Argon arc welding constant temperature control system for corrugated plate welding

Abstract

The present application belongs to the technical field of welding control, and relates to an argon arc welding constant temperature control system for corrugated plate welding, comprising an infrared acquisition module, a signal conversion module, a control module and a current execution module; the infrared acquisition module acquires the infrared light intensity signal of the molten pool; the signal conversion module converts the infrared light intensity signal into an electric signal; the control module receives the electric signal, takes the molten pool temperature represented by the electric signal as a feedback quantity, compares it with a preset target temperature, calculates and outputs a current adjustment signal based on a PID control algorithm; and the current execution module receives the current adjustment signal and adjusts the output current of the welding power supply in real time. The present application takes the infrared light intensity of the molten pool as a direct feedback quantity, dynamically adjusts the welding current through the PID algorithm, realizes the constant molten pool temperature on the full weld length of the corrugated plate, can automatically compensate the arc length fluctuation, heat dissipation difference and manual operation disturbance, effectively improves the welding quality consistency, and is suitable for the precision welding of thin-walled corrugated plate structures such as LNG film tanks.

Description

Technical Field

[0001] This invention relates to the field of welding control technology, and in particular to an argon arc welding constant temperature control system for corrugated plate welding, which is suitable for precision argon arc welding of thin-walled corrugated plate structures in marine LNG storage tank membrane compartments. Background Technology

[0002] Corrugated plates are widely used in the manufacture of thin-walled containers for LNG carrier membrane tanks due to their good structural strength and bidirectional absorption of cold shrinkage deformation. Corrugated plates are usually welded by argon arc welding (TIG / GTAW) for lap joints. The weld length is large and the quality requirements are high. The quality of the welding directly affects the safety and service life of the storage tank.

[0003] The corrugated plate welding of LNG membrane tanks has the following significant structural and technological characteristics: First, the plate thickness is extremely thin, typically between 0.8mm and 1.4mm, especially 1.2mm; the allowable heat input window is extremely narrow, and a slightly larger current will cause burn-through, while a slightly smaller current will result in incomplete fusion; Second, the corrugated plate surface has a periodically undulating corrugated shape, and the welding torch must move along the corrugated trajectory. During the welding process, the relative position and angle between the arc and the workpiece continuously change, resulting in significant differences in heat input distribution at different locations (crests, troughs, slopes, and arc segments) of the same weld bead; Third, the contact state, heat dissipation path length, and heat dissipation area between the crests and troughs of the corrugated plate and the backing plate are different. In addition, the thermal conductivity of thin plates is poor (especially stainless steel), and even small changes in heat dissipation conditions can cause drastic fluctuations in the molten pool temperature; Fourth, thin plates are prone to thermal deformation and warping during welding. Deformation, in turn, changes the contact state between the workpiece and the backing plate and the heat dissipation conditions, forming a positive feedback loop of heat input → deformation → change in heat dissipation conditions → further temperature fluctuations.

[0004] Currently, corrugated plate welding mainly employs manual TIG welding or semi-automatic welding methods, with heat input control relying on the traditional mode of preset welding current plus manual adjustment. Welders set a fixed welding current value before welding based on experience, and during the welding process, they rely on visual observation of the molten pool shape and color, and manually fine-tune the welding torch travel speed or current setting to maintain weld formation.

[0005] This control method uses welding current as the feedback quantity, and there is only a weak correlation between welding current and molten pool temperature (correlation coefficient R). 2=0.6~0.85). Welding current is essentially an indirect heat input parameter, and its relationship with the actual temperature of the molten pool is affected by multiple factors such as arc length variation, welding speed fluctuation, differences in heat dissipation conditions, workpiece assembly gap, and base material thickness deviation. Under the specific working conditions of corrugated plate welding, these interferences are significantly amplified: the arc length fluctuates continuously as the welding torch moves along the corrugated surface, the heat dissipation conditions at the crests and troughs are very different, and the heat dissipation state caused by the thermal deformation of the thin plate changes in real time. Any change in the above factors will produce drastically different molten pool temperatures under the same current setting. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide an argon arc welding constant temperature control system for corrugated plate welding, which uses the infrared light intensity of the molten pool as a direct feedback quantity to sense the temperature change of the molten pool in real time, and dynamically adjusts the welding current through a PID algorithm to achieve a constant molten pool temperature throughout the entire weld length of the corrugated plate, automatically compensates for arc length fluctuations, heat dissipation differences and manual operation disturbances, and effectively improves the consistency of welding quality.

[0007] To solve the above-mentioned technical problems, the present invention provides an argon arc welding constant temperature control system for corrugated plate welding, comprising: An infrared acquisition module, located at the end of the welding torch, acquires the infrared light intensity signal of the molten pool; A signal conversion module is used to convert the infrared light intensity signal into an electrical signal; The control module receives the electrical signal, uses the molten pool temperature represented by the electrical signal as a feedback quantity, compares it with a preset target temperature, and calculates and outputs a current adjustment signal based on a PID control algorithm. A current actuation module, which is signal-connected to the control module and connected to the welding power supply, is used to receive the current adjustment signal and adjust the output current of the welding power supply in real time according to the current adjustment signal.

[0008] Preferably, the infrared acquisition module includes: an optical fiber probe fixed to the side of the welding torch head, with its acquisition end obliquely aligned with the molten pool area; and an infrared filter disposed in the optical path of the optical fiber probe to filter out visible light and ultraviolet light radiated by the arc plasma.

[0009] Preferably, the infrared filter has a center wavelength of 850 nm and a bandwidth of ±10 nm.

[0010] Preferably, the infrared acquisition module further includes an argon purging structure, which is disposed at the acquisition end of the fiber optic probe and is used to spray argon gas onto the lens surface of the acquisition end.

[0011] Preferably, the signal conversion module includes: a silicon photovoltaic cell that converts the infrared light intensity signal into a photocurrent signal; a signal conditioning circuit that conditions the photocurrent signal into a voltage signal; and the voltage signal is input to the control module.

[0012] Preferably, the signal conditioning circuit includes: a cross-group amplifier circuit that converts the nA-level photocurrent signal output by the silicon photovoltaic cell into a mV-level voltage signal; and a differential amplifier circuit that differentially amplifies the mV-level voltage signal to output a 0~5V voltage signal.

[0013] Preferably, the control module includes: a deviation calculation unit, which calculates the deviation between the molten pool temperature represented by the electrical signal and the target temperature to obtain a deviation signal; and a PID calculation unit, which performs proportional, integral, and derivative operations on the deviation signal to obtain the current adjustment signal.

[0014] Preferably, the control module includes a storage unit for storing the target temperature; wherein the storage unit stores multiple target temperatures, each of which corresponds to a different waveform position on the corrugated plate; the control module is configured to retrieve the corresponding target temperature from the storage unit based on the current corrugated position of the welding torch, and use it as a comparison benchmark for the deviation calculation unit.

[0015] Preferably, the target temperature at different waveform positions is set such that the target temperature corresponding to the waveform valley position is not equal to the target temperature corresponding to the waveform peak position.

[0016] Preferably, the PID control algorithm is configured as negative feedback control: if the molten pool temperature represented by the electrical signal is higher than the target temperature, the welding power supply is reduced; if the molten pool temperature represented by the electrical signal is lower than the target temperature, the welding power supply is increased.

[0017] The argon arc welding constant temperature control system for corrugated plate welding described in this invention has the following advantages: The infrared light intensity signal of the molten pool is detected in real time by an infrared acquisition module integrated into the welding torch. The infrared light intensity signal is proportional to the fourth power of the molten pool temperature, with a correlation coefficient R. 2 With a value >0.95, it can reflect the instantaneous temperature state of the molten pool with high fidelity. The control module uses the molten pool temperature characterized by infrared light intensity signal as a direct feedback quantity, and continuously adjusts the welding current based on the PID control algorithm to achieve the control transition from constant current to constant temperature. The argon arc welding constant temperature control system described in this invention is applied to the welding of corrugated plates in LNG storage tanks, achieving a constant molten pool temperature throughout the entire weld length of the corrugated plate, automatically compensating for arc length fluctuations, heat dissipation differences, and manual operation disturbances, effectively improving the consistency of welding quality. Attached Figure Description

[0018] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0019] Figure 1 This is a schematic diagram of the argon arc welding constant temperature control system for corrugated plate welding in a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of the infrared acquisition module in a preferred embodiment of the present invention; Figure 3 for Figure 2 The image shows a cross-sectional view of the infrared acquisition module.

[0020] Instruction manual illustrations and labeling: 2. Welding torch; 4. Optical fiber; 6. Molten pool; 10. Infrared acquisition module; 110. Fiber optic probe; 120. Sapphire lens; 130. Air tube; 131. Nozzle; 140. Infrared filter; 20. Signal conversion module; 210. Silicon photovoltaic cell; 220. Signal conditioning circuit; 221. Transimpedance amplifier circuit; 222. Differential amplifier circuit; 30. Control module; 310. Deviation calculation unit; 320. PID calculation unit; 330. Storage unit; 40. Current execution module. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0022] Welding of corrugated plates for LNG membrane tanks requires extremely precise and rapid molten pool temperature control. Traditional constant preset current methods cannot detect and compensate for multi-source disturbances, specifically manifested as: (1) uneven heat input caused by corrugated surfaces, resulting in significant temperature differences at different locations under the same current; (2) differences in heat dissipation conditions at peaks / troughs, resulting in different temperature rise rates under the same heat input; (3) heat dissipation changes caused by thermal deformation of thin plates, resulting in real-time changes in heat dissipation conditions and temperature drift; (4) artificial fluctuations in welding speed, resulting in changes in heat input per unit length; (5) geometrical abrupt changes in lap joints, altering the flow state of the molten pool and easily causing defects.

[0023] This invention provides an argon arc welding constant temperature control system for corrugated plate welding. It uses the infrared light intensity of the molten pool as the direct feedback quantity for closed-loop current control. Only by sensing the changes in the temperature (light intensity) of the molten pool in real time can the current be automatically adjusted within milliseconds to compensate for all the above disturbances and achieve true constant temperature welding.

[0024] Specifically, refer to Figure 1 and Figure 3 As shown, the argon arc welding constant temperature control system for corrugated plate welding includes an infrared acquisition module 10, a signal conversion module 20, a control module 30, and a current execution module 40.

[0025] The infrared acquisition module 10 is set at the end of the welding torch to acquire the infrared light intensity signal of the molten pool 6.

[0026] For example, the infrared acquisition module 10 includes an optical fiber probe 110 and an infrared filter 140.

[0027] The fiber optic probe 110 is fixed to the side of the nozzle of the manual TIG welding torch, with its acquisition end aligned at a 45° angle with the molten pool 6. The fiber optic probe 110 is made of high-temperature resistant silica fiber, capable of withstanding the high-temperature radiation environment near the molten pool during welding. The distance between the acquisition end of the fiber optic probe 110 and the surface of the molten pool 6 can be pre-adjusted and fixed according to the actual welding conditions to ensure that the acquired infrared light signal has a stable and sufficiently strong amplitude. Those skilled in the art should understand that the selection of the distance between the acquisition end and the molten pool 6 should balance signal strength and acquisition stability, typically aiming to avoid obstructing the welder's view and affecting the normal swing of the welding torch. During welding, the molten pool 6 continuously radiates infrared radiation due to its high temperature; this infrared radiation is transmitted through the acquisition end of the fiber optic probe 110 into the fiber optic cable.

[0028] An infrared filter 140 is disposed in the optical path of the fiber optic probe 110. Specifically, it can be disposed at the optical inlet of the fiber optic probe 110's acquisition end, or it can be disposed inside the fiber near the acquisition end. The infrared filter 140 is used to filter out visible light and ultraviolet light generated by the arc plasma radiation, allowing only light signals of the infrared radiation wavelength of the molten pool to pass through. As an example, the center wavelength of the infrared filter 140 is 850 nm, and the bandwidth is ±10 nm. This wavelength range corresponds to the peak range of the blackbody infrared radiation of the molten pool, which can effectively isolate the strong visible light interference and ultraviolet spectral interference of the arc during argon arc welding, ensuring that the infrared signal entering the optical fiber truly reflects the thermal radiation state of the molten pool 6, and significantly improving the system signal-to-noise ratio.

[0029] Reference Figure 1 and Figure 3 As shown, the infrared acquisition module 10 may also include a sapphire lens 120. The sapphire lens 120 is disposed at the acquisition end of the fiber optic probe 110 and located at the front end of the infrared filter 140 (i.e., the side close to the molten pool 6). It is used to protect the acquisition end face of the fiber optic probe 110 from direct damage by welding spatter and high-temperature heat radiation while acquiring infrared radiation from the molten pool, and at the same time, it plays a role in preventing the light wave transmittance from deteriorating due to high temperature.

[0030] During welding, welding spatter and fumes can easily adhere to the lens surface of the fiber optic probe 110's acquisition end face, causing optical signal attenuation. Therefore, referring to... Figure 2 and Figure 3 As shown, the infrared acquisition module 10 may also include an argon purging structure. The jet nozzle of the argon purging structure may be set on one side of the sapphire lens 120, with the jet direction facing the outer surface of the lens. This is used to form a continuous air curtain barrier in front of the lens, blowing away splashes and dust from the lens surface and maintaining the optical cleanliness of the lens.

[0031] The argon purging structure is located at the acquisition end of the fiber optic probe 110. It has an argon nozzle 131 connected to the protective gas path and an external protective gas pipe 130. The nozzle 131 faces the lens surface of the acquisition end and is used to continuously spray argon gas onto the lens surface during the welding process. Argon purging can form an air curtain barrier in front of the lens to prevent welding spatter and fumes from adhering to the lens surface and causing optical signal attenuation. On the other hand, the sprayed argon gas can also provide auxiliary cooling for the acquisition end of the fiber optic probe 110, avoiding excessively high fiber end temperature caused by prolonged welding, which would affect the stability of signal transmission.

[0032] The signal conversion module 20 is connected to the infrared acquisition module 10 and is used to convert the infrared light intensity signal acquired by the infrared acquisition module 10 into an electrical signal that can be processed by the control module 30.

[0033] For example, the signal conversion module 20 includes a silicon photovoltaic cell 210 and a signal conditioning circuit 220.

[0034] The silicon photovoltaic cell 210 receives the infrared light intensity signal transmitted through optical fiber and filtered by the infrared filter 140, and converts it into a photocurrent signal using the photoelectric effect. The silicon photovoltaic cell 210 is a high-sensitivity semiconductor optoelectronic device whose output photocurrent intensity is proportional to the incident infrared radiation intensity. During the welding process, changes in the molten pool temperature cause changes in the infrared radiation intensity, and the output photocurrent of the silicon photovoltaic cell 210 changes synchronously, thus converting the infrared light intensity signal into an electrical signal in real time.

[0035] The signal conditioning circuit 220 is electrically connected to the silicon photovoltaic cell 210 and is used to condition the photocurrent signal output by the silicon photovoltaic cell 210 into a standard voltage signal for output to the control module 30. As an example, the signal conditioning circuit 220 includes a transimpedance amplifier circuit 221 and a differential amplifier circuit 222.

[0036] The first input terminal of the transimpedance amplifier circuit 221 is electrically connected to the output terminal of the silicon photovoltaic cell 210, and is used to convert the weak nA-level photocurrent signal output by the silicon photovoltaic cell 210 into a mV-level voltage signal. The transimpedance amplifier circuit 221 uses a high-precision operational amplifier in conjunction with a feedback resistor connected between its input and output terminals to achieve the current-to-voltage conversion function, and its conversion gain is determined by the resistance value of the feedback resistor.

[0037] The input terminal of the differential amplifier circuit 222 is electrically connected to the output terminal of the transimpedance amplifier circuit 221, and is used to differentially amplify the mV-level voltage signal output by the transimpedance amplifier circuit 221. The differential amplifier circuit 222 uses an instrumentation differential amplifier, which has a high common-mode rejection ratio and can effectively suppress strong common-mode electromagnetic interference generated in the welding environment due to high-frequency arc ignition and large current switching. After linear amplification by the differential amplifier circuit 222, the signal is conditioned into a standard 0~5V DC voltage signal. The amplitude of this voltage signal is proportional to the infrared radiation intensity of the molten pool 6, that is, proportional to the fourth power of the molten pool temperature (I∝T). 4 ) are positively correlated.

[0038] To ensure the accuracy and stability of signal conditioning, preferably, the signal conditioning circuit 220 is encapsulated in a fully shielded metal housing, and each resistor element in the circuit is a low-temperature drift precision resistor to prevent zero-point drift and measurement errors caused by changes in ambient temperature and environmental electromagnetic interference.

[0039] The control module 30 is connected to the signal conversion module 20 and is used to receive the electrical signal (i.e., 0~5V voltage signal) output by the signal conversion module 20. The molten pool temperature represented by the electrical signal is used as the feedback quantity, compared with the preset target temperature, and the current adjustment signal is calculated and output based on the PID control algorithm.

[0040] For example, the control module 30 includes a deviation calculation unit 310 and a PID calculation unit 320.

[0041] The deviation calculation unit 310 is used to calculate the deviation between the molten pool temperature represented by the electrical signal output by the signal conversion module 20 and the preset target temperature, thereby obtaining a deviation signal. Specifically, the deviation calculation unit 310 has a preset voltage reference value (or temperature-voltage mapping relationship) representing the target temperature. It performs a difference operation between the temperature value corresponding to the measured voltage signal and the target temperature reference value to obtain the deviation signal e(t). The sign of the deviation signal e(t) reflects the direction of the current molten pool temperature relative to the target temperature: a positive deviation indicates that the molten pool temperature is higher than the target temperature, and a negative deviation indicates that the molten pool temperature is lower than the target temperature; the absolute value of the deviation reflects the degree of temperature deviation.

[0042] The PID calculation unit 320 is electrically connected to the deviation calculation unit 310 and is used to perform proportional, integral, and derivative operations on the deviation signal e(t) to obtain the current regulation signal. The calculation formula of the PID control algorithm is: ; Kp, Ki, and Kd are the proportional coefficient, integral coefficient, and derivative coefficient, respectively; u(t) is the current regulation signal output by the PID calculation unit 320.

[0043] In terms of control direction, the control module 30 is configured in a negative feedback control mode: when the deviation calculation unit 310 determines that the molten pool temperature represented by the electrical signal is higher than the target temperature, the PID calculation unit 320 outputs a current adjustment signal to reduce the welding current, thereby lowering the molten pool temperature; when the molten pool temperature represented by the electrical signal is lower than the target temperature, the PID calculation unit 320 outputs a current adjustment signal to increase the welding current, thereby raising the molten pool temperature. This negative feedback direction ensures that the system can automatically converge to the target temperature under the drive of the PID algorithm.

[0044] The current execution module 40 is signal-connected to the control module 30 and connected to the welding power supply. It is used to receive the current adjustment signal output by the control module 30 and adjust the output current of the welding power supply in real time according to the current adjustment signal.

[0045] For example, the current adjustment signal is a standard 4~20mA industrial analog signal. The calculation result output by the PID calculation unit 320 in the control module 30 is converted from digital to analog and then output to the current execution module 40 in the form of a 4~20mA analog current. The magnitude of this 4~20mA analog signal is linearly related to the control quantity output by the PID calculation unit 320. The current execution module 40 uses this 4~20mA signal to replace the original panel potentiometer setting signal in the argon arc welding power supply. By continuously adjusting the conduction angle of the thyristor in the welding power supply, stepless, continuous, and real-time adaptive adjustment of the welding output current is achieved.

[0046] When the output current of the welding power source changes, the heat input acting on the molten pool 6 changes accordingly, which in turn causes a change in the temperature of the molten pool. The infrared acquisition module 10 then acquires the changed infrared light intensity signal and enters the next closed-loop control cycle. Thus, the above-mentioned infrared acquisition module 10 → signal conversion module 20 → control module 30 → current execution module 40 → welding power source → molten pool 6 → infrared acquisition module 10 form a complete negative feedback closed-loop control loop.

[0047] The infrared light intensity signal of the molten pool 6 is directly acquired by the infrared acquisition module 10; this infrared light intensity signal is proportional to the fourth power of the molten pool temperature (I∝T). 4 With a correlation coefficient R² > 0.95, it can reflect the instantaneous temperature state of the molten pool 6 with high fidelity. The control module 30 uses the molten pool temperature characterized by infrared light intensity signal as the direct feedback quantity. Based on the PID control algorithm, it continuously adjusts the welding current to achieve the control transition from constant current to constant temperature. The temperature control stability is more than 3 times higher than that of traditional current control. It is applied to the corrugated plate welding of LNG storage tanks to achieve constant molten pool temperature throughout the entire weld length of the corrugated plate, automatically compensate for arc length fluctuations, heat dissipation differences and manual operation disturbances, and effectively improve the consistency of welding quality.

[0048] The welding process of corrugated plates is subject to numerous random disturbances, including arc length fluctuations caused by the movement of the welding torch along the corrugated surface, uneven welder walking speed, periodic differences in heat dissipation conditions between the crests and troughs, and real-time changes in heat dissipation due to the thermal deformation of the thin plate. Any of these disturbances can lead to fluctuations in the molten pool temperature. In this embodiment of the invention, the control module 30 calculates the temperature deviation in real time with a millisecond-level response speed through the PID calculation unit 320 and outputs a current adjustment signal. The current execution module 40 immediately performs current adjustment, which can automatically compensate for all the above disturbances in a very short time after the temperature deviation occurs. This achieves real-time active suppression of disturbances, significantly reducing the sensitivity of the welding process to fluctuations caused by human operation, allowing even novice welders to obtain consistent welding quality.

[0049] Furthermore, this invention employs a modular architecture. The infrared acquisition module 10 can be directly mounted on the end of a manual TIG welding torch. The signal conversion module 20 and control module 30 can be integrated into a standalone controller or embedded within the welding machine. The current execution module 40 outputs a 4-20mA standard industrial analog signal, which can directly replace the panel potentiometer of existing thyristor TIG welding machines to achieve stepless current adjustment. The interfaces between modules are standardized, allowing for functional upgrades without large-scale modifications to existing welding machines, thus demonstrating good versatility.

[0050] Based on the above embodiment, the control module 30 further includes a storage unit 330, which stores welding process parameters, including target temperatures. During corrugated plate welding, since the corrugated plate has different waveform positions such as crests, troughs, and flat surfaces, the heat dissipation conditions and temperature response characteristics at each position are significantly different. The storage unit 330 pre-stores multiple target temperatures corresponding to different waveform positions.

[0051] For example, the storage unit 330 may be a non-volatile memory, such as EEPROM or Flash memory, which can retain multiple sets of target temperature parameters after the welding machine is powered off; the correspondence between each target temperature and waveform position stored in the storage unit 330 can be stored in tabular form.

[0052] Each target temperature is pre-determined through process experiments, and their relative values ​​are set based on the heat dissipation characteristics of different positions on the corrugated plate. During welding, the control module 30 retrieves the corresponding target temperature from the storage unit 330 based on the current waveform position of the welding torch, using it as a comparison benchmark for the deviation calculation unit 310. In this way, the target temperature can be dynamically switched within the same weld seam based on the heat dissipation differences of the waveform position of the welding torch, enabling precise control of the target temperature at each position by dynamically changing the waveform position.

[0053] The current waveform position of the welding torch can be obtained in one of the following ways: As a first exemplary approach, the control module 30 determines the current waveform position of the welding torch in real time based on the preset welding trajectory planning information of the welding torch. For the scenario of corrugated plate welding using robotic automation, the welding trajectory has been pre-planned, and the control module 30 can calculate the specific position of the welding torch on the corrugated plate trajectory in real time based on the trajectory planning data, thereby determining whether it is in the crest, trough, or flat plate area.

[0054] As a second exemplary approach, the system also includes a position sensor disposed on the end of the welding torch or on the welding fixture. The position sensor is used to detect the position signal of the welding torch relative to the waveform of the corrugated plate and send it to the control module 30. The control module 30 determines the current waveform position of the welding torch based on the position signal.

[0055] In other implementations, the target temperature can be switched by manual triggering.

[0056] More preferably, multiple target temperatures at different waveform positions are set such that the target temperature corresponding to the waveform trough position is not equal to the target temperature corresponding to the waveform peak position. Specifically, the target temperature corresponding to the waveform trough position is T1, and the target temperature corresponding to the waveform peak position is T2, and T1 and T2 satisfy T1≠T2. The specific relationship between T1 and T2 is determined based on the actual difference in heat dissipation conditions between the peak and trough positions of the corrugated plate.

[0057] As a first exemplary approach: At the troughs, due to close contact with the backing plate or tooling, the heat dissipation path is short, resulting in faster heat conduction and a lower molten pool temperature under the same heat input conditions. At the crests, due to the smaller contact area with the backing plate and the longer heat dissipation path, heat is less easily dissipated, leading to a higher molten pool temperature under the same heat input conditions. To achieve consistent molten pool temperature control across the entire weld length, a higher target temperature needs to be set at the troughs to compensate for heat loss and ensure sufficient fusion, while a lower target temperature needs to be set at the crests to prevent heat accumulation leading to overheating and burn-through. In this case, the target temperature T1 corresponding to the trough is higher than the target temperature T2 corresponding to the crest, i.e., T1 > T2.

[0058] As a second exemplary approach: In a partially corrugated plate structure, the crests, being protruding from the surface, have a large contact area with the surrounding air for convection, resulting in better heat dissipation; while the troughs, being recessed, have poor airflow, making heat dissipation difficult. In this case, the temperature at the crests is lower under the same heat input conditions, while the temperature at the troughs is higher. Therefore, a higher target temperature needs to be set at the crests to ensure sufficient fusion, and a lower target temperature needs to be set at the troughs to prevent overheating. In this case, the target temperature T1 corresponding to the trough is lower than the target temperature T2 corresponding to the crest, i.e., T1 < T2.

[0059] Regardless of the method used, the specific difference between T1 and T2 can be determined through process testing. For example, for a 1.2mm thick 304L stainless steel corrugated plate (a common material for LNG membrane tanks), welding is performed at the trough and peak positions of the corrugation using the same welding parameters. The actual molten pool temperature at which good weld formation is achieved is measured, and the measured values ​​are stored as T1 and T2 in storage unit 33, respectively. The difference between T1 and T2 is typically in the range of 5% to 15%, and the specific value depends on the geometric parameters of the corrugated plate (wave height, wave pitch, plate thickness) and the material's thermal properties (thermal conductivity, specific heat capacity).

[0060] For the flat plate area of ​​the corrugated plate, the target temperature is between T1 and T2.

[0061] During the welding process, the control module 30 calls the corresponding target temperature in real time according to the current waveform position of the welding torch: When the welding torch is currently in the trough of the waveform, T1 is used as the comparison reference for the deviation calculation unit 310. At this time, the deviation calculation unit 310 calculates the deviation between the actual molten pool temperature represented by the electrical signal output by the signal conversion module 20 and T1. The PID calculation unit 320 outputs a current adjustment signal according to the deviation to make the actual molten pool temperature approach T1.

[0062] When the welding torch is currently at the peak of the waveform, T2 is used as the comparison reference for the deviation calculation unit 310. At this time, the deviation calculation unit 310 calculates the deviation between the actual molten pool temperature and T2. The PID calculation unit 320 outputs a current adjustment signal according to the deviation to make the actual molten pool temperature approach T2.

[0063] Since T1 ≠ T2, different temperature control targets are used at the waveform trough and waveform peak positions. When the welding torch moves from the waveform trough position to the waveform peak position, the comparison reference of the deviation calculation unit 310 switches from T1 to T2 (or vice versa), and the current adjustment signal output by the system is adjusted accordingly, so that the welding current automatically adapts to the heat input requirements of different waveform positions.

[0064] In this embodiment of the invention, considering that the contact state, heat dissipation path length and heat conduction area of ​​the workpiece and the pad are different at the peak and trough, the temperature response characteristics of the two are significantly different under the same welding conditions. By setting the target temperature at the trough position and the target temperature at the peak position to be different, the system can use different temperature control targets at the peak and trough, thereby achieving consistent control of the molten pool temperature over the entire weld length.

[0065] In addition, different temperature references are automatically adapted according to the structural characteristics of the corrugated plate, which effectively avoids the temperature mismatch problem caused by the difference in heat dissipation between the peak and trough positions, and provides a reliable guarantee for the all-position welding quality of the ultra-thin corrugated plate of LNG membrane tank.

[0066] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A constant temperature control system for argon arc welding of corrugated plates, characterized in that, include: An infrared acquisition module, located at the end of the welding torch, acquires the infrared light intensity signal of the molten pool; A signal conversion module is used to convert the infrared light intensity signal into an electrical signal; The control module receives the electrical signal, uses the molten pool temperature represented by the electrical signal as a feedback quantity, compares it with a preset target temperature, and calculates and outputs a current adjustment signal based on a PID control algorithm. A current-actuating module is connected to the control module via signal connection and is also connected to the welding power supply; Used to receive the current adjustment signal and adjust the output current of the welding power supply in real time according to the current adjustment signal; The control module includes: The deviation calculation unit calculates the deviation between the molten pool temperature represented by the electrical signal and the target temperature to obtain a deviation signal; The PID calculation unit performs proportional, integral, and derivative operations on the deviation signal to obtain the current regulation signal. The control module includes a storage unit for storing the target temperature; wherein, the storage unit stores multiple target temperatures, each of which corresponds to a different waveform position on the corrugated plate; the control module is configured to retrieve the corresponding target temperature from the storage unit based on the current corrugated position of the welding torch, and use it as a comparison benchmark for the deviation calculation unit; The target temperature at different waveform positions is set such that the target temperature corresponding to the waveform valley position is not equal to the target temperature corresponding to the waveform peak position.

2. The argon arc welding constant temperature control system for corrugated plate welding according to claim 1, characterized in that, The infrared acquisition module includes: The fiber optic probe is fixed to the side of the welding torch head, with its acquisition end angled towards the molten pool area. An infrared filter, which is disposed in the optical path of the fiber optic probe, is used to filter out visible light and ultraviolet light radiated by the arc plasma.

3. The argon arc welding constant temperature control system for corrugated plate welding according to claim 2, characterized in that, The infrared filter has a center wavelength of 850nm and a bandwidth of ±10nm.

4. The argon arc welding constant temperature control system for corrugated plate welding according to claim 2, characterized in that, The infrared acquisition module also includes an argon purging structure, which is located at the acquisition end of the fiber optic probe and is used to spray argon gas onto the lens surface of the acquisition end.

5. The argon arc welding constant temperature control system for corrugated plate welding according to claim 1, characterized in that, The signal conversion module includes: A silicon photovoltaic cell that converts the infrared light intensity signal into a photocurrent signal; The signal conditioning circuit conditions the photocurrent signal into a voltage signal; the voltage signal is then input to the control module.

6. The argon arc welding constant temperature control system for corrugated plate welding according to claim 5, characterized in that, The signal conditioning circuit includes: A cross-group amplifier circuit converts the nA-level photocurrent signal output by the silicon photovoltaic cell into a mV-level voltage signal. The differential amplifier circuit differentially amplifies the mV-level voltage signal and outputs a 0~5V voltage signal.

7. The argon arc welding constant temperature control system for corrugated plate welding according to claim 1, characterized in that, The PID control algorithm is configured as negative feedback control: If the molten pool temperature represented by the electrical signal is higher than the target temperature, then reduce the welding power supply. If the molten pool temperature represented by the electrical signal is lower than the target temperature, then the welding power supply is increased.

Images