A welding method for preheating weld seams by recycling residual light

Abstract

The present invention proposes a welding method for recycling residual light to preheat a weld. The method includes workpiece preparation, initializing welding parameters and operating parameters, welding point division, starting welding, monitoring the welding process, welding quality detection, and weld defect repairing steps. By adding a preheating device with an arc structure, not only the impact of spatter and smoke generated by the laser welding process on the welding quality and the working environment is solved, but also the reflected laser is effectively recycled and utilized as a preheating heat source, which greatly reduces the waste of welding energy and effectively avoids the damage of the laser head to the reflected laser. At the same time, the preheating speed is accurately adjusted according to the welding parameters to ensure that the weld reaches the ideal preheating temperature before welding. Appropriate adjustment of the preheating speed can ensure that the laser residual light is effectively recycled and utilized, thereby improving energy utilization efficiency. The preheating treatment reduces the temperature gradient between the weld and the base material, thereby reducing the thermal stress caused by rapid heating and cooling and improving the quality of the weld.

Description

Technical Field

[0001] The invention relates to the technical field of welding, and in particular to a welding method for preheating a weld by recycling residual light. Background Art

[0002] During the laser welding process, especially when welding stainless steel or highly reflective materials with high surface finish, part of the energy of the laser beam is not effectively converted into welding heat energy, but is reflected back to the environment, resulting in a waste of welding energy. In order to compensate for this part of the energy loss, the conventional practice is to increase the laser power to enhance the penetration of the laser to ensure that the weld can be fully penetrated. However, greater laser power means greater welding energy loss, which not only greatly increases production costs, but also increases the probability of risk. If the laser returns to the laser head through the welding gun, it will reduce the service life of the laser head or even damage the laser head; if the laser is reflected into space, it will burn the surrounding objects; secondly, high-energy-density laser welding is very likely to induce welding spatter and smoke. Spatter will not only reduce the quality of the weld, but also increase subsequent processing work, such as spatter treatment of workpieces and equipment. Welding smoke will cause laser welding energy loss and unstable welding process, causing serious pollution to the working environment.

[0003] Therefore, there is an urgent need to provide a welding method that can reduce unnecessary consumption of welding energy, suppress interference from welding spatter and smoke, and comprehensively improve welding quality and economic benefits, so as to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a welding method for recycling residual light to preheat the weld, so as to solve the above-mentioned problems of the prior art.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A welding method for preheating a weld by recycling residual light comprises the following steps:

[0007] S1. Workpiece preparation: positioning and fixing the laser welding gun and the preheating device according to the welding process requirements. The preheating device is arranged in front of the laser welding gun and directly above the joint to be welded, and is used to preheat the joint to be welded. The axial directions of the preheating device and the laser welding gun form an inclination angle α and an inclination angle β with the forward direction of the welding path respectively.

[0008] The inclination angle α formed by the axial direction of the preheating device and the advancing direction of the welding path is 180°, that is, the preheating device is parallel to the welding path, and the inclination angle β formed by the axial direction of the laser welding gun and the advancing direction of the welding path is 105° to 115°;

[0009] The laser welding gun is rotatably mounted on the first fixed plate through a rotating assembly, and a laser head is provided at the output end of the laser welding gun, and the laser head emits a laser beam to the joint to be welded;

[0010] The preheating device is rotatably mounted on the second fixed plate through the rotating assembly, and the preheating device includes a preheating shell, a reflective baffle and a heat exchange tube bundle. The open end surface of the preheating shell is matched and connected with the reflective baffle to form a heat exchange chamber. A preheating space is formed between the reflective baffle and the joint to be welded. One end of the heat exchange tube bundle is inserted into the preheating shell, and the other end is connected to an external cooling medium flow system. The laser receiving surface of the reflective baffle faces the joint to be welded. The reflective baffle is made of copper, and the reflective baffle is an arc-shaped panel, and the concave side of the arc-shaped panel is the laser receiving surface.

[0011] The first fixing plate and the second fixing plate are both slidably mounted on the slide groove, and the axial direction of the slide groove is parallel to the welding path;

[0012] The laser welding gun, the preheating device and the rotating assembly are all electrically connected to the control assembly of the external device;

[0013] The control component adjusts the angle and distance between the laser welding gun and the preheating device so that the distance between the action point of the preheating laser and the action point of the laser beam emitted by the laser head is 5 to 10 mm;

[0014] S2. Initialize the welding parameters of the laser welding gun and the operating parameters of the preheating device: Set the welding parameters of the laser welding gun and the operating parameters of the preheating device according to the material properties and welding process requirements. The welding parameters include the laser output power P 1 With welding speed v 1 The operating parameters include the preheating speed v 2 and preheating temperature T;

[0015] The preheating speed v 2 The preheating temperature T and the laser output power P 1 Determine, satisfying the following formula:

[0016] ,

[0017]

[0018] Where: R 1 is the reflectivity of the joint to be welded, R 2is the reflectivity of the reflective baffle, γ is the absorption coefficient of the joint to be welded to the preheating laser, R is the spot diameter of the preheating laser, c is the specific heat capacity of the joint to be welded, m is the mass of the preheating area, △T is the preheating temperature difference of the joint to be welded, T is the preheating temperature of the joint to be welded, T 0 is room temperature;

[0019] S3, welding point division: according to the welding process requirements and the welding gun capacity, the spot size of the laser beam is set, and the welding path is divided into n welding points according to the preset spot size, namely the first welding point, the second welding point ... the nth welding point;

[0020] S4, start welding: start the laser welding gun to weld the first welding point of the welding path, the laser beam is emitted from the laser head, and is reflected from the surface of the joint to be welded to the laser receiving surface of the reflective baffle, the laser receiving surface recovers and focuses the reflected laser beam, i.e., preheats the laser, and guides the preheated laser to the second welding point of the welding path, completing the preheating treatment of the second welding point, the laser beam emitted by the laser head performs welding treatment on the preheated second welding point, and the remaining welding points on the welding path are preheated and welded in turn until all welding points have completed the preheating and welding treatment, and the joint to be welded forms a complete weld, and the cooling medium flow system is used to cool down the preheating device during the whole welding process;

[0021] S5. Monitoring the welding process: During the whole welding process, the infrared temperature sensor is used to monitor the preheating of the welding point in real time, and the monitoring result is transmitted to the control component, and the control component dynamically adjusts the welding parameters and the operating parameters according to the monitoring result;

[0022] S6. Welding quality inspection: Perform nondestructive inspection on all the welds, randomly select several groups of weld samples for mechanical property testing, and generate a quality inspection report.

[0023] As a preferred technical solution of the present invention, it also includes:

[0024] S7. Weld defect repair: When the quality inspection result of the weld does not meet the welding quality requirements, the defective weld needs to be repaired, and the repair area needs to 100% cover the defective weld. The repair process includes laser welding repair, resistance spot welding repair, and arc welding repair.

[0025] Furthermore, the preheating speed v 2 Greater than or equal to the welding speed v 1 .

[0026] Furthermore, when the preheating speed v 2 Greater than the welding speed v1 When the laser beam is reflected by the joint to be welded, the control component adjusts the inclination angle α in real time so that the reflective baffle can always receive the laser beam reflected by the joint to be welded.

[0027] As a preferred technical solution of the present invention, a positioning tracker for real-time visual identification of the actual position of the welding spot is provided in the forward direction of the preheating device. The positioning tracker transmits the identification data to the control component for comparison and analysis. Once it is detected that the actual position of the welding spot deviates from the welding path by an amount exceeding a set threshold, an alarm signal is immediately triggered to alert the operator to take adjustment measures.

[0028] As a preferred technical solution of the present invention, the nondestructive testing in step S6 includes penetration testing, radiographic testing and ultrasonic testing, and the mechanical property testing includes transverse tensile testing, bending testing, shear tensile testing and fatigue testing.

[0029] The beneficial effects of the present invention are:

[0030] 1. The present invention realizes the recycling of residual light generated during laser welding by adding an arc-shaped preheating device in front of the laser welding gun, which not only reduces the spatter and smoke that may be generated during laser welding, thereby reducing the negative impact of these factors on welding quality and working environment, but also avoids the potential damage of reflected laser to the laser head, and prolongs the service life of the equipment; it also provides efficient protection and heat insulation functions. In addition, through preheating treatment, the temperature gradient between the weld and the base material is reduced, and the thermal stress caused by rapid heating and cooling is effectively reduced, thereby improving the overall quality of the weld.

[0031] 2. The present invention derives the preheating speed v by establishing the energy formula of the laser beam after multiple reflections 2 With preheating temperature T, laser output power P 1 The precise control relationship allows the preheating speed v to be adjusted according to the specific welding process requirements. 2 , ensuring that the solder joint reaches the ideal preheating temperature before welding, not only ensures the welding quality, but also ensures the effective recovery and utilization of the laser residual light, thereby significantly improving the energy utilization efficiency. In addition, when the preheating speed v 2 Greater than welding speed v 1 When the laser beam is reflected by the welding joint, the control component can adjust the inclination angle α of the preheating device in real time to ensure that the reflective baffle can always effectively receive the laser beam reflected by the welding joint, further optimizing the use of energy.

[0032] 3. Use infrared temperature sensors to monitor the preheating of solder joints in real time, capture subtle temperature changes in the welding area, and dynamically adjust the welding parameters and operating parameters in combination with control components to adapt to unforeseen deviations that may occur during the welding process, ensuring that the preheating temperature control during the welding process is more accurate, and effectively reducing welding defects caused by improper temperature control, such as cracks, pores, etc. For example, excessive preheating temperature causes excessive melting of the metal, making the weld brittle; too low preheating temperature results in insufficient preheating, affecting the consistency of weld quality.

[0033] 4. During the preheating process, the workpiece may be displaced due to thermal expansion, mechanical vibration or other external factors. By adding a positioning tracker in front of the preheating device to monitor the position of the weld in real time, the deviation of the weld position can be discovered in time, and the welding path can be automatically adjusted to reduce the problem of insufficient or uneven preheating caused by inaccurate position. The positioning tracker can adapt to these changes, especially for complex or irregular welding paths, and can ensure the uniformity and consistency of the preheating effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A flow chart of a welding method for preheating a weld by recycling residual light according to the present invention;

[0035] Figure 2 This is a working schematic diagram of the laser welding gun and the preheating device of the present invention;

[0036] Figure 3 It is a schematic diagram of the preheating device of the present invention;

[0037] In the figure, 1-preheating device, 11-preheating shell, 12-reflective baffle, 121-laser receiving surface, 13-heat exchange tube bundle, 14-heat exchange chamber, 2-laser welding gun, 21-laser head, 3-joint to be welded, 4-first fixed plate, 5-second fixed plate, 6-slide groove. DETAILED DESCRIPTION

[0038] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments given here are only used to illustrate and explain the present invention, and cannot be used to limit the present invention.

[0039] It should be noted that many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention may also have other implementations and variations thereof. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0040] As attached Figures 1 to 3 As shown, a welding method for preheating a weld by recycling residual light according to an embodiment of the present invention comprises the following steps:

[0041] S1. Workpiece preparation: Position and fix the laser welding gun 2 and the preheating device 1 according to the welding process requirements. The preheating device 1 is arranged in front of the laser welding gun 2 and directly above the joint 3 to be welded, and is used to preheat the joint 3 to be welded. The axial directions of the preheating device 1 and the laser welding gun 2 form an inclination angle α and an inclination angle β with the forward direction of the welding path respectively.

[0042] By precisely adjusting the inclination angle α and the inclination angle β, it can be ensured that the laser beam can efficiently transmit energy during the welding process, and the preheating device 1 can also accurately guide the reflected laser energy to the welding area.

[0043] Among them, the inclination angle α formed by the axial direction of the preheating device 1 and the forward direction of the welding path is 180°, that is, the preheating device 1 is parallel to the welding path, and the inclination angle β formed by the axial direction of the laser welding gun 2 and the forward direction of the welding path is 105°~115°.

[0044] The laser welding gun 2 is rotatably mounted on the first fixed plate 4 through a rotating assembly (not shown in the figure), and a laser head 21 is provided at the output end of the laser welding gun 2, and the laser head 21 emits a laser beam to the joint 3 to be welded;

[0045] The preheating device 1 is rotatably mounted on the second fixed plate through a rotating assembly. The preheating device 1 includes a preheating shell 11, a reflective baffle 12, and a heat exchange tube bundle 13. The open end surface of the preheating shell 11 is matched and connected with the reflective baffle 12 to form a heat exchange chamber 14. A preheating space is formed between the reflective baffle 12 and the joint to be welded 3. One end of the heat exchange tube bundle 13 is inserted into the preheating shell 11, and the other end is connected to an external cooling medium flow system (not shown in the figure). The laser receiving surface 121 of the reflective baffle 12 is arranged facing the joint to be welded 3.

[0046] The reflective baffle 12 of this embodiment is made of copper and is an arc-shaped panel structure, and the concave side of the arc-shaped panel is the laser receiving surface;

[0047] Since copper has good thermal conductivity and reflective properties, it can conduct heat energy quickly and effectively, which helps to concentrate the scattered laser energy and ensure that as much scattered laser light as possible is reflected back to the weld. Therefore, the reflective baffle 12 made of copper becomes an ideal choice for recycling laser light in laser welding.

[0048] The first fixing plate 4 and the second fixing plate 5 are both slidably mounted on the slide groove 6, and the axial direction of the slide groove 6 is parallel to the welding path;

[0049] The laser welding gun 2, the preheating device 1 and the rotating assembly are all electrically connected to the peripheral control assembly (not shown);

[0050] The control component adjusts the angle and distance between the laser welding gun 2 and the preheating device 1 so that the distance between the action point of the preheating laser and the action point of the laser beam emitted by the laser head 21 is 5 to 10 mm.

[0051] S2, initializing the welding parameters of the laser welding gun 2 and the operating parameters of the preheating device 1: setting the welding parameters of the laser welding gun 2 and the operating parameters of the preheating device 1 according to the material properties and welding process requirements. The welding parameters include the laser output power P 1 With welding speed v 1 , operating parameters include preheating speed v 2 and preheating temperature T;

[0052] In this embodiment, a steel plate made of 304 stainless steel and 2.8 mm thick is to be welded to form a steel cylinder. The welded joint 3 is a butt joint with a gap of 0.2 mm. The weld width is required to be 2.0 mm. The room temperature T 0 The laser output power P is set based on the material properties of the plate to be welded and the welding process requirements. 1 3000J / s, welding speed v 1 It is 1.8m / min.

[0053] The preheating temperature T of 304 stainless steel should be higher than the bainite transformation temperature of the joint 3 to be welded and lower than the critical temperature. The bainite transformation temperature refers to the temperature at which the material changes from ferromagnetism to non-ferromagnetism. The preheating temperature T is higher than the bainite transformation temperature of the material, which can effectively avoid deformation and cracks caused by bainite phase transformation during welding. Preheating promotes the formation of fine bainite structure, thereby improving the toughness and overall performance of the weld. The critical temperature refers to the temperature at which the thermal expansion coefficient of the material changes suddenly. The preheating temperature T is lower than the critical temperature, which can effectively avoid stress concentration and cracks caused by the sudden change of thermal expansion coefficient during welding. The bainite transformation temperature of 304 stainless steel is 200℃ and the critical temperature is 450℃, so the value of the preheating temperature T should be between 200℃ and 450℃. During the welding process, because the welding material is in a high temperature state, the metal material is very easy to absorb too much hydrogen, hydrogen embrittlement occurs, resulting in increased brittleness of the welded joint, thereby reducing the strength and toughness of the welded joint. Therefore, in order to avoid the occurrence of hydrogen embrittlement, the preheating temperature T should be greater than or equal to 200℃. In summary, based on the considerations of the bainite transformation temperature, critical temperature and hydrogen embrittlement of the material, the preheating temperature T should be between 200°C and 450°C. The preheating temperature T in this embodiment is 300°C.

[0054] Preheating speed v of preheating device 1 2 The preheating temperature T and the laser output power P 1 Determine, satisfying the following formula:

[0055] ,

[0056]

[0057] Where: R 1 is the reflectivity of the joint 3 to be welded, R 2 is the reflectivity of the reflective baffle 12, γ is the absorption coefficient of the joint 3 to be welded to the preheating laser, R is the spot diameter of the preheating laser, c is the specific heat capacity of the joint 3 to be welded, m is the mass of the preheating area, △T is the preheating temperature difference of the joint 3 to be welded, T is the preheating temperature of the joint 3 to be welded, T 0 It is room temperature.

[0058] Reflectivity R of 304 stainless steel welded joint 3 1 is 0.25, the absorption coefficient γ is 0.75, the specific heat capacity c is 522 J / (kg·℃), and the reflectivity R of the reflective baffle 12 made of copper 2 is 0.8. Since the preheating temperature T is selected as 300°C, the room temperature T 0 is 23°C, so the preheating temperature difference of the joint 3 to be welded is △T=TT 0 =277℃. Based on the design requirement that the weld seam width is 2.0mm, in order to ensure sufficient preheating of the weld seam area, the spot diameter of the preheating laser should be adjusted to be slightly larger than the weld width. In this embodiment, the spot diameter R of the preheating laser is adjusted to 3mm, which can ensure the effective distribution of the preheating laser energy in the weld seam and its surrounding areas. Therefore, the mass m of the preheating area is 0.144g. The preheating speed v can be obtained according to the above formula. 2 Satisfies the following formula:

[0059]

[0060]

[0061] Therefore, to ensure that each soldering point can be preheated to 300°C, the preheating speed v 2 The value should be 2.92m / min, that is, the preheating speed v 2 Greater than welding speed v 1 In order to ensure that the reflective baffle 12 can always receive the laser beam reflected by the joint 3 to be welded, the control component should adjust the tilt angle α in real time. Therefore, in this embodiment, the tilt angle α is dynamically changed, and the tilt angle β is set to 105°.

[0062] During laser welding, when the reflected laser energy is large, the preheating speed v should be appropriately increased. 2 It can ensure that the preheating temperature of the solder joint will not fluctuate due to changes in laser energy, thereby making full use of the laser energy for effective preheating. 2Faster than welding speed v 1 In the case of a preheating speed v, it is particularly important to adjust the inclination angle α of the reflective baffle 12 in real time. The core purpose is to maintain the precise orientation of the laser beam and ensure that the laser beam reflected from the welded joint 3 is always aligned with the best receiving surface of the reflective baffle 12. 2 Higher than welding speed v 1 In this case, the reflective baffle 12 can also play its role to the extreme, efficiently capturing and focusing laser energy. By finely adjusting the tilt angle α, the system can optimize the reflection path of the laser, promote the effective absorption and concentration of heat energy, not only greatly reducing the ineffective loss of heat energy to the surrounding environment, but also ensuring a more uniform and reasonable temperature distribution in the welding area, forming an ideal temperature gradient, and creating stable preheating conditions for the welding process.

[0063] S3. Welding point division: according to the welding process requirements and the welding gun capacity, the spot size of the laser beam is set, and the welding path is divided into n welding points according to the preset spot size, namely the first welding point, the second welding point...the nth welding point;

[0064] S4, start welding: start the laser welding gun 2 to weld the first welding point of the welding path, the laser beam is emitted from the laser head 21, and is reflected from the surface of the joint 3 to be welded to the laser receiving surface 121 of the reflective baffle 12, the laser receiving surface 121 recovers and focuses the reflected laser beam, i.e., preheats the laser, and guides the preheated laser to the second welding point of the welding path, completing the preheating treatment of the second welding point, the laser beam emitted by the laser head 21 welds the preheated second welding point, and the remaining welding points on the welding path are preheated and welded in turn until all welding points have completed the preheating and welding treatment, and the joint 3 to be welded forms a complete weld, and the cooling medium flow system is used to cool the preheating device 1 during the whole welding process;

[0065] The laser is emitted from the laser head 21 and irradiated onto the first welding point of the joint to be welded 3. In this process, part of the laser energy is reflected by the surface of the joint to be welded 3 and directed toward the laser receiving surface 121 of the reflective baffle 12 set aside. The laser receiving surface 121 of the reflective baffle 12 can not only receive these reflected laser beams, but also focus these laser beams through its special geometric shape, thereby enhancing the energy density of the beam. The focused laser beam is then accurately guided to the next welding point in the welding path. This guiding and focusing operation provides the necessary preheating treatment for the next welding point, effectively reduces the material hardness of the welding area, reduces the energy required during the welding process, and also helps to reduce welding spatter and smoke. This process will be repeated on all welding points of the entire welding joint. Each welding point undergoes preheating before the actual welding is performed, ensuring the consistency of the welding process and the uniformity of the weld. All welding points of the entire welding joint will be completed through this efficient preheating and welding cycle, thereby achieving high-quality welding results.

[0066] S5. Monitoring the welding process: During the whole welding process, an infrared temperature sensor (not shown) is used to monitor the preheating of the welding spot in real time, and the monitoring results are transmitted to the control component. The control component dynamically adjusts the welding parameters and operating parameters according to the monitoring results;

[0067] S6. Welding quality inspection: Perform non-destructive testing on all welds, randomly select several groups of weld samples for mechanical property testing, and generate a quality inspection report.

[0068] An optional method in the embodiment of the present invention further includes:

[0069] S7. Weld defect repair: When the quality inspection results of the weld do not meet the welding quality requirements, the defective weld needs to be repaired, and the repair area needs to 100% cover the defective weld. The repair processes include laser welding repair, resistance spot welding repair, and arc welding repair.

[0070] For the repair of defective welds, the laser welding repair process is preferred, followed by the resistance spot welding repair process. The arc welding repair process is used only when the first two repair processes cannot be used. When there are structural blind spots and other factors, multiple weld repair methods can be combined and carried out simultaneously. This is because laser welding can change the properties of the parent material to a minimum extent with its extremely narrow heat-affected zone, achieving highly precise local heating. Low heat input reduces the possibility of new defects caused by thermal stress and is suitable for repairing precision or thin-walled structures; although the heat input of resistance spot welding is slightly higher than that of laser welding, it can still act relatively concentratedly on the repair area, which is suitable for the repair of lightweight materials, especially heat-sensitive metals such as aluminum and magnesium alloys; arc welding has the largest heat input, a wide range of heat-affected areas, and is prone to cause large deformation and microstructural damage, so it is only used when the first two are not feasible.

[0071] When using the laser welding repair process, the minimum distance between the center of the repair weld and the original weld should be no less than 2mm, and the length of the repair weld should be at least 20mm longer than the defective weld, that is, both ends of the repair weld must cover the original weld by at least 10mm.

[0072] In an optional manner in an embodiment of the present invention, a positioning tracker (not shown in the figure) for real-time visual identification of the actual position of the welding spot is provided in the forward direction of the preheating device 1. The positioning tracker transmits the identification data to the control component for comparison and analysis. Once it is detected that the actual position of the welding spot deviates from the welding path by an amount exceeding a set threshold, an alarm signal is immediately triggered to warn the operator to take adjustment measures.

[0073] During the preheating process, the workpiece may be displaced due to thermal expansion, mechanical vibration or other external factors. By adding a positioning tracker in front of the preheating device to monitor the position of the weld in real time, the deviation of the weld position can be discovered in time, and the welding path can be automatically adjusted to reduce the problem of insufficient or uneven preheating caused by inaccurate position. The positioning tracker can adapt to these changes and is especially suitable for complex or irregular welding paths, which can ensure the uniformity and consistency of the preheating effect.

[0074] In an optional manner in an embodiment of the present invention, the nondestructive testing in step S6 includes penetration testing, radiographic testing and ultrasonic testing, and the mechanical property testing includes transverse tensile testing, bending testing, shear tensile testing and fatigue testing.

[0075] It should be understood that the above-mentioned embodiments are one or more embodiments of the present invention, and there are many other embodiments and variations thereof based on the present invention; the variations and modifications made by ordinary technicians in this industry through the present invention without making pioneering innovations all fall within the scope of protection of the present invention.

Claims

1. A welding method for preheating a weld by recycling residual light, characterized in that: The following steps are involved: S1. Workpiece preparation: positioning and fixing the laser welding gun and the preheating device according to the welding process requirements. The preheating device is arranged in front of the laser welding gun and directly above the joint to be welded, and is used to preheat the joint to be welded. The axial directions of the preheating device and the laser welding gun form an inclination angle α and an inclination angle β with the forward direction of the welding path respectively. The inclination angle α formed by the axial direction of the preheating device and the advancing direction of the welding path is 180°, that is, the preheating device is parallel to the welding path, and the inclination angle β formed by the axial direction of the laser welding gun and the advancing direction of the welding path is 105° to 115°; The laser welding gun is rotatably mounted on the first fixed plate through a rotating assembly, and a laser head is provided at the output end of the laser welding gun, and the laser head emits a laser beam to the joint to be welded; The preheating device is rotatably mounted on the second fixed plate through the rotating assembly, and the preheating device includes a preheating shell, a reflective baffle and a heat exchange tube bundle. The open end surface of the preheating shell is matched and connected with the reflective baffle to form a heat exchange chamber. A preheating space is formed between the reflective baffle and the joint to be welded. One end of the heat exchange tube bundle is inserted into the preheating shell, and the other end is connected to an external cooling medium flow system. The laser receiving surface of the reflective baffle faces the joint to be welded. The reflective baffle is made of copper, and the reflective baffle is an arc-shaped panel, and the concave side of the arc-shaped panel is the laser receiving surface. The first fixing plate and the second fixing plate are both slidably mounted on the slide groove, and the axial direction of the slide groove is parallel to the welding path; The laser welding gun, the preheating device and the rotating assembly are all electrically connected to the control assembly of the external device; S2, initializing the welding parameters of the laser welding gun and the operating parameters of the preheating device: setting the welding parameters of the laser welding gun and the operating parameters of the preheating device according to the material properties and welding process requirements, the welding parameters include the laser output power P1 and the welding speed v1, and the operating parameters include the preheating speed v2 and the preheating temperature T; S3, welding point division: according to the welding process requirements and the welding gun capacity, the spot size of the laser beam is set, and the welding path is divided into n welding points according to the preset spot size, namely the first welding point, the second welding point ... the nth welding point; S4, start welding: The laser welding gun is started to weld the first welding point of the welding path, the laser beam is emitted from the laser head, and is reflected from the surface of the joint to be welded to the laser receiving surface of the reflective baffle, the laser receiving surface recovers and focuses the reflected laser beam, i.e., preheating the laser, and guides the preheating laser to the second welding point of the welding path to complete the preheating treatment of the second welding point, the laser beam emitted by the laser head performs welding treatment on the preheated second welding point, and the remaining welding points on the welding path are preheated and welded in turn until all welding points have completed the preheating and welding treatment, and the joint to be welded forms a complete weld, and the cooling medium flow system is used to cool down the preheating device during the whole welding process; Before starting the laser welding gun, the control component adjusts the angle and distance between the laser welding gun and the preheating device so that the distance between the action point of the preheating laser and the action point of the laser beam emitted by the laser head is 5 to 10 mm; S5. Monitoring the welding process: During the whole welding process, the infrared temperature sensor is used to monitor the preheating of the welding point in real time, and the monitoring result is transmitted to the control component, and the control component dynamically adjusts the welding parameters and the operating parameters according to the monitoring result; S6. Welding quality inspection: perform nondestructive inspection on all the welds, randomly select several groups of weld samples for mechanical property testing, and generate a quality inspection report; The preheating speed v2 in step S2 is determined by the preheating temperature T and the laser output power P1, and satisfies the following formula: ， Wherein: R1 is the reflectivity of the joint to be welded, R2 is the reflectivity of the reflective baffle, γ is the absorption coefficient of the joint to be welded to the preheating laser, R is the spot diameter of the preheating laser, c is the specific heat capacity of the joint to be welded, m is the mass of the preheating area, △T is the preheating temperature difference of the joint to be welded, T is the preheating temperature of the joint to be welded, and T0 is room temperature.

2. The welding method for preheating a weld by recycling residual light according to claim 1 is characterized in that: Also includes: S7. Weld defect repair: When the quality inspection result of the weld does not meet the welding quality requirements, the defective weld needs to be repaired, and the repair area needs to 100% cover the defective weld. The repair process includes laser welding repair, resistance spot welding repair, and arc welding repair.

3. The welding method for preheating a weld by recycling residual light according to claim 1, characterized in that: The preheating speed v2 is greater than or equal to the welding speed v1.

4. A welding method for preheating a weld by recycling residual light according to any one of claims 1 and 3, characterized in that: When the preheating speed v2 is greater than the welding speed v1, the control component adjusts the tilt angle α in real time so that the reflective baffle can always receive the laser beam reflected by the joint to be welded.

5. The welding method for preheating a weld by recycling residual light according to claim 1, characterized in that: A positioning tracker for real-time visual identification of the actual position of the welding spot is provided in the forward direction of the preheating device. The positioning tracker transmits the identification data to the control component for comparison and analysis. Once it is detected that the actual position of the welding spot deviates from the welding path by an amount exceeding a set threshold, an alarm signal is immediately triggered to alert the operator to take adjustment measures.

6. The welding method for preheating a weld by recycling residual light according to claim 1, characterized in that: The nondestructive testing in step S6 includes penetration testing, radiographic testing and ultrasonic testing, and the mechanical property testing includes transverse tensile testing, bending testing, shear tensile testing and fatigue testing.

Images