Cooling device for controlling deformation of welded joint and segmented cooling control method

Abstract

The invention discloses a cooling device for controlling deformation of a welded joint and a segmented cooling control method. The cooling device comprises a cooling pipeline and a cooling pressing plate assembly. A plurality of cooling subareas are arranged on the surface of the to-be-welded workpiece from top to bottom in the longitudinal direction of the to-be-welded workpiece, every two adjacent cooling subareas arranged from top to bottom form a set of cooling areas, and each cooling area is provided with a cooling pressing plate assembly and a third stop valve; the cooling pressing plate assembly comprises an upper cooling pressing plate and a lower cooling pressing plate; the upper cooling pressing plate is fixedly arranged on the cooling subarea located on the upper portion, and the lower cooling pressing plate is fixedly arranged on the cooling subarea located on the lower portion. The third stop valve is used for controlling the cooling pipeline to flow through the upper cooling flow path of the cooling subarea at the upper part or the lower cooling flow path of the cooling subarea at the lower part; and the first stop valve, the second stop valve and the third stop valve are matched to control segmented cooling of the upper cooling pressing plate / the lower cooling pressing plate.

Description

Technical Field

[0001] The invention relates to the technical field of aerospace tank welding, in particular to a cooling device and a segmented cooling control method for controlling joint deformation during long weld (>3m) friction stir welding. Background Art

[0002] In the field of aerospace tank manufacturing, the longitudinal seam welding of large-sized thin-walled barrel sections faces the following technical bottlenecks: due to the uneven expansion of the material caused by heat accumulation during welding, long welds (>3m) will make it difficult for heat to dissipate evenly, which may form a large temperature gradient, thereby generating residual stress and ultimately causing barrel section deformation. Traditional methods for controlling barrel section deformation use post-weld correction or overall cooling methods. Post-weld correction refers to adjusting the deformation that has occurred by mechanical or heat treatment means after welding is completed. It involves the use of additional equipment, such as hydraulic straightening machines or heating furnaces. These steps increase the complexity and cost of the production process. Post-weld correction relies on accurate measurement and compensation of the completed deformation, but due to factors such as material rebound, the actual correction effect may be biased. In addition, the correction process may generate secondary stress on the material, especially during heat treatment, when temperature changes may cause changes in the microstructure, such as grain growth or phase change, which in turn affects the mechanical properties of the material. The overall cooling method uses single-channel cooling or a fixed-position cooling device to control the stability of the welding temperature field. It is suitable for shorter welding paths and cannot adapt to temperature changes in different welding stages. Especially in long welds (>3m), the problem of uneven cooling will be more obvious. Inconsistent cooling rates may cause some areas to cool too quickly and other areas to cool too slowly, increasing the risk of deformation.

[0003] Friction stir welding (FSW) is a new type of solid phase welding technology, mainly used for the connection of metal materials. Its principle is to fix the workpiece to be welded with the help of a fixture, and generate heat through the friction between the high-speed rotating stirring head and the workpiece surface, so that the interface of the metal material to be welded will flow plastically, thereby achieving the welding of the workpiece below the melting point of the metal material. Friction stir welding technology is used in the manufacture of launch vehicle tanks due to its advantages such as high joint strength and no need for filling materials.

[0004] During the friction stir welding process, the friction between the stirring head and the workpiece to be welded generates heat, which is an inevitable phenomenon in the friction stir welding process. For ultra-large-sized thin-walled pressure vessel structural parts such as launch vehicle tanks, the heat input of friction stir welding has an important influence on the tank welding quality. The welding heat input directly affects the temperature distribution of the welded joint. Excessive heat input will cause the temperature of the workpiece to be welded to rise, thereby causing thermal expansion and plastic deformation, while uneven welding heat input will also cause corresponding thermal stress and thermal deformation in different parts of the workpiece to be welded.

[0005] In order to solve this problem, external cooling measures such as water spray cooling and air cooling are usually adopted. Water spray cooling absorbs heat and reduces the temperature of the workpiece by spraying water mist or water flow into the welding area. This method can reduce heat input and deformation to a certain extent, but it may cause the uneven temperature distribution in the welding area to increase and produce high thermal stress. In addition, water spray cooling may affect the cleanliness of the welding environment and put forward higher requirements for equipment maintenance; air cooling takes away the heat from the welding area by blowing air. Compared with water spray cooling, air cooling has weaker cooling effect and is more easily affected by ambient temperature and humidity. Air cooling may also cause uneven heat distribution and has limited effect on large workpieces. Methods such as water spray cooling and air cooling have limited effects and are prone to uneven temperature in the welding area, further affecting the welding quality.

[0006] Water-cooled fixture is a more direct and effective cooling method. It absorbs the heat in the welding area through circulating cooling water, thereby reducing the temperature of the workpiece and reducing welding deformation. The water-cooled fixture consists of a cooling water pipe and a fixture body. The cooling water pipe is responsible for transporting cooling water to the welding area, while the fixture body is used to fix the workpiece. By adjusting the flow and temperature of the cooling water, the heat distribution during the welding process can be effectively controlled, thereby reducing welding deformation. Summary of the invention

[0007] The present invention aims to solve the defects of the prior art and provide a cooling device and a segmented cooling control method for controlling the welding deformation of a stir friction joint with a long weld (>3m). The circulating cooling water absorbs the heat in the welding area, reduces the workpiece temperature and reduces the welding deformation.

[0008] A cooling device for controlling joint deformation during long weld friction stir welding, wherein a plurality of cooling devices are longitudinally arranged on two oppositely arranged workpieces to be welded for segmented cooling of the workpieces to be welded; a plurality of cooling partitions are arranged on the surface of the workpieces to be welded from top to bottom in the longitudinal direction, and two adjacent cooling partitions are arranged from top to bottom as a group of cooling areas, and each cooling area is provided with the cooling device, and the cooling device comprises a cooling platen assembly, a cooling pipeline and a third stop valve;

[0009] The cooling pipeline is divided into an upper cooling flow path and a lower cooling flow path, and the cooling platen assembly includes an upper cooling platen and a lower cooling platen; the two upper cooling platens are relatively fixed on the cooling partitions where the workpiece to be welded is located at the upper part, and the two lower cooling platens are relatively fixed on the cooling partitions where the workpiece to be welded is located at the lower part; the upper cooling flow path flows through the two upper cooling platens, and the lower cooling flow path flows through the two lower cooling platens, and the upper cooling flow path and the lower cooling flow path are connected through a third stop valve, and the third stop valve is used to control the coolant to flow through the upper cooling flow path or the lower cooling flow path, thereby realizing segmented cooling of the upper cooling platen / lower cooling platen;

[0010] The cooling partition located at the upper part includes an upper cooling platen located on two workpieces to be welded and an upper cooling flow path; the upper cooling platen is provided with a liquid inlet and a liquid outlet on opposite side walls along its longitudinal direction, and the liquid inlets and liquid outlets of the two upper cooling platens are located in opposite positions; the upper cooling flow path is as follows:

[0011] The coolant flows from the cooling water tank through the cooling water pump, the third branch, the upper cooling platen on one side, the first stop valve, the third stop valve, the other first stop valve, the upper cooling platen on the other side, and then returns to the cooling water tank through the fourth branch;

[0012] The lower cooling zone includes lower cooling plates and lower cooling channels located on two workpieces to be welded; the lower cooling plates are provided with liquid inlets and liquid outlets on opposite side walls along the longitudinal direction thereof, and the liquid inlets and liquid outlets of the two lower cooling plates are located in opposite positions;

[0013] The lower cooling flow path is as follows:

[0014] The coolant flows from the cooling water tank through the cooling water pump, the first branch, the lower cooling platen on one side, the second stop valve, the third stop valve, another second stop valve, the lower cooling platen on the other side, and then returns to the cooling water tank through the second branch.

[0015] The cooling device for controlling the deformation of the joint during the friction stir welding of long welds is particularly suitable for the case where the weld of the workpiece to be welded is greater than 3m. When the welded workpiece is particularly long, multiple groups of cooling areas are arranged in the longitudinal direction of the welded workpiece, and each group of cooling areas is provided with a cooling platen assembly and a third stop valve. Each cooling area can be cooled in sections by controlling the cooling pipeline and the cooling platen assembly.

[0016] Furthermore, two relatively disposed workpieces 51 to be welded are respectively disposed on the welding platform, and a position of a welding area is reserved between the two welding workpieces 51; and the welding workpiece is a rectangular workpiece with a weld greater than 3m in length.

[0017] Furthermore, the upper cooling platen and the lower cooling platen are fixed on the workpiece to be welded by means of a clamp, and the clamp is arranged on both sides of the welding workpiece to restrict the lateral movement of the welding workpiece.

[0018] Furthermore, a plurality of key pressing blocks are arranged in parallel on the upper surfaces of the upper cooling platen and the lower cooling platen, and the key pressing blocks are fixed on the fixture, and the upper / lower cooling platens are pressed onto the welding workpiece by screws to fix the positions of the upper / lower cooling platens and the welding workpiece.

[0019] In particular, the cooling zones of two oppositely disposed workpieces to be welded correspond to each other, thereby accurately controlling the segmented cooling.

[0020] The segmented cooling control method using the cooling device comprises:

[0021] Pretreatment: Before welding, multiple cooling zones are arranged on the surface of the workpiece to be welded from top to bottom along the longitudinal direction, and the cooling platen assembly is fixed on the upper surface of the workpiece to be welded along the longitudinal direction; and a position of the welding area is reserved between the relatively arranged workpieces 51 to be welded;

[0022] Start the cooling water pump to circulate the coolant in the cooling pipes and upper / lower cooling platens of the cooling partitions to be welded, thereby pre-cooling the cooling partitions to be welded. Pre-cooling is considered completed when the temperature is 2 to 5 degrees lower than the room temperature.

[0023] Welding and cooling of the cooling zone located at the upper part: After precooling, stir friction welding is carried out, and the infrared temperature sensor located at the stirring head monitors the temperature at the stirring head;

[0024] When the temperature reaches 250-350 degrees, the first stop valve and the third stop valve of the two oppositely arranged cooling platen assemblies located in the welding area are opened, and the second stop valve is kept closed, so that the coolant flows through the upper cooling flow path, and the heat generated by welding is taken away by the coolant flowing in the upper cooling platen;

[0025] After completing the welding of the upper half of the workpiece, continue to run the cooling water pump to ensure that the welding area gradually cools down to normal temperature;

[0026] Welding and cooling of cooling zones at the bottom: Friction stir welding is performed, and the infrared temperature sensor at the stirring head monitors the temperature at the stirring head;

[0027] When the temperature reaches 250-350 degrees, the second stop valve and the third stop valve of the two oppositely arranged cooling platen assemblies located in the welding area are opened, and the first stop valves of the two cooling platen assemblies are kept closed, so that the coolant flows through the lower cooling flow path, and the heat generated by welding is taken away by the coolant flowing in the lower cooling platen;

[0028] After completing the welding of the lower half of the welding workpiece, continue to run the cooling water pump to ensure that the welding area gradually cools down to normal temperature.

[0029] The beneficial effects of the present invention are as follows: the present invention divides a weld longer than 3 meters into multiple sections (i.e., multiple groups of cooling areas), each group of cooling areas is independently equipped with a group of cooling devices, and two cooling platens symmetrically arranged on two relatively arranged welding workpieces are provided with independent cooling pipelines. The cooling pipeline is responsible for conveying cooling water to the welding area, and the fixture body is used to fix the workpiece. The cooling water is supplied by a unified cooling water tank and cooling water pump, and the circulation channel is controlled by different servo valves. By adjusting the flow rate and temperature of the cooling water, the heat distribution during the welding process can be effectively controlled, the heat in the welding area can be absorbed, the temperature of the workpiece can be reduced, and thus the welding deformation can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of the cooling device of the present invention, in which the blue and red pipes respectively mark the cold water side and the hot water side of the upper cooling section;

[0031] Figure 2 Schematic diagram of the structure of the cooling device of the present invention, in which the blue and red pipes respectively mark the cold water side and the hot water side of the lower half of the cooling section;

[0032] Figure 3 The present invention provides a comparative example of conventional friction stir welding and friction stir welding using the cooling device and segmented control method of the present invention.

[0033] in,

[0034] 10: cooling water tank; 20: cooling water pump; 31: first branch; 32: second branch; 33: third branch; 34: fourth branch; 40: fixture; 50: upper cooling platen; 53: lower cooling platen; 60: key block; 41: hexagon socket screw; 42: welding platform; 51: welding workpiece; 52: stirring head; 61: hexagon socket screw; 70: first stop valve; 71: second stop valve; 72: third stop valve; 80: temperature sensor. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution, beneficial effects and significant progress of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below in conjunction with the drawings provided in the examples of the present invention. Obviously, all the described embodiments are only partial embodiments of the present invention, rather than all embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] In the description of this application, unless otherwise clearly specified and limited, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance; the term "plurality" refers to two or more; unless otherwise specified or explained, the terms "connected", "fixed", etc. should be understood in a broad sense, for example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0037] like Figure 1-2 As shown, two welding workpieces 51 are placed side by side on the upper surface of a welding platform 42, and a position of a welding area to be welded is reserved between the two welding workpieces 51 to ensure the working space of the stirring head. A cooling device for controlling the deformation of the joint during the long weld stir friction welding process is arranged on the welding platform 42, including a cooling water tank 10, a cooling water pump 20, a cooling pipeline, a fixture 40, a cooling plate assembly, a key block 60, a first stop valve 70, a second stop valve 71 and a third stop valve 72. The cooling water tank 10, the cooling water pump 20, and the cooling plate assembly are connected in sequence through the cooling pipeline. The stirring head 52 can weld the two welding workpieces 51 together through the solid phase welding technology through high-speed rotation and forward movement. When the stirring head 52 of the stir friction welding equipment works on the welding workpiece 51, due to the stirring friction, the welding workpiece 51 generates a large amount of heat and conducts it to the surroundings. At this time, the cooling plate assembly diffuses the heat well under the circulation of cooling water inside the cooling pipeline, avoiding the stress deformation problem caused by heat accumulation. The cooling water tank 10 is used to store coolant and includes a liquid inlet and a liquid outlet. The liquid outlet of the cooling water tank 10 is connected to the cooling water pump 20. The other end of the cooling water pump 20 divides the cooling pipeline into an upper cooling flow path and a lower cooling flow path, and delivers the coolant to the upper / lower cooling platen of the cooling platen assembly respectively. The upper cooling platen 50 and the lower cooling platen 53 are both hollow structures and are placed along the longitudinal direction of the welding workpiece.

[0038] Two cooling zones are arranged on the surfaces of the two workpieces to be welded from top to bottom in the longitudinal direction. The cooling zone located at the upper part includes two upper cooling platens 50 arranged side by side and an upper cooling flow path; the cooling zone located at the lower part includes two lower cooling platens 53 arranged side by side and a lower cooling flow path. The upper cooling flow path and the lower cooling flow path are connected through the third stop valve 72. The first stop valve 70, the second stop valve 71 and the third stop valve 72 cooperate to control the on-off of the upper cooling flow path and the lower cooling flow path, thereby controlling the segmented cooling of the upper cooling platen 50 / lower cooling platen 53.

[0039] In the upper cooling partition, upper cooling platens 50 are placed side by side and correspondingly on the upper surface of the cooling partition above each welding workpiece 51; the upper cooling platens 50 are provided with liquid inlets and liquid outlets on the opposite side walls along the longitudinal direction thereof, and the liquid inlets and liquid outlets of the two upper cooling platens 50 are in opposite positions. Two first stop valves 70 are provided on the upper cooling flow path. The upper cooling flow path is as follows:

[0040] The coolant in the cooling water tank 10 flows out of the cooling water tank, flows through the cooling water pump 20 and the third branch 33 (blue flow path) in sequence, and then flows into the upper cooling platen 50 from the liquid inlet at the top of the left upper cooling platen 50, and then flows out from the liquid outlet at the bottom, passes through the first stop valve 70, the third stop valve 72, and another first stop valve 70, and then flows into the liquid inlet at the bottom of the upper cooling platen 50 on the right, and then flows out from the liquid outlet at the top, and is returned to the cooling water tank 10 through the fourth branch 34 (red flow path); the heat generated by welding is quickly taken away by the coolant flowing in the upper cooling platen 50.

[0041] In the lower cooling zone, lower cooling platens 53 are placed side by side and correspondingly on the upper surface of the lower cooling zone of each welding workpiece 51; the lower cooling platens 53 are provided with liquid inlets and liquid outlets on the opposite side walls along the longitudinal direction, and the liquid inlets and liquid outlets of the two lower cooling platens 53 are in opposite positions. Two second stop valves 72 are provided on the lower cooling flow path. The lower cooling flow path is as follows:

[0042] The coolant in the cooling water tank 10 flows out of the cooling water tank, flows through the cooling water pump 20 and the first branch 31 (blue flow path) in sequence, and then flows into the lower cooling platen 53 from the liquid inlet at the bottom of the left lower cooling platen 53, and then flows out from the liquid outlet at the top, passes through the second stop valve 71, the third stop valve 72, and another second stop valve 71, and then flows out from the liquid outlet at the bottom, and is returned to the cooling water tank 10 through the second branch 32 (red flow path); the heat generated by welding is quickly taken away by the coolant flowing in the lower cooling platen 53.

[0043] There is a certain gap between the upper cooling platen 50 and the lower cooling platen 53 which are arranged longitudinally, so as to accommodate the first stop valve 70 , the second stop valve 71 , the third stop valve 72 and part of the cooling flow path.

[0044] The welding workpiece 51 used in this embodiment is a long rectangular 2219 aluminum alloy test plate. The fixture 40 is set on both sides of the welding workpiece 51 to fix the lateral movement of the welding workpiece 51 and simulate the lateral constraint during barrel section welding. A plurality of key pressing blocks 60 are arranged in parallel on the upper surface of the upper / lower cooling platen, and the key pressing blocks 60 are fixed to the fixture 40 by means of hexagon socket screws 41, and the upper / lower cooling platen is pressed against the welding workpiece 51 by means of hexagon socket screws 61 to fix the positions of the upper / lower cooling platen and the welding workpiece 51.

[0045] The method for segmented cooling in the long weld friction stir welding process using the cooling device comprises:

[0046] Pretreatment: Before welding, multiple cooling zones are arranged on the surface of the workpiece to be welded from top to bottom along the longitudinal direction, ensuring that the cooling zones of the two relatively arranged welding workpieces 51 are of the same size and have corresponding positions;

[0047] Place the welding workpiece 51 on the welding platform 42, place the upper cooling platen 50 on the upper half of the welding workpiece 51, and place the lower cooling platen 53 on the lower half of the welding workpiece 51, and then fix it with the clamp 40, the key pressing block 60, screws and other fasteners to ensure that the workpiece is in close contact with the upper / lower cooling platens;

[0048] According to the welding process parameters, the flow rate and temperature of the coolant are adjusted, and the cooling water pump 20 is started to circulate the coolant in the cooling pipeline and the upper / lower cooling platen, so as to pre-cool the welding area. The pre-cooling is considered to be completed when the infrared temperature sensor 80 located at the stirring head detects that the temperature of the welding area is 2-5°C lower than the room temperature;

[0049] like Figure 1 The upper half welding process shown in FIG. 1 is as follows: after precooling is completed, stir friction welding is performed; when welding the upper half welding workpiece 51 (i.e., as shown in FIG. 1 ), the friction stir welding is performed; Figure 1 The upper cooling platen 50 is shown in the figure), and the infrared temperature sensor 80 located at the stirring head monitors the temperature at the stirring head;

[0050] Upper half cooling process: when the temperature reaches 300 degrees, open the first stop valve 70 and the third stop valve 72 of the two cooling platen assemblies, keep the second stop valve 71 of the two cooling platen assemblies closed, and keep the cooling water pump 20 started;

[0051] The coolant flows through the cooling water tank 10, the cooling water pump 20, the third branch 33 (blue flow path), the upper cooling platen 50, the first stop valve 70, the third stop valve 72, and another first stop valve 70, and then flows into another upper cooling platen 50. After flowing through the two upper cooling platens 50, the cooling water is returned to the cooling water tank 10 through the fourth branch 34 (red flow path); the heat generated by welding is quickly taken away by the coolant flowing in the upper cooling platen 50;

[0052] After the welding of the upper half of the welding workpiece is completed, the cooling water pump 20 continues to operate to allow the coolant to continue to circulate in the upper cooling flow path to ensure that the welding area is gradually cooled to room temperature before starting the lower half of the welding.

[0053] like Figure 2 As shown, the lower half welding process: when welding the lower half welding workpiece 51 (i.e. Figure 2 The lower cooling platen 53 is shown in the figure), and the infrared temperature sensor 80 located at the stirring head monitors the temperature at the stirring head, and the lower cooling flow path is started when the temperature reaches 300 degrees;

[0054] Cooling process in the lower half: close the first stop valve 70, open the second stop valves 71 of the two cooling platen assemblies, open the third stop valve 72, and the coolant flows into the right cooling platen 53 after passing through the cooling water tank 10, the cooling water pump 20, the first branch 31 (blue flow path), the left lower cooling platen 53, the second stop valve 71, the third stop valve 72, and another second stop valve 71. The cooling water flows through the two lower cooling platens 53 and then returns to the cooling water tank 10 through the second branch 32 (red flow path), so that the heat generated by welding is quickly taken away by the coolant flowing in the lower cooling platen 53.

[0055] After welding is completed, the cooling water pump 20 is continued to operate to ensure that the welding area of ​​the lower cooling flow path is gradually cooled to room temperature; then the cooling water pump is turned off, the clamping device is removed, and the welded workpiece is removed.

[0056] During the friction stir welding process, a large amount of heat is generated in the welding area, causing the temperature of the workpiece to rise. The cooling device of the present invention absorbs the heat in the welding area through circulating cooling water, reduces the temperature of the workpiece, and reduces welding deformation. The flow rate and temperature of the cooling water can be adjusted according to the welding process parameters to achieve the best welding effect.

[0057] Figure 3 The comparative example of conventional friction stir welding and friction stir welding using the cooling device and segmented control method of the present invention is shown. It can be clearly seen from the figure that the deformation deviation is reduced from more than 0.2 mm in the traditional method to less than 0.1 mm, which significantly improves the manufacturing accuracy and process economy.

[0058] In addition, according to the test carried out in this embodiment, when the cooling device described in the present invention is not used, the cooling time is more than 30 minutes. After installing the cooling device described in the present invention, it can be cooled to room temperature within 10 minutes, which can effectively shorten the process time by 30%.

[0059] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode includes only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in the embodiments may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A cooling device for controlling deformation of a welded joint, characterized in that: A plurality of cooling devices are longitudinally arranged on two oppositely arranged workpieces to be welded (51) for cooling the workpieces to be welded in sections; a plurality of cooling partitions are arranged on the surface of the workpiece to be welded from top to bottom in the longitudinal direction, and two adjacent cooling partitions are arranged from top to bottom as a group of cooling areas, and each cooling area is provided with a cooling device, and the cooling device comprises a cooling platen assembly, a cooling pipeline and a third stop valve (72); The cooling pipeline is divided into an upper cooling flow path and a lower cooling flow path, and the cooling platen assembly includes an upper cooling platen (50) and a lower cooling platen (53); the two upper cooling platens (50) are relatively fixed on the cooling partition located at the upper part of the workpiece (51) to be welded, and the two lower cooling platens (53) are relatively fixed on the cooling partition located at the lower part of the workpiece (51) to be welded; the upper cooling flow path flows through the two upper cooling platens (50), and the lower cooling flow path flows through the two lower cooling platens (53), and the upper cooling flow path and the lower cooling flow path are connected through a third stop valve 72, and the third stop valve (72) is used to control the coolant to flow through the upper cooling flow path or the lower cooling flow path, thereby realizing segmented cooling of the upper cooling platen (50) / lower cooling platen (53); The cooling partition located at the upper part comprises an upper cooling platen (50) located on two workpieces to be welded and an upper cooling flow path; the upper cooling platen (50) is provided with a liquid inlet and a liquid outlet on opposite side walls along its longitudinal direction, and the liquid inlets and liquid outlets of the two upper cooling platens (50) are located at opposite positions; the upper cooling flow path is as follows: The coolant flows from the cooling water tank (10) in sequence through the cooling water pump (20), the third branch (33), the upper cooling platen (50) on one side, the first stop valve (70), the third stop valve (72), the other first stop valve (70), the upper cooling platen (50) on the other side, and then is returned to the cooling water tank (10) through the fourth branch (34); The lower cooling zone includes a lower cooling platen (53) and a lower cooling flow path located on two workpieces to be welded; the lower cooling platen (53) is provided with a liquid inlet and a liquid outlet on opposite side walls along its longitudinal direction, and the liquid inlets and liquid outlets of the two lower cooling platens (53) are located in opposite positions; The lower cooling flow path is as follows: The coolant flows from the cooling water tank (10) in sequence through the cooling water pump (20), the first branch (31), the lower cooling platen (53) on one side, the second stop valve (71), the third stop valve (72), another second stop valve (71), the lower cooling platen (53) on the other side, and then is returned to the cooling water tank (10) through the second branch (32).

2. The cooling device for controlling deformation of a welded joint according to claim 1, characterized in that: A plurality of cooling zones are arranged along the longitudinal direction of the welding workpiece (51), and each cooling zone is provided with a cooling platen assembly and a third stop valve (72); each cooling zone can achieve segmented cooling through the control of the cooling pipeline and the cooling platen assembly.

3. The cooling device for controlling deformation of a welded joint according to claim 1, characterized in that: Two workpieces (51) to be welded that are arranged opposite to each other are respectively arranged on a welding platform (42), and a position of a welding area is reserved between the two welding workpieces (51); the welding workpiece (51) is a rectangular workpiece with a weld seam greater than 3m in length.

4. The cooling device for controlling deformation of a welded joint according to claim 1, characterized in that: The upper cooling platen (50) and the lower cooling platen (53) are fixed on the workpiece (51) to be welded via a clamp (40); the clamp (40) is arranged on both sides of the welding workpiece (51) to restrict the lateral movement of the welding workpiece (51).

5. The cooling device for controlling deformation of a welded joint according to claim 4, characterized in that: A plurality of key pressing blocks (60) are arranged in parallel on the upper surfaces of the upper cooling platen (50) and the lower cooling platen (53); the key pressing blocks (60) are fixed on the fixture (40); the upper / lower cooling platens are pressed onto the welding workpiece (51) by screws, so as to fix the positions of the upper / lower cooling platens and the welding workpiece (51).

6. The cooling device for controlling deformation of a welded joint according to claim 1, characterized in that: The cooling zones of two workpieces (51) to be welded that are arranged opposite to each other are located at corresponding positions.

7. The segmented cooling control method of a cooling device according to claim 1, comprising: Pretreatment: before welding, a plurality of cooling zones are arranged on the surface of the workpiece to be welded from top to bottom along the longitudinal direction, and the cooling plate assembly is fixed on the upper surface of the welding workpiece (51) along the longitudinal direction; and a position of a welding area is reserved between the relatively arranged workpieces to be welded (51); Starting the cooling water pump (20) to circulate the coolant in the cooling pipelines and the upper / lower cooling platens of the cooling partitions to be welded, thereby precooling the cooling partitions to be welded. The precooling is considered to be completed when the temperature is 2 to 5 degrees lower than the room temperature. Welding and cooling of the cooling zone at the upper part: After precooling is completed, friction stir welding is performed, and an infrared temperature sensor (80) located at the stirring head monitors the temperature at the stirring head; When the temperature reaches 250-350 degrees, the first stop valve (70) and the third stop valve (72) of the two cooling platen assemblies arranged opposite to each other in the welding area are opened, and the second stop valves (71) of the two cooling platen assemblies are kept closed, so that the coolant flows through the upper cooling flow path, and the heat generated by welding is taken away by the coolant flowing in the upper cooling platen (50); After the welding of the upper half of the welding workpiece is completed, the cooling water pump (20) continues to operate to ensure that the welding area is gradually cooled to room temperature; The cooling zone welding and cooling at the lower part: Stir friction welding is performed, and the infrared temperature sensor 80 located at the stirring head monitors the temperature at the stirring head; When the temperature reaches 250-350 degrees, the second stop valve (71) and the third stop valve (72) of the two cooling platen assemblies located in the welding area are opened, and the first stop valves (70) of the two cooling platen assemblies are kept closed, so that the coolant flows through the lower cooling flow path, and the heat generated by welding is taken away by the coolant flowing in the lower cooling platen (53); After the welding of the lower half of the welding workpiece is completed, the cooling water pump 20 is continued to operate to ensure that the welding area is gradually cooled to room temperature, and then the cooling water pump (20) is turned off.

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