Automobile steel plate cold metal transition welding deformation control method and system

Abstract

The invention relates to the technical field of automobile body manufacturing, and discloses an automobile steel plate cold metal transition welding deformation control method and system.The method comprises the steps that a rear gutter channel is structurally enhanced, the plate thickness is set to range from 1.2 mm to 1.5 mm, and a local reinforcing structure is arranged in an area close to a welding bead to improve the section modulus; planning a segmented intermittent welding path comprising a single-segment welding seam and a non-welding interval to disperse heat input; a conformal T2 red copper heat dissipation block integrated with a circulating cooling flow channel is configured, and a low-thermal-resistance forced heat dissipation channel is established through mechanical pressing; and executing the assembly sequence of preferentially welding the side body sub-assemblies and strictly controlling the pre-welding fitting degree. Through the synergistic effect of structural rigidity enhancement, thermal stress discretization, forced heat dredging and assembly stress decoupling, the peak temperature of a welding seam area is remarkably reduced, stress accumulation is blocked, thin plate welding deformation is effectively restrained, and the size precision of a vehicle body is improved.

Description

Technical Field

[0001] This invention relates to the field of automotive body manufacturing technology, specifically to a method and system for controlling deformation during cold metal transition welding of automotive steel sheets. Background Technology

[0002] In the field of modern automotive body-in-white manufacturing, with the increasing demands for lightweighting and refined appearance, the application of thin-walled high-strength steel structures is becoming increasingly widespread. Among these, the connection area between the rear diffuser and the side panel is a critical visible area at the rear of the vehicle. Its welding quality directly affects not only the vehicle's sealing and structural strength but also the flatness of the matching gaps around the taillights and trunk lid. To reduce welding heat input, cold metal transfer (CMT) welding technology, due to its low heat input and spatter-free characteristics, is often used for this connection.

[0003] Although cold metal transfer welding reduces heat input compared to conventional gas metal arc welding (MAG), welding deformation remains a serious problem when dealing with large-span thin-plate structures. In existing technologies, for weight reduction, stamped parts such as backflow channels typically use thinner steel plates (e.g., 0.8 mm or less), and often lack specific reinforcement features designed to resist thermal deformation around the weld bead. This design results in a low local section modulus of the workpiece and insufficient out-of-plane bending stiffness. During continuous welding, the heat generated by the arc accumulates along the weld direction, causing uneven thermal expansion of the base material. During the cooling and contraction phase, the weak plate structure cannot offset the enormous shrinkage stress, leading to significant wavy warping deformation.

[0004] Existing welding fixtures typically focus only on workpiece positioning and clamping, lacking proactive thermal management mechanisms. Heat generated in the welding area relies primarily on natural air convection or slow conduction through ordinary steel support blocks, resulting in low heat dissipation efficiency. This keeps the welding area at a high temperature for extended periods, increasing the heat-affected zone and exacerbating the degree of plastic deformation in the material. Furthermore, the presence of microscopic gaps between the workpiece and the support blocks creates significant contact thermal resistance, further hindering rapid heat dissipation.

[0005] Traditional assembly and welding processes typically employ a multi-part, all-series positioning strategy, attempting to simultaneously clamp and weld components such as the rear diffuser, side panels, and taillight mounting plates. Due to inherent manufacturing tolerances in stamped parts, simultaneous matching of multiple parts easily leads to the accumulation and interference of dimensional tolerances. To ensure proper weld alignment, tooling fixtures often require immense constraint forces to correct part positions, pre-installing extremely high elastic potential energy (assembly stress) within the workpiece before welding. When the welding thermal cycle activates the material's microstructure, these sealed assembly stresses are released in conjunction with thermal stress, causing unpredictable twisting deformation of the components, severely impacting the final vehicle body dimensional accuracy and subsequent assembly consistency. Current production often relies on post-weld manual sheet metal correction to compensate for deformation, but this not only reduces production efficiency but also makes it difficult to guarantee product quality stability. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method and system for controlling deformation during cold metal transition welding of automotive steel sheets. This method solves the problem of severe out-of-plane warping deformation and dimensional deviations after welding in existing thin-walled steel sheet structural parts (such as rear drainage channels and side outer panels) during cold metal transition welding, caused by insufficient local rigidity of the workpiece, concentrated heat input, and assembly stress coupling.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] The first aspect of this invention provides a method for controlling welding deformation during cold metal transition welding of automotive steel sheets. This method suppresses welding deformation by synergistically controlling the rigidity of the part structure, the distribution of heat input paths, the heat conduction boundary conditions of the tooling, and the assembly constraint sequence.

[0009] Specifically, the method includes pre-designing structural reinforcement for the post-flow channel components. This design is not solely for the entire sheet metal, but focuses on enhancing the bending resistance near the weld heat-affected zone. Specifically, by setting a predetermined reinforcement thickness for the sheet metal and incorporating localized reinforcement structures within a specific distance from the centerline of the cold metal transition weld, a high section modulus resistance zone is created to utilize the material's inherent mechanical properties to resist thermal shrinkage stress.

[0010] Based on this, the method performs segmented, intermittent welding path planning. This planning abandons the continuous heat input pattern and discretizes the weld joint into a topology consisting of several alternating single weld segments and non-welded intervals. This path distribution physically breaks the continuous thermal stress field, utilizing the non-welded intervals as buffer zones for thermal expansion and contraction.

[0011] Simultaneously, the method introduces a tooling configuration with active heat dissipation function. A heat dissipation metal block with a conformal curved surface is set on the welding fixture. This metal block is closely fitted to the back or sides of the weld bead and integrates circulating cooling channels internally. Through this configuration, the originally inefficient heat dissipation relying on natural convection is transformed into a highly efficient forced heat dissipation mode relying on solid-state heat conduction and fluid heat exchange.

[0012] At the process execution level, the method follows a specific assembly logic. By pre-determining the assembly sequence, the relative positions of the rear drainage channel and the side panel are first established and welded and cured, followed by the introduction of other components such as the taillight mounting plate. During welding, mechanical pressure is applied using a clamping arm to force the workpiece into close contact with the heat dissipation metal block, eliminating contact gaps and completing positioning, followed by cold metal transition welding.

[0013] As a preferred embodiment of the first aspect of the present invention, in order to maximize rigidity gains without significantly increasing the vehicle body weight in the reinforced design of the part structure, the sheet thickness of the rear water channel is selected to be in the range of 1.2 mm to 1.5 mm.

[0014] Furthermore, the local reinforcement structure is constructed in the form of a stamped boss or an enlarged rounded corner structure, increasing local stiffness through abrupt changes in geometry. This structure is precisely positioned to effectively resist thermal stress, specifically with its edge perpendicular to the weld centerline within the range of 5mm to 15mm. Specifically, when using a stamped boss, its height is controlled between 1.0mm and 2.0mm; when using an enlarged rounded corner structure, its radius is set to be greater than 8mm.

[0015] As a preferred embodiment of the first aspect of the present invention, in order to balance the connection strength and deformation control in the welding path planning, the specific parameters of the segmented intermittent welding path are set as follows: the length of a single weld segment is between 20mm and 40mm, and the length of the non-welding interval between two adjacent weld segments is between 10mm and 20mm.

[0016] In a preferred embodiment of the first aspect of the present invention, in the tooling heat dissipation configuration, the heat dissipation metal block is made of T2 copper with a high thermal conductivity, and its position is close to the heat source. Specifically, the horizontal distance between the edge of the heat dissipation metal block and the edge of the weld bead is maintained between 3mm and 8mm, so as to conduct the heat out before it diffuses to the surrounding base material.

[0017] In a preferred embodiment of the first aspect of the present invention, the predetermined assembly sequence during the assembly and welding process aims to decouple the complex constraints caused by multiple parts. Specifically, the rear water channel is first matched and welded with the side outer panel to form the side outer panel process sub-assembly. After the structure of this sub-assembly is stable, it is then welded to the taillight fixing plate.

[0018] Furthermore, to ensure the consistency of the welding gap and the quality of the weld nugget, a fit test is performed before welding begins. This test uses a measurement reference length of 200mm and requires that the parallelism error between the rear drainage channel and the side panel outer plate to be welded be strictly controlled within the range of less than 0.2mm.

[0019] Furthermore, the operation of clamping the workpiece with the clamping arm is essentially to eliminate the microscopic air gap at the interface between the workpiece and the heat dissipation metal block by applying mechanical pressure, thereby reducing the contact thermal resistance. Combined with the flow of the medium in the circulating cooling channel, a low thermal resistance heat conduction channel is established.

[0020] A second aspect of the present invention provides a cold metal transition welding deformation control system for automotive steel sheets, the system comprising multiple functional modules working together, including:

[0021] The workpiece structure module is characterized by including a rigidly optimized rear drainage channel, which has a predetermined reinforcement thickness and integrates a local reinforcement structure within a predetermined distance from the weld centerline.

[0022] The welding execution module is configured to drive the welding torch to perform discontinuous welding operations, specifically to perform cold metal transition welding on the rear flow channel and the side outer panel according to a segmented intermittent welding path that includes single weld seams and non-welding intervals.

[0023] The tooling clamping module has a welding fixture as its core component. This fixture integrates positioning and heat dissipation functions. It is equipped with a heat dissipation metal block that conforms to the weld area and a clamping arm for applying mechanical pressure. The heat dissipation metal block has a circulating cooling channel for fluid heat exchange.

[0024] The assembly control module is configured to perform specific process flow control to ensure that the welding connection between the rear water channel and the side panel is completed before the assembly connection of the taillight mounting plate.

[0025] As a preferred embodiment of the second aspect of the present invention, the specific parameter features of the workpiece structure module are as follows: the thickness of the back water channel plate is 1.2mm to 1.5mm, and the local reinforcement structure is located within a range of 5mm to 15mm from the center line of the weld.

[0026] As a preferred embodiment of the second aspect of the present invention, the path parameters executed by the welding execution module are characterized as follows: the length of a single weld segment is 20mm to 40mm, and the interval length is 10mm to 20mm.

[0027] This invention provides a method and system for controlling deformation during cold metal transition welding of automotive steel sheets. It offers the following advantages:

[0028] 1. This invention improves the section modulus of the part's resistance to thermal shrinkage at the physical level by setting the thickness of the back flow channel plate to 1.2mm to 1.5mm and setting a local reinforcement structure in the area near the weld bead, combined with segmented intermittent welding path planning. At the same time, it uses non-welding intervals to block the accumulation of continuous thermal stress, thus synergistically suppressing welding deformation from both the source of stress generation and the structural resistance.

[0029] 2. This invention utilizes a T2 copper heat sink with a conformal curved surface and a mechanical clamping mechanism to establish a low thermal resistance forced heat dissipation channel on the back of the weld. Combined with the internal circulating cooling channel, the welding heat is quickly dissipated, reducing the peak temperature of the weld area and the range of the heat-affected zone. This reduces the shrinkage stress caused by local thermal expansion of the material and uneven cooling after welding.

[0030] 3. By setting the assembly sequence of priority welding between the rear water channel and the side outer panel, and strictly controlling the parallelism error of the matching surface before welding to be less than 0.2mm, the present invention effectively decouples the additional assembly constraints introduced by the taillight fixing plate, eliminates the forced assembly stress caused by the accumulation of tolerances of multiple parts, ensures the stability of the welding reference and the consistency of the weld nugget formation, and thus improves the dimensional accuracy of the welded assembly. Attached Figure Description

[0031] Figure 1 This is a flowchart of the welding deformation control process of the present invention;

[0032] Figure 2 This is a system principle block diagram of the present invention. Detailed Implementation

[0033] 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.

[0034] See attached document Figure 1 and attached Figure 2This invention provides a cold metal transition welding deformation control system for automotive steel sheets, comprising a workpiece structure module. This workpiece structure module primarily relates to the structural configuration of the rear drainage channel and the side outer panel to be welded. Before implementing the cold metal transition welding process, specific structural parameters and local feature optimizations are performed on the rear drainage channel to enhance its rigidity performance during the welding thermal cycle.

[0035] The rear drainage channel in the workpiece structure module is made of steel plate. To improve the part's resistance to out-of-plane bending deformation caused by welding heat input, the plate thickness of the rear drainage channel is [specific details needed]. The predetermined reinforcement thickness is set. This predetermined reinforcement thickness is significantly higher than the conventional design standard, increasing the section modulus of the sheet material by increasing the physical thickness. In this embodiment, the sheet thickness of the rear drainage channel... The value range is set to 1.2mm to 1.5mm. Within this thickness range, when the sheet is subjected to thermal shrinkage stress, its own bending stiffness is sufficient to offset part of the displacement tendency caused by the stress, thereby maintaining the macroscopic geometric stability of the part.

[0036] In addition to optimizing the substrate thickness, the workpiece structure module also incorporates localized reinforcement structures on the rear runner. These reinforcement structures are located in the area immediately adjacent to the cold metal transition weld bead, using the centerline of the cold metal transition weld bead as a reference baseline. Define the edge of the locally reinforced structure to this reference baseline. The vertical distance is To ensure the reinforced structure effectively covers the heat-affected zone and provides rigid support, while avoiding interference with welding operations, this vertical distance... The value range is set to 5mm to 15mm.

[0037] In practice, the physical forms of locally reinforced structures include two types: stamped boss structures and enlarged rounded corner structures. Both of these forms increase the moment of inertia by changing the geometry of the local cross-section.

[0038] When a stamped boss structure is used for local reinforcement, its geometry includes hemispherical bosses or elongated bosses. The boss is formed on the sheet surface through a stamping process, protruding from a reference surface. The protrusion height of the stamped boss is defined as... This height parameter determines the effective cross-sectional height of the locally reinforced region. In this embodiment, the protrusion height of the stamped boss... The value range is set to 1.0mm to 2.0mm. Within this parameter range, the stamped boss structure is equivalent to adding reinforcing ribs to the thin plate near the weld bead, using the structural geometric stiffness to resist welding deformation perpendicular to the plate surface.

[0039] When a larger fillet is used for local reinforcement, it involves optimizing the bending characteristics of the back flow channel near the weld bead. The radius of this larger fillet is defined as... To disperse stress concentration and enhance structural stability, this radius... The value is set to be greater than 8mm.

[0040] By precisely defining and combining the above structural parameters, the workpiece structure module constructs a welding base with high resistance to thermal deformation, providing structural protection for subsequent welding processes.

[0041] See attached document Figure 1 and attached Figure 2 As a core component of the cold metal transition welding deformation control system for automotive steel sheets, this invention provides a tooling clamping module. This tooling clamping module not only undertakes the functions of workpiece positioning and fixing, but also intervenes in the welding thermal cycle process through an active thermal management mechanism.

[0042] The tooling clamping module includes a base and a heat-dissipating metal block mounted on the base. The heat-dissipating metal block is positioned on the back or sides of the cold metal transition weld between the rear drainage channel and the outer side panel. To achieve rapid heat conduction and prevent excessive heat accumulation in the base material around the welding area, the heat-dissipating metal block is made of T2 copper, which has a high thermal conductivity. The high thermal diffusivity of T2 copper ensures that the heat generated during welding is rapidly dissipated inwards after being transferred to the contact surface of the metal block, preventing excessive local temperature rise at the contact interface.

[0043] To ensure effective heat conduction area, the contact surface of the heat dissipation metal block is designed with a conformal surface feature. The geometric profile of this conformal surface strictly conforms to the theoretical digital model surface shape of the rear drainage channel and side outer plate in the weld area. This surface-to-surface matching design aims to ensure that after the workpiece is placed in the fixture, the heat dissipation metal block can completely conform to the back contour of the workpiece, avoiding heat conduction blind spots caused by local point contact or line contact.

[0044] In terms of spatial positioning, the placement of the heat dissipation metal blocks is strictly limited. The horizontal distance from the edge of the heat dissipation metal block to the edge of the cold metal transition weld bead is defined as... To maximize heat absorption without interfering with welding torch operation and molten pool flow, this horizontal distance... The value range is set to 3mm to 8mm. This distance setting prevents the copper block from being too close to the weld, which could lead to arc erosion or contamination of the molten pool, while also preventing the heat-affected zone from being ineffectively covered due to excessive distance.

[0045] The heat dissipation metal block integrates a circulating cooling channel. This channel is a closed cavity or pipe system within the copper block, with its two ends connected to the inlet and outlet of an external cooling medium source, respectively. During welding, a low-temperature cooling medium (such as industrial circulating water) continuously flows within the circulating cooling channel, carrying away the heat transferred from the workpiece to the heat dissipation metal block. Through fluid convection heat transfer, the temperature of the heat dissipation metal block is maintained within a low and stable range, thereby establishing a constant low-temperature boundary condition on the back of the workpiece. This forcibly increases the temperature gradient in the welding area and accelerates the post-weld cooling process.

[0046] Furthermore, the circulating cooling channels within the heat dissipation metal block are not simply straight lines, but are designed as a serpentine flow channel structure. This serpentine flow channel structure is arranged in an S-shape or U-shape reciprocating meandering pattern on a cross-section parallel to the workpiece contact surface, and the distance from the centerline of the flow channel to the contact surface of the heat dissipation metal block remains constant, specifically set to 3mm to 5mm. This equidistant meandering design aims to ensure a uniform temperature field distribution on the surface of the heat dissipation metal block, avoid heat accumulation blind spots caused by localized discontinuities in the flow channels, and ensure consistent cooling rates along the entire length of the weld bead.

[0047] The tooling clamping module also includes a clamping arm. The clamping arm is configured to apply mechanical pressure perpendicular to the contact surface to the workpiece during welding. This mechanical pressure not only restricts the rigid displacement of the workpiece, but more importantly, it reduces contact thermal resistance. At the microscopic level, even with high machining precision, direct contact between the workpiece surface and the heat sink metal block surface still presents microscopic roughness peaks, filled with an air layer with extremely low thermal conductivity. By applying a predetermined clamping force through the clamping arm, the workpiece is forced to undergo slight elastic deformation to fill the microscopic gaps, eliminating the air gap between the workpiece and the heat sink metal block.

[0048] With the above configuration, the tooling clamping module creates a highly efficient heat dissipation channel that combines mechanical clamping, low contact thermal resistance, solid-state heat conduction, and fluid convection heat transfer. This channel rapidly removes the heat input from the welding process from the thin-plate structure, significantly reducing the peak temperature around the weld and thus suppressing plastic deformation and post-weld shrinkage stress caused by overheating.

[0049] See attached document Figure 1 and attached Figure 2 The present invention provides a welding execution module configured to control the motion trajectory and light output logic of welding equipment (such as industrial welding robots or automated special machines) to execute a specific heat input strategy.

[0050] The welding execution module employs a segmented, intermittent welding path instead of the traditional continuous straight welding path to alter the distribution pattern of thermal stress on the workpiece. At the connection interface between the rear drainage channel and the side outer panel, the welding path is planned as a topology consisting of several alternating single-segment welds and non-welded intervals. This discontinuous connection method physically severs the continuous transmission channel of longitudinal residual stress.

[0051] Specifically, the segmented intermittent welding path strictly defines the length parameter of a single weld segment. In this embodiment, the length of a single weld segment is set to range from 20mm to 40mm. This length range is based on a balance between connection strength and heat input: if the weld segment length is too short, it may not meet the strength and stiffness requirements of the body-in-white structure, and frequent arc starting and ending can easily lead to welding defects; if the weld segment length exceeds 40mm, the single continuous arc burning time is too long, causing the local heat input to accumulate and exceed the critical instability threshold of the thin plate, triggering wave deformation similar to continuous welds. By limiting the weld segment length to between 20mm and 40mm, the total heat injection in a single welding cycle is effectively controlled.

[0052] Simultaneously, a non-welded interval is provided between adjacent single-segment welds. In this embodiment, the length of the non-welded interval is set to a range of 10mm to 20mm. Mechanically, this non-welded interval acts as a stress-relieving zone and an elastic buffer. During the welding cooling stage, when a single-segment weld undergoes volume shrinkage, the adjacent non-welded intervals utilize their own cold metal state and elastic deformation capacity to absorb and compensate for part of the shrinkage displacement. This prevents the linear superposition of shrinkage forces along the weld direction, decomposing the overall large deformation into several small, localized deformations that can be dissolved by structural rigidity.

[0053] The control logic of the welding execution module is set to operate in a cyclical mode of arc initiation welding, arc extinguishing and idle movement, and arc re-initiation welding. During the idle movement through the non-welding interval, the welding arc is extinguished, and the workpiece area does not receive heat input, thus forming a periodic hot, cold, and hot temperature field distribution on the macroscopic welding line, reducing the average temperature gradient of the entire connection area.

[0054] To complement the segmented path and structural design described above, the welding execution module is configured with specific welding process parameters to match plate thicknesses of 1.2mm to 1.5mm when performing cold metal transfer (CMT) welding. In one specific embodiment, the welding current is set to 100A to 140A, the arc voltage to 12V to 15V, the wire feed speed to 4.0m / min to 6.0m / min, and the welding travel speed to 0.6m / min to 1.0m / min. This parameter combination ensures full penetration welding can still be achieved in low heat input mode, and the segmented path further controls the heat input below the material deformation threshold.

[0055] See attached document Figure 1 and attached Figure 2 The present invention provides an assembly control module configured to coordinate the process logic and quality threshold of the entire welding operation. By decoupling the timing of assembly constraints and quantifying the pre-welding state, it provides process-level assurance for welding deformation control.

[0056] The assembly control module's process flow first establishes a strict entry inspection mechanism. Before the rear runner and side panel are physically assembled, or before initial positioning but before applying full distributed clamping force, a fit inspection step is performed. This inspection step aims to identify geometric deviations in the mating surfaces caused by stamping springback or previous processes.

[0057] Specifically, the fit detection focuses on the parallelism error between the mating surfaces to be welded. In this embodiment, the measurement reference length is set to 200mm. Within this reference length, the mating gap is sampled at multiple points using a gap measuring tool (such as a feeler gauge or laser profile scanner). The system's set process threshold is a parallelism error of less than 0.2mm. Only when the mating gap between the rear drainage channel and the side outer panel meets the above threshold condition under natural conditions or with a small preload, will the assembly control module allow the subsequent welding process to begin. This threshold is set to ensure the stability of the droplet transfer during welding, preventing melt-through due to excessive gaps or the introduction of excessive initial elastic potential energy due to forced compression of large gaps. This initial elastic potential energy is often one of the main driving forces for deformation caused by post-weld stress release.

[0058] If the parallelism error measured during the fit test exceeds the process threshold of 0.2mm, the assembly control module will trigger a correction procedure. This correction procedure includes: first, releasing the clamping arm and checking for foreign objects or burrs between the workpiece positioning hole and the clamping positioning pin; if the error still exceeds the standard after cleaning, adjusting the fine-tuning shims on the clamping reference surface or replacing the out-of-tolerance rear runner part is performed until the parallelism error measured again falls within the acceptable range of 0.2mm before the lockout is released and a welding start signal is sent.

[0059] After passing the fit test, the assembly control module executes specific sequential assembly logic. This logic breaks down the complex assembly welding process of multiple parts into sub-processes implemented step by step.

[0060] First, the first stage of assembly and welding is performed. The rear drainage channel and the side panel are positioned in the tooling clamping module, and the clamping arms are used to press them onto the heat dissipation metal block. The welding execution module then performs cold metal transition welding. During this stage, other related components such as the taillight mounting plate are not involved in the assembly or welding. After the welding cools down, the rear drainage channel and the side panel solidify and connect, forming a relatively stable side panel process sub-assembly.

[0061] Next, the second stage of assembly is performed. Based on the side panel assembly, a taillight mounting plate is introduced for positioning and matching. At this point, since the relative positions of the rear diffuser and the side panel have already been fixed by welding, eliminating the degree of freedom between these two parts, the assembly of the taillight mounting plate only needs to adapt to the existing geometry of this assembly. Finally, the taillight mounting plates are welded together.

[0062] The core technical principle of this step-by-step assembly strategy lies in preventing tolerance accumulation and stress coupling. If the traditional process of positioning and clamping the rear water channel, side panel, and taillight mounting plate all at once before welding is used, the manufacturing tolerances of the three parts will overlap, causing interference between the positioning references. This forces the tooling to apply enormous constraint forces to correct the part positions, thus pre-setting extremely high assembly stress within the workpiece before welding. This embodiment, by first forming sub-assemblies and then integrating accessories, decouples the complex constraint relationships between the three into two relatively simple two-body constraint relationships, ensuring that each welding process is performed under low-stress constraint.

[0063] See attached document Figure 1 and attached Figure 2 In order to verify the actual engineering effect of the cold metal transition welding deformation control method and system for automotive steel plates provided by the present invention, this embodiment constructs a specific application verification scenario, selects the connection process between the rear water channel and the side outer panel of a certain model as the verification object, and sets up a control group and an experimental group for quantitative comparison.

[0064] In this verification embodiment, the experimental group strictly followed the technical solution of the present invention. Specific process parameters were set as follows:

[0065] Regarding the workpiece structure, the experimental group selected DC04 deep-drawing steel as the material for the backflow channel plate, with a plate thickness of 1.4mm. A long strip-shaped stamped boss with a height of 1.5mm was prefabricated as a local reinforcement structure at a position 8mm away from the center line of the cold metal transition weld.

[0066] In terms of welding path planning, the welding execution module is programmed to execute a segmented intermittent welding strategy, where the length of a single weld segment is set to 30mm and the length of the interval between adjacent non-welding sections is set to 15mm.

[0067] In terms of tooling configuration, the tooling clamping module uses a heat-dissipating metal block made of T2 copper, with its edge 5mm away from the edge of the weld bead, and is internally circulated with cooling water at a flow rate of 5L / min and a temperature of 20℃. The clamping force applied by the clamping arm is set to 500N to ensure low thermal resistance at the contact interface.

[0068] In terms of assembly logic, the process of welding the side panel outer assembly first, and then welding the taillight fixing plate is followed, and the parallelism error of the pre-welding inspection is controlled within 0.15mm.

[0069] In contrast, the control group adopted the existing conventional process. The specific parameters were: the thickness of the post-flow trough plate was 0.8mm, with no local reinforcement structure; a continuous straight welding path was used; ordinary carbon steel support blocks were used, without active water cooling circulation; and a one-time full-sequence assembly followed by welding process was adopted.

[0070] After the welding operation is completed, a coordinate measuring machine (CMM) is used to perform multi-point scanning measurement of the out-of-plane deformation (i.e., the warping displacement perpendicular to the plate surface) of the weld area of ​​the two sets of workpieces.

[0071] The scanning results showed that after the weld cooled, the control group workpiece exhibited obvious wavy deformation along the length of the weld, with a maximum deformation of 1.85 mm, accompanied by twisting due to the release of assembly stress, which exceeded the allowable range of the vehicle matching tolerance (usually ±0.5 mm).

[0072] In contrast, the maximum deformation of the experimental group workpiece at the same location was only 0.28 mm, and the overall contour maintained the geometric characteristics of the design model without any visible warping or twisting.

[0073] Data analysis shows that the deformation in the experimental group was reduced by approximately 85% compared to the control group. This difference confirms that the present invention effectively controls the thermal deformation problem during the cold metal transition welding process of thin plates through the synergistic effect of multiple means such as increasing local stiffness, discretizing heat input, forced heat dissipation, and decoupling assembly stress, so that the dimensional accuracy of the final product meets the high standard manufacturing requirements of body-in-white.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling deformation during cold metal transfer welding of automotive steel sheets, characterized in that, Includes the following steps: Step S1: Set the plate thickness of the back flow channel to a predetermined reinforcement thickness, and set a local reinforcement structure on the back flow channel within a predetermined distance range relative to the center line of the cold metal transition weld bead; Step S2: Plan the connection weld between the rear water channel and the side outer panel as a segmented intermittent welding path consisting of several single-segment welds and non-welded intervals. Step S3: Configure the welding fixture, and set a heat dissipation metal block with a conformal curved surface on the welding fixture. The heat dissipation metal block is arranged on the back or both sides of the cold metal transition weld, and the heat dissipation metal block is provided with a circulating cooling channel inside. Step S4: Position and fit the rear water channel and the side panel according to the predetermined assembly sequence. Use the clamping arm to press the workpiece onto the heat dissipation metal block and perform cold metal transition welding.

2. The method for controlling deformation during cold metal transfer welding of automotive steel sheets according to claim 1, characterized in that, In step S1, the thickness of the sheet material of the rear water trough is set to a range of 1.2mm-1.5mm.

3. The method for controlling deformation during cold metal transfer welding of automotive steel sheets according to claim 1, characterized in that, In step S1, the local reinforcement structure is a stamped boss or an enlarged rounded corner structure, and the vertical distance from the edge of the local reinforcement structure to the center line of the cold metal transition weld is in the range of 5mm-15mm.

4. The method for controlling deformation during cold metal transfer welding of automotive steel sheets according to claim 3, characterized in that, When the local reinforcement structure is a stamped boss, the height of the stamped boss ranges from 1.0mm to 2.0mm. When the local reinforcement structure is an enlarged rounded corner structure, the radius of the enlarged rounded corner structure is greater than 8mm.

5. The method for controlling deformation during cold metal transfer welding of automotive steel sheets according to claim 1, characterized in that, In step S2, the parameters of the segmented intermittent welding path are set as follows: the length of a single weld segment is in the range of 20mm-40mm, and the length of the non-welding interval between two adjacent weld segments is in the range of 10mm-20mm.

6. The method for controlling deformation during cold metal transfer welding of automotive steel sheets according to claim 1, characterized in that, In step S3, the heat dissipation metal block is made of T2 copper, and the horizontal distance from the edge of the heat dissipation metal block to the edge of the cold metal transition weld is in the range of 3mm-8mm.

7. The method for controlling deformation during cold metal transfer welding of automotive steel sheets according to claim 1, characterized in that, In step S4, the predetermined assembly sequence is as follows: The rear water channel is matched with the side panel and cold metal transition welding is completed to form the side panel process sub-assembly; The side panel assembly is welded together with the taillight mounting plate.

8. The method for controlling deformation during cold metal transfer welding of automotive steel sheets according to claim 1, characterized in that, In step S4, the fit detection includes: Before welding, measure the parallelism error between the matching surfaces of the rear water channel and the side outer panel to be welded. When the measurement reference length is 200mm, the parallelism error must be less than 0.2mm before welding can begin.

9. The method for controlling deformation during cold metal transfer welding of automotive steel sheets according to claim 1, characterized in that, In step S4, the step of pressing the workpiece onto the heat dissipation metal block using the clamping arm includes: Mechanical pressure is applied by the clamping arm to eliminate the air gap between the workpiece and the heat dissipation metal block, and the welding heat is carried away by the cooling medium in the circulating cooling channel.

10. A cold metal transition welding deformation control system for automotive steel sheets, characterized in that, The method for controlling deformation during cold metal transfer welding of automotive steel sheets as described in any one of claims 1-9 includes: The workpiece structure module includes a rear drainage channel with a plate thickness of 1.2mm-1.5mm and local reinforcement within a range of 5mm-15mm from the weld centerline; The welding execution module is used to drive the welding torch to perform cold metal transition welding on the rear water channel and the side outer panel according to the segmented intermittent welding path with a single weld length of 20mm-40mm and an interval length of 10mm-20mm. The tooling clamping module includes a welding fixture, which is provided with a heat dissipation metal block that conforms to the weld area and a clamping arm for applying pressure. The heat dissipation metal block has an integrated circulating cooling channel inside. The assembly control module controls the welding process to ensure that the rear water channel and the side panel are welded together before the taillight mounting plate.

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