A Method for Welding Thin-Walled Metal Rotary Shells Based on Local Heat Input Control in Electron Beam Welding

Abstract

This invention belongs to the field of electron beam welding technology and discloses a method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding. The method obtains the wall thickness variation along the circumferential weld, the weld path curvature variation, and the clamping point position and corresponding constraint strength value to determine heat-sensitive locations, forming welding sections and transition sections. It sets the electron beam welding process parameter set, target unit length heat input, and allowable deviation range for each welding section. During welding, parameters are adjusted based on the offset of the molten pool radiation center relative to the weld centerline, as well as the weld front and back widths. Furthermore, compensation and correction are performed on the next welding section based on the actual heat input and cooling time of the current welding section. This method can improve the consistency of the welding state along the circumferential weld.

Description

Technical Field

[0001] This invention belongs to the field of electron beam welding technology, specifically a method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding. Background Technology

[0002] Electron beam welding has the advantages of concentrated heat input, large weld depth-to-width ratio, small deformation, and suitability for precision connection in a vacuum environment. It has been applied to the circumferential weld connection of thin-walled metal rotating shells. For such shell components, the welding quality not only affects the weld formation, but also the post-weld circular runout, local deformation, and overall dimensional consistency. Therefore, electron beam welding is usually used as one of the more common connection processes in the manufacturing of thin-walled rotating components.

[0003] In existing technologies, for circumferential welding of thin-walled metal rotating shells, the workpiece is usually rotated around its own axis after the shell is clamped, and full-circumference welding is performed using pre-set electron beam welding process parameters. Some solutions adjust the beam current, focusing position, or welding speed in segments according to the general structure of the shell, while others monitor the molten pool or weld formation during the welding process and then correct the current welding parameters. Although these methods can adapt to changes in the state during the welding process to some extent, their adjustment objects are mostly concentrated on the current welding position, and parameter switching usually revolves around a single segment.

[0004] However, the circumferential weld of a thin-walled metal rotating shell often involves variations in wall thickness, weld path curvature, and uneven distribution of clamping constraints. Different locations exhibit varying sensitivities to heat input. When uniform parameters are used for the entire circumferential weld, or when parameters are adjusted only in a coarse segmented manner, the actual heat input at local locations may not match the welding conditions at those locations. This can lead to a shift in the molten pool radiation center relative to the weld centerline, and fluctuations in the width of the weld's front and back sides. Furthermore, the heat accumulation at the previous welding location continues to affect the welding state at the next location. If there is a lack of continuous transition and correlation adjustment between adjacent locations, unstable welding conditions are more likely to occur at segment transition points, ultimately affecting the consistency of the entire circumferential weld. Summary of the Invention

[0005] The purpose of this invention is to provide a method for welding thin-walled metal rotary shells based on local heat input control in electron beam welding, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding, comprising: The thin-walled metal rotating shell to be welded is clamped, and the wall thickness change along the circumferential weld, the weld path curvature change, the clamping point position, and the constraint strength value corresponding to each clamping point are obtained. Based on the wall thickness variation, weld path curvature variation, clamping point position and corresponding constraint strength value, the heat-sensitive position on the circumferential weld is determined, and the weld segment between adjacent heat-sensitive positions is taken as the welding section, and a transition section is set between adjacent welding sections. For each welding section, an electron beam welding process parameter set, a target unit length heat input, and corresponding first and second deviation allowable ranges are set. The electron beam welding process parameter set includes beam current, focusing position, welding speed, and beam oscillation parameters. The thin-walled metal rotating shell is rotated around its own axis and electron beam welded sequentially through each welding section and transition section along the circumferential weld seam in a vacuum environment. During the welding process, the offset of the molten pool radiation center relative to the weld centerline is determined based on the collected molten pool monitoring image, and the front and back widths of the weld are determined based on the collected weld formation monitoring image. The offset is then compared with the first allowable deviation range corresponding to the current welding section, and the front and back widths of the weld are compared with the second allowable deviation range corresponding to the current welding section. When the offset exceeds the first allowable deviation range, adjust the focusing position and the oscillation center offset in the beam oscillation parameters corresponding to the current welding section. When the width of the front or back of the weld exceeds the second allowable deviation range, the beam current and welding speed corresponding to the current welding section are adjusted, and the corresponding parameters in the electron beam welding process parameter set are continuously changed in the transition section adjacent to the current welding section. After the current welding section is completed, the compensation correction amount for the next welding section is determined based on the difference between the actual heat input per unit length of the current welding section and the target heat input per unit length, the cooling time between the end of the current welding section and the start of the next welding section, and the offset, the change in the width of the weld front and the width of the weld back. The target heat input per unit length, the first allowable deviation range, the second allowable deviation range, and the electron beam welding process parameter set corresponding to the next welding section are then compensated and corrected based on the compensation correction amount.

[0007] Furthermore, the heat-sensitive locations on the circumferential weld may include one or more of the following: locations of abrupt changes in wall thickness, locations of significant changes in weld path curvature, locations corresponding to clamping points, welding start locations, welding end locations, locations adjacent to structural openings, and locations of reinforced structural connections. When determining the heat-sensitive locations, the amount of change in wall thickness, the amount of change in weld path curvature, and the amount of change in constraint strength can be compared with corresponding thresholds. When at least one of them exceeds the corresponding threshold, the location is determined as a heat-sensitive location. Adjacent heat-sensitive locations with a spacing less than the preset minimum segment length can be merged to form a welding segment with a length not less than the preset minimum segment length.

[0008] In this way, the welding section can be avoided due to the excessive density of heat-sensitive locations, which makes it easier to maintain a relatively stable welding state within a single welding section and also facilitates parameter switching between adjacent welding sections.

[0009] After the welding sections are formed, transition sections can be formed by extending a predetermined length outward from both sides of the boundary of two adjacent welding sections. Within the transition sections, the beam current, focusing position, welding speed, and beam oscillation parameters are continuously changed between the electron beam welding process parameter values ​​corresponding to the previous welding section and the electron beam welding process parameter values ​​corresponding to the subsequent welding section. The beam oscillation parameters may include the oscillation direction, oscillation amplitude, oscillation frequency, and the offset of the oscillation center relative to the weld centerline.

[0010] The first and second allowable deviation ranges can be set based on data measured in a stable welding state from test weldments with the same base material type, nominal wall thickness, and joint type as the corresponding welding section.

[0011] Therefore, the parameter settings of different welding sections can be adapted to the actual welding conditions of the section, while the transition section maintains the continuity of parameter changes between adjacent welding sections, reducing the possibility of sudden changes in heat input at the section switching position.

[0012] Furthermore, the compensation correction amount can be determined based on the difference between the actual heat input per unit length and the target heat input per unit length of the current welding section, the cooling time between the end of the current welding section and the beginning of the next welding section, the change in the offset of the molten pool radiation center relative to the weld centerline, the change in the width of the weld front side, and the change in the width of the weld back side.

[0013] If the actual heat input per unit length of the current welding section is greater than the target heat input per unit length and the cooling time is less than the preset time, the initial value of the beam current and the target heat input per unit length of the next welding section can be reduced, or the initial value of the welding speed of the next welding section can be increased; if the actual heat input per unit length of the current welding section is less than the target heat input per unit length and the cooling time is less than the preset time, the initial value of the beam current and the target heat input per unit length of the next welding section can be increased, or the initial value of the welding speed of the next welding section can be decreased.

[0014] By incorporating the actual heat input and cooling states of the previous welding section into the parameter adjustment process of the next welding section, the impact of heat accumulation differences between adjacent welding sections on the stability of subsequent welding can be reduced, making the local heat input control along the entire circumferential weld more continuous.

[0015] In addition, before electron beam welding, the assembly gap distribution can be obtained, and the electron beam action position can be compensated according to the assembly gap distribution, so that the welding section and the transition section are both based on the compensated welding trajectory.

[0016] After welding is completed, the local high-constraint area can be determined based on the clamping point position and the weld position that exceeds the constraint threshold in the constraint strength value of each clamping point, as well as the offset of the molten pool radiation center relative to the weld center line measured within the preset number of samplings during the welding process, and the weld position where the number of times the weld front width or back width exceeds the corresponding allowable deviation range exceeds the preset number threshold. The local high-constraint area is then reciprocated by using the defocused electron beam along the offset scanning path on both sides of the weld.

[0017] The local high-constraint areas can also be sorted according to the frequency or amplitude of exceeding the corresponding deviation allowable range during the welding process, and the defocused electron beam performs reciprocating scanning in the sorting order.

[0018] After the reciprocating scan is completed, the weld runout, weld width consistency and shell local deformation can be detected. When at least one of the weld runout, weld width consistency and shell local deformation exceeds the corresponding evaluation threshold, the actual unit length heat input of the corresponding welding section, the offset of the molten pool radiation center relative to the weld centerline, the weld front width, the back width and the compensation correction amount can be used for parameter correction in subsequent welding of similar shells.

[0019] By combining pre-weld path compensation, in-weld zonal control, and post-weld local treatment, the welding consistency along the entire circumferential weld can be further improved.

[0020] The beneficial effects of this invention are as follows: 1. This invention determines heat-sensitive locations by acquiring the wall thickness variation, weld path curvature variation, clamping point position, and corresponding constraint strength value along the circumferential weld. The weld segment between adjacent heat-sensitive locations is then used as the welding zone, and a transition section is set between adjacent welding zones. This eliminates the need for uniform parameters or coarse segmentation in welding the entire circumferential weld; instead, it allows for localized control based on the heat input sensitivity at different locations. Consequently, the effects of wall thickness variation, curvature variation, and uneven constraint distribution on the welding state are decomposed and processed within each welding zone. The transition section facilitates smooth transitions between adjacent welding zones, reducing the possibility of sudden heat input changes and welding state fluctuations at section switching points, and improving the continuity and stability of the welding process along the circumferential weld.

[0021] 2. This invention sets electron beam welding process parameters, target unit length heat input, and first and second allowable deviation ranges for each welding section. During welding, it acquires the offset of the molten pool radiation center relative to the weld centerline, the weld front width, and the back width, allowing the molten pool position deviation and weld formation deviation to correspond to different adjustment parameters. Specifically, when the offset exceeds the tolerance, the focusing position and the offset of the oscillation center relative to the weld centerline are adjusted; when the weld front width or back width exceeds the tolerance, the beam current and welding speed are adjusted. This allows molten pool position correction and weld formation correction to act on their respective control links, avoiding the introduction of new disturbances by uniformly adjusting all parameters based on a single monitoring quantity. This helps to bring the offset and weld width back within their respective allowable ranges, improving the consistency of the welding state within each welding section.

[0022] 3. This invention determines a compensation correction amount after the current welding section is completed, based on the difference between the actual unit length heat input and the target unit length heat input of the current welding section, the cooling time, the offset, and the changes in the width of the weld front and back sides. This compensation correction amount is then used to compensate and correct the target unit length heat input, allowable deviation range, and electron beam welding process parameter set for the next welding section. Simultaneously, combined with pre-weld path compensation and post-weld defocused electron beam reciprocating scanning of locally high-constraint areas, the actual heat input state and cooling state formed in the previous welding section can participate in the parameter adjustment of the subsequent welding section. This reduces the impact of heat accumulation differences between adjacent welding sections on the stability of subsequent welding and reduces the interference of assembly gap changes and locally high-constraint positions on the consistency of the entire circumferential weld, thereby facilitating the control of post-weld circular runout, weld width consistency, and local deformation of the shell. Attached Figure Description

[0023] Figure 1 This is a flowchart of the thin-walled metal rotary shell welding method based on local heat input control in electron beam welding according to the present invention; Figure 2This is a block diagram of real-time monitoring and parameter adjustment during welding according to the present invention; Figure 3 This is the cross-segment thermal input compensation correction frame of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] like Figures 1 to 3 As shown in the figure, this embodiment of the invention provides a method for welding thin-walled metal rotary shells based on local heat input control in electron beam welding. First, the thin-walled metal rotary shell to be welded is clamped and fixed.

[0026] After clamping, the wall thickness change, weld path curvature change, position of each clamping point, and corresponding constraint strength value are obtained along the extension direction of the circumferential weld. The constraint strength value corresponding to each clamping point can be determined based on at least one of the clamping force and support stiffness of the clamping point, and is used to characterize the degree of constraint on different positions of the circumferential weld during the welding process.

[0027] Subsequently, based on the wall thickness variation, weld path curvature variation, clamping point location, and the constraint strength value corresponding to each clamping point, the heat-sensitive locations on the circumferential weld are determined.

[0028] The heat-sensitive location may be one or more of the following: a location where the wall thickness changes abruptly, a location where the curvature of the weld path changes significantly, a location corresponding to the clamping point, a welding start location, a welding end location, a location near a structural opening, and a location for strengthening structural connections.

[0029] After determining the heat-sensitive locations, the weld section between adjacent heat-sensitive locations is taken as the welding section, and a transition section is set between adjacent welding sections. In this way, the welding influencing factors at different locations along the circumferential weld can be classified into different welding sections, and the transition section can be used to achieve a smooth connection between adjacent welding sections.

[0030] After the welding section and transition section are formed, the electron beam welding process parameter set, target unit length heat input, and corresponding first and second deviation allowable ranges are set for each welding section. The electron beam welding process parameter set includes beam current, focusing position, welding speed and beam oscillation parameters. The beam oscillation parameters include oscillation direction, oscillation amplitude, oscillation frequency and the offset of the oscillation center relative to the weld centerline.

[0031] The first allowable deviation range is used to limit the offset of the molten pool radiation center relative to the weld centerline, and the second allowable deviation range is used to limit the width of the weld front and back sides.

[0032] The first and second allowable deviation ranges can be determined based on the offset, the fluctuation range of the front and back widths of the weld, measured in a stable welding state of the test weld with the same base material type, nominal wall thickness, and joint type as the corresponding welding section.

[0033] During the actual welding process, the thin-walled metal rotating shell is rotated around its own axis, and electron beam welding is performed sequentially through each welding section and transition section along the circumferential weld seam in a vacuum environment.

[0034] During the welding process, the offset of the molten pool radiation center relative to the weld centerline is determined using the molten pool monitoring image, and the width of the front and back sides of the weld is determined using the weld formation monitoring image, and then compared with the first and second allowable deviation ranges corresponding to the welding section.

[0035] When the offset exceeds the first allowable deviation range, the focus position of the current welding section and the offset of the oscillation center relative to the weld centerline are adjusted to bring the offset back to the first allowable deviation range.

[0036] When the width of the weld front or back exceeds the second allowable deviation range, the beam current and welding speed of the current welding section are adjusted, and the corresponding parameters in the electron beam welding process parameter set are continuously changed in the transition section adjacent to the current welding section, so that the parameter values ​​of the previous welding section are smoothly transitioned to the parameter values ​​of the next welding section.

[0037] By mapping the offset adjustment and weld width adjustment to different process parameters, the molten pool position correction and weld formation correction can be applied to the corresponding control links, while reducing the possibility of sudden changes in heat input at the section switching position.

[0038] Once a welding section is completed, the compensation correction amount for the next welding section is determined based on the difference between the actual heat input per unit length and the target heat input per unit length of the welding section, the cooling time between the end of the welding section and the start of the next welding section, the offset, and the changes in the width of the weld front and back.

[0039] Subsequently, the compensation correction amount is used to correct at least one of the following for the next welding section: target unit length heat input, beam current, welding speed, offset of the oscillation center relative to the weld centerline, first allowable deviation range, and second allowable deviation range. By incorporating the actual heat input state and cooling state formed in the previous welding section into the parameter setting process of the next welding section, the impact of heat accumulation differences between adjacent welding sections on the stability of subsequent welding can be reduced, making the local heat input control along the entire circumferential weld more continuous.

[0040] In this embodiment, a method for welding thin-walled metal rotary shells based on local heat input control in electron beam welding firstly involves clamping and fixing the thin-walled metal rotary shell to be welded.

[0041] The welding joint of the thin-walled metal rotary shell is a circumferential butt joint. During welding, the rotary drive mechanism drives the shell to rotate around its own axis. The electron beam maintains a stable spatial position relative to the shell and acts on each welding position sequentially along the circumferential weld.

[0042] After clamping, the wall thickness change, weld path curvature change, position of each clamping point, and corresponding constraint strength value are obtained along the extension direction of the circumferential weld. The wall thickness change is determined based on the machining drawing of the shell to be welded and the actual thickness measured before welding. The weld path curvature change is determined based on the curvature change of the weld centerline at different positions. The constraint strength value corresponding to each clamping point is determined based on at least one of the clamping force and support stiffness of the clamping point.

[0043] In practice, the clamping force is determined by the clamping fixture setting value or the clamping force detection result, and the support stiffness is determined by the displacement response of the support structure under preset loading conditions. Then, the constraint strength value, which characterizes the degree of constraint at the clamping point, is obtained according to the preset conversion relationship. In this way, the constraint strength value can directly correspond to the actual clamping state.

[0044] After obtaining the aforementioned data, the heat-sensitive locations on the circumferential weld are determined based on the wall thickness change, the weld path curvature change, the clamping point location, and the constraint strength value corresponding to each clamping point. The heat-sensitive locations include one or more of the following: locations of sudden changes in wall thickness, locations of significant changes in weld path curvature, locations corresponding to clamping points, welding start locations, welding end locations, locations near structural openings, and locations of reinforced structural connections.

[0045] In this embodiment, the wall thickness change, weld path curvature change, and constraint strength change are compared with corresponding thresholds. When any one of them exceeds the corresponding threshold, the location is determined to be a heat-sensitive location.

[0046] The threshold is determined by the test results of the test weldment with the same type of base material, nominal wall thickness and joint type as the current shell. Specifically, the threshold is determined based on the offset measured by the test weldment under stable welding conditions, the wall thickness change, curvature change and constraint strength change when the width of the weld front and back exceeds the corresponding allowable deviation range.

[0047] For adjacent heat-sensitive locations with a spacing less than the preset minimum segment length, this embodiment performs a merging process to form a welding segment with a length not less than the preset minimum segment length.

[0048] The preset minimum segment length is determined by the response time required to complete one adjustment of the electron beam welding process parameters and the weld length formed by the shell rotation within that response time. This ensures that each welding segment has the length to complete parameter adjustment and enter a stable welding state. In this way, it is possible to avoid forming excessively short welding segments due to excessively dense heat-sensitive positions, thereby avoiding interference with welding stability caused by frequent parameter switching.

[0049] After the welding section is formed, a transition section is set between two adjacent welding sections; specifically, the transition section is formed by extending a predetermined length outward from both sides of the boundary of the two adjacent welding sections.

[0050] The predetermined length is determined by the weld seam linear velocity formed by the rotation of the shell, the response time of the electron beam welding process parameters, and the weld seam length required to reach a stable welding state after parameter adjustment; thus, it can be ensured that there is sufficient change distance when the parameters transition from the previous welding section to the next welding section.

[0051] Subsequently, electron beam welding process parameter sets, target unit length heat input, and corresponding first and second deviation allowable ranges are set for each welding section. The electron beam welding process parameter set includes beam current, focusing position, welding speed, and beam oscillation parameters. The beam oscillation parameters include oscillation direction, oscillation amplitude, oscillation frequency, and the offset of the oscillation center relative to the weld centerline.

[0052] The first allowable deviation range is used to limit the offset of the molten pool radiation center relative to the weld centerline, and the second allowable deviation range is used to limit the width of the weld front and back sides; the target unit length heat input, the first allowable deviation range, and the second allowable deviation range are determined based on the data measured by the test weldment with the same base material type, nominal wall thickness, and joint type as the corresponding welding section under stable welding conditions.

[0053] In practice, a continuous welding section is selected from the test weld where the offset is within the first allowable deviation range and the width of the weld face and back is within the second allowable deviation range. The fluctuation range of heat input per unit length, offset, width of the weld face and back within this section is statistically analyzed, and this fluctuation range is used as the basis for setting the target heat input per unit length and the first and second allowable deviation ranges for the corresponding welding section. Thus, the control targets for each welding section are derived from stable welding data under the same conditions as the welding object.

[0054] During the formal welding process, the thin-walled metal rotating shell is rotated around its own axis and electron beam welding is performed sequentially through each welding section and transition section along the circumferential weld in a vacuum environment. During the welding process, the molten pool monitoring device is used to collect molten pool monitoring images, and the offset of the molten pool radiation center relative to the weld centerline is determined based on the molten pool monitoring images. In specific implementation, the actual centerline of the weld is first determined based on the positions of the two edges of the joint before welding, and then the position of the molten pool radiation center is extracted during welding, and the offset of the molten pool radiation center position relative to the actual centerline of the weld is calculated.

[0055] Simultaneously, weld formation monitoring images are acquired using a weld formation monitoring device, and the width of the front and back sides of the weld are determined based on these images. Subsequently, the offset is compared with the first allowable deviation range corresponding to the current welding section, and the width of the front and back sides of the weld is compared with the second allowable deviation range corresponding to the current welding section. When the offset exceeds the first allowable deviation range, the offset of the focusing position and the oscillation center relative to the weld centerline corresponding to the current welding section is adjusted to bring the offset back within the first allowable deviation range. By limiting the offset correction to the adjustment of the focusing position and the oscillation center offset, the radiant center of the molten pool can be re-aligned with the weld centerline without having to change all process parameters simultaneously.

[0056] When the width of the weld face or back exceeds the second allowable deviation range, the beam current and welding speed corresponding to the current welding section are adjusted, and the corresponding parameters in the electron beam welding process parameter set are continuously changed in the transition section adjacent to the current welding section. In specific implementation, the process parameter value corresponding to the previous welding section is taken at the beginning position of the transition section, and the process parameter value corresponding to the next welding section is taken at the end position of the transition section. The beam current, focusing position, welding speed and beam oscillation parameters are continuously changed within the length of the transition section, so that the process parameter value of the previous welding section continuously changes to the process parameter value of the next welding section. After this processing, the offset control and weld width control act on different parameters, which avoids adjusting all parameters uniformly based on a single monitoring value and avoids obvious heat input abrupt changes at the switching position of adjacent welding sections.

[0057] Once a welding section is completed, the compensation correction amount for the next welding section is determined based on the difference between the actual heat input per unit length and the target heat input per unit length of the welding section, the cooling time between the end of the welding section and the start of the next welding section, the offset, and the changes in the width of the weld front and back.

[0058] The actual heat input per unit length is determined based on the actual applied beam current and welding speed within the current welding segment, provided that the electron gun acceleration voltage remains at a set value. The compensation correction amount is obtained by comparing the difference between the actual heat input per unit length of the current welding segment and the target heat input per unit length, combined with the cooling time, offset, and changes in the width of the weld face and back. In this embodiment, if the actual heat input per unit length of the current welding segment is greater than the target heat input per unit length, and the cooling time between the end of the current welding segment and the start of the next welding segment is less than a preset time, the initial value of the beam current and the target heat input per unit length of the next welding segment are reduced, or the initial value of the welding speed of the next welding segment is increased; if the actual heat input per unit length of the current welding segment is less than the target heat input per unit length, and the cooling time between the end of the current welding segment and the start of the next welding segment is less than a preset time, the initial value of the beam current and the target heat input per unit length of the next welding segment are increased, or the initial value of the welding speed of the next welding segment is decreased; when the cooling time reaches the preset time, the compensation correction amount is reduced to a preset lower limit or set to zero.

[0059] Subsequently, the compensation correction amount is used to correct at least one of the following for the next welding section: target unit length heat input, beam current, welding speed, offset of the oscillation center relative to the weld centerline, first allowable deviation range, and second allowable deviation range.

[0060] Through this cross-segment compensation process, the actual heat input and cooling states of the previous welding segment can be incorporated into the parameter settings of the next welding segment, thereby reducing the impact of heat accumulation differences between adjacent welding segments on the stability of subsequent welding.

[0061] In a further embodiment, before electron beam welding, the assembly gap distribution is obtained, and path compensation is performed on the electron beam application position based on the assembly gap distribution.

[0062] In practice, the width of the butt joint opening and the center position of the joint are measured along the circumferential weld first, and then the trajectory of the electron beam is corrected accordingly, so that the welding section and the transition section are both based on the compensated welding trajectory. After this treatment, the impact of the assembly gap change on the identification of the weld center line and the control of the molten pool position can be reduced.

[0063] In another further embodiment, after welding is completed, a local high-constraint area is determined based on the clamping point position and the weld position that exceeds the constraint threshold in the constraint strength value corresponding to each clamping point, as well as the offset measured within a preset number of samplings during the welding process, and the weld position where the number of times the front or back width of the weld exceeds the corresponding allowable deviation range exceeds a preset number threshold.

[0064] In practice, first determine the high constraint positions distributed along the weld. Then, overlay the positions where the offset, weld front width or back width exceeds the corresponding allowable deviation range within a preset number of samplings during the welding process with the high constraint positions. The position area that simultaneously meets both conditions is determined as the local high constraint area.

[0065] Subsequently, the local high-constraint area is reciprocated by using a defocused electron beam along an offset scanning path on both sides of the weld. The offset scanning path is located on both sides of the weld centerline and maintains a predetermined offset distance from the weld centerline. This predetermined offset distance is determined by trial welding based on the corresponding shell material and weld width.

[0066] Furthermore, the local high-constraint areas are sorted according to the frequency or amplitude of exceeding the corresponding allowable deviation range during the welding process, and the defocused electron beam performs reciprocating scanning in the sorting order.

[0067] With this setup, post-weld treatment is not a uniform heat treatment of the entire weld, but rather a localized treatment of areas with high constraints and where abnormalities actually occur during welding.

[0068] After the reciprocating scan is completed, the weld runout, weld width consistency, and local deformation of the shell are then detected. When any of the weld runout, weld width consistency, and local deformation of the shell exceeds the corresponding evaluation threshold, the actual unit length heat input, offset, weld front width, back width, and compensation correction amount of the corresponding welding section are used for parameter correction in subsequent welding of similar shells.

[0069] Therefore, pre-welding path compensation, in-welding zoning control, inter-segment compensation correction, and post-welding local treatment can form a continuous implementation process, enabling those skilled in the art to implement the present invention according to the specific embodiments described in the specification.

[0070] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding, characterized in that, include: The thin-walled metal rotating shell to be welded is clamped, and the wall thickness change along the circumferential weld, the weld path curvature change, the clamping point position, and the constraint strength value corresponding to each clamping point are obtained. Based on the wall thickness variation, weld path curvature variation, clamping point position and corresponding constraint strength value, the heat-sensitive position on the circumferential weld is determined, and the weld segment between adjacent heat-sensitive positions is taken as the welding section, and a transition section is set between adjacent welding sections. For each welding section, an electron beam welding process parameter set, a target unit length heat input, and corresponding first and second deviation allowable ranges are set. The electron beam welding process parameter set includes beam current, focusing position, welding speed, and beam oscillation parameters. The thin-walled metal rotating shell is rotated around its own axis and electron beam welded sequentially through each welding section and transition section along the circumferential weld seam in a vacuum environment. During the welding process, the offset of the molten pool radiation center relative to the weld centerline is determined based on the collected molten pool monitoring image, and the front and back widths of the weld are determined based on the collected weld formation monitoring image. The offset is then compared with the first allowable deviation range corresponding to the current welding section, and the front and back widths of the weld are compared with the second allowable deviation range corresponding to the current welding section. When the offset exceeds the first allowable deviation range, adjust the focusing position and the oscillation center offset in the beam oscillation parameters corresponding to the current welding section. When the width of the front or back of the weld exceeds the second allowable deviation range, the beam current and welding speed corresponding to the current welding section are adjusted, and the corresponding parameters in the electron beam welding process parameter set are continuously changed in the transition section adjacent to the current welding section. After the current welding section is completed, the compensation correction amount for the next welding section is determined based on the difference between the actual heat input per unit length of the current welding section and the target heat input per unit length, the cooling time between the end of the current welding section and the start of the next welding section, and the offset, the change in the width of the weld front and the width of the weld back. The target heat input per unit length, the first allowable deviation range, the second allowable deviation range, and the electron beam welding process parameter set corresponding to the next welding section are then compensated and corrected based on the compensation correction amount.

2. The method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding according to claim 1, characterized in that: The heat-sensitive locations include one or more of the following: locations where the wall thickness changes abruptly, locations where the weld path curvature changes significantly, locations corresponding to clamping points, welding start locations, welding end locations, locations near structural openings, and locations where reinforced structures are connected.

3. The method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding according to claim 2, characterized in that, When determining the heat-sensitive location, the wall thickness change, weld path curvature change, and constraint strength change are compared with corresponding thresholds. When at least one of them exceeds the corresponding threshold, the location is determined as a heat-sensitive location. Adjacent heat-sensitive locations with a spacing less than the preset minimum segment length are merged to form a welding segment with a length not less than the preset minimum segment length.

4. The method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding according to claim 3, characterized in that: The transition section is formed by extending outwards by a predetermined length from both sides of the boundary of two adjacent welding sections; within the transition section, the beam current, focusing position, welding speed and beam oscillation parameters are continuously changed between the electron beam welding process parameter values ​​corresponding to the previous welding section and the electron beam welding process parameter values ​​corresponding to the next welding section.

5. The method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding according to claim 4, characterized in that: The beam oscillation parameters include oscillation direction, oscillation amplitude, oscillation frequency, and the offset of the oscillation center relative to the weld centerline.

6. The method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding according to claim 5, characterized in that: The first allowable deviation range and the second allowable deviation range are set based on data measured in a stable welding state from test weldments that have the same base material type, nominal wall thickness and joint type as the corresponding welding section.

7. The method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding according to claim 6, characterized in that: The determination of the compensation correction amount includes: determining the compensation correction amount for the next welding section based on the difference between the actual heat input per unit length of the current welding section and the target heat input per unit length, the cooling time between the end of the current welding section and the beginning of the next welding section, the change in the offset of the molten pool radiation center relative to the weld centerline, the change in the width of the weld front side and the change in the width of the weld back side. If the actual heat input per unit length of the current welding section is greater than the target heat input per unit length and the cooling time is less than the preset time, reduce the initial value of the beam current and the target heat input per unit length of the next welding section, or increase the initial value of the welding speed of the next welding section. If the actual heat input per unit length of the current welding section is less than the target heat input per unit length and the cooling time is less than the preset time, the initial value of the beam current and the target heat input per unit length of the next welding section shall be increased, or the initial value of the welding speed of the next welding section shall be decreased.

8. The method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding according to claim 7, characterized in that: Before electron beam welding, the process includes obtaining the assembly gap distribution and performing path compensation on the electron beam application position based on the assembly gap distribution; the welding section and the transition section are both based on the compensated welding trajectory.

9. A method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding according to claim 8, characterized in that: After welding is completed, based on the clamping point positions and the weld positions that exceed the constraint threshold in the constraint strength values ​​corresponding to each clamping point, as well as the weld positions where the offset, weld front width, or weld back width exceeds the corresponding allowable deviation range more than the preset number threshold within the preset number of samplings during the welding process, a local high constraint region is determined, and the local high constraint region is reciprocated by using a defocused electron beam along the offset scanning path on both sides of the weld.

10. A method for welding thin-walled metal rotating shells based on local heat input control in electron beam welding according to claim 9, characterized in that, The local high-constraint regions are sorted according to the frequency or amplitude of exceeding the corresponding allowable deviation range during the welding process, and the defocused electron beam performs reciprocating scanning sequentially according to the sorting results; After the reciprocating scan is completed, the weld runout, weld width consistency and shell local deformation are detected. When at least one of the weld runout, weld width consistency and shell local deformation exceeds the corresponding evaluation threshold, the actual unit length heat input of the corresponding welding section, the offset, the front width of the weld, the back width and the compensation correction amount are used as the parameter correction basis for subsequent similar shell welding.

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