Multi-parameter cooperative control laser welding method and system

Abstract

The invention belongs to the technical field of laser welding, and discloses a multi-parameter cooperative control laser welding method and system.The method comprises the steps that a laser energy control model is established based on material strength-thickness-gap ternary coupling, and the output power of an optical fiber laser is controlled; coaxial three-layer gradient gas is adopted for protection of a welding area, preheating before welding and double-temperature-zone gradient annealing after welding are adopted, the output power of an optical fiber laser and the three-layer gradient gas protection flow are regulated and controlled in real time through combination of multiple sensors and a control algorithm, the temperature of a heat affected zone is monitored in real time, and a cooling nozzle is controlled for cooling. And continuous parameter optimization is achieved through machine learning, and multi-parameter control laser welding is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of laser welding, and particularly relates to a multi-parameter cooperative control laser welding method and system. BACKGROUND

[0002] At present, with the continuous development of industry, the demand for high-strength variety steel continues to rise in many fields. With excellent performance such as high strength, good toughness and corrosion resistance, etc., as the production of high-strength variety steel increases rapidly and the variety specifications expand rapidly, the market competition is becoming increasingly fierce High-grade high-strength steel is the main product of major steel mills. In order to meet the needs of "lightweight energy saving", more and more automobile parts are made of high-strength automobile sheet. Compared with other steels, DP dual-phase steel, low-alloy high-strength steel and hot forming stamping steel have the advantages of high yield strength, tensile strength and ductility, as well as stamping forming capacity, and are widely used in automobile manufacturing. As the main production line of high-grade high-strength steel, the design idea of acid continuous rolling is to use a welding machine to weld the strip steel at the head and tail of the upper and lower channels to realize uninterrupted continuous production and subsequent process treatment. This is an important process technology for modern steel enterprises to improve production efficiency and reduce production cost.

[0003] The laser welding machine of the acid continuous rolling production line radiates high-intensity laser beam to the metal surface, and through the interaction of laser and metal, the metal absorbs the laser and converts it into heat energy, so that the metal is melted and cooled to realize welding. In laser welding, the welded workpiece is deformed very little, there is almost no joint gap, and the welding depth / width ratio is high, so the welding quality is better than that of traditional welding methods, and the welded seam can be directly rolled in the continuous rolling mill.

[0004] The prior art patent with publication number CN112719582A discloses a laser welding device with preheating function and a preheating welding method, which comprises a laser preheating system and a laser welding platform. The laser preheating welding system comprises a semiconductor laser for outputting 800nm wavelength laser and a fiber laser for outputting 1060nm wavelength laser, and a laser preheating head and a laser welding head outside the laser for adjusting the focal length and working distance to obtain a suitable size spot; the welding platform is provided with a tool clamp for clamping the welding piece and a working platform for supporting the tool clamp, wherein the tool clamp can move relative to the working platform. The present application uses a large-size diameter laser beam of a semiconductor laser to preheat the welding seam of the welding piece, which can heat welding pieces of different structures and sizes, has strong applicability, high heating efficiency, precise preheating area, and no problems of excess parts outside the preheated welding seam and internal and external temperature difference of the welding piece.

[0005] In summary, the existing pickling line laser welding machine has the technical problems of easy generation of pores and cracks in the weld, especially in the HAZ area, the number of pores is greater than 7, the hardening of the heat affected zone causes the rolling breakage rate to be 1 ‰, the weld strength is only 85-90% of the base material, the cross-steel welding adjustment time is long, and the steel grade adjustment time is 5-8 rolls of welding time. SUMMARY

[0006] In order to solve the above technical problems, the present application establishes a laser energy control model based on the ternary coupling of material strength-thickness-gap, controls the output power of the fiber laser, uses coaxial three-layer gradient gas to protect the welding area, reduces the generation of bubbles through preheating before welding and double-temperature-zone gradient annealing after welding, and realizes real-time regulation and control of the output power of the fiber laser and the three-layer gradient gas protection flow through the combination of multiple sensors and control algorithms, real-time monitoring of the temperature of the heat affected zone, cooling through the cooling nozzle, and continuous parameter optimization through machine learning.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme: The first aspect of the present application provides a multi-parameter collaborative control laser welding method, comprising the following steps: Step S1, obtaining steel data through a front-end detection device, establishing a laser energy control model according to the steel data, and adjusting the output power according to the model to control the fiber laser; Step S2, preheating the heat affected zone of the steel to be welded before welding; Step S3, after completing the preheating, programming a control algorithm of the welding process through a programmable logic controller, controlling the power of the fiber laser and the flow of the protective gas, and welding the steel; Step S4, using a three-stage control algorithm to perform steel grade transition during the welding process, and using three gases to protect the welding position; Step S5, after completing the welding, annealing the heat affected zone through a double-temperature-zone gradient heating method.

[0008] The second aspect of the present application provides a multi-parameter collaborative control laser welding system, which comprises a front-end steel data acquisition module, a steel data processing module, a heat affected zone fire control module, a steel welding area data acquisition module, an editable logic controller module, and a gas protection module. The front-end steel data acquisition module comprises a thickness detector, a material strength detector, and a plate gap detector, which obtains data through multi-directional detection of steel data, so as to accurately control the output of the laser welding power P; The steel data processing module retrieves the database related parameters by the data obtained by the front-end steel data acquisition module, obtains the material yield strength σ, adaptive coefficients k1, k2 and k3, establishes a ternary coupling laser energy control model of material strength-thickness-gap, and obtains the power P by using a laser power calculation formula, and the calculation formula is:

[0009] The output power is set to adjust the fiber laser.

[0010] The heat affected zone fire control module is divided into a pre-welding preheating submodule and a post-welding annealing submodule. The pre-welding preheating submodule: before welding starts, the heat affected zone is uniformly heated to 200-300 DEG C by a heating device, and the temperature is maintained during welding. The preheating temperature of 200-300 DEG C can slow down the cooling speed of the heat affected zone after welding is completed, reduce the formation of brittle and hard structures such as martensite, and improve the toughness of the heat affected zone. Preheating can reduce the temperature difference between the welding area and the base material, reduce the temperature difference stress of heating expansion and cooling shrinkage, and reduce the generation of residual stress from the source. Preheating can reduce the melting resistance of the base material, making the molten pool metal more easily spread, reducing unmelted, slag forming defects. The heat affected zone needs to be uniformly heated as a whole to avoid local overheating leading to coarse grains or local temperature deficiency with quenching risk.

[0011] The post-welding annealing submodule: after welding is completed, the weld is cooled to room temperature, and the weld and the heat affected zone are subjected to double-temperature gradient heating treatment by a heating device. The first temperature zone is heated to 350 DEG C, and after 15s of holding, it is cooled from 350 DEG C to 150 DEG C at a rate of 30 DEG C / s. After holding at 150 DEG C for 30s, it is naturally cooled. The metal atoms have a certain activity at 350 DEG C, which can release the residual stress generated during welding through dislocation slip and grain boundary diffusion, reducing the risk of cold cracking. The slow cooling from 350 DEG C to 150 DEG C is to avoid secondary stress. After dropping to 150 DEG C, the activity of metal atoms decreases, and the shrinkage deformation tends to be stable. At this time, slow cooling to room temperature, the stress residual is very low. The steel welding area data acquisition module includes a laser scanning galvanometer and a pulse frequency modulator. The laser scanning galvanometer is used to detect the temperature field distribution of the welding area, and the pulse frequency modulator detects the state of the plasma through the feathering stability to adjust the welding output power, the protective gas rate, the activated cooling nozzle and the parameters in real time by giving the collected data to the editable logic controller module. The editable logic controller module includes an intelligent control submodule and a steel grade transition submodule. The intelligent control sub-module transmits data collected by the steel welding area data acquisition module to a pre-edited logic control program, and realizes corresponding control operation according to logic processing, and the main functions are adjusting welding output power, protective gas rate, activating cooling nozzle and parameter optimization. The steel grade transition sub-module divides the transition process into three stages of parameter locking, parameter gradual change and new steel grade adaptation, and realizes smooth switching by sequentially adjusting the welding parameters; in the first stage, all welding parameters are fixed and no longer dynamically adjusted for the last 10 meters before the current steel grade welding is completed, so as to avoid unstable tail end welding quality caused by parameter fluctuation when approaching the transition zone; in the second stage, the transition zone length is set to 2-3 meters, and k gradually increases from 0 to 1 in this distance, so as to avoid welding energy fluctuation caused by parameter mutation; The third stage: when switching to a new steel material, first increase the standard parameter P_new of the new steel material by 10%, and then when the first roll is welded for a period of time, the parameter is adjusted back to the standard value P_new after confirming the stable welding quality through the sensor, so as to avoid the heat affected zone being too large and the grain being too coarse caused by long-term over-power on the premise of ensuring the initial welding quality; through the three-stage control of locking, gradual change and adaptation, seamless transition is realized: The gas protection module protects the molten pool from oxidation by spraying high-purity He in the inner layer as the core, directly covering the surface of the molten pool, forming an inert barrier to prevent O2 from contacting the high-temperature metal, and inhibiting oxidation from the source to avoid introducing trace impurities; the strong jet of 15-20L / min of the middle layer CO2 can penetrate the plasma cloud generated during welding to ensure that the gas reaches the molten pool; the outer layer N2 forms a closed space to isolate the environment air; a "three-layer barrier" is formed from the core of the molten pool to the peripheral environment, and the oxidation inhibition rate is increased.

[0012] The beneficial effects of the present application are: a laser energy control model is established by material strength, plate thickness and plate gap value, the output power of the fiber laser for the present steel material is determined, the output power and protective gas flow are adjusted according to the real-time parameters of the welding area by the control program during welding, precise welding is achieved, the strength retention rate is increased, the bubble generation is reduced, and the strip breakage rate is reduced; the high-temperature oxidation of the welding area is inhibited by the coaxial three-layer gradient gas, the strength retention rate is increased, the bubble generation is reduced, and the strip breakage rate is reduced; the residual stress is reduced by pre-heating before welding and double-temperature zone gradient annealing after welding, thereby further reducing the strip breakage rate; the adjustment time of cross-steel welding is greatly reduced by the cooperation of the three-stage steel grade transition and the laser energy control model, and the final effect is that the welding bubble is less than 3, the rolling breakage rate is less than 0.1‰, the strength retention rate is greater than or equal to 95%, and the adjustment time of the steel grade is the time of welding one roll. Attached Figure Description

[0013] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 A flowchart illustrating the method of this invention; Figure 2 This is a schematic diagram of the system structure of the present invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this application and in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0017] Example 1 provides a multi-parameter collaborative control laser welding method, the specific steps of which are as follows: Step S1: Obtain steel data through the front-end detection device, establish a laser energy control model based on the steel data, and adjust the output power according to the model to control the fiber laser; the specific steps are as follows: Step S11: Obtain the plate thickness h, material strength, and plate gap value g through the pre-installed thickness detector, material strength detector, and plate gap detector, and transmit the detection data back to the programmable logic controller; Step S12: The editable logic controller has a database that maintains data correspondence. The material yield strength σ is determined from the database based on the material strength. The corresponding adaptive coefficients k1, k2, and k3 are retrieved from the database based on the material yield strength σ, where k1 > 0 and k1 ≤ 275; k2 > 275 and k2 ≤ 400; k3 > 400 and k3 ≤ 980. Step S13, according to the material yield strength σ, the plate thickness h, the gap value g, the k1-k3 adaptive coefficient, the material strength-thickness-gap three-element coupling laser energy control model is established, the laser power calculation formula is used, the power P is obtained, the calculation formula is:

[0018] The output power of the fiber laser is adjusted according to the calculated power P.

[0019] Step S2, before welding, the heat affected zone of the steel to be welded is preheated; the specific steps are as follows: Step S21, before welding, the heat affected zone of the steel to be welded is preheated, and is uniformly heated to 200-300℃; Step S22, the heat affected zone is kept at the temperature in step S21 during the whole welding process.

[0020] Welding cracks are one of the most dangerous welding defects, and reducing the risk of cracks from the root causes is divided into two categories.

[0021] Cold cracks (delayed cracks): common in high-strength steel, low-alloy structural steel (such as Q345R, 16MnR) or thick plate welding. When this type of material is welded, the cooling speed of the molten pool is extremely fast (especially when the room temperature is low or the workpiece thickness is large), which can cause the weld and heat affected zone (HAZ) to form brittle and hard martensite structure, and the welding stress (thermal stress + organizational stress) is accumulated sharply, if there is hydrogen in the material at this time (water, oil stains decomposed during welding), hydrogen will diffuse to the stress concentration area, and finally induce cold cracks (which may occur several hours or even days after welding).

[0022] Hot cracks: common in austenitic stainless steel, aluminum alloy and other materials. When this type of material is welded, low-melting eutectic (such as eutectic of FeS and Fe in stainless steel, melting point 988℃) will be precipitated during the solidification process of the molten pool. If the temperature gradient of the welding area is too large, the tensile stress generated during solidification shrinkage will pull the low-melting eutectic apart, forming hot cracks.

[0023] Without preheating, the heat affected zone (HAZ) will form brittle and hard martensite or bainite structure due to rapid cooling, resulting in a sharp decrease in joint toughness, and even a hardened layer. Preheating can reduce the cooling rate, so that the HAZ structure is transformed into more ductile pearlite + ferrite or sorbite, which takes into account the strength and toughness. During welding, the molten pool cools rapidly from high temperature (about 1500-2000℃) to room temperature, which will cause severe thermal expansion and contraction, resulting in thermal stress (stress caused by temperature difference) and organizational stress (stress caused by volume change of phase transition) in the workpiece, which may eventually cause the workpiece to deform (such as bending, twisting) or the joint to crack.

[0024] Preheating before welding improves the thermal circulation conditions in the welding area by preheating the workpiece to be welded, thereby avoiding welding defects, ensuring joint performance, and improving welding quality. A preheating temperature of 200-300℃ can slow down the cooling rate of the heat-affected zone after welding, reducing the formation of brittle and hard structures such as martensite and improving the toughness of the heat-affected zone. Preheating can also reduce the temperature difference between the welding area and the base material, reducing thermal stress caused by thermal expansion and contraction, thus reducing residual stress from the source. Preheating can also reduce the melting resistance of the base material, making the molten pool metal easier to spread and reducing defects such as incomplete fusion and slag inclusions. The heat-affected zone needs to be heated uniformly to avoid localized overheating leading to coarse grains or insufficient localized temperature, which could result in hardening risks.

[0025] Step S3: After preheating, a control algorithm for the welding process is written using a programmable logic controller (PLC) to control the fiber laser power and shielding gas flow rate for steel welding. The specific steps are as follows: Step S31: After preheating is completed, a control algorithm for the welding process is written using a programmable logic controller. The control program is as follows: def weld_control(): while welding: temp_distribution = ir_camera.scan() plasma_state = plasma_monitor.read() if detect_keyhole_collapse(plasma_state): laser_power *= 0.95 gas_flow += 10% if hAZ_temp>critical_temp: cooling_nozzle.activate(temp_distribution.hotspots) model.predict(next_step_params) Step S32: A laser scanning galvanometer and a pulse frequency modulator are installed in the welding area. The laser scanning galvanometer is used to detect the temperature field distribution in the welding area. Its response time is ≤10ms each time. The pulse frequency modulator detects the state of the plasma through feather stability. Its response time is ≤5ms each time. The detection can be completed in a very short time to achieve precise control of welding. In step S33, when welding begins, the output power of the fiber laser is the power obtained in S13. The programmable logic controller (PLC) acquires the real-time temperature field distribution and plasma state, and according to the control program in step S31, realizes real-time control of the laser output power and the flow rate of the protective gas. The temperature of the heat-sensing zone is determined by the temperature field distribution and compared with the preset temperature, which is 30-35℃. If the temperature is higher than the preset temperature, the cooling nozzle is controlled to perform cooling treatment. The parameters acquired in this step are used for machine learning to continuously learn and optimize the parameters.

[0026] Step S4: A three-stage control algorithm is used during the welding process to transition between steel grades, and triple gas is used to protect the welding area; the specific steps are as follows: Step S41: During the welding process, a coaxial three-layer gradient gas is used to protect the welding area from oxidation. The three-layer gradient gas includes high-purity He gas, CO2, and N2. The inner layer is high-purity He gas, the middle layer is CO2, and the outer layer is N2. The outer layer of N2 forms a closed isolation space to block the intrusion of ambient air into the welding area. The middle layer of CO2 forms an annular gas curtain that surrounds the high-purity inner layer of He gas to form a protective zone, further blocking the intrusion of external air into the welding area. The high-purity He gas in the inner layer is injected at a flow rate of 15-20 L / min and acts directly on the weld to inhibit oxidation and protect the molten pool. It directly covers the surface of the molten pool to form an inert barrier, preventing O2 from contacting the high-temperature metal, inhibiting oxidation from the source, and avoiding the introduction of trace impurities. Its strong injection at a flow rate of 15-20 L / min can penetrate the plasma cloud generated by welding, ensuring that the gas reaches the molten pool directly, thus increasing the oxidation inhibition rate.

[0027] Step S42: During the welding process, if cross-steel-grade welding is involved, a three-stage steel grade transition control method is adopted to complete the cross-steel-grade welding. The three-stage steel grade transition uses the welding length as the timing reference, and from the tail end of the current steel grade to the front end of the new steel grade, the transition process is divided into three stages: parameter locking, parameter gradual change, and new steel grade adaptation. Smooth switching is achieved by orderly adjusting the welding parameters; the specific operation is as follows: Phase 1: In the last 10 meters before the current steel type is finished welding, all welding parameters are fixed and no further dynamic adjustments are made.

[0028] The second stage: The transition zone length is set to 2-3 meters. Within this distance, k increases linearly from 0 to 1. The transition zone control formula is: P_trans = k·P_new + (1-k)·P_old, where P_old is the fiber output power of the old steel plate, and P_new is the fiber output power of the steel plate to be welded. Both powers are obtained by using the laser energy control model to determine the fiber laser output power after the data is acquired from the front-end steel data acquisition. P_trans is the gradually changing power parameter. The specific transition process is as follows: At the start of the transition region, k=0 → P_trans = P_old, using the old parameters completely; At the midpoint of the transition region, k=0.5 → P_trans = 0.5·P_new + 0.5·P_old, with the old and new parameters each accounting for 50%; At the end of the transition zone, k=1 → P_trans = P_new, completely switching to the new welding parameters for the new steel.

[0029] The third stage: When welding new steel, the welding power of the first coil is increased by 10% as compensation. After the first coil has been welded for a period of time, the welding quality is confirmed to be stable by using a laser scanning galvanometer and pulse frequency modulator in the welding area. After this confirmation, the parameters are then adjusted back to the standard value P_new for new steel. The core algorithm for the three-stage steel grade transition in the editable logic controller is as follows: timeline title Steel type switching control timing section Current steel type 10m before welding completion: Parameter locking Transition zone (2-3m) Parameter Gradualization: Using a weighted average algorithm P_trans = k·P_new + (1-k)·P_old (k increases linearly from 0 to 1) new steel grades section First roll welding: 10% power increase compensation After the quality stabilizes: Switch to standard parameters Step S5: After welding, the heat-affected zone is annealed using a dual-temperature gradient heating method. The specific steps are as follows: Step S51: After welding is completed, the heat-affected zone of the welded steel is annealed using a dual-temperature gradient heating method. Step S52: The temperature in the first temperature zone is slowly heated to 350°C and maintained for 15 seconds. Step S53: After the first heat preservation zone reaches its heat preservation time, the temperature is slowly reduced to the second temperature zone. The temperature of the second temperature zone is 150℃, the cooling rate is 30℃ / s, the temperature is maintained for 30s, and after the heat preservation is stopped, the welded steel is allowed to cool naturally.

[0030] Therefore, the aforementioned multi-parameter collaborative control laser welding method establishes a three-element coupled laser energy control model based on material strength, plate thickness, and gap value. This model determines the output power of the fiber laser for the steel and, during welding, the control program adjusts the output power and shielding gas flow rate according to real-time parameters in the welding zone. This achieves precise welding, increased strength retention, reduced bubble generation, and lower breakage rate. Furthermore, the method utilizes a coaxial three-layer gradient gas to suppress high-temperature oxidation in the welding zone, further enhancing strength retention, reducing bubble generation, and lowering breakage rate. Preheating before welding and dual-temperature gradient annealing after welding control the temperature to reduce residual stress, thereby further reducing breakage rate. The combination of the three-stage steel grade transition and the laser energy control model significantly reduces the adjustment time for cross-steel grade welding. The final result is fewer than three weld bubbles, a breakage rate of less than 0.1‰, a strength retention rate ≥95%, and a steel grade change adjustment time equivalent to welding one coil.

[0031] Example 2, as Figure 2 As shown, a multi-parameter collaborative control laser welding system includes: a front-end steel data acquisition module, a steel data processing module, a heat-affected zone flame control module, a steel welding zone data acquisition module, a programmable logic controller module, and a gas protection module; The front-end steel data acquisition module includes a thickness detector, a material strength detector, and a plate gap detector. It obtains data through multi-directional detection of steel data, which facilitates accurate control of the output of laser welding power P. The steel data processing module retrieves relevant parameters from the database using data acquired by the front-end steel data acquisition module. This yields the material's yield strength σ and adaptive coefficients k1, k2, and k3. A three-dimensional coupled laser energy control model based on material strength, thickness, and gap is then established. The laser power calculation formula is used to obtain the power P. The calculation formula is as follows:

[0032] The fiber laser can be adjusted by setting the output power.

[0033] The heat-affected zone fire control module is divided into a preheating sub-module and a post-annealing sub-module. Preheating submodule: Before welding begins, the heat-affected zone (HAZ) is uniformly heated to 200-300℃ using heating equipment and maintained at this temperature during welding. This preheating temperature of 200-300℃ slows down the cooling rate of the HAZ after welding, reducing the formation of brittle and hard structures such as martensite and improving the HAZ's toughness. Preheating also reduces the temperature difference between the welding area and the base material, lowering the thermal stress caused by thermal expansion and contraction, thus reducing residual stress from the source. Furthermore, preheating reduces the melting resistance of the base material, making the molten pool metal easier to spread and reducing defects such as incomplete fusion and slag inclusions. The HAZ must be heated uniformly to avoid localized overheating leading to coarse grains or insufficient localized temperatures that could result in hardening.

[0034] Post-weld annealing submodule: After welding, once the weld has cooled to room temperature, the weld and heat-affected zone are subjected to dual-temperature gradient heating treatment using heating equipment. The first temperature zone is heated to 350℃, held for 15 seconds, and then cooled from 350℃ to 150℃ at a rate of 30℃ / s. After holding at 150℃ for 30 seconds, it is allowed to cool naturally. At 350℃, metal atoms have a certain degree of mobility and can release residual stress generated during welding through dislocation slip and grain boundary diffusion, reducing the risk of cold cracking. Slow cooling from 350℃ to 150℃ is to avoid secondary stress. After cooling to 150℃, the mobility of metal atoms decreases, and the shrinkage deformation tends to stabilize. At this point, slow cooling to room temperature results in extremely low residual stress. The data acquisition module for the steel welding area includes a laser scanning galvanometer and a pulse frequency modulator. The laser scanning galvanometer is used to detect the temperature field distribution in the welding area, and the pulse frequency modulator detects the state of the plasma through feather stability. The acquired data is then handed over to the programmable logic controller module for real-time adjustment of welding output power, protective gas rate, activation of cooling nozzles, and parameter optimization. The programmable logic controller module includes an intelligent control submodule and a steel grade transition submodule; The intelligent control submodule transmits the data collected by the steel welding area data acquisition module to the pre-edited logic control program. Based on the logic processing, it realizes the corresponding control operation. Its main functions are to adjust the welding output power, the protective gas rate, activate the cooling nozzle, and optimize parameters. Steel grade transition submodule: The transition process is divided into three stages: parameter locking, parameter gradual change, and new steel grade adaptation. Smooth switching is achieved by orderly adjusting welding parameters. First stage: In the last 10 meters before the end of welding for the current steel grade, all welding parameters are fixed and no longer dynamically adjusted to avoid unstable welding quality at the tail end due to parameter fluctuations when approaching the transition zone. Second stage: The length of the transition zone is set to 2-3 meters. Within this distance, k gradually increases from 0 to 1 to avoid welding energy fluctuations caused by abrupt parameter changes. The process involves gradually adapting the molten pool and heat-affected zone to the characteristics of the new steel grade. In the third stage, when initially switching to the new steel, the standard parameter P_new is increased by 10%. After the first coil has been welded for a period, and the welding quality is confirmed to be stable via sensors, the parameter is reverted back to the standard value P_new. This ensures initial welding quality while preventing excessive heat-affected zone and coarse grains caused by prolonged over-power welding. This three-stage control—lock-gradient-adaptation—achieves a seamless transition. The gas protection module, with its core high-purity He injection layer, provides anti-oxidation and molten pool protection, directly covering the molten pool surface to form an inert barrier. This prevents O2 from contacting the high-temperature metal, inhibiting oxidation at the source and avoiding the introduction of trace impurities. The strong injection at a flow rate of 15-20 L / min can penetrate the plasma cloud generated during welding, ensuring that the gas reaches the molten pool directly. The middle layer of CO2 forms a ring-shaped gas curtain that wraps around the inner He protection area, further blocking the intrusion of external air. The outer layer of N2 forms a closed space for isolation, completely blocking ambient air. This "triple barrier" from the core of the molten pool to the surrounding environment increases the oxidation inhibition rate.

[0035] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-parameter collaborative control laser welding method, characterized in that, Includes the following steps: Step S1: Obtain multi-dimensional data of the steel to be welded through front-end detection, establish a laser energy control model based on the obtained multi-dimensional data of the steel, and adjust the output power according to the model to control the fiber laser; Step S2: Before welding, preheat the heat-affected zone of the steel to be welded; Step S3: After preheating is completed, the control algorithm for the welding process is written through the programmable logic controller to control the power of the fiber laser, the flow rate of the protective gas, the activation of the cooling nozzle, and the parameter optimization to perform steel welding. Step S4: Triple gas is used to protect the welding area during the welding process. If cross-steel welding is involved, a three-stage control algorithm for steel grade transition is used to perform steel grade transition during the welding process. Step S5: After welding is completed, the heat-affected zone is annealed by a dual-temperature gradient heating method.

2. The multi-parameter collaborative control laser welding method according to claim 1, characterized in that: Step S1 includes the following specific steps: Step S11: Obtain the plate thickness h, material strength, and plate gap value g through the front-end thickness detector, material strength detector, and plate gap detector, and transmit the detection data back to the programmable logic controller; Step S12: The editable logic controller has a database that maintains data correspondence. The material yield strength σ is determined from the database based on the material strength, and the adaptive coefficients k1, k2, and k3 are retrieved from the database based on the material yield strength σ. Step S13: Based on the material yield strength σ, plate thickness h, gap value g, and k1-k3 adaptive coefficients, a three-element coupled laser energy control model of material strength-thickness-gap is established. The power P is obtained using the laser power calculation formula, which is: Adjust the output power of the fiber laser based on the calculated power P.

3. The multi-parameter collaborative control laser welding method according to claim 1, characterized in that: Step S2 includes the following specific steps: Step S21: Before welding, preheat the heat-affected zone of the steel to be welded to 200-300℃. Step S22: The heat-affected zone maintains the temperature of step S21 throughout the welding process.

4. The multi-parameter collaborative control laser welding method according to claim 1, characterized in that: Step S3 includes the following specific steps: Step S31: After preheating is completed, a control algorithm for the welding process is written using a programmable logic controller. The control program is as follows: def weld_control(): while welding: temp_distribution = ir_camera.scan() plasma_state = plasma_monitor.read() if detect_keyhole_collapse(plasma_state): laser_power *= 0.95 gas_flow += 10% if hAZ_temp > critical_temp: cooling_nozzle.activate(temp_distribution.hotspots) model.predict(next_step_params) Step S32: A laser scanning galvanometer and a pulse frequency modulator are installed in the welding area. The laser scanning galvanometer is used to detect the temperature field distribution in the welding area, and the pulse frequency modulator detects the state of the plasma through feather stability. In step S33, the programmable logic controller (PLC) acquires the real-time temperature field distribution and plasma state, and according to the control program in step S31, realizes real-time control of laser output power and protective gas flow rate. By comparing the temperature of the thermal sensing zone with the preset temperature through the temperature field distribution, if it is higher than the preset temperature, the cooling nozzle is controlled to perform cooling treatment. The parameters acquired this time are used for machine learning to continuously optimize the parameters.

5. The multi-parameter collaborative control laser welding method according to claim 1, characterized in that: Step S4 includes the following specific steps: Step S41: During the welding process, a coaxial three-layer gradient gas is used to protect the welding area from oxidation. The three-layer gradient gas includes high-purity He gas, CO2, and N2. Step S42: During the welding process, if there is cross-steel type welding, the three-stage control method for steel type transition is adopted to complete the cross-steel type welding.

6. The multi-parameter collaborative control laser welding method according to claim 1, characterized in that: Step S5 includes the following specific steps: Step S51: After welding is completed, the heat-affected zone of the welded steel is annealed using a dual-temperature gradient heating method. Step S52: The temperature in the first temperature zone is slowly heated to 350°C and maintained for 15 seconds. Step S53: After the first heat preservation zone reaches its heat preservation time, the temperature is slowly reduced to the second temperature zone. The temperature of the second temperature zone is 150℃, the cooling rate is 30℃ / s, the temperature is maintained for 30s, and after the heat preservation is stopped, the welded steel is allowed to cool naturally.

7. The multi-parameter collaborative control laser welding method according to claim 2, characterized in that: k1 > 0 and k1 ≤ 275; k2 > 275 and k2 ≤ 400; k3 > 400 and k3 ≤ 980.

8. The multi-parameter collaborative control laser welding method according to claim 5, characterized in that: The coaxial three-layer gradient gas consists of a high-purity He gas in the inner layer, CO2 in the middle layer, and N2 in the outer layer. The outer N2 layer forms a closed isolation space to block the intrusion of ambient air. The CO2 in the middle layer forms an annular gas curtain that surrounds the inner He layer to form a protective zone, further blocking the intrusion of external air. The high-purity He gas in the inner layer is injected at a flow rate of 15-20 L / min and acts directly on the weld to inhibit oxidation at the weld.

9. The multi-parameter collaborative control laser welding method according to claim 5, characterized in that: The three-stage steel grade transition uses welding length as the timing reference. From the end of the current steel grade to the beginning of the new steel grade, the transition process is divided into three stages: parameter locking, parameter gradual change, and new steel grade adaptation. Smooth switching is achieved by orderly adjusting welding parameters. The specific operation is as follows: Phase 1: In the last 10 meters before the current steel type is finished welding, all welding parameters are fixed and no further dynamic adjustments are made; Second stage: The transition zone length is set to 2-3 meters. Within this distance, k increases linearly from 0 to 1. At the start of the transition region, k=0 → P_trans = P_old, using the old parameters completely; At the midpoint of the transition region, k=0.5 → P_trans = 0.5·P_new + 0.5·P_old, with the old and new parameters each accounting for 50%; At the end of the transition zone, k=1 → P_trans = P_new, completely switching to the new welding parameters for the new steel; The third stage: The welding power of the first coil is increased by 10% as compensation. After the first coil has been welded for a period of time, once the welding quality is confirmed to be stable by sensors, the parameters are adjusted back to the standard value P_new for new steel. The core algorithm for the three-stage steel grade transition in the editable logic controller is as follows: timeline title Steel type switching control timing section Current steel type 10m before welding completion: Parameter locking Transition zone (2-3m) Parameter Gradualization: Using a weighted average algorithm P_trans = k·P_new + (1-k)·P_old (k increases linearly from 0 to 1) new steel grades section First roll welding: 10% power increase compensation After the quality stabilizes: Switch to standard parameters P_trans represents the power parameter that changes gradually, P_new represents the power parameter of the new material, and P_old represents the power parameter of the old material.

10. A multi-parameter collaborative control laser welding system, characterized in that: The system includes: a front-end steel data acquisition module, a steel data processing module, a heat-affected zone fire control module, a steel welding zone data acquisition module, a programmable logic controller module, and a gas protection module; The front-end steel data acquisition module includes a thickness detector, a material strength detector, and a plate gap detector. It obtains data through multi-directional detection of steel data, which facilitates accurate control of the output of laser welding power P. The steel data processing module retrieves relevant parameters from the database using data acquired by the front-end steel data acquisition module. This yields the material's yield strength σ and adaptive coefficients k1, k2, and k3. A three-dimensional coupled laser energy control model based on material strength, thickness, and gap is then established. The laser power calculation formula is used to obtain the power P. The calculation formula is as follows: The fiber laser can be adjusted by setting the output power. The heat-affected zone fire control module is divided into a preheating sub-module and a post-annealing sub-module. Preheating submodule: Before welding begins, the heat-affected zone (HAZ) is uniformly heated to 200-300℃ using heating equipment and maintained at this temperature during welding. This preheating temperature of 200-300℃ slows down the cooling rate of the HAZ after welding, reducing the formation of brittle and hard structures such as martensite and improving the toughness of the HAZ. Preheating also reduces the temperature difference between the welding area and the base material, lowering the thermal stress caused by thermal expansion and contraction, thus reducing residual stress from the source. Furthermore, preheating reduces the melting resistance of the base material, making the molten pool metal easier to spread and reducing defects such as incomplete fusion and slag inclusions. The HAZ must be heated uniformly to avoid localized overheating leading to coarse grains or insufficient localized temperatures that could result in hardening. Post-weld annealing submodule: After welding, once the weld has cooled to room temperature, the weld and heat-affected zone are subjected to dual-temperature gradient heating treatment using heating equipment. The first temperature zone is heated to 350℃, held for 15 seconds, and then cooled from 350℃ to 150℃ at a rate of 30℃ / s. After holding at 150℃ for 30 seconds, it is allowed to cool naturally. At 350℃, metal atoms have a certain degree of mobility and can release residual stress generated during welding through dislocation slip and grain boundary diffusion, reducing the risk of cold cracking. Slow cooling from 350℃ to 150℃ is to avoid secondary stress. After cooling to 150℃, the mobility of metal atoms decreases, and the shrinkage deformation tends to stabilize. At this point, slow cooling to room temperature results in extremely low residual stress. The data acquisition module for the steel welding area includes a laser scanning galvanometer and a pulse frequency modulator. The laser scanning galvanometer is used to detect the temperature field distribution in the welding area, and the pulse frequency modulator detects the state of the plasma through feather stability. The acquired data is then handed over to the programmable logic controller module for real-time adjustment of welding output power, protective gas rate, activation of cooling nozzles, and parameter optimization. The programmable logic controller module includes an intelligent control submodule and a steel grade transition submodule; The intelligent control submodule transmits the data collected by the steel welding area data acquisition module to the pre-edited logic control program. Based on the logic processing, it realizes the corresponding control operation. Its main functions are to adjust the welding output power, the protective gas rate, activate the cooling nozzle, and optimize parameters. Steel grade transition submodule: The transition process is divided into three stages: parameter locking, parameter gradual change, and new steel grade adaptation. Smooth switching is achieved by orderly adjusting welding parameters. First stage: In the last 10 meters before the end of welding for the current steel grade, all welding parameters are fixed and no longer dynamically adjusted to avoid unstable welding quality at the tail end due to parameter fluctuations when approaching the transition zone. Second stage: The length of the transition zone is set to 2-3 meters. Within this distance, k gradually increases from 0 to 1 to avoid welding energy fluctuations caused by abrupt parameter changes. The process involves gradually adapting the molten pool and heat-affected zone to the characteristics of the new steel grade. In the third stage, when initially switching to the new steel, the standard parameter P_new is increased by 10%. After the first coil has been welded for a period, and the welding quality is confirmed to be stable via sensors, the parameter is reverted back to the standard value P_new. This ensures initial welding quality while preventing excessive heat-affected zone and coarse grains caused by prolonged over-power welding. This three-stage control—lock-gradient-adaptation—achieves a seamless transition. The gas protection module, with its core high-purity He injection layer, provides anti-oxidation and molten pool protection, directly covering the molten pool surface to form an inert barrier. This prevents O2 from contacting the high-temperature metal, inhibiting oxidation at the source and avoiding the introduction of trace impurities. The strong injection at a flow rate of 15-20 L / min can penetrate the plasma cloud generated during welding, ensuring that the gas reaches the molten pool directly. The middle layer of CO2 forms a ring-shaped gas curtain that wraps around the inner He protection area, further blocking the intrusion of external air. The outer layer of N2 forms a closed space for isolation, completely blocking ambient air. This "triple barrier" from the core of the molten pool to the surrounding environment increases the oxidation inhibition rate.

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