A control method for a friction stir welding device

Abstract

The present application relates to a friction stir welding device and a control method thereof, which has a welding table with a material placement plane and a first installation groove. A plate can be placed on the material placement plane and fixed by a surrounding clamping mechanism. A first heating unit is placed in the first installation groove, and its heating surface can be lifted and lowered to fit the side of the plate facing the material placement plane. The distance between the central projection and the weld projection is a first target distance, and the temperature is regulated by a controller to a first target temperature determined according to the performance, thickness and welding temperature of the plate. This friction stir welding device effectively solves the problems of deformation and quality caused by insufficient heat by enhancing the heat input at the bottom of the weld during the friction stir welding process, and realizes a more uniform temperature gradient, welding stability and a significant improvement in joint quality.

Description

Technical Field

[0001] The present invention relates to a friction stir welding device, and particularly to a control method for a friction stir welding device. Background Art

[0002] Friction stir welding has been widely used in the fields of aerospace, rail transit, automobile manufacturing, and electronic equipment. Compared with traditional fusion welding methods, friction stir welding does not require filler materials and does not involve a melting process, so it can effectively avoid welding defects such as pores and hot cracks during the welding process and improve the mechanical properties of the welded joint.

[0003] Traditional friction stir welding is a solid-state welding method. During the welding process, the stirring head rotates at a high speed and inserts between the materials to be welded. Heat is generated by the friction between the stirring head and the materials, softening the materials and achieving welding under the pressure of the stirring head.

[0004] However, since friction stir welding generates heat through the friction between the stirring head and the materials to achieve welding, its heat input is limited by the efficiency of heat generation by friction and the thermal conductivity of the materials. When welding some aluminum alloy plates, due to the temperature gradient along the thickness direction of the plate (the temperature at the bottom of the weld is much lower than that in the middle and upper layers of the weld), the deformation amount of the area around the weld at the bottom of the plate will be too large due to insufficient heat input, thus affecting the welding quality. Therefore, in order to improve the welding quality, a new design needs to be proposed to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a friction stir welding device and a control method for reducing the deformation amount at the bottom of the weld by preheating the area near the bottom weld of the plate.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows: A friction stir welding device includes a welding table, a clamping mechanism, a first heating unit, and a controller. The welding table includes a material placement plane for placing a plate member, and a first installation groove is formed on the material placement plane. The clamping mechanism is arranged around the welding table to fix the plate member at the material placement plane during the welding process. The first heating unit is arranged in the first installation groove. The first heating unit includes a first heating surface, and the first heating surface is controlled to move up and down. The first heating surface is configured to be in contact with the side of the plate member facing the material placement plane when the plate member is placed on the material placement plane. Moreover, the distance between the orthographic projection of the center of the first heating surface on the material placement plane and the orthographic projection of the weld seam of the plate member placed at the material placement plane on the material placement plane is defined as the first target distance. The controller is connected to the first heating unit to control the temperature rise and fall of the first heating surface. Wherein, when the friction stir welding device is in a working state, the controller controls the working temperature of the first heating surface according to the target parameters of the plate member, the first target distance, and the welding temperature of the plate member. The working temperature of the first heating surface is defined as the first target temperature.

[0007] Preferably, the orthographic projection of the first heating unit on the material placement plane is located on one side of the orthographic projection of the weld seam of the plate member placed on the material placement plane on the material placement plane.

[0008] The friction stir welding device further includes a second heating unit connected to the welding table. The second heating unit is controlled to move. The second heating unit includes a second heating surface, and the temperature of the second heating surface is controlled to rise and fall. The second heating surface is configured to be in contact with the side of the plate member facing the material placement plane when the plate member is placed on the material placement plane. Moreover, the distance between the orthographic projection of the center of the second heating surface on the material placement plane and the orthographic projection of the weld seam of the plate member placed at the material placement plane on the material placement plane is defined as the second target distance, and the orthographic projection of the second heating unit on the material placement plane is located on the other side of the orthographic projection of the weld seam of the plate member placed on the material placement plane on the material placement plane. Wherein, when the friction stir welding device is in a working state, the controller controls the working temperature of the second heating surface according to the target parameters of the plate member, the second target distance, and the welding temperature of the plate member. The working temperature of the second heating surface is defined as the second target temperature.

[0009] Specifically, a control method for the above friction stir welding device includes: obtaining the welding temperature at the weld of the plate when the plate is in the welding state according to the target parameters of the plate to be welded; determining the actual temperature on the side of the weld facing the welding table when the plate is in the welding state according to the welding temperature and the target parameters; determining the first target temperature according to the actual temperature, the target parameters and the first target distance, and determining the second target temperature according to the actual temperature, the target parameters and the second target distance; controlling the first heating surface and the second heating surface to work at the first target temperature and the second target temperature respectively.

[0010] Preferably, the target parameters of the plate further include the specific heat capacity of the plate and the plastic temperature range of the plate.

[0011] The determining the first target temperature according to the actual temperature, the target parameters and the first target distance, and determining the second target temperature according to the actual temperature, the target parameters and the second target distance includes: determining the deformation sensitive parameter at the bottom of the plate according to the plastic temperature range of the plate, the thickness of the plate, the thermal conductivity of the plate and the specific heat capacity of the plate; determining the first target temperature according to the deformation sensitive parameter at the bottom of the plate, the first target distance and the actual temperature; determining the second target temperature according to the deformation sensitive parameter at the bottom of the plate, the second target distance and the actual temperature. Preferably, both sides of the weld of the plate are respectively defined as the advancing side and the retreating side according to the rotation direction of the stirring member of the friction stir welding device.

[0012] The control method further includes: correcting the first target temperature and the second target temperature according to the temperature difference between the advancing side and the retreating side of the weld when the plate is in the welding state to obtain the third target temperature and the fourth target temperature; controlling the first heating surface and the second heating surface to work at the third target temperature and the fourth target temperature respectively.

[0013] Advantages of the embodiments in the present invention:

[0014] Due to the technical means of increasing the heat input at the bottom of the weld by the heating unit during the friction stir welding process, the problems of excessive deformation and reduced welding quality caused by insufficient heat input at the bottom of the weld in the prior art are effectively solved, and thus the technical effects of more uniform weld temperature gradient, significantly improved welding stability and joint quality are achieved. Description of the Drawings

[0015] Figure 1 is a schematic structural diagram of a friction stir welding device proposed in an embodiment of the present invention.

[0016] Figure 2It is a schematic top view of a friction stir welding device proposed in an embodiment of the present invention.

[0017] Figure 3 It is a flowchart of a control method for a friction stir welding device proposed in an embodiment of the present invention.

[0018] Figure 4 It is a flowchart of a method for determining the temperature of the weld seam of a plate proposed in an embodiment of the present invention.

[0019] Figure 5 It is a flowchart of a method for determining the actual temperature on the side of the weld seam facing the welding table proposed in an embodiment of the present invention.

[0020] Figure 6 It is a flowchart of a method for determining a first target heating temperature and a second target heating temperature proposed in an embodiment of the present invention.

[0021] Figure 7 It is a flowchart of a method for determining the target temperatures of a first heating surface and a second heating surface after considering the temperature difference between the advancing side and the retreating side of the weld seam proposed in an embodiment of the present invention.

[0022] Wherein: 10, welding table; 110, material placement plane; 20, clamping mechanism; 30, first heating unit; 310, first heating surface; 40, carrier; 50, second heating unit; 510, second heating surface; 60, controller; 70, plate. Detailed implementation manners

[0023] The following combines the drawings and embodiments to further describe in detail the specific implementation manners of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0024] Please refer to Figures 1 to 2 , in a preferred embodiment of the present application, a friction stir welding device is proposed to preheat the weld area of the plate 70 to be welded before friction stir welding, so as to reduce the deformation amount at the bottom of the weld seam. Moreover, the target object applicable to this friction stir welding device is an aluminum alloy plate 70 with a thickness limited within 2 mm to 5 mm. This is because it is difficult to comprehensively process the weld seam of the thin plate 70 by means of double-sided friction stir welding, so a large range of deformation may occur on the side of the bottom of the weld seam (away from the stirring member) due to poor conduction of the welding temperature.

[0025] The friction stir welding device includes a welding table 10, a clamping mechanism 20, a first heating unit 30, and a controller 60. Among them, the welding table 10 includes a material placement plane 110 for placing a plate 70. A first installation groove is formed on the material placement plane 110. The clamping mechanism 20 is arranged around the welding table 10 to fix the plate 70 at the material placement plane 110 during the welding process.

[0026] Specifically: The welding table 10 is usually made of metal materials, preferably materials with high rigidity, high temperature resistance, and good heat conduction performance (such as cast iron or low thermal expansion alloy) to ensure stability during heating and subsequent friction stir welding. After the welding table 10 is installed on a horizontal plane, the material placement plane 110 is located at the top plane of the welding table 10 for placing the plate 70 to be welded. The material placement plane 110 can be designed according to the size and shape of the plate 70, usually adopting a rectangular or square layout to adapt to plates 70 with different thicknesses, lengths, and widths. It should be noted that the material placement plane 110 usually also has a positioning component, which is specifically represented as a positioning pin or a positioning groove for rough positioning of the plate 70, etc., so as to simplify the fine adjustment and alignment of the position of the plate 70 before formal clamping.

[0027] The clamping mechanism 20 is arranged around the welding table 10 and can be set according to the surrounding space or the peripheral contour of the welding table 10 to ensure that the plate 70 can be clamped from multiple directions during operation. The specific mechanical clamping form can adopt methods such as bolts, knobs, and pressing plates, and can be adjusted manually or with the help of auxiliary tools. Further, if higher requirements are placed on the clamping efficiency or stability, the clamping mechanism 20 can also adopt cylinders or hydraulic cylinders to achieve automatic or semi-automatic clamping. In the welding state, the clamping mechanism 20 can act downward (or inward) on the plate 70 to press and fix the plate 70 on the material placement plane 110, avoiding displacement or warping due to thermal expansion and contraction, vibration, or stirring force during the subsequent welding process.

[0028] In order to suppress the deformation amount at the bottom of the weld seam after the welding of the plate member 70, it is necessary to preheat the bottom of the weld seam of the plate member 70. Therefore, in this embodiment, the friction stir welding device further includes a first heating unit 30 and a controller 60. Among them, the first heating unit 30 is arranged in the first installation groove. The first heating unit 30 includes a first heating surface 310, and the first heating surface 310 is controlled to move up and down. The first heating surface 310 is configured to be attached to the side of the plate member 70 facing the material placement plane 110 when the plate member 70 is placed on the material placement plane 110. Moreover, the distance between the projection of the center of the first heating surface 310 on the material placement plane 110 and the projection of the weld seam of the plate member 70 placed at the material placement plane 110 on the material placement plane 110 is defined as the first target distance. The controller 60 is connected to the first heating unit 30 to control the temperature rise and fall of the first heating surface 310. And when the friction stir welding device is in a working state, the controller 60 controls the working temperature of the first heating surface 310 according to the target parameters of the plate member 70, the first target distance, and the welding temperature of the plate member 70. The working temperature of the first heating surface 310 is defined as the first target temperature.

[0029] Specifically: The first installation groove is usually opened at a position corresponding to the weld seam preheating area on the material placement plane 110 of the welding table 10. This installation groove is designed with openings or hollow-outs according to the actual size of the device and the specifications of the plate member 70, and its internal space can accommodate the first heating unit 30. The shape of the installation groove can be rectangular, circular or other regular geometric shapes to facilitate installation and maintenance.

[0030] The first heating surface 310 is usually planar and is made of a material with high temperature resistance and good thermal conductivity (such as superalloy, high temperature resistant ceramic coated metal, etc.). The heating element of the first heating unit 30 can be in the form of a resistance wire, an electric heating tube or an induction coil, etc., and is integrated on the back or inside of the first heating surface 310 to ensure the stability and uniformity of heating. Further, if rapid response or precise temperature control needs to be achieved, then zone heating or a double-layer structure can be adopted to make the heating effect more flexible and the control more precise. And in order to control the temperature of the first heating surface 310, the first heating unit 30 further includes a third temperature sensor (not shown in the figure). Specifically, the third temperature sensor can be installed on the first heating surface 310 or near it to facilitate detecting the real-time temperature of the first heating surface 310.

[0031] The first target distance refers to the distance from the center point of the first heating surface 310 to the weld. Since the purpose of the friction stir welding device in this application is to preheat the area near the weld of the plate 70, in order to control the temperature in the area near the weld, it is necessary to determine the first target temperature based on the thermal conductivity of the plate 70 and the first target distance, so as to more accurately control the temperature within a preset range at the bottom of the weld area of the plate 70 (from the center of the first heating surface 310 to the weld of the plate 70).

[0032] While the controller 60 is monitoring the real-time temperature of the first heating surface 310 in real time, it adjusts the temperature of the first heating surface 310 by adjusting the heating power or current, so that the real-time temperature of the first heating surface 310 is accurately maintained at the required first target temperature.

[0033] It should be noted that the controller 60 can obtain the first target temperature based on the target parameters of the plate 70, the first target distance, the welding temperature and the welding direction of the plate 70, and adjust the working temperature of the first heating surface 310 to the first target temperature. Among them, the specific method for obtaining the first target temperature refers to the control method described later.

[0034] When the aluminum alloy plate 70 is placed on the material placement plane 110 of the welding table 10, the first heating surface 310 of the first heating unit 30 is butted against the bottom of the plate 70. Then, under the precise control of the controller 60, the first heating surface 310 maintains the first target temperature to provide continuous and stable heat within a preset range at the bottom of the weld of the plate 70. Thus, before or during the friction stir welding process, preheating or auxiliary heat compensation can be provided for the bottom of the plate 70 and the root of the weld, so that the plate 70 maintains a more uniform and appropriate temperature distribution at the welding part, reducing welding deformation and stress concentration. Taking the aluminum alloy plate 70 as an example, the thick aluminum alloy plate 70 to be welded is placed on the material placement plane 110 and fixed by the surrounding clamping mechanism 20. The first heating surface 310 is attached to the side of the plate 70 facing the material placement plane 110. According to the specific position of the weld, the distance between the orthographic projection of the weld on the material placement plane 110 and the orthographic projection of the center point of the first heating surface 310 on the material placement plane 110 is determined, and this distance is the first target distance. The controller 60 determines the first target temperature required for the first heating surface 310 according to the target parameters (such as thickness, thermal conductivity, specific heat capacity, etc.) of the plate 70 and the planned friction stir welding temperature. After the first heating unit 30 is started, the third temperature sensor will monitor the temperature of the first heating surface 310 in real time, and the controller 60 performs closed-loop adjustment to ensure that it operates stably within the target temperature range. After heating for a preset time, the temperature at the bottom of the weld of the plate 70 will be approximately the same as the temperature of the first heating surface 310. At this time, the friction stir welding device can be started to weld the joint of the plate 70. At this time, heat is generated on the upper side due to the high-speed rotation and friction of the stirring head, and the lower side is continuously heated by the first heating surface 310, reducing the temperature gradient difference in the up-down direction of the weld area and reducing the probability of incomplete fusion and deformation caused by too low temperature at the bottom of the weld.

[0035] In this embodiment, by preheating the bottom before and during welding, the deformation amount can be effectively suppressed and the welding quality can be improved. Specifically, because the bottom temperature is compensated, the thermoplasticized area generated by the friction stir welding head is more uniform, the weld is denser, and the grain refinement effect is better, thus significantly improving the weld strength and reliability. Moreover, compared with the traditional large-area heating method, by heating at a fixed point at the bottom of the weld, energy can be saved, and the temperature of the weld area can be increased specifically, reducing the unnecessary heat influence on the surrounding non-welded parts or equipment.

[0036] It should be noted that the friction stir welding device in this embodiment should also include a controlled welding part (such as a rotating part and a stirring part, etc.), but since the welding part of the friction stir welding device is prior art, no detailed description is made in this application.

[0037] In order to further suppress the deformation amount at the bottom of the weld of the plate 70, in some embodiments, such as Figure 2As shown, the orthographic projection of the first heating unit 30 on the material placement plane 110 is located on one side of the orthographic projection of the weld seam of the plate member 70 placed on the material placement plane 110 on the material placement plane 110. The friction stir welding device further includes a second heating unit 50, which is connected to the welding table 10. The second heating unit 50 moves controllably. The second heating unit 50 includes a second heating surface 510, and the temperature of the second heating surface 510 rises and falls controllably. The second heating surface 510 is configured to be in contact with the side of the plate member 70 facing the material placement plane 110 when the plate member 70 is placed on the material placement plane 110. Moreover, the distance between the orthographic projection of the center of the second heating surface 510 on the material placement plane 110 and the orthographic projection of the weld seam of the plate member 70 placed at the material placement plane 110 on the material placement plane 110 is defined as the second target distance, and the orthographic projection of the second heating unit 50 on the material placement plane 110 is located on the other side of the orthographic projection of the weld seam of the plate member 70 placed on the material placement plane 110 on the material placement plane 110. Wherein, when the friction stir welding device is in a working state, the controller 60 controls the working temperature of the second heating surface 510 according to the target parameters of the plate member 70, the second target distance, the welding temperature of the plate member 70, and the welding direction. The working temperature of the second heating surface 510 is defined as the second target temperature.

[0038] Specifically: The first heating unit 30 is installed on one side of the bottom of the weld seam of the plate member 70, while the second heating unit 50 is installed on the other side of the bottom of the weld seam of the plate member 70. The first heating unit 30 cooperates with the second heating unit 50 to heat both sides of the bottom of the weld seam of the plate member 70 simultaneously to overcome the limitation of single-sided heating.

[0039] The second heating unit 50 is similar to the aforementioned first heating unit 30, and the second heating surface 510 is similar to the first heating surface 310. The second heating surface 510 is usually made of a material with high temperature resistance and good thermal conductivity, and can provide controlled heat when approaching or closely adhering to the bottom of the plate member 70. Moreover, in order to control the temperature of the second heating surface 510, the second heating unit 50 further includes a fourth temperature sensor. Specifically, the fourth temperature sensor can be installed on or near the second heating surface 510 to facilitate real-time monitoring of the temperature of the second heating surface 510.

[0040] It should be noted that the second heating unit 50 is designed to be movable. The second heating unit 50 is installed on a carrier 40, which can be embodied as a long strip plate in a specific manner. And this long strip plate can be moved according to the specific state of the plate 70 to be welded, so that the weld of the plate 70 is located between the first heating unit 30 and the second heating unit 50 before preheating. The second heating unit 50 moves together with the carrier 40. The moving mode of the carrier 40 can be connected by means such as slide rails, support arms or electric push rods in a specific manner, so that it can be controlled to move (or lift) within a certain range.

[0041] When the device is working, the controller 60 will obtain the second target temperature by combining factors such as the target parameters of the plate 70 (such as the thickness, thermal conductivity, specific heat capacity, etc. of the plate 70), the second target distance (the distance between the positive projection of the weld on the placement plane 110 and the positive projection of the center of the second heating surface 510 on the placement plane 110), the welding temperature of the plate 70, and the welding direction. And this second target temperature can be the same as or different from the first target temperature, specifically depending on the comprehensive requirements for the temperature gradient, heat input amount, and required welding quality during welding.

[0042] In this embodiment, for the bilateral heat compensation at the bottom of the weld of the plate 70, compared with the traditional single bottom preheating or only heating from one side, by performing controlled heating on both sides of the weld at the bottom of the plate 70, the entire welding area can be heated more evenly, reducing local stress concentration, thereby more effectively suppressing the deformation of the weld in the longitudinal or transverse direction. And the first heating surface 310 and the second heating surface 510 can be independently set with target temperatures (the first target temperature, the second target temperature), which helps to adopt different thermal management strategies for different positions and different welding stages during the welding process.

[0043] In some embodiments, to uniformly heat the entire weld before welding, the number of the first installation grooves is several, and each of the first installation grooves is arranged along a first direction, and the first direction is parallel to the extending direction of the weld of the plate 70 placed on the placement plane 110. The number of the first heating units 30 is several, and each of the first heating units 30 is correspondingly installed in each of the first installation grooves. The number of the second heating units 50 is several, and each of the second heating units 50 is configured to be arranged along the first direction when the friction stir welding device is in a working state.

[0044] Specifically, there are several first installation grooves, which are arranged at equal intervals in sequence along the first direction (i.e., parallel to the weld extension direction). The number and spacing of these installation grooves can be designed according to actual process requirements (such as the length of the plate 70, the length of the weld, heat distribution requirements, etc.). Several first heating units 30 are respectively installed in the corresponding first installation grooves, ensuring that each installation groove accommodates one heating unit. Such an arrangement enables each heating unit to play a preheating or heating role in the corresponding area below the weld, meeting the continuous or segmented heating requirements for the bottom of long welds or multiple weld segments. Moreover, each first heating unit 30 has a first heating surface 310, which is usually planar and fits or is in close contact with the bottom of the plate 70. When the plate 70 is placed on the material placement plane 110, the first heating surface 310 can provide contact or proximity heating to keep the area near the weld at an ideal temperature.

[0045] Several second heating units 50 are similar to the first heating units 30. The second heating units 50 are also arranged in multiple groups and should be distributed parallel to the weld direction. Such a multi-point or multi-segment setting can further strengthen the temperature control of different positions at the bottom of the weld of the plate 70. Each second heating unit 50 has a second heating surface 510 that fits the bottom of the plate 70 and usually fits the bottom of the plate 70 during welding or preheating. Further, in some cases, by independently regulating the temperature of the second heating surface 510, it can cooperate with the first heating units 30 to achieve multi-segment and multi-temperature heating management.

[0046] In this embodiment, by arranging multiple first installation grooves and several first heating units 30 in sequence in the first direction, even if the weld is very long, sufficient heat supply can be obtained through segmented or integral multi-point heating. Further, after the second heating units 50 are also arranged in multiple points, bottom preheating can be carried out simultaneously or sequentially in multiple segments, achieving full coverage of different weld shapes and sizes. Moreover, since each heating unit can set its own target temperature and heating timing, even for different paragraphs of the same weld, differential heating can be carried out according to factors such as the thickness difference of the plate 70 and local stress characteristics. And multi-segment heating can form a more continuous and uniform temperature field at the bottom of the weld, improving the plastic fluidity of the material during friction stir welding, reducing welding defects caused by local cold spots, enabling the plate 70 to be fully preheated and heat compensated in multiple places, reducing thermal stress concentration and weld deformation, and achieving better forming quality.

[0047] In order to accurately monitor the temperatures on both sides of the bottom weld of the plate 70, in some embodiments, the first heating unit 30 further includes a first temperature sensor (not shown in the figure), the first temperature sensor is connected to the controller 60, and the first temperature sensor is configured such that when the plate 70 is placed at the material placing plane 110, the temperature measuring part of the first temperature sensor contacts the side of the plate 70 facing the material placing plane 110. The second heating unit 50 further includes a second temperature sensor (not shown in the figure), the second temperature sensor is connected to the controller 60, and the second temperature sensor is configured such that when the plate 70 is placed at the material placing plane 110, the temperature measuring part of the second temperature sensor contacts the side of the plate 70 facing the material placing plane 110.

[0048] Specifically: Based on the original friction stir welding device (including the first heating unit 30, the second heating unit 50, the welding table 10, etc.), this embodiment adds a first temperature sensor and a second temperature sensor. The first temperature sensor and the second temperature sensor are the same temperature measuring elements, and can independently or cooperatively measure the temperature at the bottom of the welded plate 70. These two groups of temperature sensors are electrically connected to the controller 60 to form a real-time temperature detection and feedback closed loop, providing a basis for the temperature adjustment of the heating unit.

[0049] Since it is required that the temperature measuring parts of the first temperature sensor and the second temperature sensor contact the side of the plate 70 facing the material placing plane 110, the sensors are usually arranged at the material placing plane 110 of the welding table 10 so that they can naturally fit on its lower surface when the plate 70 is placed. The specific installation method can be embodied as an embedded type, that is, a through hole or a groove is reserved in the material placing plane 110, or a convex type, so that the head of the sensor is slightly higher than the material placing plane 110 to better fit the bottom of the plate 70.

[0050] The controller 60 is connected to both the first temperature sensor and the second temperature sensor, and can use their respective temperature signals for real-time monitoring. When it senses that the temperature in the area around the bottom of the weld of the plate 70 fluctuates or fails to reach the preset value, the controller 60 can adjust the working parameters (such as the heating power) of the first heating unit 30 and / or the second heating unit 50 to maintain or restore the ideal heating temperature range.

[0051] In this embodiment, by attaching the first temperature sensor and the second temperature sensor to both sides of the bottom of the weld of the plate 70, the actual heat reception conditions on both sides of the bottom of the plate 70 can be captured in a timely manner, avoiding deviations caused by relying on the indirect ambient temperature or the heating surface temperature. Moreover, compared with only monitoring the temperature of the heating element itself, directly monitoring the temperature at the bottom of the plate 70 can better reflect the heat input condition at the root of the weld. Especially when the temperature at the bottom of the plate 70 is lower than or higher than the first target temperature or the second target temperature, the controller 60 can quickly adjust the temperatures of the corresponding first heating surface 310 and / or the second heating surface 510 to ensure that the heat supply during the entire welding process is always in the best state. This plays a crucial role in friction stir welding of aluminum alloy plates (especially medium-thin plates with a thickness of 2 mm to 5 mm) that are sensitive to heat input, and can effectively reduce heat stress concentration and welding defects.

[0052] In order to make the weld of the plate 70 better under the action of the above-mentioned friction stir welding device, a control method applicable to the above-mentioned friction stir welding device is specifically proposed. This control method is for the plate 70 in the friction stir welding state. By obtaining the target parameters (including the material, thickness, thermal conductivity, specific heat capacity, etc. of the plate 70) and the ambient temperature, and combining the moving speed and the rotating speed of the stirring member or the stirring pin or the stirring head, the temperature distribution of the plate 70 during welding is deduced. Then, according to the actual temperature at the bottom of the plate 70, the plastic temperature range and the deformation sensitivity degree, the first target heating temperature and the second target heating temperature are respectively determined to control the first heating surface 310 and the second heating surface 510, so as to provide the optimal heat input at the bottom of the weld. Moreover, because there is a temperature difference between the advancing side and the retreating side of the weld, steps S500 and S600 also need to be executed for correction and compensation to balance the temperatures on both sides of the weld. As Figures 3 to 7 shown, this control method includes:

[0053] Step S100: Obtain the welding temperature at the weld of the plate 70 when the plate 70 is in the welding state according to the target parameters of the plate 70 to be welded.

[0054] Step S200: Determine the actual temperature on the side of the weld facing the welding table 10 when the plate 70 is in the welding state according to the welding temperature and the target parameters;

[0055] Step S300: Determine the first target temperature according to the actual temperature, the target parameters and the first target distance, and determine the second target temperature according to the actual temperature, the target parameters and the second target distance;

[0056] Step S400: Control the first heating surface 310 and the second heating surface 510 to work at the first target temperature and the second target temperature respectively.

[0057] Among them, please refer toFigure 4 , the target parameters of the plate 70 include the material of the plate 70 and the thickness of the plate 70. In step S100, when the plate 70 is in the welding state according to the target parameters of the plate 70 to be welded, the welding temperature at the weld of the plate 70 includes:

[0058] Step S110: Determine the optimal moving speed of the stirring member and the optimal rotating speed of the stirring member corresponding to the best range of the weld quality of the plate 70 according to the material of the plate 70 and the thickness of the plate 70.

[0059] Step S120: Obtain the welding temperature at the weld of the plate 70 when the plate 70 is in the welding state according to the material of the plate 70, the thickness of the plate 70, the optimal moving speed of the stirring member, and the optimal rotating speed of the stirring member.

[0060] Among them: In step S110, the material of the plate 70 (such as aluminum alloy or other alloys) will affect the plastic temperature range and the optimal welding speed of friction stir welding. The thickness of the plate 70 (for example, 2 mm to 5 mm) will determine the heat distribution in the weld zone of the stirring member, the penetration force of the stirring pin, and the upper limits of the moving and rotating speeds. Generally, according to a large amount of test data or technical manuals, the optimal process window (including moving speed, rotating speed, temperature, etc.) of friction stir welds under different materials and different thicknesses can be obtained. After confirming the best forming requirements of the weld, select or calculate the "optimal moving speed of the stirring member" and the "optimal rotating speed of the stirring member", which are the basic parameters for subsequent temperature calculation.

[0061] Specifically, the target object of the friction stir welding device proposed in this embodiment takes aluminum alloy as a typical example. It is usually determined by material selection during production, or given by the supplier / technical specification (such as 6061 aluminum alloy). In technical documents or material descriptions, its chemical composition, thermophysical properties, etc. will be marked. The material of the plate 70 directly determines key thermal and mechanical properties such as the plastic temperature range (see below), thermal conductivity, and specific heat capacity, thereby affecting the friction stir welding process window and heating strategy.

[0062] The thickness of the plate 70 refers to the dimension of the metal plate to be welded perpendicular to its plane, usually in millimeters. It can be specifically measured by a caliper, a micrometer or an automated thickness gauge, and is marked by the raw material during mass production. It can be understood that the greater the thickness of the plate 70, the longer the heat conduction path, the greater the temperature gradient, and the stirring pin penetration depth and the stirring head rotation speed also need to be adjusted accordingly. Many calculations in the method (such as heat conduction, deformation sensitivity assessment, etc.) rely on the plate thickness.

[0063] The moving speed of the stirring member refers to the speed at which the stirring tool (including stirring pins, stirring shoulders, etc.) moves along the weld direction, and the unit is commonly mm / min or m / min. Specifically, an appropriate range can be found in a large number of tests or empirical curves. If the moving speed is too high, insufficient heat input will cause weld defects. If it is too low, the production efficiency will be low and overheating is likely to occur. Through steps S110 and S120, the optimal value is selected in combination with the thickness and material.

[0064] The rotational speed of the stirring member refers to the rotational speed of the stirring tool in the axial direction, and the unit is rpm (revolutions per minute). Specifically, it can be determined through process tests or by referring to existing mature process windows.

[0065] Furthermore, the combination of the rotational speed and the moving speed of the stirring member determines the degree of material plasticization and the weld quality, and also affects the formation of the welding temperature. The optimal moving speed and the optimal rotational speed refer to the combination of moving / rotational speeds that can achieve the best or better balance in terms of weld quality standards such as strength, density, and surface formation. Specifically, the optimal range can be found through a large number of tests or by referring to industry standards and data literature. After locking these two parameters in steps S110 and S120, the subsequent calculations of temperature distribution and heating control are continued. And the weld quality being in the optimal range means a state where the weld metal meets or even exceeds the requirements of the design or industry standards in terms of appearance, internal defects (such as pores, cracks, etc.), and mechanical properties (tensile strength, fatigue performance, etc.). Specifically, through the comprehensive evaluation of indicators such as penetration depth, stirring adequacy, metallographic structure, or tensile test, it can be judged whether the weld reaches the "optimal" or is close to the optimal quality range. And in step S110, the process parameters (moving speed and rotational speed) of the stirring member are jointly determined with the thickness and material of the plate 70.

[0066] In a specific manner, taking a 6061 aluminum alloy sheet metal with a thickness of 3 mm as an example:

[0067] Before actual production, process window data corresponding to the best weld performance can be obtained through repeated welding tests. The specific steps are as follows: First, determine the experimental parameter range: the rotation speed range of the stirring part is 600 - 1500 rpm, and the moving speed range of the stirring part is 50 - 500 mm / min. Second, conduct orthogonal tests or single-variable tests. For example, through orthogonal tests, different rotation speeds (e.g., 600, 900, 1200, 1500 rpm) and different moving speeds (e.g., 50, 100, 200, 300, 400, 500 mm / min) are combined for welding tests. Then, after welding, the weld quality can be evaluated through the following indicators: Appearance quality, the flatness and smoothness of the weld surface can be visually inspected. Internal defects, non-destructive testing techniques such as X-ray or ultrasonic can be used to detect the holes and cracks inside the weld. Also, tensile tests can be used to detect the tensile strength at the weld. Finally, after the experiment is completed, record and analyze the test data to find the parameter range that simultaneously satisfies the strength ≥ 80% - 90% of the base material strength and has no obvious weld defects. According to the data, the best rotation speed and the best moving speed for the 6061 aluminum alloy plate 70 with the corresponding thickness can be determined. And this method can be repeatedly applied to plates 70 with different materials or thicknesses to obtain the best process parameter database.

[0068] Step S120, substitute parameters such as the material of the plate 70, the thickness of the plate 70, the best moving speed of the stirring part, and the best rotation speed into the thermal model or empirical formula of the welding process to evaluate the average or peak temperature during the formation of the friction stir weld under this combination of movement and rotation. The calculation result is the welding temperature, which can be regarded as the target temperature range in the center or near the center of the weld. This is the starting point of the high-temperature zone, and subsequent heat conduction to the bottom of the plate 70 is based on this temperature.

[0069] The welding temperature of the weld mainly depends on the heat input generated by the stirring head and the heat dissipation characteristics of the plate 70. Therefore, the following calculation formula for the welding temperature T of the weld is proposed:

[0070]

[0071] Where:

[0072] T: The welding temperature of the weld area of the plate 70 (unit: °C). T0: The ambient temperature or the initial temperature of the plate 70 (unit: °C). η: The conversion efficiency of frictional heat, dimensionless (usually between 0.8 and 0.95). M: The average frictional torque at the interface between the stirring part and the plate 70 (unit: N·m), which can be determined through tests or empirical data. ω: The rotation speed of the stirring part (rad / s). V: The moving speed of the stirring part (m / s). ρ: The material density of the plate 70 (kg / m 3 ). C p : The specific heat capacity of the material of the plate 70 (J / (kg·°C)). Aeff : Effective cross-sectional area of the friction stir welding seam region (m 2 ), usually taken as the weld thickness × the probe diameter. λ: Thermal conductivity of the 70 material of the plate (W / (m·°C)). δ: Thickness of the 70 plate (m).

[0073] The calculation formula for the welding temperature T of the weld covers the main thermodynamic factors in the actual production of friction stir welding. The friction heat efficiency, the torque of the stirring head, the rotation speed and the moving speed, and the material properties of the 70 material of the plate (density, specific heat capacity, thermal conductivity) are all reflected by real data, and the attenuation factor of heat conduction is considered. This formula is essentially a thermal model that combines energy conservation and heat conduction attenuation. It describes how the temperature T of the weld region in the friction stir welding process is determined by the heat generated by the stirring head and the material properties:

[0074] The ambient temperature (initial temperature) T0 represented in the formula is the initial temperature T0 of the 70 plate (usually the ambient temperature). Because before the actual welding starts, the 70 plate is in the ambient temperature state, which is the reference point before heat input, and any temperature rise is superimposed on the ambient temperature.

[0075] The heat input term is It reflects the contribution of the heat generated by the friction stir welding stirrer to the temperature rise in the weld region. Among them, η is the friction heat conversion efficiency, which is about between 0.8 and 0.95. When the actual stirring head rubs against the material, not all mechanical energy will be converted into heat energy, and a part of it is lost in the ways of wear, vibration, etc. Therefore, an efficiency factor η is needed to express the effective proportion actually used for material heating.

[0076] The friction heat conversion efficiency η represents the efficiency of converting the input mechanical energy into heat energy in the friction stir welding process, and its usual value range is between 0.8 and 0.95. The determination method of η is as follows:

[0077] The first step is the test preparation stage. Select the 70 material of the plate to be welded and determine the size of the stirring tool (stirring head diameter, pin length). Set a certain number of temperature sensors and place them in the weld region (such as the bottom, middle and top of the weld). Equip a torque sensor to measure the actual torque value of the stirring tool. Prepare an infrared thermal imager or thermocouple to measure the real-time temperature of the weld region. The second step is to carry out the friction stir welding experiment. Set a specific rotation speed of the stirring tool (such as 1200 rpm) and a moving speed (such as 200 mm / min). Start welding and record the torque data and temperature data during the whole process. The third step is heat calculation (measured Q value). By measuring the temperature rise and material properties, calculate the actual heat absorbed by the weld region: Q 实测 = ρ·V 焊缝 ·C p ·(T 焊后 - T0). Among them, Q实测 : Heat actually absorbed by the weld area (J). V 焊缝 : Volume of the weld area (m 3 ). T 焊后 : Average temperature of the weld area after welding (°C). Among them, V 焊缝 In friction stir welding, it is generally defined as:

[0078] V 焊缝 = Effective length of the weld × Effective width of the weld × Thickness of the weld.

[0079] Effective length: Length of the weld actually formed during welding. Effective width: Width of the weld area (usually 1 - 1.2 times the diameter of the stirring pin). Weld thickness: Thickness of the plate 70 (generally equal to the thickness δ of the plate).

[0080] The detailed steps to determine the volume of the weld area are as follows:

[0081] First, clarify the effective length of the weld. The length of the friction stir weld can be determined by actual measurement methods. For example: Use a tape measure, vernier caliper or laser rangefinder to accurately measure the actual length of the weld. Second, clarify the effective width of the weld. Usually, take 1.0 - 1.2 times the diameter of the stirring pin as the weld width W. If higher precision is required, the actual weld width can be determined by observing the actual weld cross-section (after slicing, measure through a metallurgical microscope or macroscopic image). For general engineering methods, effective width = (1.0 - 1.2) × d. Among them, d: Diameter of the stirring pin, determined by actual measurement. Then, clarify the weld thickness. The weld thickness is usually the thickness of the plate 70, and the thickness of the plate can be directly measured. For example, use a caliper or micrometer to measure the thickness of the plate. Then, calculate the volume V of the weld area 焊缝 . Substitute the above parameters into the calculation formula:

[0082] V 焊缝 = Effective length × Effective width × Thickness of the plate.

[0083] The above is the calculation method for the volume V of the weld area 焊缝 . The determination method of η will be elaborated later.

[0084] Fourth step, calculate the input mechanical energy (W input). Through the torque and rotational speed of the stirring head measured by experiments, calculate the mechanical energy input to the weld area: W 输入= M·ω·t. Wherein, M is the average frictional torque measured in the experiment (N·m), ω is the rotational speed of the stirring tool (rad / s), and t is the time used for friction stir welding (s). Moreover, the average frictional torque M reflects the magnitude of the actual frictional moment between the stirring head and the plate during welding. The method for determining the average frictional torque M is as follows: First, in the equipment preparation stage, install a high-precision torque sensor (torque meter) on the welding equipment (stirring head spindle), and confirm that the torque meter is accurately calibrated and can record data in real time. Second, in the stage of measuring the frictional torque value, start the welding process. The stirring head rotates and moves, and the sensor records the torque changes throughout the process in real time. Moreover, in a complete welding test, continuously record the torque values to form a complete torque-time curve. Then, calculate the average torque, integrate and average the torque data recorded during the entire welding process: Or a simpler method is to directly take the average of the continuously measured values: Usually, repeat the experiment multiple times and take the average to obtain a more stable and reliable torque value.

[0085] The above is the specific method for determining the average frictional torque M. Subsequently, the method steps for determining the efficiency η will be continued to be given.

[0086] Step 5: Calculate the efficiency η. The frictional heat conversion efficiency η is the ratio of the actual absorbed heat to the mechanical energy input:

[0087] Take the average of multiple groups of experimental data to obtain a relatively stable η value, usually ranging from 0.8 to 0.95.

[0088] The above are the specific steps of the method for determining η.

[0089] The frictional torque M describes the magnitude of the torque exerted by the stirring head on the plate. The greater the torque, the stronger the frictional force on the material surface and the more heat is generated. Therefore, the torque M directly determines the mechanical energy input into the weld area.

[0090] The faster the angular velocity ω of the stirring head rotates, the more friction times per unit time and the greater the heat input. Therefore, the rotational speed is one of the important variables of heat input.

[0091] The product of the above three items η, M, and ω represents the total heat input power provided by the stirring head per unit time.

[0092] The term V·ρ·Cp·Aeff in the denominator represents the ability of the plate material 70 to absorb and store heat. Specifically:

[0093] The moving speed V of the stirring head represents the speed at which heat is introduced into the weld zone. The faster the welding speed, the less heat is obtained in the same area per unit time. The greater the material density ρ, the slower the temperature rise of the same volume of material after absorbing heat. The specific heat capacity Cp represents the energy required for the material to raise the temperature by one unit. The higher the specific heat capacity, the slower the temperature rise. The effective cross-sectional area Aeff represents the size of the area where the weld material effectively absorbs heat. The larger this area, the more dispersed the input heat and the slower the temperature rise. Among them, the effective cross-sectional area refers to the cross-sectional area of the area that actually participates in thermoplasticization and forms the weld, which is usually simplified as: A eff = weld thickness × stirring pin diameter. A eff The determination method is as follows:

[0094] First, clarify the dimensions of the stirring tool and the thickness of the plate 70, measure or record the diameter d of the stirring pin, and determine the thickness of the weld area of the plate (generally the thickness δ of the plate). Then, calculate the cross-sectional area. The effective cross-sectional area is the product of the weld thickness and the stirring pin diameter: A eff = δ × d. This calculation method is practical and simple and is generally widely used in engineering applications.

[0095] The above is the determination method of the effective cross-sectional area Aeff.

[0096] In summary, the entire heat input term actually reflects that: the temperature rise of the material per unit volume ≈ frictional heat input power / (welding speed × material heat capacity × weld effective cross-sectional area). It can be seen that when the frictional heat input power is higher, the material temperature rises faster. The stronger the heat absorption capacity of the material (the greater the density and specific heat capacity), the slower the temperature rise. The faster the stirring head moves, the shorter the residence time of each area of the material for heating and the less the temperature rise. The heat conduction attenuation term reflects the heat loss caused by the heat conduction effect of the material. The higher the material thermal conductivity λ, the faster the heat conduction and loss in the welding area (especially in the direction of the deeper part of the lower plate 70 and the welding table 10), and the worse the heat accumulation effect in the weld area. Therefore, the larger λ is, the smaller the exponential term value is, and the more obvious the temperature drop in the weld area is. The greater the thickness δ of the plate 70, the longer the distance that the heat needs to penetrate, and the more serious the overall heat attenuation in the weld area. The denominator (V·ρ·Cp) represents the heat input speed and the heat capacity of the material. If the heat input is fast enough or the material heat capacity is large enough, the material temperature rises faster and sufficient heat accumulation can be formed in the weld area to effectively offset the influence of heat conduction loss; on the contrary, the temperature rises slowly and the heat is easily dissipated, and the temperature in the welding area cannot be significantly increased. Therefore, the overall physical meaning of the exponential term is that considering the material thermal conductivity and thickness, there will be an exponential decay trend in the temperature of the weld area caused by heat input.

[0097] The fundamental reason for this formula design is that the actual welding process is a process of competition between heat input (heat generated by friction) and heat output (heat dissipation through material conduction). The determining factors of heat input (η·M·ω) must be incorporated into the formula, and the heat absorption capacity of the material (ρ·Cp·V·Aeff) needs to be clearly reflected because it affects the amplitude and rate of temperature rise. The heat conduction dissipation mechanism (λ·δ) must be reflected in the form of exponential decay, which is a real phenomenon in actual welding. Therefore, through the reasonable combination of these three core factors, the actual temperature in the weld area during the friction stir welding process can be estimated more realistically and accurately. This design makes the formula highly consistent with the actual physical process and is more suitable for guiding the formulation and optimization of production processes.

[0098] Please refer to Figure 5 , the friction stir welding device further includes a thermometer to obtain the ambient temperature. The target parameters of the plate 70 further include the thermal conductivity of the plate 70. When step S200 determines that the plate 70 is in the welding state based on the welding temperature and the target parameters, the actual temperature on the side of the weld facing the welding table 10 includes:

[0099] Step S210: Determine the conduction temperature on the side of the weld facing the welding table 10 when the plate 70 is in the welding state according to the thickness of the plate 70, the thermal conductivity of the plate 70, and the welding temperature.

[0100] Step S220: Determine the actual temperature on the side of the weld facing the welding table 10 after heat dissipation correction according to the ambient temperature and the conduction temperature.

[0101] Among them: In step S210, when the temperature in the stirring zone (i.e., the "welding temperature" in S120) conducts to the bottom of the plate 70 or the root of the weld, a certain temperature gradient will be caused due to the thickness of the plate 70 and its thermal conductivity. Through the heat conduction model or empirical formula, the "conduction temperature" at the bottom of the weld, that is, the temperature theoretically transferred from the center of the weld to the lower surface of the plate 70 (before ignoring or simplifying the ambient heat dissipation), can be obtained. The specific method for determining the conduction temperature is as follows:

[0102] During the friction stir welding process, the temperature at the center (upper part) of the weld is relatively high and conducts to the bottom of the weld (i.e., the side in contact with the welding table 10) through the thickness direction of the plate 70. Due to the influence of the material's heat conduction performance and the thickness of the plate, the temperature at the bottom is necessarily lower than the temperature at the center of the weld. The Fourier heat conduction law (simplified model) under the steady heat conduction state can be used: In the formula, q is the heat flux (W), representing the heat transferred per unit time. A is the heat conduction cross-sectional area (m 2 ), that is, the effective cross-sectional area of the weld. T 焊接 is the temperature at the center of the weld (obtained from S120). T传导 is the conduction temperature at the bottom of the weld (to be determined). The specific calculation steps of the conduction temperature are as follows:

[0103] First, determine the heat flux q in the weld area. The heat input to the stirring zone mainly comes from the frictional heat of the stirring head: Welding time Second, determine the conduction cross-sectional area A. The conduction cross-sectional area is the effective cross-sectional area of the weld. The specific calculation method can be seen in the previous text. Then, according to Fourier's law, calculate the bottom conduction temperature. Specifically, substitute q, A, T 焊接 , δ, and λ into Fourier's formula to find T 传导 :

[0104] The above formula clearly shows the influence of the material thickness δ and the thermal conductivity λ on the temperature gradient: the larger the thickness δ, the greater the temperature difference, resulting in a lower temperature at the bottom of the weld of the plate 70. The smaller the thermal conductivity λ, the greater the temperature difference, resulting in a lower bottom temperature.

[0105] In the actual friction stir welding process of step S220, the lower surface of the weld will be in contact with the welding table 10 or the air, and the environmental temperature will cause heat loss. If a cooling air flow is used or the environmental temperature is relatively low, the influence will be more significant. Therefore, the environmental temperature (the value given by the thermometer) is combined with the conduction temperature of the previous step to obtain the "actual temperature" closer to the real welding environment. This actual temperature is usually lower than the theoretical conduction temperature of S210, and this value needs to be substituted into the subsequent calculations to reasonably plan the bottom heating power. And the conduction temperature obtained in step S210 is a theoretical value. The actual bottom of the weld will be cooled by the surrounding environment (such as the welding table 10 and the air), and the temperature will be lower. Therefore, correction is needed:

[0106] First, it is necessary to analyze the influence of environmental heat dissipation. When the temperature at the bottom of the plate 70 is higher than the environmental temperature, heat will be dissipated from the bottom of the plate to the environment. Specifically, Newton's cooling law can be used to estimate and correct the environmental heat dissipation. Newton's cooling law: q 散热 = h·A·(T[[ID=CODESPACE]] 传导 -T 环境 ). Where h is the convective heat transfer coefficient (W / (m 2 ·°C)), about 10 - 25 for the air environment, and about 100 - 500 for the contact with the welding table 10. A is the heat dissipation contact area (m 2 ), that is, the area at the bottom of the weld. T 传导 is the theoretical conduction temperature. T 环境 is the environmental temperature measured by the thermometer. Second, the correction formula for the actual temperature at the bottom of the weld. The actual temperature (T 实际 ) takes into account the conduction temperature and the influence of heat dissipation, and can be approximately calculated by the following method:

[0107] Method 1 is the steady-state approximation. Assume that the bottom of the plate 70 is under near-steady-state heat conduction conditions, and the actual bottom temperature:

[0108]

[0109] This formula takes into account the actual temperature after the balance of heat conduction and convective heat dissipation and is applicable to steady-state working conditions.

[0110] Method 2 is the empirical correction method. If the heat dissipation coefficient h cannot be accurately obtained, the empirical correction coefficient k can be used in engineering 修正 :

[0111] T 实际 = T 环境 + k 修正 ·(T 传导 - T 环境 ).

[0112] k 修正 Generally, it is taken between 0.75 and 0.95, specifically depending on the cooling conditions.

[0113] Among them, the empirical correction coefficient essentially reflects a reduction ratio of the actual temperature at the bottom of the weld during the friction stir welding process relative to the theoretical conduction temperature, reflecting the influence degree of the actual environmental cooling conditions on the temperature at the bottom of the weld. When the bottom heat dissipation is severe, it is relatively small (such as 0.75 - 0.85), and when the bottom heat dissipation is weak, it is relatively large (such as 0.85 - 0.95). The following is the specific method of how to specifically obtain the empirical correction coefficient in actual engineering:

[0114] First, it is the experimental preparation stage. Select the material to be welded (such as 6061 aluminum alloy), determine the plate thickness (for example, 3 mm), and clarify the parameters of friction stir welding (such as welding speed, stirring head rotation speed). Equip temperature measurement devices (thermocouples, infrared thermometers or thermal imagers), and install temperature measurement sensors on both the upper surface (weld center area) and the lower surface (contact surface with the welding table 10) to actually measure the temperature at the bottom of the weld. At the same time, the ambient temperature also needs to be measured. Secondly, it is the experimental test (actual temperature measurement) stage. Start friction stir welding under specific welding parameters. Continuously record and obtain the real-time temperature on the upper surface (weld center) of the weld. At the same time, record the actual temperature on the lower surface of the weld. Synchronously record the experimental ambient temperature. And at least 3 - 5 welding experiments are carried out to obtain reliable temperature data. Then, it is to calculate the theoretical conduction temperature. Calculate according to the heat conduction model given in step S210: Next, it is to find the k 修正 . Through the temperature data measured in each experiment, substitute it into the following formula to calculate k 修正 : In this way, a corresponding correction coefficient value can be obtained for each test. Finally, determine the final empirical correction coefficient k 修正 , for the multiple k values obtained from all experiments 修正 , take the arithmetic mean as the empirical correction coefficient for final use: Among them, if individual experimental data deviate significantly (such as excessive measurement errors), they can be excluded first and then the average is taken.

[0115] To sum up, for the recommended range of empirical correction coefficients under different working conditions, when in contact with the highly thermally conductive metal welding table 10 and with extremely strong heat dissipation (such as a copper table), it is recommended to take values between 0.70 and 0.80; when in contact with the highly thermally conductive metal welding table 10 with extremely strong heat dissipation (such as a copper table), it is recommended to take values between 0.75 and 0.85; when in contact with a low thermal conductivity welding table 10 or a heat insulation pad with weak heat dissipation, it is recommended to take values between 0.85 and 0.90; when the bottom is suspended and there is only air convection, it is recommended to take values between 0.90 and 0.95.

[0116] Through the above detailed steps, an empirical correction coefficient k that is true, accurate and suitable for actual production use can be obtained 修正 .

[0117] Further, please refer to Figure 6 , determining the first target temperature according to the actual temperature, the target parameter, the welding direction and the first target distance, and determining the second target temperature according to the actual temperature, the target parameter, the welding direction and the second target distance, includes:

[0118] Step S310: Determine the deformation sensitivity parameter at the bottom of the plate 70 according to the plastic temperature range of the plate 70, the thickness of the plate 70, the thermal conductivity of the plate 70 and the specific heat capacity of the plate 70.

[0119] Step S320: Determine the first target temperature according to the deformation sensitivity parameter at the bottom of the plate 70, the first target distance and the actual temperature.

[0120] Step S330: Determine the second target temperature according to the deformation sensitivity parameter at the bottom of the plate 70, the second target distance and the actual temperature.

[0121] Among them: The determination of the deformation sensitivity parameter at the bottom of the plate 70 in step S310. The deformation sensitivity parameter characterizes the sensitivity of the material to temperature changes under welding thermal cycle conditions, and is directly related to the tendency of the material to undergo plastic deformation under a specific heat input. General expression of the deformation sensitivity parameter (DSP, Deformation Sensitivity Parameter): . Among them: DSP is the deformation sensitivity parameter (m 2 ·s / ℃). Cp is the specific heat capacity (J / (kg·℃)). T p is the upper limit of the plastic temperature of the material (℃). T e is the lower limit of the plastic temperature of the material (℃). C p , ρ and δ reflect the heat storage capacity of the sheet, that is, the larger the heat capacity, the slower the temperature rise of the sheet 70, and it is more difficult to quickly enter the plastic state. λ reflects the heat conduction ability of the material, that is, the stronger the heat conduction ability, the easier the heat diffuses, and it is not easy to form local high temperature. And T p -T e reflects the plastic temperature range. The wider the range, the wider the plastic region of the material and the easier it is to deform. The core idea of this formula design is to clarify the relationship between the plastic deformation trend of the material and heat input and heat diffusion. During the friction stir welding process, whether the material is prone to obvious deformation (such as warping, twisting) depends on the temperature rise rate caused by the welding heat input and the heat diffusion rate to the surrounding. Therefore, the design idea of this formula is divided into two parts:

[0122] Firstly, the numerator part C p ·ρ·δ (heat capacity effect). The specific heat capacity C p represents the heat required to raise the temperature of a unit mass of material by 1℃. The larger C p , the slower the temperature rise, and it is more difficult for the material to quickly reach the high-temperature plastic state. Among them, the larger the density ρ, the more mass contained in a unit volume. The larger ρ leads to more heat required, making the temperature rise process slower and more stable. And the larger the sheet thickness δ, the longer the heat conduction path, and more heat is required in the unit thickness direction to raise the temperature as a whole. The larger δ leads to a more obvious temperature gradient, making it difficult for the temperature at the bottom of the material to quickly reach the plastic state.

[0123] In summary, the numerator part (C p ·ρ·δ) reflects the overall heat capacity of the material, representing the ability of the material to resist rapid temperature rise and slow down the plastic deformation trend.

[0124] Secondly, the denominator part λ·(T p -T e ) (heat diffusion and plastic temperature zone effect). The thermal conductivity λ reflects the ability of the material to diffuse heat outward. The higher λ leads to rapid heat diffusion, making the temperature field around the weld more uniform and difficult to form local high temperature, weakening the plastic deformation trend. On the contrary, the lower λ will lead to obvious local heat accumulation, causing rapid local temperature rise and easy to appear obvious deformation. In the plastic temperature range (T p -T e ), T p is the upper limit of the plastic temperature, and T eis the lower limit of the plastic temperature, and the difference between the two is the temperature range in which plastic deformation of the material occurs. If the plastic temperature range is wide (large), the material may undergo plastic deformation within a wide temperature range, is not sensitive to temperature changes, and deformation is likely to occur but not violently. If the plastic temperature range is narrow (small), even a slight change in temperature may cause violent deformation. Therefore, the denominator part (λ(T p -T e )) comprehensively reflects the inhibitory effect of heat diffusion on the sensitivity of plastic deformation. The faster the heat diffusion or the wider the plastic range, the lower the local deformation tendency of the material.

[0125] In summary, the larger the DSP value, the more sensitive the sheet material 70 is to temperature changes and the more likely it is to exhibit plastic deformation. Conversely, it is more stable. Through this parameter, the heating conditions during welding can be reasonably optimized to keep the deformation amount of the weld within a controllable range. The thermal conductivity λ in the above formula can be obtained from material manuals or thermal conductivity measurement experiments, while the plastic temperature range T p 、T e can be determined from material manuals, welding material data, or high-temperature mechanical experiments. Moreover, the design of this formula conforms to the basic laws of thermophysics and material deformation, can relatively truly reflect the influence of the actual conditions of friction stir welding on the material deformation trend, and is applicable to welding process optimization. The parameters can be obtained from conventional tests and material databases, and have strong usability in actual production. This formula has a clear physical basis and a definite practical use, and can effectively guide the optimization design of the bottom heating conditions in actual welding processes.

[0126] The determination method of the first target temperature in step S320 is specifically described as follows:

[0127] The first target temperature (near the advancing side of the weld) and the second target temperature (near the retreating side of the weld) can be expressed as:

[0128]

[0129] where: T1 is the first target temperature (°C). T2 is the second target temperature (°C). T 实际 is the actual temperature at the bottom of the weld (obtained in S220) (°C). DSP is the deformation sensitivity parameter. D1 is the first target distance (m) (the distance from the weld center to the first heating surface). D2 is the second target distance (m) (the distance from the weld center to the second heating surface 510). k is the correction coefficient, initially taken as 1.0, and determined by gradual correction through experiments (see later).

[0130] Among them, the determination method of the correction coefficient k is specifically as follows:

[0131] In order to obtain more accurate temperature compensation, the correction coefficient k needs to be determined through actual tests.

[0132] Step 1: When conducting the initial welding test, take k = 1.0. Step 2: Conduct the initial welding test. Calculate the target temperatures T1 and T2 according to the above formula, and then conduct the welding test. Measure the weld quality and the actual deformation amount at the bottom of the weld. Step 3: Evaluate the results of the initial test. If the plasticity at the bottom of the weld is significantly insufficient (excessive deformation, poor quality), it indicates that the compensation temperature is too low, and the value of k should be appropriately increased, such as k = 1.1 - 1.3. If the temperature at the bottom of the weld is too high and the deformation increases instead, it indicates overcompensation, and k should be decreased, such as k = 0.7 - 0.9. Step 4: Repeat the test. Use the adjusted new value of k to conduct the welding experiment again, and then repeat the above Step 2 several times until the deformation amount and the weld quality at the bottom of the weld reach the ideal state.

[0133] The above target formula is designed in this way to ensure that the temperature in the bottom area of the weld reaches a reasonable plastic deformation range, so as to reduce the welding deformation at the bottom of the weld and improve the weld quality. The following points are specifically considered:

[0134] First, the actual temperature T at the bottom of the weld 实际 is usually low and cannot effectively enter the ideal plastic temperature range of the material. Therefore, additional compensation heating is required. The magnitude of the compensation temperature depends on the sensitivity DSP of the material to changes in heat input and the distance D from the heating position to the weld. Therefore, the compensation part of the formula is designed as: Secondly, the higher the deformation sensitivity of the material, the more easily the material is affected by temperature gradient and heat input and deformed, and a larger compensation temperature rise is required. Therefore, the compensation temperature is designed to be proportional to DSP to intuitively reflect the influence of material sensitivity on the temperature compensation amount. Then, as the heating position moves away from the center of the weld, the efficiency of heat transfer to the center of the weld decreases. Therefore, the farther away from the center of the weld, the weaker the required temperature compensation effect. Therefore, the compensation temperature is designed to be inversely proportional to the distance D to reasonably reflect the influence of the heating distance on the heat input efficiency. Finally, there will be certain differences in different welding conditions, environments, and equipment efficiencies, and fixed theoretical values may not be applicable to all actual situations. Introducing the coefficient k is to adjust the actual compensation amount through experiments, reflecting the flexibility and adjustability of the formula, and making it more accurately applicable to specific welding conditions.

[0135] In step S400, the controller 60 is used to execute the control. The controller 60 sends temperature setting or power commands to the first heating surface 310 and the second heating surface 510 respectively. And the controller 60 can form a closed-loop control through the third temperature sensor and the fourth temperature sensor to continuously maintain the target temperature.

[0136] Specifically, the first target temperature / second target temperature refers to the set temperature values of the first heating surface 310 and the second heating surface 510 obtained in step S320, which are used to achieve local preheating / thermal insulation at the bottom of the plate 70 or on different sides of the weld, so as to regulate the "actual temperature" to the ideal range. Specifically, it can be jointly calculated by combining deformation-sensitive parameters, actual temperature, and parameters such as the first target distance and the second target distance. In the controller 60, this temperature will be converted into heating power or current parameters.

[0137] Please refer to Figure 7 , on both sides of the weld of the plate 70, they are respectively defined as the advancing side and the retreating side according to the rotation direction of the stirring member of the friction stir welding device. In order to balance the influence of the temperature difference between the advancing side and the retreating side of the weld on both sides of the weld at the bottom of the plate 70, the above control method further includes:

[0138] Step S500: Correct the first target temperature and the second target temperature according to the temperature difference between the advancing side and the retreating side of the weld in the welding state of the plate 70, so as to obtain the third target temperature and the fourth target temperature.

[0139] Step S600: Control the first heating surface 310 and the second heating surface 510 to work at the third target temperature and the fourth target temperature respectively.

[0140] During the friction stir welding process, there is often a temperature difference between the advancing side AS and the retreating side RS of the weld. This is because at the advancing side, the rotation direction of the stirring head is the same as the welding movement direction, resulting in more frictional heat input and a higher temperature; while at the retreating side, the rotation direction of the stirring head is opposite to the welding movement direction, with less frictional heat input and a lower temperature. Therefore, to ensure temperature balance on both sides of the weld, it is necessary to adjust the heating temperatures on both sides of the bottom of the weld respectively, that is, to correct the first target temperature and the second target temperature determined previously to obtain the third target temperature and the fourth target temperature that are closer to the actual requirements.

[0141] The method for determining the third target temperature and the fourth target temperature in step S500 is specifically as follows:

[0142] The first step: Define the temperature difference. During the welding process, through actual measurement or thermal simulation methods, obtain the true temperature difference between the advancing side and the retreating side of the weld: ΔT = T 前进侧实测 -T 后退侧实测 . Where: if ΔT > 0, it means the temperature of the advancing side is higher than that of the retreating side; if ΔT < 0, it means the temperature of the retreating side is higher than that of the advancing side (with a very small probability). It should be noted that: generally, the temperature of the advancing side is higher, and ΔT is positive in the conventional process. This article also takes this as an example for illustration. The second step: For the convenience of calculation, introduce a temperature difference correction factor Where: T 焊接中心is the temperature of the weld center region (obtained from the aforementioned steps); the corresponding factor for the advancing side (higher temperature) is temperature reduction; the corresponding factor for the retreating side (lower temperature) is temperature increase. Third step: Formulas for the third target temperature and the fourth target temperature. Among them, the third target temperature T3 corresponding to the advancing side (correction of the original first target temperature T1), and the fourth target temperature T4 corresponding to the retreating side (correction of the original second target temperature T2). Where: α and β are empirical correction coefficients (generally between 0.3 and 0.8), and their function is to control the compensation or reduction amplitude to avoid excessive adjustment. T1 and T2 are the first target temperature and the second target temperature (bottom compensation temperature) respectively, which can be obtained in steps S330 and S340. ΔT is the actual temperature difference between the advancing side and the retreating side, which can be measured or simulated by thermocouples during the welding process. T 焊接中心 is the welding temperature at the weld center, which can be obtained through the aforementioned steps.

[0143] During friction stir welding, the temperature difference between the advancing side and the retreating side is an important reason for unstable welding quality. On the advancing side AS, due to the same rotation direction of the stirring head and the welding direction, local heat accumulation occurs and the temperature is higher. On the retreating side RS, due to the opposite rotation direction and the welding direction, the heat input is relatively insufficient and the temperature is lower. If not treated, it will lead to inconsistent tissue properties on both sides of the weld and welding defects (such as deformation, cracks, etc.). Therefore, it is necessary to perform a certain degree of temperature reduction correction on the temperature of the advancing side, while a certain degree of temperature increase correction is required for the temperature of the retreating side. Such a design starts from the physical mechanism and actual process requirements, and is more in line with the actual welding production requirements. The correction formula can effectively reduce or eliminate the temperature difference between both sides of the weld in actual engineering, making the thermal field in the weld area more uniform. It can also improve the uniformity of plastic flow in the weld and significantly reduce the welding deformation. Further, it can improve the microstructure of the weld, enhance the mechanical properties and reliability of the welded joint, thereby improving the stability and consistency of production, and making it easier for standardization and quality control.

[0144] The basic target temperature in the above formula is the ideal compensation temperature initially calculated based on the actual bottom temperature and material sensitivity, which can provide a reasonable temperature benchmark. On this basis, adjustments are made considering the differences between the advancing side and the retreating side to ensure the rationality of the initial temperature setting.

[0145] The temperature difference directly reflects the true heat input difference between the advancing side and the retreating side of the weld. It can be used as the core adjustment basis. The larger the temperature difference, the greater the required adjustment amplitude. It directly determines the size and direction (temperature increase or decrease) of the compensation amplitude. Specifically, it can be obtained by actually measuring the true temperature difference between both sides during the welding process through experiments. The welding center temperature T 焊接中心A reasonable temperature reference benchmark is provided to reflect the relative proportion relationship of the temperature difference ΔT within the overall welding temperature range. Thus, the absolute temperature difference is converted into a relative temperature difference ratio. Ensure that adjustments can be made on a unified proportional scale under different welding conditions and for different materials, making it easier to promote and use. The correction factors α and β are used to control the amplitude and flexibility of the actual compensation, providing a flexible adjustment function. Optimized according to experimental results to prevent over-compensation or under-compensation. It can adapt to different welding conditions, material types, and changes in plate thickness. It can be determined through repeated adjustments during actual welding tests in the process of experimental measurement of welding quality.

[0146] α and β are adjustment amplitude control factors, and the specific determination method is as follows: First step: Initially determine the range. Usually, the values are both 0.5 during the first test, that is, α = 0.5 and β = 0.5. Second step: Conduct the initial welding test. The initial third and fourth target temperatures T3 and T4 can be calculated using the above formula and welding experiments can be carried out. Real-time measure the bottom temperatures of the welds on the advancing side and the retreating side, and record the actual weld quality and deformation amount. Third step, evaluate the results of the initial welding and adjust α and β. If the adjusted temperature difference decreases significantly and the weld quality improves significantly, it indicates that the selected α and β are appropriate. If the temperature drop on the advancing side is too much or insufficient, or the temperature rise on the retreating side is too much or insufficient, make appropriate adjustments. If the temperature on the advancing side does not decrease significantly, increase α; if the temperature on the retreating side does not increase significantly, increase β. Then, repeat the experiment until the temperature difference decreases significantly and the weld quality improves significantly.

[0147] After determining the third target temperature and the fourth target temperature T3 and T4 in step S600, the actual control process is as described below:

[0148] First, control the first heating unit 30 (below the advancing side) to operate at the third target temperature T3; second, control the second heating unit 50 (below the retreating side) to operate at the fourth target temperature T4.

[0149] In this way, by applying different target heating temperatures to the advancing side and the retreating side of the weld bottom respectively, the temperature difference naturally formed between the advancing side and the retreating side during the welding process is effectively offset, making the temperatures on both sides of the weld bottom tend to be balanced, and finally effectively controlling the overall quality and deformation of the weld. It should be noted that in the field of friction stir welding, general technicians usually focus on the overall heat compensation of the weld area and believe that setting only the first heating unit 30 on one side of the weld bottom can meet the heating requirements of the weld bottom and reduce deformation. Usually, the temperature difference between the advancing side and the retreating side of the weld is not considered. Because, for the conventional technical solution, only by using the bottom heating unit can the effect of ensuring uniform heat input during the welding process be achieved to avoid defects (such as cracks, deformation, etc.) caused by local overheating or overcooling. However, the difficulty of this conventional solution lies in that when further considering the temperature difference problem, it is very difficult for the existing heating strategies to cope with the temperature difference generated between the advancing side and the retreating side of the weld due to the inconsistent rotation direction of the stirring head and the welding direction. This temperature difference leads to uneven distribution of temperatures on both sides, directly affecting aspects such as welding quality, weld formation, and deformation. But in the existing technology, it is usually very difficult to further balance this difference in a refined manner. This is mainly reflected in:

[0150] First, the design inertia of the existing heating unit. Conventional heating units are usually designed according to the overall temperature requirements and do not consider the temperature difference between the two sides of the weld. This results in the configuration of the heating system not fully considering the influence of the temperature difference, leading to limitations in subsequent technological improvements. Second, the complexity of thermodynamics regulation. In friction stir welding, the existence of the temperature difference makes the heat diffusion modes, heat input amounts, and their impacts on the weld quality on the advancing side and the retreating side asymmetric. Traditional methods mainly focus on overall heating balance and fail to effectively cope with this local difference, resulting in the "roughness" of overall compensatory heating. Even if heating units are set on both sides, it is still difficult to accurately control different welding areas. And usually, technicians have ensured the uniformity of the bottom temperature through the heating unit during the design, but have not fully realized the profound impact of the temperature difference between the advancing side and the retreating side on the weld quality, so no refined compensation design has been specifically carried out for this difference.

[0151] This application, through an in-depth analysis of the profound impact of the temperature difference between the forward and backward sides of friction stir welding on weld quality, proposes a control method that uses the temperature difference ΔT between the forward and backward sides of the weld as a core decision factor, and then achieves a refined balance between the forward and backward temperatures by correcting the target temperature formula. The core of this technical solution lies in the following aspects: First, the clear identification and quantification of the temperature difference. The present invention first accurately identifies and quantifies the temperature difference ΔT between the forward and backward sides of the weld, which is a key factor affecting weld quality. While prior art often ignores this point, the present invention incorporates it as a core parameter into the control system, significantly improving the accuracy of the heating strategy. Second, the forward and backward target temperatures are corrected. By incorporating the temperature difference ΔT into the target temperature correction formula (see step S500 above), the present invention differentially adjusts the target temperatures of the first heating unit 30 and the second heating unit 50. This technical solution allows the heating temperatures on the forward and backward sides to flexibly adapt to the temperature difference, thereby ensuring that the temperatures on both sides of the weld tend to be balanced. Moreover, through precise measurement and experimental verification, the correction coefficients α and β were further determined, which made the adjustment of the forward and backward side temperatures more precise, avoided over- or under-correction of temperature, and ensured the reasonable distribution of heat input during welding.

[0152] In summary: The difficulty of the existing technology is that the design of the heating unit is usually based on the assumption of uniform heating, while ignoring the temperature difference between the forward and backward sides caused by the characteristics of stir friction welding. To further consider the influence of temperature difference within this design framework, it involves the complex interaction of heat input, heat diffusion and heat compensation, which has not been fully taken into account in conventional designs. Moreover, in conventional technology, technicians habitually believe that temperature difference is a natural phenomenon in the welding process and can be compensated by uniform heating, lacking systematic thinking on temperature difference correction. The present invention breaks through this cognitive limitation by taking temperature difference as a decision factor and proposes a temperature compensation scheme with practical application value. It breaks through the mindset in traditional heating unit design, makes temperature control in the welding process more refined and accurate, and significantly improves the quality of the weld. This innovative idea and technical solution provides a new solution for further improving welding quality and has significant engineering application value.

[0153] The above contents described in this specification are merely examples of the present invention. Those skilled in the art may make various modifications, additions, or substitutions to the described embodiments, without departing from the contents of this specification or exceeding the scope defined by the claims, and such modifications, additions, or substitutions may be made to the described embodiments. Such modifications, additions, or substitutions may be made by persons skilled in the art. Such modifications, additions, or substitutions may be made to the described embodiments without departing from the contents of this specification or exceeding the scope defined by the claims, and such modifications shall fall within the scope of protection of the present invention.

Claims

1. A control method for a friction stir welding device, characterized in that: The friction stir welding device includes: A welding table, including a material placement plane for placing a plate, and a first installation groove is formed on the material placement plane; A clamping mechanism, arranged around the welding table to fix the plate at the material placement plane during the welding process; A first heating unit, arranged in the first installation groove, the first heating unit includes a first heating surface, the first heating surface is controlled to move up and down, and the first heating surface is configured to fit with the side of the plate facing the material placement plane when the plate is placed on the material placement plane; and, the distance between the projection of the center of the first heating surface on the material placement plane and the projection of the weld of the plate placed on the material placement plane on the material placement plane is defined as the first target distance; the projection of the first heating unit on the material placement plane is located on one side of the projection of the weld of the plate placed on the material placement plane on the material placement plane; A second heating unit, connected to the welding table, the second heating unit is controlled to move, the second heating unit includes a second heating surface, the temperature of the second heating surface is controlled to rise and fall, and the second heating surface is configured to fit with the side of the plate facing the material placement plane when the plate is placed on the material placement plane; and, the distance between the projection of the center of the second heating surface on the material placement plane and the projection of the weld of the plate placed on the material placement plane on the material placement plane is defined as the second target distance, and the projection of the second heating unit on the material placement plane is located on the other side of the projection of the weld of the plate placed on the material placement plane on the material placement plane; A controller, connected to the first heating unit and the second heating unit to respectively control the temperature rise and fall of the first heating surface and the temperature rise and fall of the second heating surface; The two sides of the weld of the plate are respectively defined as the advancing side and the retreating side according to the rotation direction of the stirring member of the friction stir welding device; The control method includes: Obtaining the welding temperature at the weld of the plate when the plate is in the welding state according to the target parameters of the plate to be welded, and the target parameters include the material of the plate, the thickness of the plate, the thermal conductivity of the plate, the specific heat capacity of the plate, and the plastic temperature range of the plate; Determining the actual temperature of the side of the weld facing the welding table when the plate is in the welding state according to the welding temperature and the target parameters; Determining a first target temperature according to the actual temperature, the target parameters and the first target distance, and determining a second target temperature according to the actual temperature, the target parameters and the second target distance; Correcting the first target temperature and the second target temperature according to the temperature difference between the advancing side and the retreating side of the weld of the plate in the welding state to obtain a third target temperature and a fourth target temperature; Controlling the first heating surface and the second heating surface to work at the third target temperature and the fourth target temperature respectively.

2. The control method for a friction stir welding device according to claim 1, characterized in that: The number of the first mounting grooves is several, and each of the first mounting grooves is arranged along a first direction, and the first direction is parallel to the extending direction of the weld seam of the plate member placed on the material placing plane; The number of the first heating units is several, and each of the first heating units is correspondingly mounted in each of the first mounting grooves one by one.

3. The control method of a friction stir welding device according to claim 1, characterized in that: The number of the first mounting grooves is several, and each of the first mounting grooves is arranged along a first direction, and the first direction is parallel to the extending direction of the weld seam of the plate member placed on the material placing plane; The number of the first heating units is several, and each of the first heating units is correspondingly mounted in each of the first mounting grooves one by one; The number of the second heating units is several, and each of the second heating units is configured to be arranged along the first direction when the friction stir welding device is in a working state.

4. The control method of a friction stir welding device according to claim 3, characterized in that: The first heating unit further includes a first temperature sensor, the first temperature sensor is connected to the controller, and the first temperature sensor is configured such that when the plate member is placed at the material placing plane, the temperature measuring part of the first temperature sensor contacts the side of the plate member facing the material placing plane; The second heating unit further includes a second temperature sensor, the second temperature sensor is connected to the controller, and the second temperature sensor is configured such that when the plate member is placed at the material placing plane, the temperature measuring part of the second temperature sensor contacts the side of the plate member facing the material placing plane.

5. The control method of a friction stir welding device according to claim 1, characterized in that: The step of obtaining the welding temperature at the weld seam of the plate member when the plate member is in a welding state according to the target parameters of the plate member to be welded includes: Determining the optimal moving speed of the stirring member and the optimal rotating speed of the stirring member corresponding to the best range of the weld seam quality of the plate member according to the material of the plate member and the thickness of the plate member; Obtaining the welding temperature at the weld seam of the plate member when the plate member is in a welding state according to the material of the plate member, the thickness of the plate member, the optimal moving speed of the stirring member and the optimal rotating speed of the stirring member.

6. The control method of a friction stir welding device according to claim 5, characterized in that: The friction stir welding device further includes a thermometer to obtain the ambient temperature; The step of determining the actual temperature on the side of the weld seam facing the welding table when the plate member is in a welding state according to the welding temperature and the target parameters includes: Determining the conduction temperature on the side of the weld seam facing the welding table when the plate member is in a welding state according to the thickness of the plate member, the thermal conductivity of the plate member and the welding temperature; Determining the actual temperature on the side of the weld seam facing the welding table after heat dissipation correction according to the ambient temperature and the conduction temperature.

7. The control method of a friction stir welding device according to claim 6, characterized in that: Determining the first target temperature according to the actual temperature, the target parameter, and the first target distance, and determining the second target temperature according to the actual temperature, the target parameter, and the second target distance, includes: Determining a deformation sensitivity parameter at the bottom of the plate according to the plastic temperature range of the plate, the thickness of the plate, the thermal conductivity of the plate, and the specific heat capacity of the plate; Determining the first target temperature according to the deformation sensitivity parameter at the bottom of the plate, the first target distance, and the actual temperature; Determining the second target temperature according to the deformation sensitivity parameter at the bottom of the plate, the second target distance, and the actual temperature.

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