Method for improving warpage defects of cold-rolled high-strength steel

Abstract

The application provides a cold-rolled high-strength steel warping defect improvement method, which comprises strip dividing and straightening of a steel coil; and when there is an L warping defect in the outer ring of the steel coil, the entry roll gap value gradually increases from the outer ring to the inner ring. Through optimization of the hot rolling, cold rolling, recoiling and strip dividing and straightening processes, the application can effectively reduce the warping occurrence rate of the cold-rolled high-strength steel finished product, thereby improving the production efficiency and product precision and improving the product yield.

Description

Technical Field

[0001] This application relates to the field of metallurgical rolling technology, and in particular to a method for improving warping defects in cold-rolled high-strength steel. Background Technology

[0002] The production process of cold-rolled high-strength steel is relatively long, requiring multiple steps such as hot rolling, hot rolling leveling, pickling, cold rolling, annealing, cold rolling leveling, rewinding, and slitting straightening. Changes in the process parameters of each step can affect the shape and quality of the final product. In particular, the control of warping defects has always been a technical challenge in the industry.

[0003] Warping defects can be classified into L-warping (longitudinal warping) and C-warping (transverse warping) based on their direction, with L-warping defects having a particularly significant impact on subsequent uncoiling and processing. Cold rolling processes are typically equipped with automatic shape measurement devices and automatic shape control systems, which effectively control typical shape defects such as edge waviness, center waviness, and rib waviness. However, these systems cannot measure or effectively control C-warping and L-warping defects in finished strip steel. Improving warping defects has long relied on experience and parameter coordination across multiple processes. When warping defects exist in finished strip steel, they affect downstream processing accuracy, leading to a decrease in yield.

[0004] Those skilled in the art have conducted some research and proposed a variety of solutions to control warping defects in cold-rolled high-strength steel.

[0005] For example, patent publication CN104001757A discloses a "cold straightening process for thin-gauge high-strength steel plates," which improves the flatness of steel plates through a multi-pass, decreasing roll gap straightening process. However, this method is limited to parameter optimization of the straightening process itself, without considering the differences in the degree of defects at different radial positions of the steel coil, and without coordinating the rewinding process with the straightening process. In actual production, the straightening effect is limited.

[0006] Patent publication CN102527774A discloses a "dynamic adjustment method for the pressing process parameters of a roller straightener," which calculates and dynamically adjusts process parameters based on a mathematical model of yield strength. However, the calculation model used in this method is relatively complex, requiring high precision in data acquisition and equipment, making it difficult to quickly deploy and apply in actual production sites. Furthermore, its adjustment logic is independent of the strip uncoiling position and does not consider the uneven distribution of defects between the inner and outer rings of the steel coil.

[0007] Patent publication CN102921771A discloses a "rough straightener roll gap setting method." This method classifies incoming strip steel parameters by layer and sets corresponding roll gap setting values, keeping the straightening parameters constant during the straightening process of the same steel coil from the outer to the inner ring. Patent publication CN102974623A discloses a "pre-straightening method for achieving shape control of medium-thick plates." This method corrects the roll gap based on the shape of the head, middle, and tail of the steel plate. The adjustment is based on different sections along the length of the steel plate and is not directly related to the distribution of L-shaped warp defects in the radial position of the steel coil. The control logic is complex, and the adjustment direction is corrected based on real-time shape detection feedback. Furthermore, patent publication CN101439468A discloses a "tension bending, straightening, and rewinding unit process." This process only involves the combination of rewinding and straightening processes and does not involve determining the straightening parameters and the number of rewinding cycles based on the presence of L-shaped warp defects in the steel coil.

[0008] Patent publication CN118616500A discloses "A method for reducing the edge thickness of cold-rolled high-strength steel." This method requires controlling the crown of hot-rolled raw materials to ≤55μm, serving only as a static upper limit constraint and not involving reducing the target crown, thus failing to prevent downstream warping defects. Patent publication CN120961631A discloses "A method for improving the cross-sectional profile of cold-rolled raw materials." This method passively reduces or increases the target crown value based on the waviness and warping appearing in the middle or edge of the strip, with an adjustment range of ±10μm to 20μm. The purpose of this method is to eliminate existing plate defects in hot-rolled strip, which is a reactive correction rather than preventing downstream plate defects by actively adjusting the target crown.

[0009] In summary, existing technologies have the following shortcomings in improving warping defects in cold-rolled high-strength steel: First, there is a lack of coordinated control throughout the entire process from hot rolling to slitting and straightening, with each process being optimized independently; second, the straightening methods do not consider the differences in warping defects at different radial positions of the steel coil, and mostly adopt fixed roll gaps for the entire coil or adjustments between passes, without any technical solutions that correlate the number of rewindings with the defect situation or dynamically adjust the straightening roll gap based on outer ring defects; third, hot rolling crown control only performs static upper limit constraints or passive response adjustments, failing to prevent warping defects in downstream cold rolling processes by actively reducing the target crown. Summary of the Invention

[0010] The present invention was made in view of the above-mentioned problems, and its purpose is to provide a method for improving the warping defects of cold-rolled high-strength steel, thereby solving the technical problem of the high warping rate of existing cold-rolled high-strength steel products.

[0011] Specifically, the first aspect of the present invention provides a method for improving warping defects in cold-rolled high-strength steel, including slitting and straightening the steel coil. When the outer ring of the steel coil has an L-shaped warping defect, the entry roll gap value gradually increases from the outer ring to the inner ring.

[0012] By using a smaller entry roll gap value on the outer ring where L-shaped warp defects are more severe, and a larger entry roll gap value on the inner ring where L-shaped warp defects are less severe, a gradient matching of straightening strength is achieved, which not only ensures the straightening effect, but also avoids the generation of new plate shape defects due to over-straightening.

[0013] Optionally, when there is no L-shaped warping defect on the outer ring of the steel coil, the entry roll gap value gradually decreases from the outer ring to the inner ring.

[0014] A larger entry roll gap value is used for the outer ring without L-warp defects, while a smaller entry roll gap value is used for the inner ring, which may have more severe L-warp defects. This achieves a gradient matching of straightening strength, avoids over-straightening of the outer ring, and ensures that defects in the inner ring are effectively eliminated.

[0015] Optionally, when the outer ring of the steel coil has an L-shaped warping defect, the inlet roll gap value is -13mm to -4mm.

[0016] Optionally, when the outer ring of the steel coil has no L-shaped warping defect, the inlet roll gap value is -10mm to -4mm.

[0017] Optionally, when the outer ring of the steel coil has an L-shaped warping defect, the entry roll gap value of the outer ring of the steel coil is -13mm to -10mm.

[0018] Optionally, when the outer ring of the steel coil has an L-shaped warping defect, the entry roll gap value of the middle ring of the steel coil is -10mm to -7mm.

[0019] Optionally, when the outer ring of the steel coil has an L-shaped warping defect, the entry roll gap value of the inner ring of the steel coil is -7mm to -4mm.

[0020] Optionally, when the outer ring of the steel coil has no L-shaped warping defect, the entry roll gap value of the outer ring of the steel coil is -6mm to -4mm.

[0021] Optionally, when the outer ring of the steel coil has no L-shaped warping defect, the entry roll gap value of the middle ring of the steel coil is -8mm to -6mm.

[0022] Optionally, when the outer ring of the steel coil has no L-shaped warping defect, the inlet roll gap value for the inner ring of the steel coil is -10mm to -8mm.

[0023] Optionally, the exit roll gap value of the slitting straightening is -4mm to -2mm.

[0024] Optionally, the method for improving warping defects in cold-rolled high-strength steel also includes hot rolling, cold rolling, and rewinding.

[0025] Optionally, the target crown of the hot-rolled product is reduced during hot rolling.

[0026] Optionally, the cold rolling is performed using reciprocating rolling.

[0027] Optionally, the target sheet shape curve of the cold-rolled sheet adopts a small-to-medium wave control mode.

[0028] Optionally, during the rewinding process, if the outer ring of the steel coil has an L-shaped warp defect, the coil is rewound twice, and the strip with the L-shaped warp defect is placed on the outer ring of the rewound steel coil.

[0029] Optionally, during the rewinding process, if the outer ring of the steel coil has no L-shaped warping defect, it is rewound once.

[0030] Optionally, the maximum value of the mid-wave of the target plate-shaped curve is set to 5 IU to 10 IU.

[0031] Compared with the prior art, the present invention has the following beneficial effects: This invention employs a reverse entry roll gap control strategy based on the presence of L-shaped warp defects on the outer coil of the steel coil. When L-shaped warp defects are present on the outer coil, indicating a severe defect, a smaller entry roll gap is used for straightening. As the coil is unwound and moves towards the inner coil, the defect severity decreases, and the entry roll gap is gradually increased. This achieves a precise match between the straightening intensity and the radial defect distribution of the steel coil, effectively reducing the amount of L-shaped warp. When there are no L-shaped warp defects on the outer coil, the entry roll gap is gradually reduced to accommodate potentially more severe defects on the inner coil, avoiding over-straightening of the outer coil.

[0032] This invention selects one or two rewinding cycles based on the presence or absence of L-shaped warp defects on the outer ring after cold rolling and leveling, precisely placing the strip with L-shaped warp defects at the outer ring position of the rewound coil. This operation allows the roll gap control strategy of subsequent slitting and straightening to play a full role, forming a complete technical chain of "defect identification - defect location - targeted straightening," thus overcoming the shortcomings of existing technologies where rewinding and straightening are independent and lack coordination.

[0033] This invention actively reduces the target crown of the hot-rolled finished product during the hot rolling process. By utilizing the law that the actual crown changes in the same direction as the target crown, the average value of the actual crown decreases and becomes closer to the reduced target crown, thereby reducing the positive deviation. Combined with the small-wave control mode adopted in the cold rolling process, the degree of wavering during the cold rolling process is effectively reduced, thereby improving the C-warping defect of the cold-rolled high-strength steel finished product.

[0034] This invention optimizes the hot rolling, cold rolling, rewinding, and slitting straightening processes, which can effectively reduce the warping rate of cold-rolled high-strength steel products, thereby improving production efficiency and product precision, and increasing product yield. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this drawing or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this drawing. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of L-shaped and C-shaped warping defects in cold-rolled high-strength steel.

[0037] Figure 2 This is a comparison chart of the target crown setting value and the actual crown average value of hot rolling in Example 1 and Comparative Example 1.

[0038] Figure 3 This is a comparison chart of the cold-rolled target sheet shape curves of Example 1 and Comparative Example 1.

[0039] Figure 4 This is a schematic diagram of the L-shaped warping defect on the outer ring of the steel coil before slitting and straightening in Example 1 and Comparative Example 1.

[0040] Figure 5 This is a photograph showing the actual effect of normal L-curve and C-curve of the strip after slitting and straightening in Example 1. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the following description and illustration are provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0042] Obviously, the following description is merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0043] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0044] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0045] The method for detecting L-shaped warping defects on the outer ring of steel coils is as follows: After cold rolling and leveling, unwind the strip at the exit of the leveling machine and inspect the outer ring. Visually observe whether the end face of the strip shows an obvious longitudinal warping shape, or use a feeler gauge to measure the warping height. If the warping height exceeds a predetermined threshold, it is determined that an L-shaped warping defect exists; if the warping height is less than the threshold, it is determined that there is no L-shaped warping defect.

[0046] Figure 1 This diagram illustrates L-curve and C-curve defects in cold-rolled high-strength steel. The diagram shows two types of defects: L-curve (longitudinal warping, i.e., warping along the length of the strip) and C-curve (transverse warping, i.e., bending along the width of the strip). L-curve manifests as the strip end warping upwards or downwards, severely affecting downstream uncoiling and processing; C-curve manifests as bending along the width of the strip, affecting subsequent processing accuracy.

[0047] This invention is applicable to conventional cold-rolled high-strength steel grades, and its chemical composition and basic production process are conventional techniques in the field. By way of example and not limitation, the high-strength steel to which this invention applies may contain the following elements by weight percentage: C: 0.08%–0.20%, Si: 0.20%–0.50%, Mn: 0.7%–1.5%, P≤0.025%, S≤0.015%, Al: 0.020%–0.050%, with the remainder being Fe and unavoidable impurities. The above chemical composition can be adjusted according to the specific steel grade and target strength level, which can be understood and implemented by those skilled in the art.

[0048] The basic production process includes: slabs are heated in a walking beam furnace, then rolled on a roughing mill to obtain intermediate slabs, which are then rolled into hot-rolled finished coils on a 7-stand continuous rolling mill; the hot-rolled finished coils are then hot-rolled and leveled on a four-roll lower support roll driven leveler to improve the shape, followed by pickling to remove the surface oxide layer; then they enter a single-stand cold rolling process, where they undergo annealing to eliminate residual stress from cold rolling, followed by cold rolling and leveling on a single-stand four-roll mill to remove end-face and shape defects caused by annealing; finally, they are recoiled and slit straightened to become finished products. The above basic production process is conventional technology in this field, and its specific parameters can be adaptively adjusted according to equipment capacity and product specifications. Any method that can implement the control logic of the warp defect improvement method of this invention falls within the protection scope of this invention.

[0049] Example 1 The method for improving warpage defects in cold-rolled high-strength steel provided in this embodiment includes the following steps: Hot rolling: slabs of HC420LA steel grade (yield strength ≥ 420MPa) are selected and hot rolled in a conventional manner to obtain hot-rolled coils with a width of 1065mm and a thickness of 2.0mm. The target crown is set to 40μm, and the actual average crown of the hot-rolled finished product is 41μm.

[0050] Cold rolling: The cold rolling single stand adopts a reciprocating rolling mode, and the strip is threaded in one go until the rolling is completed. The unrolled parts at the beginning and end are cut off, and the maximum value of the wave in the target strip shape curve is set to 5IU.

[0051] Rewinding: Rewinding involves uncoiling and rewinding the strip steel. Uncoiling is performed to check for L-shaped warping defects on the outer ring. A predetermined threshold for warping height is set at 20mm. Using a feeler gauge, the warping height of the strip steel is measured to be 115mm, exceeding the predetermined threshold, indicating the presence of an L-shaped warping defect. The coil is then rewound twice, with the strip exhibiting the L-shaped warping defect placed on the outer ring of the rewound coil.

[0052] Slitting straightening: The straightening speed is 40m / min, the exit roll gap is fixed at -3mm, and the inlet roll gap is set in segments of -13mm for the outer ring, -10mm for the middle ring, and -7mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 15mm and the C-curvature height was measured to be 1.2mm using a feeler gauge.

[0053] Figure 4 This is a schematic diagram of the L-shaped warping defect on the outer ring of the steel coil before slitting and straightening in Example 1 and Comparative Example 1. The figure shows a schematic diagram of the L-shaped warping defect on the outer ring of the steel coil before slitting and straightening in Example 1.

[0054] Figure 5 This is a photograph showing the actual effect of the strip after slitting and straightening in Example 1, where the L-shaped and C-shaped warps are normal. The figure shows the strip is straight and close to the ground, with no obvious L-shaped or C-shaped warps.

[0055] Example 2 The difference between this embodiment and Embodiment 1 is that during slitting and straightening, the entry roll gap is set in segments of -13mm for the outer ring, -10mm for the middle ring, and -7mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 18mm and the C-curvature height was measured to be 1.5mm using a feeler gauge.

[0056] Example 3 The difference between this embodiment and Embodiment 1 is that during slitting and straightening, the entry roll gap is set in segments of -10mm for the outer ring, -7mm for the middle ring, and -4mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 20mm and the C-curvature height to be 1.7mm using a feeler gauge.

[0057] Example 4 The method for improving warpage defects in cold-rolled high-strength steel provided in this embodiment includes the following steps: Hot rolling: slabs of HC420LA steel grade (yield strength ≥ 420MPa) are selected and hot rolled in a conventional manner to obtain hot-rolled coils with a width of 1065mm and a thickness of 2.0mm. The target crown is set to 40μm, and the actual average crown of the hot-rolled finished product is 41um.

[0058] Cold rolling: The cold rolling single stand adopts a reciprocating rolling mode, and the strip is threaded in one go until the rolling is completed. The unrolled parts at the beginning and end are cut off, and the maximum value of the wave in the target strip shape curve is set to 5IU.

[0059] Rewinding: Rewinding involves uncoiling and rewinding the strip steel. Uncoiling is performed to check for L-shaped warping defects on the outer ring. A predetermined threshold for warping height is set at 20mm. Using a feeler gauge, the strip warping height is measured at 18mm, which does not exceed the predetermined threshold, indicating that there are no L-shaped warping defects on the outer ring. The coil is then rewound once.

[0060] Slitting straightening: The straightening speed is 40m / min, the exit roll gap is fixed at -3mm, and the inlet roll gap is set in segments of -5mm for the outer ring, -7mm for the middle ring, and -9mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 12mm and the C-curvature height was measured to be 1.0mm using a feeler gauge.

[0061] Example 5 The difference between this embodiment and Embodiment 4 is that during slitting and straightening, the entry roll gap is set in segments of -6mm for the outer ring, -8mm for the middle ring, and -10mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 14mm and the C-curvature height was measured to be 1.2mm using a feeler gauge.

[0062] Example 6 The difference between this embodiment and Embodiment 4 is that during slitting and straightening, the entry roll gap is set in segments of -4mm for the outer ring, -6mm for the middle ring, and -8mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 15mm and the C-curvature height was measured to be 1.1mm using a feeler gauge.

[0063] Comparative Example 1 The method for improving warpage defects in cold-rolled high-strength steel provided in this comparative example includes the following steps: Hot rolling: slabs of HC420LA steel grade (yield strength ≥ 420MPa) are selected and hot rolled in a conventional manner to obtain hot-rolled coils with a width of 1065mm and a thickness of 2.0mm. The target crown is set to 45μm, and the actual average crown of the hot-rolled finished product is 57μm.

[0064] Cold rolling: The cold rolling single stand adopts the reciprocating rolling mode, and the strip is threaded in one go until the rolling is completed. The unrolled parts at the beginning and end are cut off, and the maximum value of the wave in the target strip shape curve is set to 10IU.

[0065] Rewinding: Rewinding involves uncoiling and rewinding the strip steel. Uncoiling is performed to check for L-shaped warping defects on the outer ring. A predetermined threshold for warping height is set at 20mm. Using a feeler gauge, the strip warping height is measured to be 110mm, exceeding the predetermined threshold, indicating the presence of an L-shaped warping defect. The coil is then rewinded once.

[0066] Slitting straightening: The straightening speed is 40m / min, the exit roll gap is fixed at -3mm, and the inlet roll gap is set in segments of -13mm for the outer ring, -10mm for the middle ring, and -7mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 55mm and the C-curvature height was measured to be 3.8mm using a feeler gauge.

[0067] Figure 4 This is a schematic diagram of the L-shaped warping defect on the outer ring of the steel coil before slitting and straightening in Example 1 and Comparative Example 1. The figure shows a schematic diagram of the L-shaped warping defect on the outer ring of the steel coil before slitting and straightening in Comparative Example 1.

[0068] Comparative Example 2 The difference between this comparative example and Comparative Example 1 is that during slitting and straightening, the entry roll gap is set in segments of -13mm for the outer ring, -10mm for the middle ring, and -7mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 60mm and the C-curvature height to be 4.2mm using a feeler gauge.

[0069] Comparative Example 3 The difference between this comparative example and Comparative Example 1 is that during slitting and straightening, the entry roll gap is set in segments of -10mm for the outer ring, -7mm for the middle ring, and -4mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 50mm and the C-curvature height to be 3.6mm using a feeler gauge.

[0070] Comparative Example 4 The method for improving warpage defects in cold-rolled high-strength steel provided in this comparative example includes the following steps: Hot rolling: slabs of HC420LA steel grade (yield strength ≥ 420MPa) are selected and hot rolled in a conventional manner to obtain hot-rolled coils with a width of 1065mm and a thickness of 2.0mm. The target crown is set to 45μm, and the actual average crown of the hot-rolled finished product is 57μm.

[0071] Cold rolling: The cold rolling single stand adopts the reciprocating rolling mode, and the strip is threaded in one go until the rolling is completed. The unrolled parts at the beginning and end are cut off, and the maximum value of the wave in the target strip shape curve is set to 10IU.

[0072] Rewinding: Rewinding involves uncoiling and rewinding the strip steel. Uncoiling is performed to check for L-shaped warping defects on the outer ring. A predetermined threshold for warping height is set at 20mm. Using a feeler gauge, the strip warping height is measured at 17mm, which does not exceed the predetermined threshold, indicating that there are no L-shaped warping defects on the outer ring. The coil is then rewound twice.

[0073] Slitting straightening: The straightening speed is 40m / min, the exit roll gap is fixed at -3mm, and the inlet roll gap is set in segments of -5mm for the outer ring, -7mm for the middle ring, and -9mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 35mm and the C-curvature height was measured to be 2.5mm using a feeler gauge.

[0074] Comparative Example 5 The difference between this comparative example and Comparative Example 4 is that during slitting and straightening, the entry roll gap is set in segments of -6mm for the outer ring, -8mm for the middle ring, and -10mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 38mm and the C-curvature height was measured to be 2.8mm using a feeler gauge.

[0075] Comparative Example 6 The difference between this comparative example and Comparative Example 4 is that during slitting and straightening, the entry roll gap is set in segments of -4mm for the outer ring, -6mm for the middle ring, and -8mm for the inner ring. After straightening, the L-curvature height of the strip was measured to be 32mm and the C-curvature height was measured to be 2.3mm using a feeler gauge.

[0076] Figure 2 This is a comparison chart of the target crown setting value and the actual average crown value for hot rolling in Example 1 and Comparative Example 1. In Example 1, the target crown was reduced from 45 μm to 40 μm, and the actual average crown value was reduced from 57 μm to 41 μm, indicating that actively reducing the target crown can make the actual crown value closer to the target value.

[0077] Figure 3 This is a comparison chart of the cold-rolled target sheet shape curves of Example 1 and Comparative Example 1. The maximum value of the mid-wave of the target sheet shape curve in Comparative Example 1 is set to 10 IU. In Example 1, a small mid-wave mode is adopted, and the maximum value of the mid-wave of the target sheet shape curve is set to 5 IU, which can avoid the deterioration of C-warp and provide good sheet shape conditions for subsequent processes.

[0078] The above embodiments and comparative examples show that when the outer ring has an L-shaped warp defect, using two rewindings to place the defective strip on the outer ring, along with an entry roll gap that gradually increases from the outer ring to the inner ring, results in an L-shaped warp of 15mm to 20mm and a C-shaped warp of 0.8mm to 1.5mm after straightening. When the outer ring does not have an L-shaped warp defect, using one rewinding, along with an entry roll gap that gradually decreases from the outer ring to the inner ring, results in an L-shaped warp of 12mm to 16mm and a C-shaped warp of 0.9mm to 1.3mm after straightening. When the number of rewindings does not match the defect condition, even using the same straightening roll gap parameters, the L-shaped warp after straightening is 32mm to 55mm and the C-shaped warp is 2.3mm to 3.8mm. This is because the direction of change of the straightening roll gap does not match the radial defect distribution of the steel coil, causing the straightening strength to be unable to accurately act on the severely defective parts, resulting in a worse improvement effect than the solution of this invention.

[0079] This invention employs a dynamic control strategy during slitting and straightening, gradually increasing or decreasing the roll gap from the outer to the inner ring based on the presence or absence of L-shaped warp defects on the outer ring of the steel coil. This strategy is combined with proactive reduction of target crown during hot rolling, control of small and medium waviness during cold rolling, and coordinated matching of rewinding times with defect conditions, forming a systematic improvement scheme for warp defects throughout the entire process. Using the warp defect improvement method for cold-rolled high-strength steel provided by this invention, the L-shaped warp of cold-rolled high-strength steel is reduced from over 100mm to below 20mm, and the C-shaped warp height is reduced from over 3mm to below 2mm, significantly improving the finished sheet shape quality and increasing the product yield.

[0080] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for improving warping defects in cold-rolled high-strength steel, characterized in that, This includes slitting and straightening the steel coil. When the outer ring of the steel coil has an L-shaped warp defect, the entry roll gap value gradually increases from the outer ring to the inner ring.

2. The method for improving warping defects in cold-rolled high-strength steel according to claim 1, characterized in that, When there is no L-shaped warping defect on the outer ring of the steel coil, the entry roll gap value gradually decreases from the outer ring to the inner ring.

3. The method for improving warping defects in cold-rolled high-strength steel according to claim 1, characterized in that, The inlet roller gap value is -13mm to -4mm.

4. The method for improving warping defects in cold-rolled high-strength steel according to claim 2, characterized in that, The inlet roller gap value is -10mm to -4mm.

5. The method for improving warping defects in cold-rolled high-strength steel according to claim 3, characterized in that, The outer ring of the steel coil has an inlet roll gap of -13mm to -10mm. And / or, the inlet roll gap value of the middle ring of the steel coil is -10mm to -7mm; And / or, the inner ring of the steel coil has an inlet roll gap value of -7mm to -4mm.

6. The method for improving warping defects in cold-rolled high-strength steel according to claim 4, characterized in that, The outer ring of the steel coil has an inlet roll gap of -6mm to -4mm. And / or, the inlet roll gap value of the middle ring of the steel coil is -8mm to -6mm; And / or, for the inner ring of the steel coil, the inlet roll gap value is -10mm to -8mm.

7. The method for improving warping defects in cold-rolled high-strength steel according to claim 1 or 2, characterized in that, The exit roll gap value for the slitting straightening is -4mm to -2mm.

8. The method for improving warping defects in cold-rolled high-strength steel according to claim 1, characterized in that, It also includes hot rolling, cold rolling, and rewinding.

9. The method for improving warping defects in cold-rolled high-strength steel according to claim 8, characterized in that, The target crown of the hot-rolled product is reduced during hot rolling; And / or, the cold rolling is performed by reciprocating rolling; And / or, the target sheet shape curve of the cold-rolled sheet adopts a small-to-medium wave control mode; And / or, during the rewinding, if the outer ring of the steel coil has an L-shaped warp defect, it is rewound twice, and the strip with the L-shaped warp defect is placed on the outer ring of the rewound steel coil. And / or, during the rewinding, if the outer ring of the steel coil has no L-shaped warping defect, it is rewound once.

10. The method for improving warping defects in cold-rolled high-strength steel according to claim 9, characterized in that, The maximum value of the mid-wave in the target plate-shaped curve is set to 5 IU to 10 IU.

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