An electromagnetic sensor, method and system for weld tracking of a spiral welded pipe

Abstract

This invention discloses an electromagnetic sensor, method, and system for tracking the weld seam of spiral welded pipes, belonging to the field of spiral welded pipe processing technology. The electromagnetic sensor of this invention uses an integrally molded E-type magnetic core, with a primary coil wound around the central magnetic post and two secondary coils symmetrically arranged on both sides. During weld seam tracking, a low-frequency alternating current is passed through the primary coil to generate alternating magnetic flux. The weld seam divides the magnetic flux, and the direction and amount of welding torch deflection can be determined based on the voltage difference and phase. The system consists of an electromagnetic sensor, a microcontroller, and a welding torch motion control system, enabling real-time correction of the welding torch position. This invention features a simple structure, excellent magnetic circuit performance, high anti-interference capability, and high sensitivity, effectively solving the problem of tracking failure of traditional arc and laser sensors under narrow bevel and strong reflective conditions. It is suitable for submerged arc welding of spiral welded pipes, significantly improving tracking accuracy and operational stability.

Description

Technical Field

[0001] This invention belongs to the field of spiral welded pipe processing technology, and in particular relates to an electromagnetic sensor, method and system for tracking the weld seam of spiral welded pipes. Background Technology

[0002] Pipeline transportation, as a modern and specialized method of material transport, has become an indispensable and important component of energy and material transportation systems due to its outstanding advantages such as low cost, small footprint, high efficiency, low pollution, and safety and reliability. Especially against the backdrop of continuous economic development and the ongoing advancement of industrialization and urbanization, the demand for critical materials such as oil, natural gas, and water resources continues to grow, and pipeline transportation is playing an increasingly crucial role, providing vital guarantees for long-distance, large-scale, continuous, and stable material transportation. In this process, spiral welded pipes, due to their advantages such as large diameter, strong pressure-bearing capacity, flexible production, and good economic efficiency, have become the preferred pipe material for long-distance pipeline construction. They not only meet the demands of high-pressure, high-flow transportation but also exhibit excellent adaptability and durability under complex environmental conditions, and are widely used in oil and gas transportation, water conservancy projects, and urban pipe networks.

[0003] The significance of spiral welded pipes lies not only in their inherent performance but also in the continuous advancements in their manufacturing processes and the constant improvement in quality control. Automated welding is a crucial step, as automated welding technology significantly improves weld quality and consistency, ensuring the overall strength and sealing of the pipe body. The core of automated welding relies on the development and application of high-precision tracking sensors. These sensors can monitor and correct the welding path in real time, ensuring the stability and accuracy of the process, thereby comprehensively improving the safety and service life of the pipeline system. Therefore, promoting the development of welding automation and intelligent sensing technologies is of paramount importance for achieving high-quality development in pipeline transportation.

[0004] The manufacturing process of spiral welded pipes typically includes core steps such as plate coiling, internal and external submerged arc welding, and post-weld treatment. Among these, the internal and external submerged arc welding process is particularly crucial, as it determines the quality and service life of the steel pipe; its importance is self-evident. The application of automated submerged arc welding technology enables high-precision and high-efficiency operation during the welding process. Compared to traditional manual welding, automated submerged arc welding ensures the uniformity and consistency of the weld, which is essential for ensuring the strength and durability of the weld. Furthermore, the introduction of automated submerged arc welding significantly improves the level of automation in the production process. This not only shortens the production cycle but also reduces labor costs and operational risks. By optimizing welding parameters and monitoring the welding status in real time, automated submerged arc welding can effectively prevent welding defects, thereby improving the overall quality of the final product. Therefore, automated submerged arc welding plays a key role in the manufacturing of spiral welded pipes and is an important technological means to improve product quality and production efficiency.

[0005] To automate and intelligentize the submerged arc welding process of spiral welded pipes, the first step is to solve the problem of automatic weld seam tracking, and the core of tracking control lies in sensor technology. Currently, weld seam tracking sensors mainly fall into two categories: laser vision sensors and arc sensors. Arc sensors operate on the principle of real-time monitoring of the arc discharge process. When an arc forms during welding, it generates specific current and voltage fluctuations and releases a large amount of light and heat. By sensing these changes in current and voltage, arc sensors can acquire characteristic signals of the arc. These signals reflect the state of the weld seam during welding, including information such as weld seam position, width, and depth. The sensor transmits these signals to the control system, which adjusts the position and parameters of the welding equipment based on real-time data to ensure that the welding head and weld seam remain optimally aligned. In contrast, laser vision sensors utilize laser beams for measurement and imaging, enabling high-precision acquisition of the three-dimensional shape and position of objects. Their basic working principle is to emit a laser beam and calculate the distance between the object and the sensor by receiving the reflected laser signal. This type of sensor can monitor the shape and position of the weld seam in real time during welding, ensuring that the welding head remains aligned with the weld seam, thereby improving welding quality and consistency.

[0006] However, both of these sensors have certain limitations in the application of submerged arc welding of spiral welded pipes.

[0007] Arc sensors require arc oscillation or rotation to extract deviation signals during tracking. However, submerged arc welding of spiral welded pipes prevents the welding torch from oscillating or rotating. Furthermore, submerged arc welding uses variable-speed wire feeding and employs thicker welding wire; slight changes in arc length result in insignificant current changes, limiting the arc sensor's ability to extract deviation signals and thus restricting its application. Laser vision sensors, on the other hand, utilize laser beams to detect changes in the shape characteristics of the weldment surface. They offer advantages such as high sensitivity and measurement accuracy, strong resistance to electromagnetic interference, and non-contact operation. However, when laser vision automatic tracking systems encounter steel pipes formed from thin spiral steel plates, the extremely narrow I-shaped bevel (without beveling) causes the system to fail to accurately locate weld feature points, resulting in unsatisfactory tracking. Moreover, extremely bright workpiece bevel surfaces saturate almost all pixels on the CCD camera, hindering image processing and causing automatic tracking failure in the left-right direction. Summary of the Invention

[0008] The problem to be solved by the present invention is to provide an electromagnetic sensor, method and system for tracking weld seams of spiral welded pipes that avoids the generation of eddy currents in the magnetic core and effectively improves the accuracy and reliability of weld seam tracking.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an electromagnetic sensor for tracking the weld seam of a spiral welded pipe, comprising a coil and an E-type magnetic core, wherein the E-type magnetic core is an integrally formed structure; the coil comprises a primary coil and two secondary coils, wherein the primary coil is wound on the middle magnetic post of the E-type magnetic core, and the secondary coils are symmetrically wound on the two side magnetic posts of the E-type magnetic core.

[0010] Furthermore, the material of the E-type magnetic core is soft iron, which can improve the reliability of the sensing data.

[0011] Furthermore, both the primary coil and the secondary coil are wound with enameled wire, and the diameter of the enameled wire of the primary coil is larger than the diameter of the enameled wire of the secondary coil.

[0012] The present invention also provides a method for tracking the weld seam of a spiral welded pipe, comprising the following steps: S1. The electromagnetic sensor is installed in front of the submerged arc welding torch, with its center aligned with the center of the weld seam of the workpiece to be welded. S2. Apply a low-frequency alternating excitation current to the primary coil of the electromagnetic sensor, generating an alternating magnetic flux in the magnetic circuit formed by the E-type magnetic core, the workpiece to be welded, and the air. F Based on the boundary conditions of the magnetic field, it can be known that the weld seam of the workpiece to be welded will... F Divided into two parts, left and right magnetic flux, when the left and right magnetic fluxes change continuously, an induced electromotive force is generated in the closed circuit of the two secondary coils: ; In the formula, e To induce electromotive force. N s The number of turns of the secondary coil. F For magnetic flux, m r The relative permeability of the material. m 0 The permeability of free space, l Let A be the length of the magnetic circuit and A be the cross-sectional area of ​​the magnetic circuit. S3. When the electromagnetic sensor is aligned with the weld center of the workpiece to be welded, the main magnetic flux on the middle magnetic column of the E-type magnetic core is equally distributed on both magnetic columns. Since the E-type magnetic core has a symmetrical structure, the magnetic circuit remains symmetrical after passing through the weld. Therefore, the induced electromotive force measured in the left and right secondary coils is the same. U 左 = U 右 ; S4. When the electromagnetic sensor deviates from the center of the weld, the magnetic flux distribution on the left and right sides is unequal. The weld will cause the magnetic flux in one side of the magnetic circuit to increase and the magnetic flux in the other side to decrease. Therefore, the difference in the induced electromotive force measured in the left and right coils will not be zero.U 左 ≠ U 右 When the electromagnetic sensor deviates from the center of the weld to the left, that is... U 左 > U 右 Conversely, if the electromagnetic sensor deviates from the center to the right, that is... U 左 < U 右 ; S4. When the electromagnetic sensor moves relative to the workpiece to be welded. At that time, the magnetic flux in the left and right magnetic circuits changes differentially, and the difference is proportional to the displacement. Therefore, the output voltage of the electromagnetic sensor is also proportional to the displacement. Its phase corresponds to two opposite displacement directions, and the phase difference is... The direction and distance of the welding torch deviating from the weld seam are determined based on the output voltage of the electromagnetic sensor.

[0013] This invention also provides a system for tracking the weld seam of spiral welded pipes, including an electromagnetic sensor, a microcontroller, and a welding torch motion control system. The output terminal of the electromagnetic sensor is connected to the input terminal of a differential amplifier circuit to amplify the original signal to a reasonable factor. The differential amplifier circuit outputs the amplified signal to the A / D module of the microcontroller, which converts the analog signal into a digital signal. The microcontroller's signal processing algorithm calculates the positional deviation between the welding torch and the weld seam. The deviation information is sent to the welding torch motion control system via an Ethernet interface to achieve real-time adjustment of the welding torch position.

[0014] Furthermore, the welding torch motion control system includes a motion controller and a servo drive unit. The motion controller receives deviation information sent by the microprocessor, outputs control signals according to a preset control strategy, drives the servo motor to adjust the position of the welding torch, eliminates deviation, and realizes automatic tracking of the weld seam.

[0015] This invention relates to a sensor designed for automatic submerged arc welding of spiral welded pipes at the submerged arc welding station of a spiral welded pipe production unit. Its advantages are as follows: (1) Strong anti-interference ability and adaptable to complex working conditions: The electromagnetic sensor of the present invention is based on the principle of electromagnetic induction. Its performance is almost unaffected by welding current, arc spatter, workpiece surface scratches or oxide layer. In particular, it can effectively overcome the problem that laser vision sensors cannot identify welds under extremely narrow bevels, no bevels or strong reflective conditions.

[0016] (2) Simple structure and high reliability: The E-type magnetic core and the three sets of coils form a complete closed magnetic circuit with no moving parts, which avoids the problem of magnetic core heating and performance drift caused by eddy current effect in the eddy current sensor, and improves the stability and reliability of long-term operation.

[0017] (3) High sensitivity and good linear response: The output signal of the electromagnetic sensor has an approximately linear relationship with the lateral offset distance, which facilitates the real-time response of the signal processing and control system, and improves the tracking accuracy and dynamic performance.

[0018] (4) Easy to manufacture and integrate: The E-type magnetic core is made of high permeability soft iron in one piece, avoiding air gap and magnetic resistance problems caused by assembly or welding. The coil winding process is simple, the overall structure is compact, and it is easy to install in the limited space in front of the welding gun.

[0019] (5) Robust and low maintenance cost: The electromagnetic sensor of the present invention is not sensitive to common industrial interferences such as external vibration, dust and smoke, and has no optical components, so it is not easy to be contaminated or damaged, reducing maintenance needs and downtime.

[0020] (6) Good compatibility and easy system integration: The output is a voltage signal, which can be connected to the controller system (such as STM32) through conventional signal conditioning circuit and A / D module, making it easy to integrate with existing automated welding equipment and reducing the difficulty and cost of system transformation.

[0021] As can be seen, the electromagnetic sensor of this invention, through its magnetic circuit design, avoids the generation of eddy currents in the magnetic core, while effectively improving the accuracy and reliability of weld seam tracking. This innovation not only enhances the stability of the welding process but also provides a new technical path for automated submerged arc welding of spiral welded pipes, promoting the development of welding automation and intelligence. The application of this invention can significantly improve welding quality, reduce the need for human intervention, and thus achieve a more efficient production process.

[0022] In summary, the electromagnetic sensor of this invention not only significantly outperforms traditional arc and laser vision sensors in performance, but also exhibits outstanding advantages in structural reliability, environmental adaptability, and engineering applicability. It aims to solve the problem of unstable weld seam tracking caused by extremely narrow bevels, no bevels, or severe surface reflection of the bevel during the automatic submerged arc welding of spiral welded pipes, and provides a practical and feasible technical guarantee for achieving high-precision and high-reliability automatic submerged arc welding of spiral welded pipes. Attached Figure Description

[0023] The present invention will be described in detail below with reference to the accompanying drawings and examples. The advantages and implementation methods of the present invention will become more apparent from this description. The accompanying drawings are for illustrative purposes only and do not constitute any limitation on the present invention. In the accompanying drawings: Figure 1 It is the induced voltage of the primary coil under different magnetic core structures.

[0024] Figure 2 This is a schematic diagram showing the usage state of the electromagnetic sensor of the present invention.

[0025] In the picture: 1. E-type magnetic core; 2. Primary coil; 3. Secondary coil. Detailed Implementation

[0026] An electromagnetic sensor for tracking the weld seam of a spiral welded pipe includes a coil and an E-type magnetic core 1.

[0027] The material of the E-type magnetic core 1 is soft iron. Soft iron is a magnetic core material with low coercivity, narrow and thin hysteresis loop, and high permeability, which can improve the reliability of sensing data.

[0028] The E-type magnetic core 1 is a one-piece molded structure. When the E-type magnetic core 1 is an assembled structure, even if it is connected by welding, there is still an air gap at the connection position, which will cause the magnetic resistance in the closed magnetic circuit to become very large, thereby making the magnetic flux passing through the coil very small and the induced electromotive force on the coil significantly reduced.

[0029] like Figure 1 As shown, the integrated E-type magnetic core 1, cut from a single piece of soft iron using wire cutting, exhibits significantly higher voltage than the welded magnetic core 1 at the same excitation current and height. The integrated E-type magnetic core 1 demonstrates superior magnetic coupling capability compared to the welded magnetic core: its induced voltage is several times higher at the same distance; the integrated E-type magnetic core 1 has a range of 0-4V, while the welded magnetic core's range is only 0-0.4V, a tenfold difference, clearly indicating stronger magnetic permeability. At a height of 0mm (sensor close to the workpiece), all voltage curves reach their peak values, indicating the strongest coupling. The welded magnetic core's voltage drops to zero at a distance of 3mm from the workpiece; beyond 3mm, the magnetic coupling essentially disappears, resulting in no effective coil induction. In contrast, the integrated E-type magnetic core 1 maintains approximately 1.6V (2A) and 2.3V (3A) at a distance of 5mm from the workpiece, demonstrating superior long-distance detection capability. It is evident that the magnetic conductivity of the integrated E-type magnetic core 1 is superior to that of the welded magnetic core: the seam disrupts magnetic continuity, increases magnetic resistance, and significantly weakens magnetic sensing sensitivity; the welded magnetic core is only suitable for short-range (<3mm) magnetic detection, while the integrated E-type magnetic core 1 can achieve a greater detection range.

[0030] The coil includes a primary coil 2 and two secondary coils 3. The primary coil 2 is wound on the middle magnetic post of the E-type magnetic core 1, and the secondary coils 3 are symmetrically wound on the two magnetic posts on both sides of the E-type magnetic core 1. Both the primary coil 2 and the secondary coils 3 are wound with enameled wire, and the diameter of the enameled wire of the primary coil 2 is larger than the diameter of the enameled wire of the secondary coil 3.

[0031] When winding the primary coil 2, the enameled wire needs to balance miniaturization and operating current requirements. The aim is to ensure that the enameled wire can safely carry the current while avoiding a significant increase in coil volume due to excessive wire diameter. Therefore, the diameter here can be 0.3~1mm. The induced current generated by the secondary coil 3 is smaller, and there are no strict requirements on the diameter of the enameled wire. Based on miniaturization considerations, the diameter can be within 0.6mm.

[0032] like Figure 2 As shown, the present invention also provides a method for tracking the weld seam of a spiral welded pipe, comprising the following steps: S1. The electromagnetic sensor is installed at a certain position in front of the submerged arc welding gun, with its center aligned with the weld center of the workpiece to be welded; S2. Apply a low-frequency alternating excitation current to the primary coil 2 in the electromagnetic sensor, generating alternating magnetic flux in the magnetic circuit consisting of the E-type magnetic core 1, the workpiece to be welded, and air. F Based on the boundary conditions of the magnetic field, it can be known that the weld seam of the workpiece to be welded will... F Divided into two parts, left and right magnetic flux, when the left and right magnetic fluxes change continuously, according to Faraday's law of electromagnetic induction, an induced electromotive force will be generated in the closed circuit of the two secondary coils 3: ; In the formula, e To induce electromotive force. N s The secondary coil has 3 turns. F For magnetic flux, m r The relative permeability of the material. m 0 The permeability of free space, l Let A be the length of the magnetic circuit and A be the cross-sectional area of ​​the magnetic circuit. S3. When the electromagnetic sensor is aligned with the weld center of the workpiece to be welded, the main magnetic flux on the middle magnetic column of the E-type magnetic core 1 is equally distributed on both magnetic columns. Since the E-type magnetic core 1 has a symmetrical structure, the magnetic circuit remains symmetrical after passing through the weld. Therefore, the induced electromotive force measured in the two secondary coils 3 is the same, i.e. U 左 = U 右 ; S4. When the electromagnetic sensor deviates from the center of the weld, the magnetic flux distribution on the left and right sides is unequal. The weld will cause the magnetic flux in one side of the magnetic circuit to increase and the magnetic flux in the other side to decrease. Therefore, the difference in the induced electromotive force measured in the two coils will not be zero. U 左 ≠ U 右 When the electromagnetic sensor deviates from the center of the weld to the left, that is... U 左 > U 右 Conversely, if the electromagnetic sensor deviates from the center to the right, that is... U 左 < U 右 ; S4. When the electromagnetic sensor moves relative to the workpiece to be welded. At that time, the magnetic flux in the left and right magnetic circuits changes differentially, and the difference is proportional to the displacement. Therefore, the output voltage of the electromagnetic sensor is also proportional to the displacement. Its phase corresponds to two opposite displacement directions, and the phase difference is... The direction and distance of the welding torch deviating from the weld can be determined based on the output voltage of the electromagnetic sensor.

[0033] This invention also provides a system for tracking the weld seam of spiral welded pipes, including an electromagnetic sensor, a microcontroller, and a welding torch motion control system. The output terminal of the electromagnetic sensor is connected to the input terminal of a differential amplifier circuit to amplify the original signal to a reasonable factor. The differential amplifier circuit outputs the amplified signal to the A / D module of the microcontroller, which converts the analog signal into a digital signal. The microcontroller's signal processing algorithm (such as threshold comparison, feature extraction, and deviation calculation) calculates the positional deviation value between the welding torch and the weld seam. The deviation information is sent to the welding torch motion control system via an Ethernet interface to achieve real-time adjustment of the welding torch position.

[0034] The welding torch motion control system includes a motion controller and a servo drive unit. The motion controller receives deviation information sent by the microprocessor and outputs control signals according to a preset control strategy (such as PID control) to drive the servo motor to adjust the position of the welding torch, eliminate deviation, and realize automatic tracking of the weld seam.

[0035] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. An electromagnetic sensor for tracking the weld seam of spiral welded pipes, characterized in that: It includes a coil and an E-type magnetic core, wherein the E-type magnetic core is a one-piece molded structure; the coil includes a primary coil and two secondary coils, wherein the primary coil is wound on the middle magnetic post of the E-type magnetic core, and the secondary coils are symmetrically wound on the two magnetic posts on both sides of the E-type magnetic core.

2. The electromagnetic sensor for tracking the weld seam of a spiral welded pipe according to claim 1, characterized in that: The material of the E-type magnetic core is soft iron.

3. The electromagnetic sensor for tracking weld seams in spiral welded pipes according to claim 1, characterized in that: Both the primary coil and the secondary coil are wound with enameled wire, and the diameter of the enameled wire of the primary coil is larger than the diameter of the enameled wire of the secondary coil.

4. A method for tracking the weld seam of a spiral welded pipe, implemented based on an electromagnetic sensor for tracking the weld seam of a spiral welded pipe as described in any one of claims 1 to 3, characterized in that: Includes the following steps: S1. The electromagnetic sensor is installed in front of the submerged arc welding torch, with its center aligned with the center of the weld seam of the workpiece to be welded. S2. Apply a low-frequency alternating excitation current to the primary coil of the electromagnetic sensor, generating an alternating magnetic flux in the magnetic circuit formed by the E-type magnetic core, the workpiece to be welded, and the air. Φ Based on the boundary conditions of the magnetic field, it can be known that the weld seam of the workpiece to be welded will... Φ Divided into two parts, left and right magnetic flux, when the left and right magnetic fluxes change continuously, an induced electromotive force is generated in the closed circuit of the two secondary coils: ； In the formula, ε To induce electromotive force. N s The number of turns of the secondary coil. Φ For magnetic flux, μ r The relative permeability of the material. μ 0 The permeability of free space, l Let A be the length of the magnetic circuit and A be the cross-sectional area of ​​the magnetic circuit. S3. When the electromagnetic sensor is aligned with the weld center of the workpiece to be welded, the main magnetic flux on the middle magnetic column of the E-type magnetic core is equally distributed on both magnetic columns. Since the E-type magnetic core has a symmetrical structure, the magnetic circuit remains symmetrical after passing through the weld. Therefore, the induced electromotive force measured in the left and right secondary coils is the same. U 左 = U 右 ; S4. When the electromagnetic sensor deviates from the center of the weld, the magnetic flux distribution on the left and right sides is unequal. The weld will cause the magnetic flux in one side of the magnetic circuit to increase and the magnetic flux in the other side to decrease. Therefore, the difference in the induced electromotive force measured in the left and right coils will not be zero. U 左 ≠ U 右 When the electromagnetic sensor deviates from the center of the weld to the left, that is... U 左 > U 右 Conversely, if the electromagnetic sensor deviates from the center to the right, that is... U 左 < U 右 ; S4. When the electromagnetic sensor moves relative to the workpiece to be welded. At that time, the magnetic flux in the left and right magnetic circuits changes differentially, and the difference is proportional to the displacement. Therefore, the output voltage of the electromagnetic sensor is also proportional to the displacement. Its phase corresponds to two opposite displacement directions, and the phase difference is... The direction and distance of the welding torch deviating from the weld seam are determined based on the output voltage of the electromagnetic sensor.

5. A system for tracking the weld seam of a spiral welded pipe, comprising the electromagnetic sensor for tracking the weld seam of a spiral welded pipe as described in any one of claims 1 to 3, characterized in that: It also includes a microcontroller and a welding torch motion control system. The output of the electromagnetic sensor is connected to the input of the differential amplifier circuit to amplify the original signal to a reasonable factor. The differential amplifier circuit outputs the amplified signal to the microcontroller's A / D module, which converts the analog signal into a digital signal. The microcontroller's signal processing algorithm calculates the positional deviation between the welding torch and the weld seam. The deviation information is sent to the welding torch motion control system via an Ethernet interface to achieve real-time adjustment of the welding torch position.

6. The system for tracking weld seams in spiral welded pipes according to claim 5, characterized in that: The welding torch motion control system includes a motion controller and a servo drive unit. The motion controller receives deviation information sent by the microprocessor, outputs control signals according to the preset control strategy, drives the servo motor to adjust the position of the welding torch, eliminates deviation, and realizes automatic tracking of the weld.

Images