Liquid nitrogen spraying welded plate cooling device and design method thereof

Abstract

The invention relates to the technical field of welding cooling, and provides a liquid nitrogen spraying welded plate cooling device and a design method thereof.The cooling device comprises a liquid nitrogen source used for providing liquid nitrogen; the input end of the spraying module is connected with a liquid nitrogen source through a main pipeline, the output end of the spraying module is provided with a plurality of spraying holes corresponding to the surface of the welded plate, and the main pipeline is provided with a flow regulating valve; the temperature acquisition module comprises a plurality of temperature sensors which are arranged at temperature measuring points of a welding plate; the control module is electrically connected with the temperature acquisition module and the flow regulating valve respectively; the structure of the spraying device is optimized through flow field simulation, it is ensured that liquid nitrogen is evenly distributed to the surface of a welded plate, local supercooling or superheating is avoided, and uniform cooling of the welded plate is achieved; data are collected through the temperature sensor, closed-loop control is formed in cooperation with the PID controller and the multiple adjusting valves, the liquid nitrogen flow, the spraying area and the spraying time can be accurately regulated and controlled, the inter-channel temperature is effectively controlled, the temperature is prevented from being too high, and it is guaranteed that the welding process is continuously and stably carried out.

Description

Technical Field

[0001] This invention relates to the field of welding cooling technology, and in particular to a liquid nitrogen spray welding plate cooling device and its design method. Background Technology

[0002] With the rapid development of modern industry, high-quality and high-efficiency welding technology has become increasingly important. How to improve welding efficiency while simultaneously enhancing welding quality has become a key issue. Improving welding quality is crucial for product performance and reliability. To ensure the optimization of material properties at the welded joint, the post-weld cooling process has become a focus of research. Traditional welding cooling methods typically employ water cooling and air cooling. While these methods can meet basic requirements in some situations, their cooling rates are generally slow, resulting in poor cooling uniformity. Furthermore, under certain special requirements (such as rapid cooling and precise control of the cooling rate), they cannot effectively address the stress distribution and material property optimization issues of the weld joint.

[0003] While liquid nitrogen spray cooling technology offers advantages such as high cooling rate and precise temperature control, making it suitable for rapid cooling of high-temperature materials after welding, there is currently no detailed design scheme for a liquid nitrogen spray cooling device for welded plates. Furthermore, the design of such a device needs to address the following issues: Uneven cooling efficiency: Existing cooling devices have not undergone actual flow field simulation to optimize internal flow channel design, making it difficult to provide uniform cooling effects under different operating conditions. Different locations on the welded plate require different cooling intensities, and existing designs cannot flexibly adjust cooling parameters.

[0004] Lack of control system and imprecise adjustment: Existing liquid nitrogen spray cooling devices lack a control system for flow rate and spray pressure, making it impossible to accurately control the amount of liquid nitrogen sprayed, resulting in the cooling process not being optimized.

[0005] Insufficient design optimization: Existing cooling devices are usually designed using empirical methods and lack scientific optimization methods based on temperature field and flow field simulation, resulting in unsatisfactory cooling effects and unreliable device design.

[0006] Therefore, there is an urgent need for a new type of liquid nitrogen spray cooling device that can improve cooling efficiency through simulation optimization design. Summary of the Invention

[0007] This invention provides a liquid nitrogen spray cooling device for welded plates and its design method, which solves the problem of low cooling efficiency in the prior art, and can achieve efficient and uniform cooling effect, significantly improving the quality and speed of cooling of welded plates.

[0008] In a first aspect, the present invention provides a liquid nitrogen spray welding plate cooling device, comprising: A liquid nitrogen source, used to provide liquid nitrogen; The spray module has its input end connected to the liquid nitrogen source through a main pipe, the main pipe is equipped with a flow regulating valve, and the output end of the spray module is equipped with multiple spray holes corresponding to the surface of the welding plate. The temperature acquisition module includes multiple temperature sensors, which are arranged at the temperature measurement points of the welding plate to collect temperature data at the temperature measurement points of the welding plate in real time during the liquid nitrogen spray cooling process. The control module is electrically connected to both the temperature acquisition module and the flow regulating valve.

[0009] According to the liquid nitrogen spraying welding plate cooling device provided by the present invention, multiple spraying modules are provided, the multiple spraying modules are arranged in parallel and are respectively connected to the main pipeline through distribution pipes, and each distribution pipe is provided with a regulating valve.

[0010] According to the liquid nitrogen spray welding plate cooling device provided by the present invention, the spray module includes: The bus distribution pipe is arranged in a ring shape and includes: The diversion section is connected to the main pipeline or the distribution pipe and is used to divert the transported liquid nitrogen at the connection point and transport it to both ends of the diversion section respectively. The confluence section, whose two ends are respectively connected to the two ends of the diversion section, is used to collect the diverted liquid nitrogen; Multiple spray pipes are connected at equal intervals to the confluence section, and each spray pipe has spray holes evenly distributed along the axial direction.

[0011] According to the liquid nitrogen spraying welding plate cooling device provided by the present invention, the confluence section is a straight pipe, and a plurality of spraying straight pipes are perpendicularly connected to the confluence section. The two ends of the confluence section are connected to the two ends of the branch section through arc-shaped pipes.

[0012] The liquid nitrogen spray welding plate cooling device provided by the present invention further includes an inlet section, one end of which is connected to the middle of the diversion section, and the other end of which is used to connect to the main pipe or the distribution pipe.

[0013] The liquid nitrogen spray welding plate cooling device provided by the present invention The spray nozzles include: The first spray nozzle is perpendicular to the surface of the welded plate. The second spray holes are distributed on both sides of the first spray holes, and the axis of the second spray holes makes an angle of 45° with the axis of the first spray holes.

[0014] According to the liquid nitrogen spray welding plate cooling device provided by the present invention, baffles are arranged around the plurality of spray pipes in each spray module, and the height of the baffles is greater than the diameter of the spray pipes.

[0015] According to the liquid nitrogen spray welding plate cooling device provided by the present invention, the distance between adjacent first spray holes and second spray holes is 5-15mm, and the diameter of the first spray holes and second spray holes is 0.5-2mm.

[0016] According to the liquid nitrogen spray welding plate cooling device provided by the present invention, the temperature sensor is a contact temperature sensor or a non-contact temperature sensor. The contact temperature sensor is in contact with the surface of the welding plate, and the non-contact temperature sensor corresponds to the temperature measuring point.

[0017] According to the liquid nitrogen spray welding plate cooling device provided by the present invention, the control module is a PID controller.

[0018] Secondly, the present invention also provides a design method for a cooling device for welded plates based on liquid nitrogen spraying, comprising the following steps: The initial structure of the liquid nitrogen spraying device was determined and the flow field was simulated. The pipe structure and the opening parameters of the spray holes were optimized until the flow field distribution met the requirements for uniform spraying. Cooling temperature data of the welded plates were collected through experiments, and the relationship between the equivalent convective heat transfer coefficient and liquid nitrogen flow rate and temperature was fitted by numerical calculation. Select a welding heat source model and simulate the temperature field distribution during the welding cooling process based on the heat transfer coefficient; Based on the structural optimization results and temperature field simulation, the layout and flow control scheme of the spray module were designed and determined.

[0019] According to the design method of the liquid nitrogen spray welding plate cooling device provided by the present invention, the steps of determining the initial structure of the liquid nitrogen spray device and performing flow field simulation, optimizing the pipe structure and spray hole opening method until the flow field distribution meets the uniform spraying requirements include: Based on the size, shape, and cooling requirements of the welded plates, determine the initial structure of the spray device, including the inlet method of the manifold distribution pipe, the number and spacing of the spray straight pipes, the opening method of the spray holes, and the design parameters. The initial structure was simulated using numerical calculation methods to analyze the flow state and distribution uniformity of liquid nitrogen in the pipe. The initial structure is iteratively optimized based on the flow field simulation results until the preset flow field uniformity index is met.

[0020] According to the design method of the liquid nitrogen spray welding plate cooling device provided by the present invention, the step of collecting cooling temperature data of the welding plate through experiments and fitting the relationship between the equivalent convective heat transfer coefficient and the liquid nitrogen flow rate and temperature through numerical calculation includes: An experimental platform was built, which included a liquid nitrogen source, a spray module, and a temperature acquisition module. The liquid nitrogen spray was started after the welding plate was heated to the preset temperature. Temperature change data at multiple temperature measurement points on the welded plate during the cooling process are collected using temperature sensors. By combining numerical calculation methods, the equivalent convective heat transfer coefficient of the spray surface and the corresponding relationship between liquid nitrogen flow rate and temperature are obtained by fitting the temperature change data.

[0021] According to the design method of the liquid nitrogen spray welding plate cooling device provided by the present invention, a welding heat source model is selected, and the temperature field distribution of the welding cooling process is simulated based on the heat transfer coefficient, including: A heat source model matching the welding process is selected, and the temperature field control equation for the welding process is established. The obtained equivalent convective heat transfer coefficient is used as a boundary condition, and the temperature field distribution of the welded plate is simulated in combination with the welding heat source model during welding and cooling.

[0022] According to the design method of the liquid nitrogen spray welding plate cooling device provided by the present invention, based on the initial structural optimization results and temperature field simulation, the spray module layout and flow control scheme are designed and determined, including: Based on the optimized structure, a spraying device is designed that includes a spraying module, a temperature acquisition module, a control module, and a liquid nitrogen source. Based on the temperature field simulation results, the layout scheme of the spray module, the liquid nitrogen flow control strategy, and the cooling time parameters are determined for different welding plates.

[0023] This invention provides a liquid nitrogen spray cooling device for welded plates, which significantly improves cooling efficiency. Compared with traditional water cooling and natural air convection cooling methods, liquid nitrogen spray cooling achieves rapid temperature reduction and greatly shortens cooling time. It is particularly suitable for cooling large-size, thick metal plates after welding, improving overall welding efficiency. The main pipeline is equipped with a flow regulating valve, which, combined with a PID controller, forms a closed-loop control system. A temperature acquisition module obtains real-time temperature data from the plate's temperature measurement points, and the control module dynamically adjusts the liquid nitrogen flow rate based on temperature deviations, achieving precise control of cooling intensity and avoiding over- or under-cooling. Multiple spray holes cover the surface of the welded plate, allowing for targeted cooling coverage. Combined with multi-point monitoring by temperature sensors, it adapts to temperature differences at different locations on the welded plate, reducing localized temperature variations and lowering the risk of welding deformation, porosity, and other defects, thus improving welding quality stability. The flexible flow rate adjustment by the control module can adapt to the cooling needs of welded plates of different materials and thicknesses, eliminating the need for frequent equipment structure changes and enhancing the device's applicability.

[0024] This invention provides a design method for a liquid nitrogen spray cooling device for welded plates. The method optimizes the spray device structure through flow field simulation to ensure uniform distribution of liquid nitrogen onto the surface of the welded plate, avoiding localized overcooling or overheating and achieving uniform cooling. By combining experiments and numerical simulations, the corresponding relationship between the equivalent convective heat transfer coefficient of the spray surface and the liquid nitrogen spray flow rate and temperature is obtained. Data is collected by a temperature sensor, and a closed-loop control system is formed with a PID controller and multiple regulating valves. This system can precisely control the liquid nitrogen flow rate, spray area, and spray time, effectively controlling the interpass temperature, preventing excessively high temperatures, and ensuring continuous and stable welding.

[0025] In addition, the spray module can be adjusted according to the size combination of the welding plates, which can adapt to the welding needs of different materials and thicknesses. It has good flexibility and applicability. Through precise cooling control, it avoids overcooling or overheating, reduces welding defects, and improves welding quality. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of a liquid nitrogen spray welding plate cooling device provided in an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of a liquid nitrogen spray welding plate cooling device provided in another embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram of the structure of the spray module provided in an embodiment of the present invention.

[0030] Figure 4 This is a cross-sectional schematic diagram of the spray pipe provided in an embodiment of the present invention.

[0031] Figure 5 This invention provides a design method for a cooling device for welded plates based on liquid nitrogen spraying.

[0032] Figure label: 1. Liquid nitrogen source; 2. Spray module; 3. Main pipeline; 4. Flow regulating valve; 5. Temperature acquisition module; 6. Temperature sensor; 7. Control module; 8. Distribution pipe; 9. Regulating valve; 10. Thermal insulation base plate; 11. Welded plate; 21. Combination and distribution pipe; 211. Diversion section; 212. Combination section; 22. Spray straight pipe; 23. Inlet section; 24. First spray orifice; 25. Second spray orifice; 26. Baffle. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] The following is combined with Figures 1-5 This invention describes a liquid nitrogen spray welding plate cooling device and its design method.

[0035] Reference Figure 1This invention provides a liquid nitrogen spray cooling device for welded plates, comprising: a liquid nitrogen source 1, a spray module 2, a temperature acquisition module 5, and a control module 7. The liquid nitrogen source 1 provides liquid nitrogen and is equipped with a main switch valve for easy start-up and shutdown control, ensuring the stability of the liquid nitrogen supply and enabling rapid supply cut-off in abnormal situations, thus improving the operational safety of the device. The input end of the spray module 2 is connected to the liquid nitrogen source 1 via a main pipe 3, which is equipped with a flow regulating valve 4. The output end of the spray module 2 has multiple spray holes corresponding to the surface of the welded plate 11. The temperature acquisition module 5 includes multiple temperature sensors. The device 6, with multiple temperature sensors 6 arranged at the temperature measuring points of the welding plate 11, is used to collect temperature data at the temperature measuring points of the welding plate 11 in real time during the liquid nitrogen spray cooling process; the control module 7 can be a PID controller, which is electrically connected to the temperature acquisition module 5 and the flow regulating valve 4 respectively. The PID controller is a closed-loop controller based on proportional, integral, and derivative algorithms, which is a product in the prior art. Its structure and principle are not the focus of this article and will not be elaborated here.

[0036] As can be seen from the above scheme, the present invention can significantly improve cooling efficiency. Compared with traditional water cooling and natural air convection cooling methods, liquid nitrogen spray cooling can achieve rapid cooling and greatly shorten the cooling time. It is especially suitable for cooling large-size, thick metal plates after welding, improving the overall welding efficiency. The main pipe 3 is equipped with a flow regulating valve 4, which, combined with a PID controller, forms a closed-loop control. The temperature acquisition module 5 acquires the temperature data of the plate temperature measurement points in real time, and the control module 7 dynamically adjusts the liquid nitrogen flow rate according to the temperature deviation, achieving precise control of the cooling intensity and avoiding over-cooling or under-cooling. Multiple spray holes correspond to the surface of the welded plate 11, which can target the cooling area. With the multi-point monitoring of the temperature sensor 6, it can adapt to the temperature differences at different locations of the welded plate 11, reduce local temperature differences, reduce the risk of welding deformation, porosity and other defects, and improve the stability of welding quality. Through the flexible adjustment of the flow rate by the control module 7, it can adapt to the cooling needs of welded plates 11 of different materials and thicknesses without frequent changes to the equipment structure, thus enhancing the applicability of the device.

[0037] It should be noted that the location of the temperature measuring point must be able to accurately and quickly reflect the temperature changes between weld passes, providing effective data feedback for the PID controller. Temperature measuring points should be preferentially arranged in key cooling areas such as near the weld and the edge of the heat-affected zone. Temperature should be measured on the back side of the weld surface first, so as to obtain a more stable temperature that is closer to the true temperature inside the material.

[0038] The location of the temperature measuring point can be calculated based on the thickness of the welding plate 11. When the thickness of the welding plate 11 does not exceed 50mm, the temperature measuring point should be located on the surface of the workpiece facing the welder, or preferably at the corresponding position on the back side. The distance between the temperature measuring point and the edge of the weld bevel should be 4 times the plate thickness, but the total distance should not exceed 50mm.

[0039] For example, if the plate thickness is 10mm, the temperature measuring point should be 40mm away from the edge of the bevel; if the plate thickness is 20mm, the calculated distance is 80mm, but since it is stipulated that it should not exceed 50mm, the measuring point should be 50mm away from the edge of the bevel.

[0040] When the workpiece thickness exceeds 50mm, the temperature measuring point should be at least 75mm away from the weld bevel edge in any direction of the base material or the bevel edge, preferably at the corresponding position on the back side.

[0041] For large-sized plates, a single measuring point cannot reflect the overall temperature field, so multiple temperature measurements are required. For example, along the welding path, multiple measuring points can be arranged along the direction of weld advancement to monitor the cooling process in different areas; or measuring points can be arranged symmetrically on both sides of the weld in the direction perpendicular to the weld to monitor the width and temperature gradient of the heat-affected zone and ensure cooling uniformity.

[0042] Reference Figure 2 In some implementations, multiple spray modules 2 are set up in parallel and connected to the main pipeline 3 through distribution pipes 8. Each distribution pipe 8 is equipped with a regulating valve 9, which independently controls the flow rate of each module to avoid the waste of cooling energy caused by global uniform spraying. When local areas of the welding plate 11 do not need cooling, the corresponding module can be turned off to reduce liquid nitrogen consumption.

[0043] With this configuration, multiple spray modules 2 can independently control the liquid nitrogen flow rate for different areas of the welded plate 11, such as the weld zone, heat-affected zone, and base material zone. Combined with the zoned monitoring of the temperature sensor 6, differentiated cooling strategies can be implemented. For example, the spray volume can be increased for the high-temperature weld zone to enhance cooling; a moderate flow rate can be used for the heat-affected zone to avoid stress concentration caused by excessively rapid cooling; and the flow rate can be reduced for the base material zone to reduce unnecessary cooling consumption. By combining multiple spray modules 2, they can be applied to large welded plates 11 to cover a larger area and avoid uneven cooling caused by insufficient coverage of a single module. Furthermore, the spray modules 2 can be flexibly arranged according to the contour of the welded plate 11 to adjust the cooling intensity of each area. In addition, when a single spray module 2 fails, the regulating valve 9 of the corresponding distribution pipe 8 can be closed without affecting the operation of other modules, improving the system's fault tolerance, facilitating modular maintenance and replacement, and reducing equipment downtime.

[0044] Furthermore, it also includes a thermal insulation base plate 10, which is set at the bottom of the welding plate 11. This plate blocks heat conduction from the bottom of the welding plate 11 to the environment below, preventing the plate from losing heat unnecessarily from the bottom. This allows the cooling energy of the liquid nitrogen spray to be more concentrated on the upper part of the plate that needs cooling, such as the welding surface, improving cooling efficiency and shortening cooling time. In addition, it improves the accuracy of temperature monitoring. The thermal insulation base plate 10 stabilizes the thermal environment at the bottom of the welding plate 11, allowing the temperature data acquired by the temperature acquisition module 5 to more accurately reflect the temperature state of the welding area, providing a reliable basis for the control module 5 to adjust the liquid nitrogen flow rate.

[0045] like Figure 3 As shown, the spray module 2 includes: a manifold distribution pipe 21 and multiple spray straight pipes 22. The manifold distribution pipe 21 is arranged in a ring and is integrally formed, including a diversion section 211 and a confluence section 212. The diversion section 211 is connected to the main pipe 3 or the distribution pipe 8, and is used to divert the liquid nitrogen being transported at the connection point, and deliver it to both ends of the diversion section 211 respectively. The two ends of the confluence section 212 are respectively connected to the two ends of the diversion section 211, and are used to collect the diverted liquid nitrogen. Multiple spray straight pipes 22 are connected to the confluence section 212 at equal intervals, and each spray straight pipe 22 has spray holes evenly distributed along the axial direction.

[0046] With this configuration, the manifold distribution pipe 21 adopts a ring design. After the liquid nitrogen is split to both ends through the diversion section 211, it is re-collected and redistributed to each spray pipe 22 through the manifold section 212. This structure can balance the pressure within the ring pipe, avoiding the problem of excessive flow at the near end and insufficient flow at the far end caused by traditional single-sided liquid supply, and ensuring that the liquid nitrogen supply to multiple spray pipes 22 is consistent. The diversion section 211 of the ring manifold distribution pipe 21 is directly connected to the main pipe 3 or the distribution pipe 8, which can be flexibly connected to the overall system and adapted to scenarios where a single module works independently or multiple modules are connected in parallel. Multiple spray pipes 22 are connected at equal intervals. On the manifold 212, each straight pipe has spray holes evenly distributed along the axial direction, which can form a dense and regular coverage of the surface of the welded plate 11. This allows liquid nitrogen to form a continuous and stable spray area on the plate surface, maximizing the contact area between liquid nitrogen and the plate, making full use of the latent heat of vaporization and cooling capacity of liquid nitrogen, increasing the heat exchange per unit time, and further shortening the cooling time. It can also adapt to the cooling requirements of plates of different sizes, especially for large-size or circumferential weld areas, achieving cooling without dead angles and reducing local temperature differences. The axially evenly distributed spray holes can be further adapted to different cooling intensity requirements by optimizing the hole diameter and spacing. Furthermore, the manifold 212 is a straight pipe, and multiple spray straight pipes 22 are perpendicularly connected to the manifold 212, either by welding or by sealing rings, to ensure a sealing effect. The two ends of the manifold 212 are connected to the two ends of the branching section 211 by arc-shaped pipes. The smooth transition design of the arc-shaped pipes avoids local pressure loss caused by right-angle turns, allowing the liquid nitrogen after branching to flow more smoothly into the manifold 212, ensuring that the inlet pressure of each spray straight pipe 22 is consistent, and further improving the uniformity of flow distribution.

[0047] With this configuration, the two ends of the manifold 212 form opposing inlets perpendicular to the axial direction of the spray pipes 22. These opposing inlets allow liquid nitrogen to flow in simultaneously and in opposite directions from both ends of the manifold 212. The fluid counteracts the kinetic energy difference caused by the unilateral inflow, avoiding the problem of excessive flow at the near end and insufficient flow at the far end caused by traditional axial unilateral inlets. This ensures that the amount of liquid nitrogen obtained by each spray pipe 22 is relatively consistent. This lays the foundation for the uniform spraying of liquid nitrogen onto the surface of the plate through the spray holes, avoiding excessive or insufficient local cooling due to uneven flow. After the amount of liquid nitrogen in each spray pipe 22 is uniform, it can effectively reduce the welding stress and deformation caused by local temperature differences on the surface of the plate. Combined with temperature feedback control, this further ensures the stability of welding quality.

[0048] like Figure 3 As shown, it also includes an inlet section 23, one end of which is connected to the middle of the branch section 211, and the other end of which is used to connect to the main pipe 3 or the distribution pipe 8.

[0049] With this configuration, the inlet section 23 is connected to the middle of the diversion section 211, allowing liquid nitrogen to be injected from the middle point of the diversion section 211 and then diverted to both ends. This balances the fluid pressure and flow rate at both ends of the diversion section 211, preventing excessive flow on one side and insufficient flow on the other side due to inlet position offset, thus ensuring uniform diversion. The other end of the inlet section 23 can be flexibly connected to the main pipe 3 or the distribution pipe 8, which is suitable for single-module independent working scenarios and also facilitates connection to multi-module parallel systems, improving the versatility and assembly flexibility of the device.

[0050] As a preferred option, such as Figure 4 As shown, the spray holes include: a first spray hole 24 and a second spray hole 25. The axis of the first spray hole 24 is parallel to the direction of gravity of the spray pipe 22, so that it can be perpendicular to the surface of the welding plate 11. The second spray hole 25 is distributed on both sides of the first spray hole 24, and the axis of the second spray hole 25 makes an angle of 45° with the axis of the first spray hole 24.

[0051] With this setup, during cooling, the first spray hole 24 can directly act on the plate area directly below, ensuring high-intensity heat exchange in the core cooling zone; the second spray hole 25 can cover the gap area between the spray pipes 22, achieving full coverage of the plate surface and avoiding uneven cooling; on the basis of ensuring uniform distribution of liquid nitrogen, the spray hole layout with differentiated angles makes the overall cooling effect more in line with the temperature control requirements of the welding process.

[0052] In this embodiment, baffles 26 are arranged around the multiple spray pipes 22 in each spray module 2, and the height of the baffles 26 is greater than the diameter of the spray pipes 22. The baffles 26 are made of heat-insulating materials, such as ceramic fiber or polyurethane foam. Thus, the baffles 26 surrounding the spray pipes 22 can prevent the cold nitrogen gas generated by the vaporization of liquid nitrogen from directly escaping into the surrounding environment, allowing the cold nitrogen gas to fully exchange heat with the surface of the plate within the relatively enclosed space formed by the baffles 26, improving the utilization rate of cold energy and enhancing cooling efficiency. If the low-temperature nitrogen gas generated by the vaporization of liquid nitrogen were to escape directly, it would form a large amount of white mist, affecting the welding operation's visibility and operational safety. The baffles 26 can constrain the diffusion range of the cold nitrogen gas, reducing the interference of white mist on the working environment and improving operational convenience.

[0053] In some specific embodiments, along the length of the spray pipe 22, the distance between two adjacent first spray holes 24 and two adjacent second spray holes 25 is 5-15mm, and the diameter of the first spray holes 24 and the second spray holes 25 is 0.5-2mm.

[0054] In this embodiment, the temperature sensor 6 is a contact temperature sensor, such as a platinum resistance thermometer or a thermocouple, or a non-contact temperature sensor, such as an optical or electronic temperature measuring device. The contact temperature sensor 6 is in contact with the surface of the welding plate 11, while the non-contact temperature sensor 6 corresponds to the temperature measurement point. This allows for flexible application to temperature measurement points that are difficult to directly contact, such as confined spaces or easily deformable areas, achieving full-area coverage. The combination of the two types meets the temperature measurement needs of different scenarios. The sensor type can be flexibly selected based on the material of the welding plate 11, the temperature range (e.g., non-contact sensors are preferred for ultra-high temperature areas), and the structural form (e.g., non-contact sensors are adapted to curved surfaces or irregularly shaped parts), thereby improving the versatility of the equipment.

[0055] The usage process of the liquid nitrogen spray welding plate 11 cooling device provided in this embodiment of the invention is as follows: Place the metal sheet to be welded below the spray area of ​​the cooling device, ensuring that the distance between the sheet surface and the spray module 2 meets the design requirements to guarantee the uniformity of liquid nitrogen spraying.

[0056] The liquid nitrogen source 1, such as a liquid nitrogen Dewar or liquid nitrogen storage tank, is connected to one or more spray modules 2 via the main pipe 3.

[0057] Select and connect the appropriate spray module 2 according to the size of the welding plate 11 and the cooling requirements.

[0058] Platinum resistance or thermocouple temperature sensors 6 or non-contact infrared temperature measurement devices are installed in key cooling areas of the weld plate 11, such as near the weld, the edge of the heat-affected zone, or representative locations. The sensor signals are then connected to the temperature acquisition module 5 to ensure that the data can be transmitted to the PID controller in real time.

[0059] Inspect all pipes, valves, sensors, and electrical connections to ensure the system is in good working order and leak-free.

[0060] Start the control module 7, enter the operation interface, and input the detailed information of the welding plate 11, including material type, plate thickness, welding process parameters such as welding current, voltage, welding speed, and desired cooling target, such as the control range of interpass temperature of the weld (e.g., 200-250°C, cooling rate such as 50°C / s), final cooling temperature, etc.

[0061] Based on the database and algorithms established in advance through flow field simulation, heat transfer coefficient measurement experiments and temperature field numerical simulation, the control module 7 automatically calculates and recommends the initial liquid nitrogen spraying parameters, including the total flow rate, the on-state of each spraying module 2, the spraying pressure, and the spraying time strategy.

[0062] Welding operation begins; the welding torch moves along the preset path.

[0063] As the welding heat source moves, the temperature of the plate increases. Temperature acquisition module 5 monitors the temperature changes at each temperature measurement point on the plate in real time and transmits the data to the PID controller.

[0064] When the temperature of the plate reaches the set cooling start threshold, the PID controller opens the corresponding valve, and liquid nitrogen begins to spray.

[0065] The PID controller continuously compares the deviation between the real-time temperature and the target temperature range, and dynamically adjusts the opening of the electric regulating valve 9 according to the preset proportional, integral, and derivative parameters, thereby precisely controlling the flow rate of liquid nitrogen.

[0066] For large-sized or complex-shaped boards, the PID controller can independently control the liquid nitrogen flow rate and spraying time of different spray modules 2 according to the temperature distribution of each area, so as to achieve precise cooling of each area, ensure the overall cooling uniformity, and avoid local overcooling or overheating.

[0067] The cooling process continues until the plate temperature drops to the final target temperature, or when all welding work is completed and no further cooling is needed.

[0068] This invention optimizes the structure of the spray device, such as the manifold distribution pipe 21, the spray straight pipe 22, and the arrangement and size of the spray orifices, through flow field simulation. This ensures uniform distribution of liquid nitrogen on the plate surface, preventing localized cold spots or insufficient cooling. Real-time feedback from the temperature sensor 6 allows the PID controller to dynamically adjust the liquid nitrogen flow rate based on actual temperature changes, achieving precise control of cooling rate and temperature. This effectively solves the problems of slow cooling rate, poor uniformity, and low control accuracy in traditional cooling methods. The design of the spray module 2 allows for combination and adjustment according to different plate sizes and welding requirements, improving the adaptability and flexibility of the device. By precisely controlling the liquid nitrogen flow rate, spray area, and spray time, the interpass temperature is effectively controlled, preventing excessive temperature, ensuring continuous and stable welding, and reducing welding defects, thereby significantly improving welding quality and consistency.

[0069] Reference Figure 5 The present invention also provides a design method for a cooling device for welded plates based on liquid nitrogen spraying, comprising the following steps: Step S1: Determine the initial structure of the liquid nitrogen spraying device and perform flow field simulation, optimize the pipe structure and the opening parameters of the spray holes until the flow field distribution meets the requirements for uniform spraying; Step S2: Collect cooling temperature data of welding plate 11 through experiments, and combine numerical calculations to fit the relationship between the equivalent convective heat transfer coefficient and liquid nitrogen flow rate and temperature; Step S3: Select a welding heat source model and simulate the temperature field distribution during the welding cooling process based on the heat transfer coefficient; Step S4: Based on the structural optimization results and temperature field simulation, design and determine the layout and flow control scheme of spray module 2.

[0070] As can be seen from the above scheme, compared with traditional water cooling and natural air convection cooling methods, the present invention can achieve rapid cooling by using liquid nitrogen spray cooling, shortening the cooling time and significantly improving the cooling efficiency. It is especially suitable for cooling large-size, high-thickness metal plates after welding, improving the overall welding efficiency. The structure of the spray device is optimized by flow field simulation to ensure that liquid nitrogen is evenly distributed on the surface of the welding plate 11, avoiding local overcooling or overheating, and achieving uniform cooling of the welding plate 11. By combining experiments and numerical simulations to obtain the correspondence between the equivalent convective heat transfer coefficient of the spray surface and the liquid nitrogen spray flow rate and temperature, and by collecting data through temperature sensor 6, and forming a closed-loop control with PID controller and multiple regulating valves 9, the liquid nitrogen flow rate, spray area and spray time can be precisely controlled to effectively control the interpass temperature, prevent the temperature from being too high, and ensure the continuous and stable operation of the welding process.

[0071] In addition, the spray module 2 can be adjusted according to the size combination of the welding plate 11, which can adapt to the welding needs of different materials and thicknesses, and has good flexibility and applicability. Through precise cooling control, it avoids overcooling or overheating, reduces welding defects, and improves welding quality.

[0072] In this embodiment, step S1 includes: determining the initial structure of the spray device according to the size, shape and cooling requirements of the welding plate 11, including the inlet method of the manifold distribution pipe 21, the number and spacing of the spray straight pipes 22, the opening method and design parameters of the spray holes; using numerical calculation methods to simulate the flow field of the initial structure and analyze the flow state and distribution uniformity of liquid nitrogen in the pipe; iteratively optimizing the initial structure based on the flow field simulation results until the preset flow field uniformity index is met.

[0073] The initial structure was simulated by numerical calculation, and the pipeline structure and orifice parameters were iteratively optimized until the flow field distribution met the requirements for uniform spraying. The optimization points included: the inlet direction of the manifold distribution pipe 21, the orifice parameters of the spray straight pipe 22, and the pipe size.

[0074] Taking the butt welding of two flat steel plates as an example, without considering special cooling requirements, the goal is to ensure that liquid nitrogen is sprayed evenly onto the surface of the steel plates being cooled, avoiding interference with the normal welding operation. To this end, the main structure of the spraying device is initially designed, using closely spaced spray pipes 22 as the main body of the spraying system. Spray holes are opened in the gravity direction and circumference of the spray pipes 22. Baffles 26 are designed to surround the spray pipes 22 to prevent cold nitrogen from escaping directly into the environment, reducing cold loss and the generation of white mist. Liquid nitrogen is distributed to each spray pipe 22 through a manifold distribution pipe 21.

[0075] During structural design, numerical calculations were used to simulate the flow field to assist in the optimization of the pipeline structure and spray nozzles. Through continuous optimization, the final design was as follows: Figure 3 The pipeline structure shown distributes fluid to each spray pipe 22 through the manifold distribution pipe 21. The liquid nitrogen flow from the main pipe 3 is divided into two streams, which enter from both ends of the manifold distribution pipe 21 to ensure that the fluid can be distributed to each spray pipe relatively evenly. The liquid nitrogen is evenly distributed to the surface of the steel plate being cooled through the densely arranged spray holes on the spray pipe 22 to ensure uniform cooling.

[0076] Flow field simulation of the optimized spray device revealed that the direction of fluid entry into the manifold distribution pipe 21 is a crucial factor affecting the uniformity of flow distribution in the spray pipes 22. An axial entry into the spray pipes 22 results in excessive flow distribution to the pipes closer to the inlet, and insufficient flow distribution to those further away. Using opposing inlets perpendicular to the axial direction of the spray pipes 22 allows for more uniform fluid distribution. Furthermore, the number of spray holes along the axial and circumferential directions of the spray pipes 22 also affects the uniformity of liquid nitrogen distribution on the surface of the cooled component. The number of axial holes influences the concentration and dispersion of liquid nitrogen on the surface of the cooled steel plate, while additional circumferential holes fill the gaps between the spray pipes. Additionally, the diameter of the spray pipes 22 cannot be too small; otherwise, it will be difficult to create holes and the maximum flow rate will be limited to a lower level.

[0077] like Figure 3 As shown, the optimized structure of the spray module 2 adopts a structure with opposing inlets on both sides and additional circumferential openings in the spray pipe 22. The angle between the axis of the additional lateral openings and the direction of gravity is 45°, that is, the angle between the axis of the second spray hole 25 and the axis of the first spray hole 24 is 45°. By simulating and comparing the flow field distribution on the spray surface in two cases: when only the first spray hole 24 is opened in the spray pipe 22, and when the second spray hole 25 is opened on both sides, the results show that when only a single hole is opened, the flow field distribution on the spray surface is relatively dispersed in the axis perpendicular to the spray pipe 22, and the area between the pipes is limited by the diameter of the spray pipe 22. The area cannot be directly covered by the spray fluid; however, this problem is solved by adding additional lateral openings. The intensity of the flow field is higher in the area near the top of the spray pipe 22 and lower in the area further away from the top. That is, the closer the area is to the source of the liquid nitrogen spray from the spray pipe 22, the faster the liquid nitrogen flows, the larger the liquid nitrogen flow per unit area, and the stronger the impact on the plate surface. On the other hand, the farther the area is from the source of the liquid nitrogen spray from the spray pipe 22, the slower the liquid nitrogen flows, the lower the flow density, and the weaker the impact force due to diffusion, kinetic energy attenuation, etc. This corresponds to the temperature field distribution of the steel plate during welding, which enables the welded steel plate to be cooled more effectively.

[0078] In this embodiment, step S2 includes: building an experimental platform containing a liquid nitrogen source 1, a spray module 2, and a temperature acquisition module 5; heating the welding plate 11 to a preset temperature and then starting the liquid nitrogen spray; collecting temperature change data at multiple temperature measurement points of the welding plate 11 during the cooling process through a temperature sensor 6; and combining numerical calculation methods to obtain the equivalent convective heat transfer coefficient of the spray surface and the correspondence between the liquid nitrogen flow rate and temperature based on the temperature change data.

[0079] Specifically, the experimental setup includes a self-pressurized liquid nitrogen container, a main pipeline 3, a spray module 2, a steel plate to be cooled for welding, a thermally insulated base plate 10, and a temperature acquisition module 5 with multiple sets of contact or non-contact temperature sensors 6. The temperature measurement points can be evenly distributed around the center of the steel plate. The setup simulates the high-temperature environment after actual welding. After heating the steel plate to the target temperature, the liquid nitrogen spray is activated, and the temperature sensors 6 record the temperature changes over time at different measurement points in real time.

[0080] Equivalent heat transfer coefficient fitting: Because the steel plate temperature is higher than the Leidenfrost point, film boiling occurs when liquid nitrogen comes into contact with the high-temperature steel plate, forming a gas film that hinders direct contact between the liquid nitrogen and the steel plate surface, thus impeding direct heat transfer and complicating the heat transfer process. In fact, this problem belongs to a class of inverse heat transfer problems, requiring the inverse calculation of the internal temperature field and boundary conditions of the object using temperature data from one or more points. During the experiment, the temperature changes over time at several representative temperature measurement points on the steel plate during the cooling process were recorded to characterize the temperature field of the plate. By combining the experimentally obtained temperature measurement data with numerical calculations, the equivalent convective heat transfer coefficient at different liquid nitrogen flow rates and plate temperatures during the liquid nitrogen spray cooling process was fitted, establishing its correspondence with the spray parameters (flow rate, pressure).

[0081] In this embodiment, step S3 includes: selecting a heat source model that matches the welding process, establishing the temperature field control equation for the welding process; using the obtained equivalent convective heat transfer coefficient as a boundary condition, and combining it with the welding heat source model to simulate the temperature field distribution of the welding plate 11 during the welding and cooling process.

[0082] Specifically, a suitable heat source model is selected based on the welding process, such as arc welding or laser welding, to simulate the heat input during welding. Available models include concentrated heat source models, surface heat source models, volume heat source models, or combined heat source models. Concentrated heat source models treat the heat source as a concentrated point, line, or surface domain, representing the simplest approximation of the welding heat source. Surface heat source models, also known as planar Gaussian heat source models, assume that the heat flux density of the heat source is distributed according to a Gaussian function within a planar circular region, effectively simulating the distribution of surface heat flux. Currently, commonly used volume heat source models include: rotating Gaussian volume heat source models, hemispherical heat source models, and double ellipsoidal heat source models. Combined heat source models are more accurate, considering both arc and droplet heat effects. By combining different heat source models, such as a Gaussian surface heat source model + a double ellipsoidal heat source model, they can better simulate different weld cross-sectional shapes and adapt to various complex weld pool shapes.

[0083] Based on the law of heat conduction, the governing equations for the temperature field distribution are established. Combined with the equivalent heat transfer coefficient obtained in step S2, the temperature field changes of the plate caused by the movement of the heat source during welding are simulated. In addition, the temperature field evolution of the plate under different spray flow rates, regions, and times during liquid nitrogen spray cooling is simulated, and key indicators such as cooling rate and interpass temperature control range are determined.

[0084] The key to numerical simulation of the welding cooling process lies in determining the form of heat source application and the heat transfer boundary conditions. The temperature field distribution changes with time during the welding process, and its governing equation is as follows: In the formula The distribution function of the temperature field ρ is the material density , Specific heat capacity of the material , Thermal conductivity of the material , For internal heat source intensity During the simulation, the input heat of the welding torch is equal to the intensity of the internal heat source. Apply in the form of The form is determined by the heat source model.

[0085] By combining the welding heat source model with the experimentally measured convective heat transfer coefficient, the temperature field of the entire welding and cooling process can be simulated, which can help design spraying schemes.

[0086] In this embodiment, step S4 includes: designing a spray device including a spray module 2, a temperature acquisition module 5, a control module 7 and a liquid nitrogen source 1 according to the optimized structure; and determining the arrangement scheme of the spray module 2 and the liquid nitrogen flow control strategy for different welding plates 11 based on the temperature field simulation results.

[0087] For example, spray modules 2 are placed in high-temperature areas of the sheet metal or in key cooling locations such as near welds to ensure targeted cooling. For sheet metal of different materials and thicknesses, the number of spray modules 2, opening parameters, and flow rate adjustment range are adjusted to ensure the flexibility of the cooling scheme. Closed-loop control based on temperature feedback is adopted, and a target temperature range is set (such as interpass temperature 200-250℃). When the sensor detects that the temperature exceeds the threshold, the PID controller increases the liquid nitrogen flow rate in the corresponding area; when it is below the threshold, the flow rate is reduced to avoid overcooling or overheating.

[0088] Specifically, the spraying device includes a spraying module 2, a temperature acquisition module 5, a control module 7, and a liquid nitrogen source 1. The spraying module 2 is designed with the aid of flow field simulation. Depending on the size of the welding plate 11 to be cooled, one or more spraying modules 2 can be selected for cooling.

[0089] The temperature acquisition module 5 includes multiple temperature sensors 6. The temperature sensors 6 can be selected from contact type such as platinum resistance or thermocouple temperature sensors 6, or directly use non-contact temperature sensors such as optical or electronic temperature measuring devices. By collecting temperature data at the temperature measuring point of the welding plate 11 in real time, it can assist in the control and adjustment of the liquid nitrogen spray flow rate.

[0090] The arrangement of spray module 2 is designed based on the full-field temperature simulation results of the welded plate 11. The specific arrangement needs to be selected according to the actual temperature distribution and changes obtained from the simulation. The spray flow rate needs to be adjusted in real time according to the temperature changes at the monitoring points to achieve precise cooling control.

[0091] Specifically, the location of temperature measuring points is determined based on the actual welding method used. One or more temperature measuring points can be selected and arranged according to the size of the welding plate 11. The purpose of arranging temperature measuring points is to monitor the temperature change of the welding plate 11 in real time during the cooling process. The equivalent heat transfer coefficient of the spray surface, the relationship between surface temperature distribution and spray flow rate are determined through experiments and numerical simulations. The relationship between temperature change and spray flow rate is also determined. Furthermore, it is necessary to determine the target temperature range for different areas, such as the target cooling temperature of the welding area and the temperature requirements of the cooling transition zone. When the temperature exceeds a certain threshold, the liquid nitrogen flow rate can be appropriately increased; when the temperature is below a certain threshold, the flow rate is reduced.

[0092] The data from temperature sensor 6 is input into control module 7. Control module 7 adjusts the flow rate of liquid nitrogen spraying based on the deviation between the current temperature and the target temperature. Control module 7 uses a PID controller. By adjusting the PID parameters (proportional, integral, and derivative constants), the system responds smoothly and promptly to temperature changes, avoiding excessive or insufficient flow rate adjustment. Control module 7 adjusts the opening of valve 9 via electrical signals, thereby changing the liquid nitrogen delivery flow rate and achieving precise regulation of the liquid nitrogen flow rate.

[0093] For welding operations on large plates, multiple temperature measuring points are set up and multiple spray modules are used to cool different areas. Each module is controlled by an individual regulating valve, which can achieve precise control of the liquid nitrogen spray flow rate and spray time in each area.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid nitrogen spray welding plate cooling device, characterized in that, include: Liquid nitrogen source (1), used to provide liquid nitrogen; The spray module (2) has its input end connected to the liquid nitrogen source (1) through the main pipe (3). The main pipe (3) is equipped with a flow regulating valve (4). The output end of the spray module (2) is equipped with multiple spray holes corresponding to the surface of the welding plate (11). The temperature acquisition module (5) includes multiple temperature sensors (6), which are arranged at the temperature measurement points of the welding plate (11) to collect temperature data at the temperature measurement points of the welding plate (11) in real time during the liquid nitrogen spray cooling process. The control module (7) is electrically connected to the temperature acquisition module (5) and the flow regulating valve (4).

2. The liquid nitrogen spray welding plate (11) cooling device according to claim 1, characterized in that, The spray module (2) is provided in multiple ways. The multiple spray modules (2) are arranged in parallel and are respectively connected to the main pipeline (3) through the distribution pipe (8). Each distribution pipe (8) is provided with a regulating valve (9).

3. The liquid nitrogen spray welding plate cooling device according to claim 1 or 2, characterized in that, The spray module (2) includes: The bus distribution pipe (21) is arranged in a ring shape and includes: Diversion section (211), which is connected to the main pipeline (3) or the distribution pipe (8), is used to divert the liquid nitrogen being transported at the connection point and transport it to both ends of the diversion section (211). The confluence section (212) is connected at both ends to the two ends of the diversion section (211) to collect the diverted liquid nitrogen; Multiple spray pipes (22) are connected to the confluence section (212) at equal intervals, and each spray pipe (22) has spray holes evenly distributed along the axial direction.

4. The liquid nitrogen spray welding plate cooling device according to claim 3, characterized in that, The confluence section (212) is a straight pipe, and multiple spray straight pipes (22) are vertically connected to the confluence section (212). The two ends of the confluence section (212) are connected to the two ends of the branch section (211) through arc-shaped pipes.

5. The liquid nitrogen spray welding plate cooling device according to claim 3, characterized in that, It also includes an inlet section (23), one end of which is connected to the middle of the branch section (211), and the other end of which is used to connect to the main pipe (3) or the distribution pipe (8).

6. The liquid nitrogen spray welding plate cooling device according to claim 3, characterized in that, The spray nozzles include: The first spray hole (24) is perpendicular to the surface of the welded plate (11); The second spray holes (25) are distributed on both sides of the first spray holes (24), and the axis of the second spray holes (25) makes an angle of 45° with the axis of the first spray holes (24).

7. The liquid nitrogen spray welding plate cooling device according to claim 3, characterized in that, A baffle (26) is provided around a plurality of spray pipes (22) in each of the spray modules (2), and the height of the baffle (26) is greater than the diameter of the spray pipe (22).

8. The liquid nitrogen spray welding plate cooling device according to claim 6, characterized in that, The distance between adjacent first spray holes (24) and second spray holes (25) is 5-15mm, and the diameter of the first spray holes (24) and second spray holes (25) is 0.5-2mm.

9. The liquid nitrogen spray welding plate cooling device according to claim 1, characterized in that, The temperature sensor (6) is either a contact temperature sensor (6) or a non-contact temperature sensor (6). The contact temperature sensor (6) is in contact with the surface of the welding plate (11), and the non-contact temperature sensor (6) corresponds to the temperature measurement point.

10. The liquid nitrogen spray welding plate cooling device according to claim 1, characterized in that, The control module (7) is a PID controller.

11. A design method for a cooling device for welded plates based on liquid nitrogen spraying, characterized in that, Includes the following steps: The initial structure of the liquid nitrogen spraying device was determined and the flow field was simulated. The pipe structure and the opening parameters of the spray holes were optimized until the flow field distribution met the requirements for uniform spraying. The cooling temperature data of the welding plate (11) was collected by experiment, and the relationship between the equivalent convective heat transfer coefficient and the liquid nitrogen flow rate and temperature was fitted by numerical calculation. Select a welding heat source model and simulate the temperature field distribution during the welding cooling process based on the heat transfer coefficient; Based on the structural optimization results and temperature field simulation, the layout and flow control scheme of the spray module (2) were designed and determined.

12. The design method of the cooling device for welded plates based on liquid nitrogen spraying according to claim 11, characterized in that, The process of determining the initial structure of the liquid nitrogen spraying device and performing flow field simulation, optimizing the pipeline structure and spray hole opening method until the flow field distribution meets the requirements for uniform spraying includes: Based on the size, shape and cooling requirements of the welding plate (11), the initial structure of the spray device is determined, including the inlet method of the manifold distribution pipe (21), the number and spacing of the spray straight pipes (22), the opening method of the spray holes and the design parameters. The initial structure was simulated using numerical calculation methods to analyze the flow state and distribution uniformity of liquid nitrogen in the pipe. The initial structure is iteratively optimized based on the flow field simulation results until the preset flow field uniformity index is met.

13. The design method of the cooling device for welded plates based on liquid nitrogen spraying according to claim 11, characterized in that, The process involves collecting cooling temperature data of the welded plate (11) through experiments, and then combining this with numerical calculations to fit the relationship between the equivalent convective heat transfer coefficient and the liquid nitrogen flow rate and temperature; including: An experimental platform containing a liquid nitrogen source (1), a spray module (2), and a temperature acquisition module (5) was built. The welding plate (11) was heated to the preset temperature and then the liquid nitrogen spray was started. Temperature change data of the welding plate (11) at multiple temperature measurement points during the cooling process are collected by temperature sensor (6); By combining numerical calculation methods, the equivalent convective heat transfer coefficient of the spray surface and the corresponding relationship between liquid nitrogen flow rate and temperature are obtained by fitting the temperature change data.

14. The design method of the cooling device for welded plates based on liquid nitrogen spraying according to claim 13, characterized in that, Select a welding heat source model and simulate the temperature field distribution during the welding cooling process based on the heat transfer coefficient, including: Select a heat source model that matches the welding process and establish the temperature field control equation for the welding process; use the obtained equivalent convective heat transfer coefficient as the boundary condition, and combine it with the welding heat source model to simulate the temperature field distribution of the welding plate (11) during the welding and cooling process.

15. The design method of the cooling device for welded plates based on liquid nitrogen spraying according to claim 14, characterized in that, Based on the initial structural optimization results and temperature field simulation, the layout and flow control scheme of the spray module (2) were designed and determined, including: Based on the optimized structure, a spraying device is designed that includes a spraying module (2), a temperature acquisition module (5), a control module (7), and a liquid nitrogen source (1); Based on the temperature field simulation results, the arrangement scheme of the spray module (2), the liquid nitrogen flow control strategy and the cooling time parameters are determined for different welding plates (11).

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