage prioritizes breaking down the oxide layer and microscopic protrusions on the surface of the reinforcing steel. Microscopic fusion at the interface is achieved through a moderate current combined with pre-pressure. Too low a current will lead to discontinuous initial weld nuggets, while too high a current will cause premature spattering. Appropriate selection of the first current ensures stable initial weld nugget formation. In this stage, the dynamic value of the contact resistance characterizes the metallurgical reaction process at the welding interface. Specifically, the resistance is high initially due to the oxide layer and microscopic unevenness on the surface of the reinforcing steel. As the microscopic protrusions melt and spread under the pre-pressure, the effective contact area increases, and the resistance dynamically decreases. When it drops to the first threshold (preferably 80μΩ in this embodiment), it indicates that a continuous liquid metal layer has formed at the interface, and the foundation for stable weld nugget formation is ready. The electrode pressure fluctuation value reflects the mechanical stability of the melt nucleus growth process. Specifically, under ideal conditions, the electrode pressure should remain constant. When the absolute value of the fluctuation exceeds the second threshold, which is preferably 150N in this embodiment, it indicates an abnormality. Negative fluctuations indicate that the melt nucleus may shrink due to local collapse, while positive fluctuations indicate the risk of splashing. Controlling the fluctuation within the threshold can prevent the generation of structural defects.

[0041] In the second stage, the preferred second current is 70% to 90% of the rated current, such as a current range of 14kA to 18kA. In this stage, based on the already formed stable weld nugget, a high current is used to achieve depth expansion of the weld nugget. If the current is too low, the weld depth will be insufficient; if it is too high, excessive heat accumulation will lead to grain coarsening. In this stage, the dynamic resistance decay slope indicates the saturation state of the weld nugget depth. Specifically, the high current in the second stage causes the weld nugget to grow centripetally, and the resistance decreases slowly due to heat diffusion. When the weld depth reaches a certain level, the resistance change approaches stagnation, indicating that the penetration is complete. At this point, disconnecting the power can prevent overheating and grain coarsening, ensuring the toughness of the weld joint. In this embodiment, the third threshold is preferably 0.5μΩ / ms.

[0042] As a preferred embodiment of the above, the rate of decrease of the dynamic value of the contact resistance in the first stage is recorded. If the rate of decrease is less than a fourth threshold, the solder joint is marked as a potential cold solder joint. In this preferred embodiment, a two-level quality evaluation system is constructed by real-time monitoring of the dynamic rate characteristics of the welding process. Specifically, when the rate of decrease of the dynamic value of the contact resistance in the first stage is less than the fourth threshold (preferably 1.8 to 2.5 μΩ / ms in this embodiment), it indicates that the interface weld nugget expansion is slow, which may be caused by oil or excessive oxide layer. This situation should be marked as a cold solder joint risk point.

[0043] As a preferred embodiment of the above, the dynamic value of contact resistance can be acquired in real time by a separate four-wire probe installed on the electrode arm. The separate probe uses the electrode arm as a current conduction path to directly acquire voltage signals in the near field of the weld joint, such as within 10mm. The acquisition of electrode pressure fluctuation values ​​can be achieved by an industrial-grade strain sensor built into the pressure cylinder of the welding machine. The strain sensor is directly integrated into the piston rod of the pressure cylinder to analyze axial pressure fluctuations in real time.

[0044] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for welding reinforcing mesh for bridge construction, characterized in that, include: Pretension is applied to several first steel bars arranged at a set interval in the first direction to keep the first steel bars in a straight line and fix both ends; Several second steel bars arranged at a set interval in the second direction are placed one by one on the first steel bar to form a vertical intersection point; For each of the second reinforcing bars, the actual position of each intersection point is obtained sequentially by the detection system, and the gap value between the first and second reinforcing bars is obtained in real time at the actual position. Based on the deviation between the actual position and the design position, the welding torch performs adaptive displacement compensation during the continuous welding of each intersection point. The welding pressure is dynamically adjusted based on the gap value, and welding is completed at the compensated position.

2. The method for welding steel mesh for bridge construction according to claim 1, characterized in that, The actual positions of each intersection point are obtained sequentially by the detection system, including: Images of the intersection area are acquired using a visual sensor, and the coordinates of the center point of the overlapping area between the first and second reinforcing bars are determined based on an image recognition algorithm, which serves as the actual location of the intersection.

3. The method for welding steel mesh for bridge construction according to claim 2, characterized in that, The gap value between the first and second reinforcing bars is acquired in real time at the actual location, including: A laser beam is emitted vertically above the coordinates of the center point to obtain distance measurement data from the laser beam to the surface of the second reinforcing bar. The gap value is calculated based on the ranging data.

4. The method for welding steel mesh for bridge construction according to claim 3, characterized in that, When the gap value is greater than the set threshold, the following is executed: After adjusting the position of the second reinforcing bar, the gap value was re-tested; If the gap value is less than or equal to the set threshold, welding is performed. If the gap value is still greater than the set threshold after N consecutive adjustments, then the second steel bar is replaced, where N≥3.

5. The method for welding steel mesh for bridge construction according to claim 4, characterized in that, During the repeated welding of the same type of steel mesh, the probability value of the gap value exceeding the set threshold at each intersection point on each of the second steel bars is continuously counted. For each of the second reinforcing bars, the welding positions are sorted from low to high according to the probability value.

6. The method for welding steel mesh for bridge construction according to claim 4, characterized in that, Adjusting the position of the second reinforcing bar includes: A vibrator is installed at the fixed end of the first reinforcing bar; The vibrator is controlled to drive the first steel bar to vibrate at a frequency of 20 to 50 Hz. Vibration is transmitted through the contact between the first and second reinforcing bars, causing the second reinforcing bar to shift in the direction of gravity.

7. The method for welding steel mesh for bridge construction according to claim 2, characterized in that, Obtaining the actual position of each intersection point includes: Identify the four corner points of the overlapping area between two steel bars in the image; Connect two pairs of diagonal points to obtain two straight lines; The intersection of the two straight lines is taken as the coordinate of the center point of the overlapping area between the first and second reinforcing bars.

8. The method for welding steel mesh for bridge construction according to claim 1, characterized in that, The welding includes: At the actual location of the intersection, a preload is applied to the overlapping first and second reinforcing bars using the dual electrode head of a resistance welding machine. The preload is adjusted according to the gap value. While maintaining the pre-pressure state, the first current is applied, and the dynamic value of the contact resistance and the fluctuation value of the electrode pressure are monitored in real time. When the dynamic value of the contact resistance is less than the first threshold and the absolute value of the electrode pressure fluctuation value is less than the second threshold, the first stage is completed and the second stage is entered. Switch to a second current higher than the first current, and simultaneously monitor the dynamic resistance attenuation slope. When the dynamic resistance attenuation slope is less than a third threshold, stop the power supply to complete the welding.

9. The method for welding steel mesh for bridge construction according to claim 8, characterized in that, The first current is 40% to 60% of the rated current of the resistance welding machine, and the second current is 70% to 90% of the rated current of the resistance welding machine.

10. The method for welding steel mesh for bridge construction according to claim 8, characterized in that, Record the rate of decrease of the dynamic value of the contact resistance in the first stage. If the rate of decrease is less than the fourth threshold, mark the corresponding solder joint as a potential dummy solder joint.

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