Method for controlling stability of molten drop transition state during swinging electric arc welding

Abstract

The invention discloses a method for controlling the stability of a molten drop transition state during swinging electric arc welding, which comprises the following steps of: obtaining a time-varying function of a minimum distance from the tail end of a welding wire to a substrate by analyzing a swinging function equation of a motion trail of the tail end of the welding wire and a space position of the substrate, and calculating the stability of the molten drop transition state according to the characteristics of different molten drop transition states during welding; the system optimization method for keeping the molten drop transition state stable during welding is provided, and an unstable molten drop transition mode is avoided. According to the optimized scheme, the distance between the tail end of the welding wire and the two substrates is related to the distance between the welding gun and the two substrates when the welding gun swings at different positions, and the minimum distance between the tail end of the welding wire and the two substrates is kept relatively stable when the welding gun swings at any position by adjusting the wire feeding speed and the spatial position of the welding gun when the welding gun swings at different positions; the peak distance of the efficient molten drop transition state is kept. The molten drop transition frequency is kept in a high range by adjusting the minimum distance in real time, large drop transition is prevented, particle splashing is reduced, and the forming quality is improved.

Description

Technical Field

[0001] The invention relates to a method for controlling the stabilization of a molten droplet transition state during swing arc welding, and belongs to the technical field of welding automation. Background Art

[0002] Swinging arc automatic welding is an automated welding method with high efficiency and high-quality welding. It is widely used in the production and manufacturing of large structural parts such as ships, gantries, railways, pressure vessels, containers, etc. Arc welding consumes a lot of energy, and due to the rough operation of welding technology, it may lead to various problems such as insufficient weld filling, welding defects and porosity, which significantly reduce production efficiency and welding efficiency. Controlling the droplet transfer mode during welding can effectively reduce particle splashing and improve welding quality, while saving materials and reducing production processes. Methods for changing the droplet transfer mode include changing parameters such as wire feeding speed and spatial position of welding gun during welding.

[0003] Automatic welding reduces the impact of human factors on welding quality and improves the consistency of production quality. At present, domestic research on reducing automatic welding losses mainly focuses on welding technology and material thermodynamics performance, and there is less research on the control of droplet transition state changes in swing arc automatic welding. However, the droplet transition state directly determines the welding quality, production efficiency and energy conversion. Controlling the stability of the droplet transition mode is particularly important in swing arc welding. Summary of the invention

[0004] The purpose of the present invention is to provide a method for reducing particle splashing, improving weld formation quality, saving materials, and controlling the stable droplet transition state during swing arc welding with a wide range of applications.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows:

[0006] The method is characterized in that the motion trajectory function of the end of the welding wire is obtained by the spatial position coordinates of the substrate and the swing head, the frequency and speed of the arc swing, and the dry extension length of the welding gun and the welding wire. Based on this, the theoretical value of the minimum distance between the end of the welding wire and the substrate when the welding gun swings can be calculated, and then the time-varying function of the minimum distance between the end of the welding wire and the substrate is obtained, and the value of the molten droplet transition mode at this time is established. At the same time, the image information of the welding gun swinging to different positions is captured by a visual sensor, and a set of shooting values ​​of the minimum distance and the molten droplet transition mode are obtained again after image processing. The two sets of theoretical value and shooting value data are compared and analyzed to obtain the initial distance between the end of the welding wire and the substrate and the more accurate minimum distance, and to judge the numerical change law of the minimum distance between the end of the welding wire and the substrate.

[0007] The working principle of this method is that during the swing arc automatic welding process, the change trend of the droplet transfer frequency is opposite to the change trend of the minimum distance value from the end of the welding wire to the substrate. The higher the droplet transfer frequency, the smaller the minimum distance value from the end of the welding wire to the substrate, the more stable the droplet transfer state, and when the minimum distance value from the end of the welding wire to the substrate is similar, the droplet transfer frequency is also similar. Figure 3 During the swing welding, the minimum distance value from the end of the welding wire to the substrate is constantly changing during the trajectory of the welding wire end swinging from point A to point C, increasing from d2 to d3, the distance values ​​of d3 and d4 are equal, and then decreasing from d3 to d5. The droplet transition frequency first decreases and then increases, and the droplet transition state also changes accordingly. When the swing angle of the welding gun reaches the maximum, that is, at points A and C, the minimum distances d2 and d5 between the end of the welding wire and the two substrates reach the minimum value. At this time, the droplet transition frequency is the highest and the droplet state is stable. When the welding gun swings to the angle bisector, that is, at point B, the minimum distance value d3 from the end of the welding wire to the substrate reaches the maximum peak value, the droplet transition frequency is the lowest, and the droplet state is unstable, showing a large droplet transition. Therefore, the difference between the initial distance value from the end of the welding wire to the substrate and the optimal minimum distance value can be calculated to obtain the optimal adjustment value of the distance from the end of the welding wire to the substrate, maintain the minimum distance from the end of the welding wire to the substrate in this efficient droplet transition state, and maintain the stability of the droplet transition mode.

[0008] See also Figure 2 It can be obtained that the distances between the end of the welding wire and the two substrates are d1 and d2 respectively when the angle bisector is at the angle bisector, and the distances between the end of the welding wire and the substrates are d3 and d4 when the welding wire is swung to the maximum angle, and the minimum distance d4 between the end of the welding wire and the substrates when the welding wire is swung to the maximum angle is the optimal minimum distance. At this time, the molten droplet transition state is optimal, the molten droplet diameter is small during the transition, and no spatter is generated. Figure 1 When welding, the spatial position O(x, y, z) of the swing head is determined with the substrate as the spatial coordinate axis. After the spatial positions of the substrate and the swing head are determined, the swing function of the welding gun is obtained according to the length L of the welding gun, the swing speed v, and the frequency f. To keep the end of the welding wire and the substrate at the optimal minimum distance, the controller needs to obtain the wire feeding speed reached when swinging to different spatial positions based on known data during the welding process. When the welding gun swings to weld, the welding speed is changed to keep the distance between the end of the welding wire and the substrate at d4. At this time, the droplet transition in the welding process maintains a stable and efficient transition state, the metal splash is reduced, and the diameter of the droplet is always kept at an appropriate size to prevent the generation of large droplet transition.

[0009] The control method is based on the frequency and mode of droplet transition and the distance from the end of the welding wire to the two substrates when the welding gun swings to different positions. After obtaining the optimal adjustment parameters, in order to achieve the purpose, the present invention creatively adopts: while the welding gun is swinging, the wire feeding speed and the forward and backward movement of the welding gun are also changed to ensure that the minimum distance between the end of the welding wire and the substrate is always the optimal minimum distance difference, thereby avoiding the generation of large droplet transition. By adjusting the wire feeding speed and the spatial position of the welding gun during welding, the minimum distance value from the end of the welding wire to the substrate is controlled to remain constant, thereby obtaining a stable droplet transition mode. When controlling the droplet mode and frequency of the swinging arc automatic welding, the wire feeding speed is modified according to the minimum distance to ensure a stable and efficient droplet transition mode. When the welding gun swings to different positions, the wire feeding speed is changed so that the minimum distance remains unchanged, so that the droplet transition always maintains a stable, high-frequency transition state during the entire welding process, reducing particle splashing. The adjustment method is to reduce the minimum distance from the end of the welding wire to the substrate by increasing the wire feeding speed and moving the welding gun forward during the process of the welding gun swinging from the maximum height to the angle bisector. When swinging from the angle bisector to the maximum angle, the wire feeding speed should be reduced to prevent the end of the welding wire from directly contacting the substrate.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] 1) The present invention can keep the droplet transition state stable during swing arc welding. The minimum distance between the end of the welding wire and the workpiece is mainly controlled by changing the real-time wire feeding speed. Compared with directly changing the position of the welding gun, it is more convenient and easy to operate. It can ensure the threshold of the extension amount of the end of the welding wire, that is, the threshold of the wire feeding speed. Compared with changing other conditions to achieve the required conditions and the difficulty of operation, it is more suitable for the actual production of swing arc automatic welding.

[0012] 2) The present invention plays a significant role in improving production efficiency in automated welding. The method keeps the droplet transition in a good state of jet transition, reduces the large droplet splashing phenomenon during the droplet process, appropriately enhances the side wall welding stability, and is conducive to side wall fusion. At the same time, this method can improve the weld forming rate, maximize the use of welding raw materials, maintain a better welding effect, and improve energy utilization, saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The device parameter diagram of the present invention is

[0014] Figure 2 The working diagram of the device of the present invention

[0015] Figure 3 The working principle diagram of the present invention is

[0016] Figure 4 The system optimization design idea diagram of the present invention

[0017] Figure 5 This is the optimization comparison diagram of the present invention DETAILED DESCRIPTION

[0018] In order to better express the technical solution and beneficial effects of the entire invention, the present invention is further described in detail below with reference to the accompanying drawings and implementation cases.

[0019] See also Figure 4 This is the system optimization design idea diagram of the present invention. Before welding the workpiece, firstly, the image information of the welding gun when it swings to different positions is obtained by shooting, and the shooting value of the minimum distance size D1 and the molten droplet transfer mode M1 at this time is obtained after image processing. At the same time, the theoretical value of the minimum distance size D2 and the molten droplet transfer mode M2 ​​is calculated according to the motion trajectory function and the welding parameters. The shooting value and the theoretical value are analyzed and compared to obtain the initial distance between the end of the welding wire and the substrate and the time-varying function of the minimum distance between the end of the welding wire and the substrate, and the difference between the initial distance and the optimal minimum distance value is calculated, so as to obtain the optimal adjustment amount of the distance from the end of the welding wire to the substrate. After obtaining the optimal adjustment amount, the wire feeding adjustment function is obtained by establishing the relationship between the droplet transition mode and the wire feeding speed. The computer calculates the wire feeding speed of the welding wire when the welding gun swings to different position parameters according to the wire feeding speed adjustment function, and sends the wire feeding speed parameters to the controller. After the welding gun is controlled to adjust to the required wire feeding speed, it is ensured that the end of the welding wire does not directly contact the weldment, and the optimal minimum distance value from the end of the welding wire to the substrate, that is, the peak distance of the efficient droplet transition state, remains unchanged, so as to maintain the efficient droplet transition mode, thereby reducing particle splashing, improving the forming quality, and achieving welding optimization. For the specific optimization comparison of the motion trajectory of the end of the welding wire of the swing welding gun in the present invention, see Figure 5 The swing of the welding gun is an arc motion with the center of the circle (swing head) as a fixed point. The distance between the welding gun and the side walls of the two plates is related to the arc motion function of the swing. The minimum distance from the end of the welding wire to the base plate is adjusted. By changing the wire feeding speed, the maximum peak value of the distance between the end of the welding wire and the two base plates when the welding gun swings on the angle bisector is made the same as the minimum value of the distance between the end of the welding wire and the two base plates when the swing angle of the welding gun reaches the maximum. In this way, the frequency of droplet transfer can be maximized, and the droplet transfer state during welding changes from large droplet transition splashing to small droplet without splashing.

[0020] Since the invention adjusts the minimum distance between the end of the welding wire and the weldment by changing the wire feeding speed and thus controls the stable state of the molten droplet transition during swing arc welding, it has a wide range of uses.

[0021] Implementation case 1: Reduce metal particle splashing during welding and save materials.

[0022] The present invention is applied to the swing arc welding process, and a wire feeding speed adjustment function for the welding material is established according to the optimal adjustment amount of the distance from the end of the welding wire to the substrate. The computer calculates the wire feeding speed of the welding wire required by the welding gun at different spatial position parameters according to the wire feeding speed adjustment function, and sends the speed parameter to the controller to control the welding gun to change the wire feeding speed of the welding wire when it reaches the target spatial position. Since the distance from the end of the welding wire to the substrate is adjusted, it can ensure that the minimum distance value from the end of the welding wire to the substrate, that is, the peak distance to maintain the efficient droplet transition state, remains unchanged, so that the droplet transition frequency is maintained within a higher range, the stable droplet transition state is maintained, and the large droplet transition is avoided, which reduces the generation of molten metal particle splashing, and further reduces the energy consumption rate, the generation of particulate matter in the welding process, and other problems, reduces the difficulty of the cleaning process, and saves materials.

[0023] Implementation case 2: Improving weld formation quality.

[0024] The present invention improves the welding accuracy by controlling the stability of the molten droplet transition state during swing arc automatic welding, thereby increasing the welding speed. Under the condition of other constant conditions, increasing the welding speed will lead to a decrease in welding heat input, thereby reducing the weld width and weld depth. Since the amount of wire metal deposited per unit length of the weld is inversely proportional to the welding speed, the weld excess height is also reduced. Therefore, the method of controlling the stability of the molten droplet transition state during swing arc welding improves the weld formation quality during welding.

[0025] The above description is only the preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. For those skilled in the art, the present invention may have various modifications and variations. Any conceivable changes or substitutions, any modifications, improvements or combinations made within the technical scope disclosed in the present invention shall be covered within the protection scope of the present invention.

Claims

1. A method for controlling the stable state of droplet transition during swing arc automatic welding, characterized in that: The method comprises the following steps: S1, according to the motion trajectory function of the end of the welding wire, calculating and judging the minimum distance value from the end of the welding wire to the substrate and the variation law of the minimum distance value when the welding gun swings, obtaining the time-varying function of the minimum distance between the end of the welding wire and the substrate, and establishing the mapping relationship between the minimum distance value and the droplet transfer mode. S2, establishing the optimal droplet transfer mode and the optimal minimum distance value. S3, during welding, in the process of the welding gun swinging, by changing the minimum distance from the end of the welding wire to the substrate, the droplet transfer mode is changed to maintain a stable and efficient optimal droplet transfer mode, thereby reducing the splashing of metal particles, improving the formation of the weld, and saving materials.

2. A method for controlling the stable state of droplet transition during swing arc automatic welding, characterized in that: The image information of the welding gun when it swings to different positions is obtained by capturing with a visual sensor. After image processing, the shooting values ​​of the minimum distance size D1 and the molten droplet transfer mode M1 at this time are obtained. At the same time, the theoretical values ​​of the minimum distance size D2 and the molten droplet transfer mode M2 ​​are obtained according to the motion trajectory function and welding parameters. The shooting values ​​and the theoretical values ​​are analyzed and compared to obtain the initial distance between the end of the welding wire and the substrate and the time-varying function of the minimum distance between the end of the welding wire and the substrate. The difference between the initial distance value and the optimal minimum distance value is calculated to obtain the optimal adjustment value of the distance from the end of the welding wire to the substrate.

3. The method for controlling the stable droplet transfer state during swing arc automatic welding according to claim 1, characterized in that: The motion trajectory function is obtained through the swinging mode of the welding gun and the spatial position relationship between the substrate and the welding gun; the minimum distance value refers to the vertical distance between the end of the welding wire and each of the two substrates when the welding gun swings, and the two vertical distances are compared. The smaller value is the minimum distance value from the end of the welding wire to the substrate.

4. The method for controlling the stable droplet transfer state during swing arc automatic welding according to claims 1 and 2 is characterized in that: When the welding gun swings to different positions, after obtaining the optimal adjustment amount, the distance from the end of the welding wire to the substrate is adjusted by controlling the wire feeding speed and the spatial position of the welding gun to ensure that the minimum distance value from the end of the welding wire to the substrate, that is, the peak distance for maintaining an efficient droplet transition state, remains unchanged, thereby maintaining a stable droplet transition state.

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