A method for improving the shape quality of an online quenched steel strip

Abstract

The present application relates to the technical field of strip steel heat treatment and metal processing, and particularly relates to a method for improving the shape quality of on-line quenched strip steel, which comprises the following steps: presetting large and medium wave target values in the finishing rolling process to offset the quenched edge wave stress; performing heat field homogenization stacking of the steel coil in the warehouse area; performing edge cutting pretreatment on the coil with width exceeding the standard before flattening; maintaining the efficiency of the deviation correction sensor; implementing segmented control of the flattening speed; and performing multi-point measurement of the flattened shape and real-time feedback correction of the rolling force and bending force. Through the whole-process deformation compensation, heat field management and process optimization, the present application solves the problem that the edge wave of high-hardness on-line quenched strip steel is serious due to large cooling intensity and cannot be eliminated by conventional flattening, significantly reduces the residual wave height, and improves the yield of the cross-cutting process and the adaptability of automatic processing.

Description

Technical Field

[0001] This invention belongs to the field of strip heat treatment and metal processing technology, specifically a method for improving the shape quality of online quenched strip. Background Technology

[0002] Hot-rolled online quenched steel plates are widely used in industrial wear-resistant equipment due to their unique material structure and excellent wear resistance. Their production process typically includes ironmaking, steelmaking, continuous casting, hot rolling, leveling, cross-cutting, and surface treatment. By employing a direct quenching process in the hot-rolled layer cooling stage, subsequent heat treatment steps can be eliminated, thus significantly reducing process costs.

[0003] However, online quenching technology also presents significant challenges to strip shape control in actual production. Due to the high cooling intensity and low coiling temperature during the hot rolling layer cooling process, strip steel is highly susceptible to severe edge waviness defects after layer cooling. Even when the rolling force and bending roll force are set to the equipment limits during the leveling process, incomplete elimination of edge waviness from the incoming material is often still present. During the cross-cutting and leveling process, residual edge waviness may remain after precision straightening, limiting the yield. Furthermore, when strip waviness leads to unsatisfactory straightening results, frequent coiling retraction or multiple leveling operations are required, which not only increases transportation costs but also negatively impacts the production efficiency of the leveling process. Therefore, more effective control methods are urgently needed to address strip shape defects in hot-rolled online quenched strip steel.

[0004] Patent CN121183088A discloses a method and apparatus for controlling the shape of quenched steel plates. This method, by designing the steel plate composition and coordinating specific heating temperatures, furnace time, rolling shape control parameters, and quenching and tempering parameters, aims to achieve a desired level of flatness in the plate shape after quenching. This solution improves the shape control level of thin-gauge plates through optimized composition design and multi-process parameter control. However, this technical solution mainly focuses on the static coordination of process parameters throughout the entire process. Its dynamic compensation capability still needs improvement when dealing with severe local stress fluctuations caused by uneven cooling in the layer cooling process, and there is room for improvement in eliminating extreme edge waviness in the leveling process.

[0005] Patent CN114888096B discloses a method for segmented control of strip shape using bending rolls. This method activates the segmented control function of bending rolls, filters the detected strip shape value, and performs feedback control on the bending rolls based on the target waviness value, thereby achieving automatic adjustment of the strip waviness. This solution reduces manual intervention and improves control accuracy through a real-time feedback mechanism. However, this technical solution is mainly aimed at the waviness adjustment of ordinary hot-rolled strip steel. When dealing with special steels such as online quenched strip steel, which have high hardness and complex residual stress distribution, there is still room for optimization in the response characteristics of its feedback adjustment and the adjustment stability under high load conditions. This results in limited strip shape improvement when dealing with extreme edge waviness after the equipment parameters reach their limits. Summary of the Invention

[0006] This invention provides a method for improving the shape quality of online quenched strip steel. It aims to solve the technical problem that the edge waviness of online quenched strip steel caused by high cooling intensity and low coiling temperature under direct quenching process is difficult to eliminate by conventional leveling through deformation compensation control, thermal field homogenization management, pretreatment process optimization, and fine segmented adjustment of leveling parameters.

[0007] In a first aspect, the present invention provides a method for improving the shape quality of online quenched strip steel, comprising the following steps: S10: Control of large and medium waves at the exit of the finishing mill: In the finishing mill process, the target value of the strip shape at the exit of the finishing mill is set according to the width specification of the strip, so that the strip reserves medium wave deformation before entering the laminar cooling process, which is used to offset the edge wave shrinkage stress in the subsequent laminar cooling quenching process. S20: Homogenized stacking of hot-rolled steel coils in warehouse: Transporting the online quenched steel coils after hot rolling to a designated constant temperature or low heat interference area, so that the operating side and the transmission side of the steel coil are in a symmetrical heat exchange environment, avoiding asymmetrical thermal stress caused by unilateral high temperature radiation. S30: Width pretreatment before leveling: For online quenched strip steel with excessive hot-rolled width, an edge trimming process is performed before the leveling process to remove the stress concentration area at the edge and change the transverse stress distribution of the strip steel before leveling. S40: Correction sensor performance maintenance: Before starting the leveling operation, clean the surface dust of the infrared lamps and receivers of the inlet center position control device CPC and the outlet edge position control device EPC to keep the transmittance of the photoelectric signal within the set threshold range. S50: Segmented control of leveling speed: Differentiated running speeds are set according to different positions along the length of the strip, with reduced running speed at the head and tail of the strip and constant medium speed in the middle area; S60: Multi-point measurement and feedback adjustment of strip shape during leveling: During the leveling process, the strip shape is measured on the outer ring of the strip at a decreasing spacing frequency, and fixed-distance measurement is performed in the middle and rear areas. The rolling force and bending roll force of the leveling machine are corrected in real time based on the IU value obtained from the measurement.

[0008] According to this invention, by pre-setting a large and medium wave control strategy during the finishing rolling stage, the reserved medium wave deformation variable is used to neutralize the edge wave tensile stress generated by the cold quenching of the layer, thereby reducing the original wave amplitude before entering the leveling process from the source. Combined with the uniform stacking of the thermal field in the storage area, secondary thermal deformation caused by environmental temperature differences is eliminated. By using the process sequence of cutting the edges before leveling, secondary edge waves caused by the release of edge constraint forces after leveling are avoided. With the physical cleaning of CPC and EPC sensors, the logical segmentation of leveling speed, and the increased plate shape measurement frequency, the leveling equipment can accurately capture plate shape fluctuations and perform rolling parameter corrections when processing high-hardness online quenched strip steel. This solves the problem that conventional leveling processes cannot eliminate severe edge waves under extreme equipment conditions, and improves the yield of the cross-cutting process.

[0009] In some embodiments, in step S10, the specific parameters for controlling the large and medium waves at the finishing mill exit are set according to the strip width W: When W is greater than or equal to 1500 mm, the target value for waviness at the finish rolling exit is set to 100 to 150 IU; When W is less than 1500mm, the target value for the waviness at the finish rolling exit is set to 150 to 200 IU.

[0010] In some embodiments, the technical means for homogenizing the thermal field of the steel coils in step S20 include: A separate storage area for online quenched steel coils shall be designated within the steel coil warehouse. The physical distance between this area and the storage area for high-temperature steel coils with a furnace exit temperature of over 500°C shall be no less than 10 meters. When steel coils are stacked in single or multiple layers, ensure that the temperature difference between the surfaces of symmetrically distributed objects in the operating side space and the transmission side space along the axis of the steel coil is less than 20°C.

[0011] In some embodiments, the operation process of pre-processing the width before leveling in step S30 includes: The hot-rolled quality control system extracts the full-length width data of the strip steel to identify abnormal coils whose width exceeds the upper limit of the order tolerance by more than 5mm. The defective roll is transported to the disc shearing line and symmetrically cut on both sides according to the order specifications, with the cutting amount on each side controlled between 10 and 25 mm. The steel coils after trimming are wound up again, with the winding tension set to 1.1 to 1.2 times the normal production tension.

[0012] In some implementations, in step S40, the CPC and EPC lamps are cleaned at least once per shift, the lamp lens surface is wiped with anhydrous ethanol, and the signal feedback strength is checked to ensure that the signal attenuation rate is less than 5%.

[0013] In some implementations, the specific logic for segmented control of the leveling speed in step S50 is as follows: In the 0 to 100 meter range at the head of the strip, the leveling speed is set to 10 to 30 meters per minute; In the middle area of ​​the strip, the leveling speed is set at 120 to 150 meters per minute, and the maximum speed is limited to 200 meters per minute. In the section from 100 meters to 0 meters from the tail of the strip, the leveling speed is reduced to 10 to 30 meters per minute.

[0014] In some embodiments, the selection rule for the location of the multi-point measurement of the flat plate shape in step S60 is as follows: A contact or non-contact plate shape measurement was performed once at positions with outer ring lengths of 30 meters, 50 meters, and 100 meters respectively. In the middle section where the raw material length exceeds 100 meters, the plate shape is measured every 100 meters; Plate shape measurements were performed at positions where the remaining length of the inner circle of the raw material was 100 meters, 50 meters, and 30 meters, respectively.

[0015] In some embodiments, the technical means of adjusting the flatness parameters based on the plate shape measurement results in step S60 include: When the measured edge waviness value is greater than 20 IU, the leveling rolling force is increased in increments of 50 to 100 kN, and the positive bending roll force is increased in increments of 20 to 50 kN. When the measured wave value is greater than 15 IU, keep the rolling force constant and increase the negative bending roll force in increments of 30 to 60 kN.

[0016] In some embodiments, the online quenched strip has a tensile strength of 1000 to 1500 MPa, a yield strength of 800 to 1200 MPa, and a strip thickness of 2.0 to 8.0 mm.

[0017] In some embodiments, in step S10, the reduction rate of the finishing mill stand is set to 10% to 18%, and the crown of the work roll is set to 0.05 to 0.15 mm.

[0018] In some embodiments, in step S20, the online quenched steel coil is cooled in the warehouse for no less than 48 hours, so that the temperature difference between the core and the surface of the steel coil is reduced to within 50°C.

[0019] In some embodiments, in step S50, the constant tension during the leveling process is set to 15 to 45 MPa, with the tension setting value linearly increased according to the increase in strip thickness.

[0020] Secondly, the present invention provides an application of a method for improving the shape quality of online quenched strip steel in the production of wear-resistant steel, wherein the method is the method described in any embodiment of the first aspect.

[0021] According to the present invention, this method employs a comprehensive control approach throughout the entire process from finishing rolling to leveling. Through physical thermal field intervention, prestress cancellation, segmented speed fine-tuning, and high-frequency measurement feedback, the residual waviness height of the online quenched strip before the cross-cutting process is reduced to below 3 mm per meter, significantly reducing the load on the finishing straightening process. In actual production, this method increases the first-grade yield of cross-cutting and leveling from 88% to the range of 90% to 93%, effectively solving the industrial problem of frequent uncoiling and low leveling efficiency caused by shape defects in high-strength quenched strip.

[0022] In practical implementation, the feasibility of the solution is ensured through the following technical details: Regarding the in-depth implementation of the large-scale wave control (S10) at the finishing mill exit: In the hot rolling finishing stage, the bending roll force and reduction distribution of the last stand are intervened in real time through an automated control system (Level 2). For wide strips with a width greater than 1500mm, due to their relatively low transverse stiffness, the heat dissipation rate at the edges during the laminar cooling process is much higher than that at the center, easily leading to severe edge waviness. At this time, the control system automatically reduces the positive bending roll force of the last stand and appropriately increases the negative crown wear compensation of the work rolls, so that the center part of the strip at the exit exhibits a significant bulge, forming a central waviness with an IU value of 100 to 150. This artificially constructed non-straight state can provide deformation space for the severe cooling and shrinkage of the strip edges during the subsequent high-strength direct quenching process, utilizing the "excess length" of the central waviness to absorb the strain energy at the edges. For narrow strips with a width less than 1500mm, due to the more concentrated edge effect, the target value of the central waviness is further increased to 150 to 200 IU to cope with the stronger edge shrinkage trend.

[0023] Physical methods for homogenizing the thermal field of the reservoir (S20): The coiling temperature of online quenched strip steel is typically controlled between 200 and 400°C, far lower than that of ordinary hot-rolled products. If it is mixed with high-temperature steel coils with coiling temperatures above 600°C, the enormous heat emitted by the high-temperature steel coils will act on one side of the online quenched steel coils through radiation and air convection. This asymmetrical thermal load will cause a temperature gradient in the axial direction of the steel coil, thereby inducing uneven thermal stress and causing the originally balanced strip shape to twist again. This invention provides a near-constant temperature cooling environment for online quenched steel coils by designating a special low-heat interference zone in the flat finished product warehouse area, taking advantage of the fact that the temperature of the finished product warehouse steel coils is generally below 60°C. By controlling the heat transfer coefficients on both sides of the steel coil to be consistent, the symmetry of the stress release process is ensured.

[0024] Regarding the process logic for width pretreatment (S30) before leveling: Due to their extremely high hardness, the metal flow at the edges of online-quenched strips is restricted by lateral constraints during the leveling process. If the width of the hot-rolled incoming material exceeds the standard, severe microstructural inhomogeneity and residual stress concentration often exist in the edge area. If leveling is performed before edge trimming, the enormous rolling force applied during leveling will further accumulate edge stress. The instantaneous loss of constraint during edge trimming will trigger a severe "springback effect," generating new edge waviness. This invention changes the process sequence by first removing abnormal edges with a disc shear, allowing the strip to enter the leveling machine with a standard width and a more uniform edge stress state, greatly improving the leveling effect on waviness reduction.

[0025] Regarding the coordination between sensor performance and leveling speed control (S40, S50): Due to the presence of iron oxide scale debris and dust in the leveling process environment, dirt easily accumulates on the lamp surfaces of the CPC and EPC sensors, leading to weakened photoelectric signals. For online quenched strips with extremely poor shape, even slight deviations in the sensor signals can trigger overcompensation or undercompensation by the correction system, causing the strip to sway left and right within the frame, resulting in unilateral wavy patterns. Forced alcohol wiping and cleaning ensure signal transmittance. Simultaneously, in conjunction with segmented speed control, the speed is limited to below 30 meters per minute in the most complex strip shape areas at the beginning and end (typically the first and last 100 meters), allowing sufficient response time (milliseconds) for the hydraulic pressing system and bending roll control system, preventing "crushing" or "loss of control" due to adjustment lag at high speeds.

[0026] Refinement of multi-point measurement and closed-loop correction (S60): Conventional strip leveling only involves sampling measurements at the beginning and end, failing to cover the shape fluctuations across the entire length of the online-quenched strip. This invention establishes a precise initial section shape profile by densifying measurement points (30 meters, 50 meters, and 100 meters) along the outer edge of the strip (the area of ​​most severe deformation). Based on the acquired real-time data, operators or automated systems can quickly determine whether the current combination of rolling force and bending roll force is sufficient to flatten the waviness. If the measurement shows residual waviness, the rolling force is immediately increased in 50 kN increments until 95% of the equipment's maximum pressure is reached; if residual waviness still exists, local deformation correction is achieved by increasing the positive bending roll force. This high-frequency measurement and adjustment cycle ensures the consistency of the strip shape along its entire length.

[0027] In summary, this invention, through deep involvement in the entire online quenching strip steel production process, constructs a complete strip shape quality improvement system from three dimensions: thermal stress, mechanical stress, and process logic. This not only overcomes the limitation of a single process in handling extreme strip shape defects, but also significantly improves the yield of high-strength wear-resistant steel through specific technical parameter settings and operating procedures, demonstrating extremely high industrial application value.

[0028] In some embodiments, step S10, the control of the large and medium waves at the finishing mill exit, further includes optimizing the opening mode of the layer cooling spray manifold: Based on the transverse thickness difference measured at the finishing mill exit, the shielding width of the nozzles at the edge of the cooling zone is dynamically adjusted, and the shielding width is set to 50 to 150 mm inward from the edge of the strip. By reducing the intensity of edge cooling and incorporating the pre-reserved mid-wave in the finishing mill, the probability of edge wave generation is further reduced.

[0029] In some embodiments, in step S30, the height of the burr on the edge of the strip after trimming is controlled to be below 0.1 mm. This is achieved by adjusting the side clearance and overlap of the disc shear. The side clearance is set to 8% to 12% of the strip thickness, and the overlap is set to 0.5 to 1.5 mm. During the leveling process, the surface of the leveling roller is sprayed with rust-preventive oil or process lubricant, and the lubrication flow rate is set to 10 to 30 liters per minute to reduce the impact of frictional heat on the plate shape.

[0030] In some embodiments, in step S60, the plate shape measurement uses a laser ranging array for non-contact scanning: The laser sensor is arranged with no fewer than 9 measuring points along the transverse direction of the strip, and the sampling frequency is no less than 100Hz; The system automatically calculates the length difference at each measuring point and converts it into an IU value, which is then displayed on the operation interface as a direct basis for adjusting the rolling force.

[0031] In some embodiments, the method for improving the shape quality of online quenched strip also includes managing the crown of the leveling rolls: The leveling roller adopts a continuously variable crown (CVC) roller type, and the movement range is set from -100 to +100 mm. Based on the trend of strip shape measurement along its entire length, the zero position of the leveling roll is recalibrated after processing 5 to 10 coils, according to the wear condition of the roll surface.

[0032] By combining the aforementioned series of specific technical means, this invention effectively addresses the stringent sheet shape challenges posed by online quenching processes. Experimental data shows that, using the method described in this invention, the flatness and uncoiling rate of online quenched strip steel is reduced from the original 15% to below 3%, and the production efficiency of the cross-cutting process is increased by more than 20%. The surface unevenness of the strip steel is significantly improved, meeting the stringent requirements for sheet flatness in high-precision laser cutting and automated welding. This invention does not rely on large-scale equipment modifications but achieves a leapfrog improvement in product quality through the refined reconstruction of process parameters in existing production lines, demonstrating significant potential for widespread application and economic benefits.

[0033] In some embodiments, in step S20, the flatness deviation of the ground in the steel coil storage area is controlled within 2 mm per meter to prevent the steel coil from generating local indentations or stress concentrations on uneven ground due to its own weight.

[0034] In some embodiments, in step S50, the bending roll force adjustment range of the leveling machine is set to -500 to +1200 kN, and the rolling force adjustment range is set to 2000 to 12000 kN.

[0035] In some embodiments, in step S60, during the last 30 meters of the inner ring of the strip, the leveling speed is smoothly reduced to 5 meters per minute to ensure the stability of the strip shape at the moment the tail tension disappears.

[0036] This invention, through the precise combination of the aforementioned technical means, achieves closed-loop control of shape defects in online quenched strip steel, providing high-quality wear-resistant steel base materials for the industrial sector. Because the method is supported by specific parameters in each stage of steelmaking, hot rolling, and leveling, the feasibility and stability of the technical solution are ensured. In long-term industrial practice, this method has demonstrated excellent robustness and can adapt to the production needs of online quenched strip steel with different chemical compositions and thicknesses.

[0037] In some embodiments, the method of the present invention further includes optimizing the roll changing cycle of the leveling machine's work rolls: For online quenching of strip steel, the steel throughput after a single roll change is set to 800 to 1200 tons; When the amount of steel passing through reaches 90% of the set value, the frequency of plate shape measurement is increased to once every 50 meters to monitor the plate shape deterioration trend caused by roller wear.

[0038] In some embodiments, in step S10, the temperature at the finishing mill exit is controlled at 820 to 880°C, and the coiling temperature is controlled at 250 to 350°C. By using narrow window temperature control in conjunction with the large and medium wave strategy, the phase transformation stress and thermal stress inside the strip are balanced.

[0039] In some implementations, in step S40, the response time of the CPC and EPC systems is set to less than 50 milliseconds, and the correction accuracy is controlled within ±2mm, thereby eliminating the dynamic waviness caused by physical deviation through high-precision position control.

[0040] Through the above comprehensive technical description, this invention provides a systematic solution that can fundamentally solve the plate shape and quality bottleneck in the hot-rolled online quenched strip steel production process, and significantly improve the market competitiveness and industrial application value of related products.

[0041] In its implementation, the method of this invention not only focuses on optimizing individual parameters but also emphasizes the logical coupling between various processes. For example, the target value of the large and medium wave at the finishing mill exit is not fixed but dynamically adjusted based on the remaining adjustment capacity of the leveling mill. If the bending roll force of the leveling mill is close to its upper limit, the IU value of the medium wave at the finishing mill exit will be automatically increased slightly in the next batch of hot rolling plans. This cross-process feedback mechanism enables the entire production line to have self-adjustment and fault tolerance capabilities.

[0042] Furthermore, considering the high hardness and springback characteristics of online quenched strip steel, this invention employs a special "overcompensation" strategy in the leveling process. After obtaining the strip shape data, the rolling force correction given by the system is typically 5% to 10% higher than the calculated theoretical value, to offset the deformation resistance caused by the material's high elastic modulus. This empirical correction based on material properties is one of the key technical details for ensuring strip shape quality.

[0043] In terms of warehouse management, this invention also introduces infrared thermal imaging monitoring. During the first 12 hours after the steel coils are stored, the surface temperature of the steel coils in the dedicated stacking area is scanned every 4 hours. If the temperature difference between the two sides of a steel coil exceeds 15°C, immediate intervention is taken by moving adjacent steel coils or adjusting ventilation barriers to ensure absolutely uniform heat distribution.

[0044] In the cross-cutting process, because the shape of the strip after leveling has been fundamentally improved, the reduction of the precision straightening rollers on the cross-cutting machine can be reduced by 30% to 50%. This not only extends the service life of the straightening rollers but also avoids surface scratches and work hardening caused by over-straightening, resulting in wear-resistant plates delivered to customers with better surface quality and subsequent processing performance.

[0045] The method described in this invention, through meticulous refinement of each technical step, transforms the previously difficult-to-control problem of online quenching strip shape into a series of quantifiable, executable, and monitorable standard operating procedures. This marks a significant shift in online quenching strip production technology from experience-based to scientific and precise approaches. In future industrial applications, with further improvements in automation, the technical parameters described in this invention can be further coupled and optimized using artificial intelligence algorithms to unlock the potential of the equipment and achieve even higher levels of strip shape control.

[0046] In summary, this invention successfully solves the industry problem of severe edge waviness in online quenched strip steel through the synergistic effect of six technical means: controlling large and medium waviness at the finishing mill exit, homogenizing the thermal field of the steel coil storage area, pre-processing the width before leveling, maintaining the effectiveness of the correction sensor, segmented control of the leveling speed, and multi-point measurement and feedback adjustment of the leveling plate shape. This method is logically rigorous, has specific parameters, and is highly operable, providing solid technical support for the large-scale production of high-strength wear-resistant steel. Detailed Implementation

[0047] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0048] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with an embodiment or example that are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0050] As described in the background section above, in the direct quenching process, online quenched strip steel exhibits a significant residual stress gradient due to its high cooling intensity and low coiling temperature. This stress distribution manifests as severe edge waviness defects after coiling. Furthermore, because online quenched strip steel typically possesses extremely high hardness (tensile strength reaching 1000 to 1500 MPa), conventional leveling processes often struggle to completely eliminate these deformations through simple pressure adjustment, leading to excessive strip shape during subsequent cross-cutting.

[0051] Based on this, the present invention provides a method for improving the shape quality of online quenched strip steel, which achieves precise intervention in complex stress fields through coordinated control of the entire process from finishing rolling to leveling.

[0052] In a first aspect, the present invention provides a method for improving the shape quality of online quenched strip steel, comprising the following steps: S10: Finishing Mill Exit Wave Control. In the finishing mill process, the target strip shape value at the mill exit is set based on the strip width specification W by adjusting the bending roll force and work roll crown of the last stand. Specifically, when W is greater than or equal to 1500 mm, the target wave value at the finishing mill exit is set to 100 to 150 IU; when W is less than 1500 mm, the target wave value is set to 150 to 200 IU. During this process, the reduction rate of the last stand is set to 10% to 18%, and the work roll crown is set to 0.05 to 0.15 mm. Furthermore, the opening mode of the laminar flow spray manifold is set through the L2 level automation system. Based on the transverse thickness difference measured at the finishing mill exit, the shielding width of the edge nozzles in the laminar flow zone is dynamically adjusted, with the shielding width set to 50 to 150 mm inward from the strip edge.

[0053] S20: Homogenized thermal field stacking in the steel coil storage area. Hot-rolled, online-quenched steel coils are transported to a designated dedicated storage area. This area is physically at least 10 meters away from the storage area for high-temperature steel coils with a furnace temperature exceeding 500°C. The flatness deviation of the ground in the steel coil storage area is controlled within 2mm per meter. During the stacking process, ensure that the surface temperature difference of symmetrically distributed objects in the operating and transmission spaces along the steel coil axis is less than 20°C. The cooling time for online-quenched steel coils in the storage area is set to be no less than 48 hours, controlling the temperature difference between the core and surface of the steel coil to within 50°C.

[0054] S30: Width Pre-treatment Before Leveling. The full-length width data of the strip is extracted using the hot-rolling quality control system to identify abnormal coils whose width exceeds the order tolerance limit by more than 5mm. These abnormal coils are transported to the disc shearing line and symmetrically trimmed on both sides according to order specifications, with the trimming amount controlled to 10-25mm on each side. After trimming, the burr height on the strip edge is controlled below 0.1mm, the disc shearing side clearance is set to 8%-12% of the strip thickness, and the overlap is set to 0.5-1.5mm. The trimmed coils are then re-wound, with the winding tension set to 1.1-1.2 times the normal production tension.

[0055] S40: Maintenance of the alignment sensor performance. Before starting the leveling operation, wipe the infrared lamps and receiver surfaces of the inlet center position control device (CPC) and the outlet edge position control device (EPC) with anhydrous ethanol to remove dust. Cleaning should be performed once per shift. The signal attenuation rate of the photoelectric signal should be kept below 5% by checking the signal feedback strength. The response time of the CPC and EPC systems should be set to less than 50 milliseconds, and the alignment accuracy should be set within ±2mm.

[0056] S50: Segmented speed control for leveling. Different operating speeds are set according to different positions along the strip's length. In the head section (0-100 meters), the leveling speed is set to 10-30 meters per minute; in the middle section, it is set to 120-150 meters per minute, with a maximum speed limited to 200 meters per minute; in the tail section (100 meters to 0 meters), the leveling speed decreases to 10-30 meters per minute; and in the last 30 meters of the inner strip, the leveling speed decreases to 5 meters per minute. The constant tension during leveling is set to 15-45 MPa, increasing linearly with strip thickness. The leveling machine's work rolls are of the continuously variable crown (CVC) type, with a movement range set from -100 to +100 mm.

[0057] S60: Multi-point measurement and feedback adjustment of strip shape during leveling. During the leveling process, non-contact scanning is performed using a laser ranging array. Nine measuring points are arranged along the transverse direction of the strip using laser sensors, with a sampling frequency of 100Hz. Strip shape measurements are performed at 30m, 50m, and 100m intervals on the outer edge of the raw material; in the middle section after the raw material length exceeds 100m, strip shape measurements are performed every 100m; and at 100m, 50m, and 30m intervals on the remaining inner edge of the raw material. The rolling force and bending roll force of the leveling mill are adjusted in real time based on the measured IU value: when the edge waviness value is greater than 20 IU, the leveling rolling force is increased in steps of 50 to 100 kN, while the positive bending roll force is increased in steps of 20 to 50 kN; when the waviness value is greater than 15 IU, the rolling force is kept constant, while the negative bending roll force is increased in steps of 30 to 60 kN. The bending roll force adjustment range of the leveling machine is set to -500 to +1200 kN, and the rolling force adjustment range is set to 2000 to 12000 kN.

[0058] In this embodiment, the online quenched strip has a tensile strength of 1000 to 1500 MPa, a yield strength of 800 to 1200 MPa, and a strip thickness of 2.0 to 8.0 mm. The temperature at the finishing mill exit is controlled at 820 to 880°C, and the coiling temperature is controlled at 250 to 350°C. The steel throughput after a single roll change on the leveling roll is set to 800 to 1200 tons. When the steel throughput reaches 90% of the set value, the strip shape measurement frequency is adjusted to once every 50 meters.

[0059] The technical solution and effects of the present invention will be described in detail below through specific embodiments.

[0060] Example 1 This embodiment relates to an online quenched wear-resistant steel strip with a tensile strength of 1200 MPa, a thickness of 4.0 mm, and a width of 1600 mm.

[0061] 1. Finishing stage: Set the exit waviness target value to 130 IU. Set the last stand reduction rate to 15%, and the work roll crown to 0.10 mm. Set the laminar flow edge shielding width to 100 mm. Set the coiling temperature to 300℃.

[0062] 2. Storage Area Stage: Steel coils are stored in a dedicated storage area, 15 meters away from high-temperature coils. The cooling time in the storage area is 50 hours, and the measured temperature difference between the core and surface is 42℃.

[0063] 3. Pre-processing stage: The width of the roll exceeds the tolerance by 6mm, and it enters the cutting line. The single-sided cutting amount is 15mm, and the cutting tension is 1.15 times the normal value.

[0064] 4. Leveling Phase: CPC / EPC sensors are cleaned every shift. The speed is 25 meters per minute for the first 100 meters, 130 meters per minute for the middle section, and reduced to 20 meters per minute for the last 100 meters.

[0065] 5. Measurement and Adjustment: A waviness of 25 IU was measured at 30 meters from the outer edge. The rolling force was immediately increased by 100 kN, and the positive bending roll force was increased by 40 kN. Subsequent measurements stabilized within 5 IU.

[0066] Example 2 This embodiment relates to an online quenched wear-resistant steel strip with a tensile strength of 1500 MPa, a thickness of 6.0 mm, and a width of 1200 mm.

[0067] 1. Finishing stage: Set the exit waviness target value to 180 IU. Set the last stand reduction rate to 12 percent and the work roll crown to 0.12 mm. Set the laminar flow edge shielding width to 120 mm. Set the coiling temperature to 280℃.

[0068] 2. Storage area stage: Cooling time is 60 hours, and the ground flatness deviation is 1.5mm / m.

[0069] 3. Preprocessing stage: The width is normal and no edge trimming has been performed.

[0070] 4. Leveling stage: The running speed in the middle section is set to 120 meters per minute, and the tension is set to 40 MPa.

[0071] 5. Measurement and Adjustment: Automatic measurement every 100 meters in the middle section, and fine adjustment (+20mm) of CVC roller movement to maintain the plate shape.

[0072] Example 3 This embodiment relates to an online quenched wear-resistant steel strip with a tensile strength of 1000 MPa, a thickness of 2.5 mm, and a width of 1800 mm.

[0073] 1. Finishing stage: Set the exit mid-wave target value to 110 IU. Set the last stand reduction rate to 18 percent and the work roll crown to 0.08 mm.

[0074] 2. Storage area stage: The temperature difference between the surfaces of objects on both sides of the steel coil axis is controlled within 15℃.

[0075] 3. Pre-treatment stage: 20mm cut on one side, 0.05mm burr height.

[0076] 4. Leveling stage: The surface of the leveling roller is sprayed with process lubricant at a flow rate of 20 liters per minute.

[0077] 5. Measurement and adjustment: The mid-wave is measured at 18 IU at 50 meters inside the inner ring. Maintain the rolling force and increase the negative bending roll force by 50 kN.

[0078] Comparative Example 1 The conventional hot rolling leveling process is adopted: the finish rolling exit is set to a flat plate shape (0 to 20 IU), no hot field intervention is carried out in the storage area (mixed with high temperature coils), no pre-cutting is performed before leveling, the leveling speed is constant at 80 meters per minute throughout the entire length, and the plate shape is measured only at the beginning and end.

[0079] Comparative Example 2 Based on Example 1, the large and medium wave control at the finish mill exit (S10) is cancelled, that is, the target value at the finish mill exit is set to 0IU, and the remaining steps are the same as in Example 1.

[0080] The online quenched strip steel produced in the above embodiments and comparative examples was subjected to strip shape quality inspection. The inspection indicators included: residual waviness height after cross-cutting (mm / m), flattening uncoiling rate (%), and first-grade cross-cutting rate (%). The experimental data are shown in the table below:

[0081] As shown in the table above, the full-process control method provided in this embodiment of the invention can significantly reduce the residual waviness height of online quenched strip. Comparing Example 1 with Comparative Example 1, it can be seen that without pre-reserved waviness in the finishing rolling process, thermal field management in the storage area, and segmented speed control, the original edge waviness of the strip before leveling is extremely large (115 IU), resulting in a residual waviness height of 8.5 mm / m after leveling, which seriously affects the yield.

[0082] Comparing Example 1 and Comparative Example 2, it can be found that the control of large and medium waviness at the finishing mill exit (S10) is one of the core steps of this scheme. Although Comparative Example 2 adopted subsequent leveling optimization methods, the original edge waviness before entering the leveling process was too large (95IU), exceeding the adjustment limit of the leveling unit, resulting in the final plate shape quality still being significantly worse than that of Example 1.

[0083] Furthermore, data from Examples 1 to 3 show that, for specifications of different widths and strengths, by adjusting the preset value of the waviness at the finishing mill exit (range of 100 to 200 IU) and the width of the layer cooling shield, the edge waviness stress before leveling can be effectively neutralized, keeping the leveling uncoiling rate stable below three percent. During the leveling process, the synergistic effect of S40, S50, and S60, especially the high-frequency point measurement and step-by-step correction of rolling force / bending roll force, ensures the plate shape stability of high-hardness materials under severe fluctuations in deformation resistance.

[0084] Regarding warehouse management, the uniform stacking of the heat field in the embodiment effectively avoids secondary deformation caused by asymmetric thermal stress. Experimental observations show that the axial temperature difference of the steel coils in Example 1 after 48 hours in the warehouse is controlled within 50°C, while the axial temperature difference of the control coils without intervention measures often exceeds 120°C, and the latter is very prone to generating unilateral waves during the leveling process.

[0085] Regarding the edge trimming process, Examples 1 and 3 eliminated edge stress concentration by trimming the edges before flattening. Testing revealed that the edge springback of the strip at the flattening exit was reduced by more than 60%, effectively solving the problem of "secondary edge waviness" after flattening of high-strength steel.

[0086] In summary, this invention, through the deep coupling of six key technologies—large and medium wave control at the finishing mill exit, uniform thermal field stacking in the coil storage area, width pretreatment before leveling, performance maintenance of the correction sensor, segmented control of leveling speed, and multi-point measurement and feedback adjustment of leveling strip shape—increases the first-grade yield of online quenched strip from approximately 88% to the range of 91% to 93%. This method, without relying on large-scale hardware modifications, achieves effective control of extreme strip shape defects through refined reconstruction of process parameters, demonstrating significant industrial application value.

[0087] 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 improving the shape quality of online quenched strip steel, characterized in that, Includes the following steps: S10: Finishing mill exit wave control: In the finishing mill process, the target value of the strip shape at the exit of the finishing mill is set according to the width W of the strip; when W is greater than or equal to 1500mm, the target value of the wave at the finishing mill exit is set to 100 to 150 IU; when W is less than 1500mm, the target value of the wave at the finishing mill exit is set to 150 to 200 IU. S20: Homogenized stacking of hot-rolled steel coils in the warehouse: transporting the online quenched steel coils after hot rolling to the designated storage area, so that the operating side and the transmission side of the steel coil are in a symmetrical heat exchange environment, and ensuring that the surface temperature difference of symmetrically distributed objects in the operating side space and the transmission side space in the axial direction of the steel coil is less than 20℃. S30: Width pretreatment before leveling: For online quenched strip steel with a width exceeding the upper limit of the order tolerance by more than 5mm, an edge trimming process is performed before the leveling process, and the trimming amount is controlled to be 10 to 25mm on one side. S40: Correction sensor performance maintenance: Before starting the leveling operation, clean the surface of the infrared lamps and receivers of the inlet center position control device CPC and the outlet edge position control device EPC to ensure that the signal attenuation rate of the photoelectric signal is less than 5%. S50: Segmented control of leveling speed: In the section from 0 to 100 meters at the head of the strip, the leveling speed is set to 10 to 30 meters per minute; in the middle section of the strip, the leveling speed is set to 120 to 150 meters per minute; in the section from the last 100 meters to 0 meters at the tail of the strip, the leveling speed is set to 10 to 30 meters per minute. S60: Multi-point measurement and feedback adjustment of strip shape during leveling: During the leveling process, the strip shape is measured on the outer ring of the strip at a decreasing spacing frequency, and fixed-distance measurement is performed in the middle and rear areas. The rolling force and bending roll force of the leveling machine are corrected based on the IU value obtained from the measurement.

2. The method for improving the shape quality of online quenched strip steel according to claim 1, characterized in that, In step S10, the reduction rate of the finishing mill stand is set to 10% to 18%, and the crown of the work roll is set to 0.05 to 0.15 mm; the temperature at the finishing mill exit is controlled at 820 to 880°C, and the coiling temperature is controlled at 250 to 350°C.

3. The method for improving the shape quality of online quenched strip steel according to claim 1, characterized in that, Step S10 also includes optimizing the opening mode of the laminar cooling spray manifold: based on the transverse thickness difference measured at the finishing mill exit, the shielding width of the edge nozzles of the laminar cooling zone is adjusted, and the shielding width is set to 50 to 150 mm inward from the edge of the strip.

4. The method for improving the shape quality of online quenched strip steel according to claim 1, characterized in that, In step S20, the physical distance between the storage area and the storage area for high-temperature steel coils with a furnace temperature higher than 500°C is not less than 10 meters; the cooling time of the online quenched steel coils in the storage area is not less than 48 hours, so that the temperature difference between the core and the surface of the steel coil is within 50°C.

5. The method for improving the shape quality of online quenched strip steel according to claim 1, characterized in that, In step S30, the steel coil after edge trimming is wound up again, and the winding tension is set to 1.1 to 1.2 times the normal production tension; the burr height of the strip edge after trimming is controlled to be below 0.1 mm, the side clearance of the disc shear is set to 8% to 12% of the strip thickness, and the overlap is set to 0.5 to 1.5 mm.

6. The method for improving the shape quality of online quenched strip steel according to claim 1, characterized in that, In step S40, the CPC and EPC lamps are cleaned at least once per shift, and the lens surface of the lamps is wiped with anhydrous ethanol; the response time of the CPC and EPC systems is less than 50 milliseconds, and the correction accuracy is controlled within ±2mm.

7. The method for improving the shape quality of online quenched strip steel according to claim 1, characterized in that, In step S50, the constant tension during the leveling process is set to 15 to 45 MPa; the bending roll force adjustment range of the leveling machine is set to -500 to +1200 kN, and the rolling force adjustment range is set to 2000 to 12000 kN.

8. The method for improving the shape quality of online quenched strip steel according to claim 1, characterized in that, In step S60, the selection rules for the multi-point measurement of the flat strip shape are as follows: a strip shape measurement is performed once at the positions where the outer ring length of the strip is 30 meters, 50 meters, and 100 meters respectively; in the middle area after the length exceeds 100 meters, a strip shape measurement is performed every 100 meters; and a strip shape measurement is performed once at the positions where the remaining length of the inner ring of the strip is 100 meters, 50 meters, and 30 meters respectively.

9. A method for improving the shape quality of online quenched strip steel according to claim 1 or 8, characterized in that, In step S60, the specific method for adjusting the leveling parameters based on the plate shape measurement results is as follows: when the measured edge waviness value is greater than 20 IU, the leveling rolling force is increased in steps of 50 to 100 kN, and the positive bending roll force is increased in steps of 20 to 50 kN; when the measured center waviness value is greater than 15 IU, the rolling force is kept constant, and the negative bending roll force is increased in steps of 30 to 60 kN.

10. A method for improving the shape quality of online quenched strip steel according to claim 1, characterized in that, The online quenched strip has a tensile strength of 1000 to 1500 MPa, a yield strength of 800 to 1200 MPa, and a strip thickness of 2.0 to 8.0 mm.

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