Low-deformation precision straightening and residual stress regulation and control process for steel

Abstract

The invention relates to a steel low-deformation precision straightening and residual stress regulation and control process which comprises the steps of surface pretreatment and non-contact precision detection, asymmetric subsection gradient flexible clamping, normal-temperature trace presetting, intermittent micro-amplitude alternating straightening, synchronous interface stress slow release, external-force-free self-adaptive relaxation, closed-loop regulation and control, flexible shape stabilization and final detection. Synchronous operation of straightening and stress regulation and control is achieved, a traditional strong deformation and subsequent heat treatment mode is abandoned, flexible wide face contact, staggered alternating straightening and asymmetric stress dredging are adopted, and low-plasticity micro-deformation is controlled in the whole process. According to the method, steel surface damage and stress concentration are effectively avoided, the rebound rate after straightening is greatly reduced, residual stress distribution is more uniform, high-temperature treatment is not needed, the performance of a steel matrix is not changed, the procedure is simplified, energy consumption is lower, the method is suitable for machining of various kinds of precise steel, and the size precision and long-acting stability are improved.

Description

Technical Field

[0001] This invention belongs to the field of steel processing technology, and in particular relates to a process for precision straightening of steel with low deformation and control of residual stress. Background Technology

[0002] Precision straightening and residual stress control of steel are core processes in the processing of high-end profiles and precision structural components, directly determining the dimensional accuracy and subsequent stability of the workpiece. Currently, the mainstream steel straightening processes in the industry mostly employ continuous roller straightening, overall tension bending straightening, or a combination of straightening and high-temperature tempering. These methods have many inherent drawbacks in practical production applications. Firstly, conventional continuous roll forming and tension bending processes are strong plastic deformation straightening processes with large single deformation, which can easily lead to stress concentration and extremely uneven stress distribution inside the steel. Subsequent workpieces are prone to springback deformation and dimensional deviations. Furthermore, rigid roll forming and overall clamping methods can easily cause indentations and local plastic depressions on the steel surface, damaging the surface quality of the workpiece. Secondly, existing processes mostly adopt a step-by-step approach of straightening and stress relief. After straightening, residual stress is treated by means of high-temperature tempering, vibration aging, etc. This process is lengthy and energy-intensive. Moreover, high-temperature treatment can easily change the metallographic structure of the steel matrix and affect the mechanical properties of the material itself. Vibration aging and other methods are difficult to achieve stress uniformity across the entire range. They can only reduce local stress peaks and cannot solve the springback problem from the root. Third, conventional straightening processes are mostly fixed parameters and continuous reciprocating operations, lacking segmented flexible constraints and dynamic closed-loop control. They have poor adaptability to different specifications and materials of steel, making it difficult to achieve low deformation and high precision collaborative control, and thus failing to meet the processing needs of high-end precision steel.

[0003] Therefore, developing a low-deformation precision straightening and residual stress synergistic control process that can avoid the above-mentioned defects has become a technical problem that urgently needs to be solved in the industry. Summary of the Invention

[0004] The purpose of this invention is to provide a process for precision straightening of steel with low deformation and control of residual stress, so as to solve the problems mentioned in the background art.

[0005] In view of this, the present invention provides a process for precision straightening and residual stress control of steel with low deformation, comprising the following steps: S1: Perform surface pretreatment on the steel to be straightened to remove surface impurities. Use a three-dimensional laser profilometer and eddy current stress detector to detect the initial straightness and residual stress distribution, and establish a deformation and stress database. S2: Based on the detection data, the steel is subjected to asymmetric segmented flexible constraint clamping, forming a gradient constraint along the feed direction. The constraint force changes gradually to avoid rigid extrusion and stress concentration. S3: The steel under constraint is finely adjusted by a predetermined displacement at room temperature. Macroscopic warping and bending are eliminated by a small amount of axial traction and radial limiting, and the deformation is controlled in the low plasticity range. S4: Intermittent micro-amplitude alternating straightening is used to alternately straighten steel in sections, controlling the stroke and pause interval to avoid stress increase and secondary deformation caused by continuous large deformation; S5: Simultaneous interface stress relief is implemented during alternating straightening. By breaking the closed field of residual stress through flexible stress diversion, the stress gradient is reconstructed in a uniform manner. S6: After single-pass straightening and slow release, adaptive stress relaxation and static setting are performed to allow internal stress to self-balance in a closed constant temperature environment without external force or friction, thus suppressing post-straightening rebound. S7: After the steel has been left to stand, perform flatness and stress spot checks, and dynamically adjust subsequent process parameters according to the deviation to form a closed-loop control. S8: Overall stabilization treatment for steel, weakening stress peaks, solidifying flatness, and preventing springback during subsequent storage and processing; S9: Perform precision and stress final inspection on finished steel products, archive process parameters, and formulate a special straightening and stress control plan for steel of this specification.

[0006] In a further embodiment of the present invention, the asymmetric segmented flexible constraint clamp described in S2 is specifically divided into at least three independent flexible constraint units along the length of the steel. Each unit adopts a polymer elastic pressure block in conjunction with a pneumatically adjustable support seat. The constraint stiffness difference between adjacent units is constant, and the stiffness of the end constraint unit is greater than that of the middle section, forming an arrangement of tightness at both ends and slow release in the middle, which prevents lateral movement and surface plastic depression during straightening.

[0007] In a further embodiment of the present invention, the polymer elastic pressure block and the steel are in full-fit wide-surface contact, and the contact pressure is dynamically controlled by pneumatic closed loop to adapt to the thickness and strength of the steel. There are no indentations or local damage in the contact area, thus blocking the stress transmission and superposition caused by rigid contact.

[0008] In a further embodiment of the present invention, the intermittent micro-amplitude alternating straightening described in S4 specifically involves dividing the steel into multiple parallel straightening strips along the width direction, using a single-point moving straightening mechanism to straighten the steel in staggered alternations segment by segment, with each downward pressure being on the order of micro-scale and the pause duration being fixed, and the straightening actions of adjacent straightening strips having a phase difference to avoid repeated deformation in the same area.

[0009] In a further embodiment of the present invention, the single-point moving straightening mechanism is equipped with an arc-shaped flexible straightening head that makes arc-shaped flexible contact with the steel. The contact arc length is adapted to the width of the steel, and the straightening is without rigid impact. The trajectory gradually changes along the length direction.

[0010] In a further embodiment of the present invention, the interface stress relief treatment described in S5 specifically involves the simultaneous rolling of multiple sets of flexible guide rollers along the upper and lower surfaces of the steel during straightening, with the roller speed matching the feeding and straightening rhythm, and the roller surface being provided with uniform arc-shaped micro-grooves to achieve stress relief and dispersion layer by layer.

[0011] In a further embodiment of the present invention, the contact pressure of the flexible guiding roller is lower than that of the straightening head, and the upper and lower rollers are arranged in an alternating manner to form an asymmetric guiding path, thereby breaking the symmetrical distribution of residual stress and decomposing the high-amplitude peak stress into uniform low-amplitude stress throughout the entire domain.

[0012] In a further embodiment of the present invention, the staged adaptive stress relaxation settling described in S6 specifically involves transferring the steel to a sealed constant temperature settling table after a single pass is completed. The table surface is a frictionless smooth support, and there is no external force, vibration, or temperature field interference throughout the process. The settling time is adaptively set according to the material and specifications, and there is no cold or hot interference throughout the process.

[0013] In a further embodiment of the present invention, the real-time sampling inspection and closed-loop control described in S7 adopts the same three-dimensional laser profilometer as in S1 in conjunction with the eddy current stress detector. The detection points are evenly distributed in a matrix, and the data is transmitted to the control system in real time. When the deviation exceeds the standard, the subsequent alternating amplitude is automatically reduced and the stress relief time is extended to achieve adaptive fine-tuning of parameters.

[0014] In a further embodiment of the present invention, the homogenization and stabilization treatment described in S8 involves using a breathable polymer flexible wrapping layer for full-area light pressure fixation, constant pressure for a preset time, without applying additional deformation force, relying on external uniform constraints in conjunction with internal stress self-balancing, to further reduce stress peak and solidify flatness.

[0015] The beneficial effects of this invention are: 1. Compared to existing straightening processes involving strong plastic deformation such as continuous rolling and overall tension bending, this invention uses asymmetric segmented gradient flexible constraints combined with intermittent micro-amplitude alternating straightening to control the deformation of the steel within the low plasticity micro-deformation range throughout the process. Combined with the wide-faced flexible contact of the polymer elastic pressure block and the progressive straightening trajectory of the arc-shaped flexible straightening head, it fundamentally eliminates the surface indentations and localized plastic depressions on the steel caused by conventional rigid clamping and continuous strong pressure. Simultaneously, it avoids the sharp increase in internal stress and localized stress concentration caused by continuous large deformation. Compared to traditional processes, the surface integrity rate of the steel during straightening is significantly improved, the flatness control accuracy of the finished product is higher, the dimensional deviation is smaller, and the adaptability for subsequent processing is stronger.

[0016] 2. Compared to the traditional process of separate straightening and stress relief, combined with high-temperature tempering, this invention achieves simultaneous intermittent straightening and interface stress relief. Combined with adaptive relaxation and resting in a closed, temperature-controlled environment without external force or friction after each pass, it eliminates the need for high-temperature heating treatment, preserving the original metallographic structure and matrix mechanical properties of the steel. Furthermore, the use of staggered flexible guide rollers enables asymmetric stress relief, breaking down localized high-amplitude residual stress into uniformly distributed low-amplitude stress across the entire surface. This eliminates the need for a separate heat treatment process, shortens the overall processing flow, reduces production energy consumption, and simultaneously suppresses post-straightening springback at its source. The resulting residual stress homogenization is superior, significantly reducing the deformation springback rate during long-term storage and subsequent processing. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0018] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," and "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0019] This embodiment provides a process for precision straightening and residual stress control of steel with low deformation, including the following steps: S1: Surface pretreatment is performed on the steel to be straightened to remove surface impurities. Initial straightness and residual stress distribution are detected using a 3D laser profilometer and eddy current stress detector to establish a deformation and stress database. This step is a pre-processing step. The steel to be straightened is first smoothly hoisted to the pretreatment station. A dust-free nylon brush is used to thoroughly clean the steel along its length and width, combined with 0.4-0.6MPa high-pressure inert gas blowing throughout the process to completely remove oxide scale, dust, cutting oil, burrs, and sharp debris from the steel surface, avoiding scratches or interference with subsequent testing accuracy. After pretreatment, the steel is transferred to a non-contact testing station, where the 3D laser profilometer scans the steel at a constant speed along its entire length. The scanning speed is matched with the uniform feed speed of the steel, and the contour coordinate data of the entire length and width are collected synchronously to accurately locate the position and degree of macroscopic warping, lateral bending, and local bending. The eddy current stress detector is evenly distributed with detection probes along the upper and lower surfaces of the steel section to collect the internal residual stress values, peak positions and distribution gradients in a non-contact manner. The detection data of the two types of equipment are transmitted synchronously to the matching industrial control computer in real time. After system integration, the data is classified and archived according to the steel material, specifications and initial defect level to establish a dedicated initial deformation-residual stress correlation database, which provides accurate data support for the setting of parameters for all subsequent processes. After completion, the command is automatically triggered to transfer the steel to the clamping station. This step connects to the S2 clamping process.

[0020] S2: Based on the detection data, asymmetric segmented flexible constraint clamping is applied to the steel, forming a gradient constraint state along the feed direction. The constraint force gradually changes from the feed end to the discharge end to avoid rigid extrusion and stress concentration. This step follows the detection completion instruction from S1. The industrial control computer automatically matches the corresponding segmented constraint parameters according to the database established in S1 and sends them to the clamping execution mechanism. After the clamping mechanism is started, the steel is stably placed on the segmented constraint base along the feed direction of the steel length. Each segment constraint unit moves synchronously, and a polymer elastic pressure block is used to slowly press down and adhere the steel. The steel surface is completely free of rigid metal contact and instantaneous high-pressure impact. The constraint force is set linearly and gradually from the feed end to the discharge end. The pressure is controlled in a closed loop by the pneumatic system throughout the process to prevent local single-point overload compression. After clamping, the system automatically verifies the constraint status and pressure value. Once it is confirmed to be qualified, the constraint parameters are locked to ensure that the steel is firmly fixed without loosening or excessive compression, which prepares for subsequent fine-tuning of the predetermined displacement. This step is seamlessly connected with the S3 fine-tuning process, which is different from the traditional overall rigid clamping and avoids stress concentration and surface damage from the source.

[0021] S3: Fine-tune the predetermined displacement of the constrained steel at room temperature. Macroscopic warping and bending are eliminated through minute axial traction and radial multi-point limiting, controlling the deformation within the low plasticity range. This step begins after successful clamping in S2 and is conducted entirely in a natural room temperature environment without any external interference such as heating, cooling, or vibration. The axial pneumatic micro-traction device is activated to apply a gentle and constant axial traction force to the end of the steel. The traction force is set to 1 / 10-1 / 8 of the steel's yield strength, far below the critical value for plastic deformation. Simultaneously, the radial multi-point flexible limiting blocks are activated, moving along the steel... The material is evenly distributed and slowly pushed up in the width direction. It is precisely fine-tuned for the macroscopic warping and local bending points detected by S1, eliminating only macroscopic visible defects without deep deformation correction. The deformation is monitored in real time throughout the process, and the deformation of each time is strictly controlled to be in the low plasticity micro-deformation range, with elastic deformation as the main component and extremely small plastic deformation as a supplement. After the fine-tuning is completed, the radial limit block is kept in place for support, and the axial traction force is kept constant to ensure that the steel is in a flat benchmark state and directly enters the S4 straightening process. This completely abandons the traditional strong pressure and strong tension large plastic deformation mode and avoids sudden stress increase.

[0022] S4: Intermittent micro-amplitude alternating straightening is used to alternately straighten the steel in sections, controlling the stroke and pause intervals to avoid stress spikes and secondary deformation caused by continuous large deformations. This step follows the S3 fine-tuning pass signal; the straightening actuator starts, automatically dividing the steel into multiple parallel independent straightening zones along its width, with the number of zones adaptively set according to the steel width. The single-point moving straightening mechanism receives instructions from the industrial control computer and moves sequentially to the corresponding straightening zone area according to the defect points detected in S1, performing a single short-stroke micro-amplitude downward straightening. The single straightening stroke is controlled within a millimeter-level micro-range. The speed is smooth and impact-free; after a single straightening action is completed, the mechanism automatically stops and enters a fixed-duration pause buffer. The pause duration is adaptively set according to the steel material to reserve buffer space for the internal stress of the steel; the straightening actions of adjacent straightening zones are set with a fixed phase difference, and the operation is staggered and alternately segment by segment, without being synchronous, discontinuous, or repeatedly acting on the same area; after a single steel bar is straightened in a single pass, the mechanism resets, pauses the straightening action, and directly connects to the S5 synchronous stress relief. There is no continuous large deformation throughout the process, which is different from the traditional continuous reciprocating straightening and fundamentally eliminates the sudden increase in stress and secondary deformation.

[0023] S5: Interfacial stress relief is implemented simultaneously with alternating straightening. Flexible stress guidance breaks the closed field of residual stress, achieving uniform reconstruction of the stress gradient. This step, with its simultaneous start, operation, and end, is identical to the intermittent micro-amplitude alternating straightening of S4, without time difference or step-by-step operation. This is the biggest difference between this process and existing processes that involve straightening first and then stress relief. Simultaneously with the S4 straightening mechanism, multiple sets of flexible guiding rollers start synchronously, rolling uniformly along the upper and lower surfaces of the steel. The roller speed is calibrated by the system to perfectly match the steel feed speed and the rhythm of the straightening mechanism, with no relative sliding or dragging friction. The flexible guide roller applies a gentle guiding force to the steel surface through the arc-shaped micro-grooves on the roller surface, forming a continuous guiding path along the length of the steel, gradually breaking the closed residual stress field formed by the previous processing and pre-adjustment deformation; the guiding process does not forcibly eliminate stress, but only guides and disperses the locally concentrated stress layer by layer, reconstructing a smooth and uniform stress gradient over the entire area; when the S4 straightening action stops, the flexible guide roller simultaneously completes the guiding operation of the current area, maintaining low speed until the entire section of a single pass is completed, and then stops, directly connecting to the S6 static resting process, realizing the simultaneous completion of straightening and stress control, making the process more efficient.

[0024] S6: After single-pass straightening and slow release, adaptive stress relaxation and static placement are performed. Under a closed, constant-temperature environment without external force or friction, the internal stress autonomously balances, suppressing post-straightening rebound. This step is initiated after all single-pass operations (S4 and S5) are completed. First, the S2 segmental flexible constraint and S3 radial limit are released. The steel is then smoothly lifted to the closed, constant-temperature static placement table using a non-destructive suction cup. The lifting process is free from bumps, pulling, and additional forces. The table surface is made of highly polished, smooth ceramic material with a friction coefficient approaching zero. After the steel is placed flat on the table, there is no external clamping, squeezing, or pulling. The static space is sealed and kept at a constant temperature, with no airflow disturbance, vibration, temperature fluctuation, or electromagnetic interference. The static time is automatically set by the system based on the steel material, cross-sectional specifications, and single-pass deformation. During the static period, there is no manual intervention or external auxiliary means, and the steel relies entirely on the internal residual stress to adapt and balance autonomously. After the static time is completed, the system automatically sends a completion signal, preparing to enter the S7 sampling inspection process. Compared with traditional heating aging and vibration aging, this step is a purely physical autonomous relaxation that does not change the metallographic structure of the steel and has a better rebound suppression effect.

[0025] S7: After the steel has been left to stand, a flatness and stress test is performed. Subsequent process parameters are dynamically adjusted based on deviations to form a closed-loop, precise control system. This step begins after the standing timer in S6. The steel is transferred to a non-contact inspection station, where a 3D laser profilometer and eddy current stress analyzer (the same type used in S1) are used in conjunction. Inspection points are evenly distributed in a matrix along the length and width of the steel, eliminating blind spots. Inspection data is transmitted to the industrial control computer in real time. The system automatically compares the measured values ​​with preset acceptable thresholds to quickly determine whether the flatness and residual stress meet the standards. If the test data is without deviation, the system locks the current process parameters and prepares to proceed to the next pass or the S8 stabilization process. If the deviation exceeds the standard, the system automatically calculates the deviation value and adjusts the constraint force, straightening alternation amplitude, pause interval, and stress relief duration of subsequent passes in real time. It automatically reduces the straightening amplitude and extends the relief duration to achieve adaptive fine-tuning of parameters. After the adjustment is completed, the system issues an instruction to repeat the S2-S6 process, forming a complete closed loop of "detection-feedback-adjustment-rework" until the parameters meet the standard, ensuring that the straightening accuracy is controllable throughout the process.

[0026] S8: Overall stabilization treatment of the steel to weaken stress peaks, solidify straightness, and prevent springback during subsequent storage and processing. This step is initiated after the S7 sampling inspection is passed. The steel is transferred to the stabilization station and wrapped with a breathable polymer flexible wrapping layer, ensuring full coverage without any blind spots. The wrapping layer has moderate tightness, and a constant, uniform, light pressure is applied to the steel surface without applying any straightening or deformation force or making secondary deformation adjustments. After wrapping, the steel is placed in a normal temperature and pressure environment for a preset stabilization time. Relying on the uniform external constraint, the residual stress inside the steel further balances itself, continuously weakening the residual stress peaks and making the stress distribution more uniform. After the stabilization time is completed, the flexible wrapping layer is removed, and the steel maintains its final straight shape, completing the straightness solidification and completely preventing stress springback during subsequent storage, transportation, and secondary processing. This step connects to the S9 final inspection process, making up for the shortcomings of traditional processes that lack stabilization and are prone to springback.

[0027] S9: Perform precision and stress final inspection on the finished steel, archive process parameters, and form a dedicated straightening and stress control scheme for this specification of steel. This step is the final closing stage of the process. Following the S8 stabilization completion signal, the steel is transferred to the final inspection station for a full-size, full-area residual stress final inspection. The inspection items cover the straightness of the entire length, the tolerance of the cross-section dimensions, the stress distribution of the entire cross-section, and the surface integrity, comprehensively verifying whether it meets the finished product standards. Steel that passes the final inspection is labeled with specifications and transferred to the finished product storage area. Steel that fails the final inspection is sorted separately, the defect type is marked, and it is returned to the corresponding process for readjustment. At the same time, the industrial control computer organizes and archives all the constraint parameters, straightening parameters, slow-release parameters, static parameters, and stabilization parameters of this production process, along with the corresponding steel material, specifications, and initial defect level, generating a dedicated process scheme. Subsequent steel of the same type can be directly called up to achieve batch precision production and complete the entire process closed loop.

[0028] In this embodiment, the asymmetric segmented flexible constraint clamping described in S2 specifically divides the steel material into at least three independent flexible constraint units along its length. Each unit uses a polymer elastic pressure block in conjunction with a pneumatically adjustable support base. The stiffness difference between adjacent units is constant, and the stiffness of the end constraint units is greater than that of the middle section, forming an arrangement with both ends tightened and the middle section released gradually, thus preventing lateral movement and surface plastic depressions during straightening. The three independent constraint units are specifically divided into a feeding end unit, a middle section unit, and a discharging end unit. The three sections are independent of each other, individually pneumatically driven, and referenced. Individually adjustable; the pneumatically adjustable support base has a built-in pressure sensor that provides real-time feedback on constraint pressure, ensuring a constant and controllable stiffness difference; the feed and discharge end units have higher stiffness to ensure stable positioning of the steel at both ends, preventing lateral movement and forward / backward displacement during feeding and discharging; the middle section unit has lower stiffness to provide flexible deformation buffer space and avoid local pressure overload in the middle section; the edges of the polymer elastic pressure block are rounded to prevent sharp-edged scratches when fitting the steel, eliminating surface plastic dents, indentations, and scratches throughout the process, and adapting to various precision steel straightening needs.

[0029] In this embodiment, the polymer elastic pressure block and the steel are in full-fit, wide-surface contact. The contact pressure is dynamically controlled by a pneumatic closed-loop system to adapt to the steel thickness and strength. There are no indentations or local damage in the contact area, preventing stress transmission and superposition caused by rigid contact. The working surface of the polymer elastic pressure block adopts a wide-surface flat structure, with a working surface width slightly larger than the contact width of the steel, achieving full-surface contact. The contact area is 5-8 times that of traditional rigid clamp point / line contact, effectively dispersing local pressure. The pneumatic closed-loop system collects pressure data in real time and automatically adjusts the air pressure according to the steel thickness and yield strength, keeping the pressure error within a very small range to ensure that the pressure adaptation does not exceed the standard. The hardness of the pressure block material is lower than that of the steel surface, and there is no plastic deformation, indentation, or scratch in the contact area throughout the entire process. At the same time, it prevents stress transmission and superposition effects caused by rigid metal contact, further reducing the risk of internal stress concentration.

[0030] In this embodiment, the intermittent micro-amplitude alternating straightening described in S4 specifically involves dividing the steel into multiple parallel straightening strips along its width. A single-point moving straightening mechanism is used to straighten the steel in an alternating, segment-by-segment manner. Each downward pressure is on the order of micro-scales, with a fixed pause duration. The straightening actions of adjacent straightening strips are set with a phase difference to avoid repeated deformation in the same area. The number of straightening strips is adaptively adjusted according to the width of the steel; the wider the steel, the more strips are used. The single-point moving straightening mechanism is equipped with a servo drive system, ensuring high movement and positioning accuracy, and can precisely reach the defect location. The single downward pressure amplitude is on the order of micro-scales, correcting only localized minor defects without large-scale deformation. The fixed and uniform pause duration ensures sufficient stress buffering after each straightening segment. The phase difference between the actions of adjacent straightening strips is set to 180°, with alternating operations without overlap, completely avoiding repeated stress and deformation in the same area within a short period of time, minimizing stress accumulation, and ensuring a low-deformation straightening effect.

[0031] In this embodiment, the single-point moving straightening mechanism is equipped with an arc-shaped flexible straightening head that makes arc-shaped flexible contact with the steel. The contact arc length is adapted to the width of the steel, and the straightening is free from rigid impact. The trajectory gradually changes along the length direction. The arc-shaped flexible straightening head is made of a highly elastic polymer composite material, and the working surface is an arc-shaped curved surface. The curvature is adapted to the cross-sectional shape of the steel, and the contact arc length covers the effective width of the steel, making it fit tightly without gaps. The straightening head moves smoothly, with uniform speed throughout the pressing and resetting process, without rigid impact or mechanical collision. The straightening trajectory gradually changes linearly along the length direction of the steel, advancing step by step from the feeding end to the discharging end, without reciprocating cycles or localized repeated crushing, further reducing the risk of surface damage and stress concentration.

[0032] Existing methods employ rigid clamping and continuous large-stroke reciprocating straightening, with rigid clamps applying pressure through point / line contact. This results in large single-time deformation and continuous, uninterrupted operation, which can easily cause surface damage and internal stress concentration in the steel. This embodiment uses asymmetrical segmented flexible constraint clamping, combined with intermittent micro-amplitude misaligned alternating straightening. It features wide-face flexible contact, single-time micro-deformation, and intermittent buffering operation, controlling low-plasticity micro-deformation throughout the process. This is achieved through a three-step collaborative design: step S2, asymmetric segmented flexible constraint clamping; step S3, predetermined displacement fine-tuning; and step S4, intermittent micro-amplitude alternating straightening. First, step S2 divides the steel along its length into multiple independent flexible constraint units, designing a gradient constraint layout with high stiffness at both ends and low stiffness in the middle. This, combined with wide-faced flexible pressure blocks, disperses pressure, preventing rigid extrusion and stress concentration. Then, step S3 strictly controls the single-cycle deformation to be within the low plasticity range, eliminating macroscopic defects in advance and avoiding subsequent large deformation correction. Finally, step S4 designs short straightening strokes, fixed pause intervals, and phase differences between adjacent straightening zones to avoid continuous and repeated deformation in the same area. This comprehensive design from clamping to straightening reduces residual stress at the source and eliminates defects such as surface indentations and plastic depressions—something that existing rigid clamping and continuous straightening processes cannot achieve.

[0033] In this embodiment, the interface stress relief treatment described in S5 specifically involves multiple sets of flexible guide rollers rolling synchronously along the upper and lower surfaces of the steel during straightening. The roller speed is precisely matched with the feed and straightening rhythm. The roller surface is provided with uniform arc-shaped micro-grooves to achieve stress relief and dispersion layer by layer. The flexible guide rollers are symmetrically arranged vertically, and the number is adapted to the length of the steel. The roller body material is consistent with the straightening head to avoid scratching the steel. The arc-shaped micro-grooves on the roller surface are evenly distributed, with uniform groove depth and width, forming a continuous micro-guiding channel during rolling without damaging the integrity of the steel surface. The upper and lower rollers roll synchronously in the same direction, and the guiding force is uniform and gentle, acting only on stress relief and not participating in deformation correction. Straightening and stress dispersion are completed simultaneously without additional processes, greatly improving production efficiency.

[0034] In this embodiment, the contact pressure of the flexible guide roller is lower than that of the straightening head, and the upper and lower rollers are arranged in an alternating manner to form an asymmetric guide path. This breaks the symmetrical distribution of residual stress and decomposes the high-amplitude peak stress into uniform low-amplitude stress throughout the entire process. The contact pressure of the flexible guide roller is set to 1 / 3 to 1 / 2 of the straightening head pressure, providing only gentle guidance without generating additional deformation. The upper and lower guide rollers are staggered and arranged without any vertical correspondence, forming an asymmetric and nonlinear guide path. This breaks the original symmetrical residual stress field inside the steel, gradually decomposes and evenly disperses the local high-amplitude stress peaks, transforming them into a low-amplitude, gently distributed stress state throughout the entire process. This completely solves the core pain point of excessively high and unevenly distributed stress peaks in traditional processes.

[0035] In this embodiment, the staged adaptive stress relaxation settling described in S6 specifically involves transferring the steel to a sealed constant-temperature settling table after each pass. The table surface is a frictionless, smooth support, and there is no external force, vibration, or temperature field interference throughout the process. The settling time is adaptively set according to the material and specifications, and the entire process is conducted at room temperature without any hot or cold interference. The sealed constant-temperature settling table is equipped with a temperature control system, and the temperature fluctuation is controlled within ±1℃ to ensure a constant environment. The table surface is made of polished ceramic material with a friction coefficient ≤0.01, so there is no frictional resistance after the steel is placed. The settling time is set according to the toughness grade of the material, with a longer time for high-strength steel and a moderate time for ordinary carbon steel. There is no heating, cooling, vibration, or external magnetic field throughout the process, and it relies entirely on the self-balancing of internal stress without changing the metallographic structure and mechanical properties of the steel. The energy consumption is far lower than that of traditional heat treatment aging.

[0036] Existing methods often employ forced stress relief techniques such as high temperature, vibration, and ultrasound after straightening. These methods can only reduce local stress peaks and cannot achieve uniform stress distribution across the entire area, making it prone to secondary stress accumulation. In this embodiment, stress relief is achieved without any forced external force throughout the process. Peak stress is dissipated by synchronous stress diversion, resulting in uniform reconstruction of the stress gradient across the entire area and more uniform and stable stress control. The core relies on the synchronous linkage design of step S5 (interface stress relief) and step S4. S5, as a dedicated stress control step, operates synchronously with the straightening step S4. Through the design of flexible guide rollers arranged in an alternating pattern, arc-shaped micro-grooves on the roller surface, and a guide pressure lower than the straightening pressure, an asymmetric stress relief path is formed. While performing micro-straightening in S4, the original closed residual stress field inside the steel is broken, and the local high-amplitude stress is gradually relieved and dispersed throughout the entire area, rather than forcibly eliminating the stress. At the same time, in conjunction with the self-relaxation without external force in step S6, the stress distribution is further balanced. No additional heat treatment or vibration assistance is required throughout the process. Only through the synchronous coupling design of S4 and S5, the residual stress is uniformly reconstructed, completely solving the problem of uneven stress distribution in existing processes.

[0037] In this embodiment, the real-time sampling inspection and closed-loop control described in S7 uses the same three-dimensional laser profilometer as in S1, combined with an eddy current stress detector. The detection points are evenly distributed in a matrix, and the data is transmitted to the control system in real time. When the deviation exceeds the standard, the subsequent alternation amplitude is automatically reduced and the stress relief time is extended to achieve adaptive fine-tuning of parameters. The sampling equipment is completely consistent with the initial detection equipment in S1 in terms of model, parameters, and calibration standards, ensuring data uniformity and comparison accuracy. The matrix detection points are evenly spaced, with no blind spots. The system has a built-in deviation judgment algorithm, which has a fast response speed and accurate parameter adjustment. No manual operation is required, realizing intelligent closed-loop control of the entire process. It is suitable for steel of different specifications and materials, and the product consistency is far higher than that of traditional manual adjustment processes.

[0038] In this embodiment, the homogenization and stabilization treatment described in S8 employs a breathable polymer flexible wrapping layer for full-area light pressure fixation, with constant pressure and static placement for a preset time. No additional deformation force is applied during the stabilization process. Relying on external uniform constraints combined with internal stress self-balancing, the stress peak is further reduced and the straightness is solidified. The breathable polymer flexible wrapping layer has the characteristics of being breathable and moisture-proof, having moderate elasticity, and leaving no sticky residue. After full-area wrapping, a constant and uniform light pressure is applied, and the pressure magnitude remains constant. The static placement time is set according to the stress control effect to ensure that the internal stress is completely stable. No deformation correction force is applied throughout the process. Only through external constraints combined with internal balance, the residual stress peak is further weakened, and the straightness is permanently solidified, ensuring that there is no rebound or dimensional deformation during subsequent long-term storage and secondary processing.

[0039] Existing steel products all adopt a step-by-step process logic of "first strong plastic deformation straightening, then separate auxiliary stress relief". Straightening and residual stress control are two completely independent processes, which are lengthy and easily damage the steel matrix properties. This embodiment adopts a closed-loop process of "straightening and stress relief synchronous coupling + autonomous stress relaxation without external force", which realizes low deformation straightening and stress uniformity control at the same time, without the need for subsequent high temperature tempering, vibration aging and other additional stress relief processes. By synchronously linking step S4 (intermittent micro-amplitude alternating straightening) with step S5 (interface stress relief), the two core processes are started, run, and terminated simultaneously, completely breaking the existing pattern of separate implementation of straightening and stress relief. Relying on the coherent connection of step S6 (single-pass adaptive stress relaxation and static setting) and step S8 (overall homogenization and stabilization), and in conjunction with step S7 (real-time sampling and closed-loop control), a closed-loop process is formed. This abandons the idea of ​​"first creating stress through strong deformation and then forcibly eliminating stress." By relying on multi-step synergy, the integrated management of deformation correction and residual stress control is achieved, ensuring straightening accuracy while fully preserving the original metallographic structure and mechanical properties of the steel.

[0040] For example, a rectangular profile of 45# precision carbon structural steel, commonly used in the industry, is selected as the workpiece to be processed. Its specific specifications are: length 6000mm, width 80mm, and thickness 10mm. Initially, it exhibits slight lateral bending along its entire length and localized small-scale warping defects. The initial surface has a small amount of cutting oil and oxide dust. Complete straightening and stress control operations are performed according to the process steps of this invention. The specific implementation process is as follows: S1: Surface pretreatment and initial inspection First, the 6000mm long No. 45 steel profile is smoothly hoisted to the pre-treatment station. A dust-free nylon brush is used to thoroughly clean the profile along its length, combined with 0.5MPa high-pressure nitrogen blowing throughout the process, to completely remove surface cutting oil, oxidation dust, and fine burrs from the edges. After pre-treatment, the profile is transferred to the non-contact inspection station. A 3D laser profilometer is started to scan the profile at a uniform speed of 50mm / s. Simultaneously, an eddy current stress detector is started, with 5 inspection points along the width of the profile and one inspection point every 200mm along the length. Initial straightness and lateral bending values, local warping height, and internal residual stress distribution data are collected non-contactly. The data is transmitted to the industrial control computer to establish the initial deformation-stress database for the corresponding profile. After inspection, the profile is automatically transferred to the clamping station.

[0041] S2: Asymmetric segmented flexible constraint clamping Based on the S1 detection data, the industrial control computer automatically matches the constraint parameters and divides the profile into three independent flexible constraint units along its length: the feeding end, the middle section, and the discharge end. Each unit's polymer elastic pressure block, in conjunction with a pneumatically adjustable support, is activated to slowly press down onto the profile surface using a wide-face full-fit method. A constraint stiffness gradient is set: 0.35 MPa for the feeding and discharge end units, and 0.2 MPa for the middle section unit. The stiffness difference between adjacent units remains constant, forming a gradient constraint state with tight, limited restraint at both ends and flexible, gradual release in the middle. After clamping, the pressure values ​​are verified, and the parameters are locked to prevent lateral movement and rigid compression.

[0042] S3: Pre-displacement fine-tuning at room temperature In a natural environment at 25℃, the axial pneumatic micro-traction device is activated to apply a constant axial traction force of 120N to the end of the profile. At the same time, six sets of radial flexible limit blocks are activated along the width of the profile to make precise fine adjustments to the side bending and warping points detected by S1. Only macroscopic visible defects are eliminated, and the single deformation is strictly controlled to be ≤0.1mm, with elastic deformation as the main feature. After completion, the limit and traction state is maintained, and the process enters the straightening process.

[0043] S4: Intermittent micro-amplitude alternating straightening The profile is divided into four parallel straightening zones along its width. A single-point moving straightening mechanism is activated to perform staggered, alternating, segment-by-segment straightening. The single straightening pressure is set to 0.08mm, the single straightening stroke to 50mm, and the pause buffer time after straightening to 2s. The phase difference between the actions of adjacent straightening zones is 180° to avoid repeated deformation in the same area. The entire process is controlled as an intermittent, short-stroke operation with no continuous large deformation. There is no rigid impact or surface indentation throughout a single straightening pass.

[0044] S5: Synchronous Interface Stress Relief Simultaneously with the start of the S4 straightening mechanism, eight sets of upper and lower flexible guide rollers are activated. The roller speed is set to 30 mm / s, which perfectly matches the profile feed speed and straightening rhythm, with no relative slippage. The contact pressure of the flexible guide rollers is set to 0.12 MPa. The upper and lower rollers are arranged alternately, and an asymmetric guide path is formed through the arc-shaped micro-grooves on the roller surface. This simultaneously breaks the closed field of internal residual stress, realizing the gradual dispersal of stress layer by layer, and is completed synchronously with the straightening process.

[0045] S6: Adaptive stress relaxation static setting After a single pass of straightening and slow release is completed, the segmented constraints are released, and the profile is smoothly lifted to a sealed, constant-temperature settling table using a non-destructive vacuum suction cup. The table surface is made of highly polished, smooth ceramic material, and the ambient temperature is constant at 25°C, with no external force, vibration, or airflow disturbance. Based on the material of No. 45 steel and the specifications for this project, the settling time is set to 15 minutes. There is no external intervention throughout the process, and the profile relies on its internal stress to self-balance and adapt, suppressing elastic rebound.

[0046] S7: Real-time sampling and closed-loop control After the settling period, a 3D laser profilometer and eddy current stress detector of the same type as the S1 are used for random inspection. The inspection points are evenly distributed in a matrix, and the data is transmitted back to the industrial control computer in real time. After inspection, the flatness deviation is ≤0.05mm / m and the stress peak deviation is within the qualified range. No process parameters need to be adjusted and the process can directly enter the stabilization process. If the deviation exceeds the standard, the system automatically reduces the subsequent straightening amplitude and extends the release time to achieve adaptive fine adjustment.

[0047] S8: Overall homogenization and stabilization treatment The profile is transferred to the stabilization station, and a breathable polymer flexible wrapping layer is used to fully cover the profile. A constant light pressure of 0.1 MPa is applied, and the profile is left to stand at room temperature for 10 minutes to stabilize. No additional deformation force is applied during the stabilization process. Relying on the external uniform constraint and the internal stress secondary self-balancing, the residual stress peak is further weakened and the straightness is solidified. The wrapping layer is removed after the stabilization is completed.

[0048] S9: Final Inspection of Finished Products and Parameter Archiving The profiles underwent a final inspection for dimensional accuracy and residual stress across the entire cross-section. The inspection revealed that the straightness deviation of the finished product was ≤0.03mm / m, the residual stress was uniformly distributed, and there was no surface damage or indentation, meeting the requirements for precision-grade finished products. All parameters of the entire process, including constraint pressure, straightening amplitude, slow-release parameters, and settling time, were archived to form a dedicated straightening and stress control scheme for 6000mm×80mm×10mm No. 45 steel profiles, which can be directly referenced for subsequent workpieces of the same specification.

[0049] After processing in this embodiment, the profile has a springback rate of less than 0.5% after straightening, the peak residual stress is reduced, and there is no surface damage or metallographic structure change throughout the process. Compared with the traditional continuous roll straightening process, the dimensional accuracy is improved and the production energy consumption is reduced.

[0050] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A process for low-deformation precision straightening and residual stress control of steel, characterized in that, Includes the following steps: S1: Perform surface pretreatment on the steel to be straightened to remove surface impurities. Use a three-dimensional laser profilometer and eddy current stress detector to detect the initial straightness and residual stress distribution, and establish a deformation and stress database. S2: Based on the detection data, the steel is subjected to asymmetric segmented flexible constraint clamping, forming a gradient constraint along the feed direction. The constraint force changes gradually to avoid rigid extrusion and stress concentration. S3: The steel under constraint is finely adjusted by a predetermined displacement at room temperature. Macroscopic warping and bending are eliminated by a small amount of axial traction and radial limiting, and the deformation is controlled in the low plasticity range. S4: Intermittent micro-amplitude alternating straightening is used to alternately straighten steel in sections, controlling the stroke and pause interval to avoid stress increase and secondary deformation caused by continuous large deformation; S5: Simultaneous interface stress relief is implemented during alternating straightening. The residual stress closed field is broken through flexible stress diversion to achieve stress gradient homogenization and reconstruction. S6: After single-pass straightening and slow release, adaptive stress relaxation and static setting are performed to allow internal stress to self-balance in a closed constant temperature environment without external force or friction, thus suppressing post-straightening rebound. S7: After the steel has been left to stand, perform spot checks on its straightness and stress, and dynamically adjust subsequent process parameters based on the deviation to form a closed-loop control. S8: Overall stabilization treatment for steel, weakening stress peaks, solidifying flatness, and preventing springback during subsequent storage and processing; S9: Perform precision and stress final inspection on finished steel products, archive process parameters, and formulate a special straightening and stress control plan for steel of this specification.

2. The steel low-deformation precision straightening and residual stress control process according to claim 1, characterized in that, The asymmetric segmented flexible constraint clamp described in S2 is specifically divided into at least three independent flexible constraint units along the length of the steel. Each unit uses a polymer elastic pressure block in conjunction with a pneumatically adjustable support base. The constraint stiffness difference between adjacent units is constant, and the stiffness of the end constraint unit is greater than that of the middle section, forming an arrangement of tightness at both ends and slow release in the middle, which prevents lateral movement and surface plastic indentation during straightening.

3. The steel low-deformation precision straightening and residual stress control process according to claim 2, characterized in that, The polymer elastic pressure block is in full-fit, wide-surface contact with the steel. The contact pressure is dynamically controlled by a pneumatic closed loop to adapt to the thickness and strength of the steel. There are no indentations or local damage in the contact area, thus preventing the stress transmission and superposition caused by rigid contact.

4. The steel low-deformation precision straightening and residual stress control process according to claim 1, characterized in that, The intermittent micro-amplitude alternating straightening described in S4 specifically involves dividing the steel into multiple parallel straightening zones along its width direction, using a single-point moving straightening mechanism to straighten the steel in staggered alternations, with each downward press being on the order of micro-scale and the pause duration being fixed. The straightening actions of adjacent straightening zones are set with a phase difference to avoid repeated deformation in the same area.

5. The steel low-deformation precision straightening and residual stress control process according to claim 4, characterized in that, The single-point moving straightening mechanism is equipped with an arc-shaped flexible straightening head that makes arc-shaped flexible contact with the steel. The contact arc length is adapted to the width of the steel, and the straightening is without rigid impact. The trajectory gradually changes along the length direction.

6. The steel low-deformation precision straightening and residual stress control process according to claim 1, characterized in that, The interface stress relief treatment described in S5 specifically involves multiple sets of flexible guide rollers rolling synchronously along the upper and lower surfaces of the steel during straightening. The roller speed is matched with the feeding and straightening rhythm, and the roller surface is provided with uniform arc-shaped micro-grooves to achieve stress relief and dispersion layer by layer.

7. The steel low-deformation precision straightening and residual stress control process according to claim 6, characterized in that, The contact pressure of the flexible guiding roller is lower than that of the straightening head, and the upper and lower rollers are arranged in an alternating manner to form an asymmetric guiding path, which breaks the symmetrical distribution of residual stress and decomposes the high amplitude peak stress into uniform low amplitude stress throughout the entire domain.

8. The steel low-deformation precision straightening and residual stress control process according to claim 1, characterized in that, The staged adaptive stress relaxation settling described in S6 specifically involves transferring the steel to a sealed constant temperature settling table after each pass. The table surface is a frictionless, smooth support, and there is no external force, vibration, or temperature field interference throughout the process. The settling time is adaptively set according to the material and specifications, and the entire process is at room temperature without any hot or cold interference.

9. The steel low-deformation precision straightening and residual stress control process according to claim 1, characterized in that, The real-time sampling and closed-loop control described in S7 uses the same three-dimensional laser profilometer as S1, combined with an eddy current stress detector for joint inspection. The detection points are evenly distributed in a matrix, and the data is transmitted to the control system in real time. When the deviation exceeds the standard, the subsequent alternating amplitude is automatically reduced and the stress relief time is extended to achieve adaptive fine-tuning of parameters.

10. The steel low-deformation precision straightening and residual stress control process according to claim 1, characterized in that, The homogenization and stabilization treatment described in S8 uses a breathable polymer flexible wrapping layer for full-area light pressure fixation, constant pressure for a preset time, without applying additional deformation force. Relying on external uniform constraints and internal stress self-balancing, it further reduces stress peak and solidifies flatness.

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