A method for controlling the shape of a hot-rolled DP980 dual-phase steel after cooling
By classifying the specifications and waviness of hot-rolled DP980 duplex steel, adjusting the cooling path and intensity, and adopting a sparse cooling mode and waterproof device, the plate shape problem during the post-rolling cooling process was solved, thereby improving product quality and enterprise competitiveness.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUNAN HUALING LIANYUAN STEEL SPECIAL NEW MATERIAL CO LTD
- Filing Date
- 2026-04-16
- Publication Date
- 2026-06-05
AI Technical Summary
During the post-rolling cooling process of hot-rolled DP980 duplex steel, the plate shape problem is particularly prominent, especially the frequent occurrence of double-sided wave defects, which affects the surface quality of the steel and causes quality objections from downstream customers.
By classifying the strip specifications and the waviness at the finishing mill exit, the target crown value is dynamically adjusted, the post-rolling cooling path and cooling intensity are adjusted, a sparse cooling mode is adopted, the auxiliary cooling device is turned off, and a waterproof device is set up during the coiling process to increase the coiling temperature.
It significantly improves the plate shape quality of hot-rolled DP980 duplex steel, reduces plate shape defects such as double-sided waves, improves the surface quality and pass rate of products, reduces the risk of quality objections from downstream customers, and enhances the company's market competitiveness and economic benefits.
Smart Images
Figure CN122142101A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of iron and steel smelting technology, and in particular to a method for controlling the shape of the plate after cooling in hot-rolled DP980 duplex steel. Background Technology
[0002] Hot-rolled duplex steel, as a new type of high-strength steel, possesses excellent comprehensive properties and is therefore widely used in automobile manufacturing, construction, machinery, and other fields. However, during the production process of duplex steel, due to its high deformation resistance, high temperature sensitivity, and uneven cooling rate, plate shape issues become particularly prominent. Especially during the post-rolling cooling process, double-sided wavy plate shape defects frequently occur, significantly reducing the surface quality of the steel. Steel coils with edge wavy defects, when used as cold-rolled base material, are prone to surface scratches during pickling, which not only affects the appearance of the product but also weakens its corrosion resistance, leading to quality objections from downstream customers and negatively impacting the company's reputation.
[0003] Patent CN104209340B discloses a method for controlling double-sided waviness in hot-rolled martensitic stainless steel strip. From a holistic perspective, it comprehensively considers the impact of each process on product straightness, implementing a multi-process integrated control method to improve product shape quality. This method can be widely used in the field of hot-rolled strip shape control. Patent CN106987773B discloses a high-strength steel plate and its shape control method. Through appropriate heating, rolling, cooling, and straightening process design, it ensures the steel plate's straightness meets requirements and reduces manufacturing costs. Patent CN104942023B discloses a method for controlling the shape of hot-rolled thin-gauge austenitic stainless steel strip. By adopting a post-cooling mode for laminar cooling and blocking the laminar cooling manifolds within a set range at the strip edge, combined with a cooling edge shielding method that adapts to changes in product width, it improves the transverse temperature uniformity of the strip and reduces double-sided waviness defects, thus improving shape quality.
[0004] In summary, different steel grades often have different strategies for solving the problem of wavy pattern during post-rolling cooling due to their different chemical compositions and final microstructures. Therefore, it is necessary to develop a process improvement strategy for the wavy pattern problem during post-rolling cooling of DP980 duplex steel. Summary of the Invention
[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide a method for controlling the shape of the plate after cooling in hot-rolled DP980 duplex steel.
[0006] Specifically, the first aspect of this application provides a method for controlling the shape of hot-rolled DP980 duplex steel after cooling, including the following steps: Step S1: Obtain the specifications and finishing mill exit bevel data of the strip steel, and classify the strip steel specifications and finishing mill exit bevel according to the preset classification rules; Step S2: Based on the grading results, dynamically adjust the target convexity value of the strip. Step S3: Adjust the cooling path and cooling intensity during the post-rolling cooling process, including reducing the cooling intensity of the ultra-fast cooling section, switching the cooling mode of the conventional cooling section to the sparse cooling mode, and turning off the auxiliary cooling device in the later stage. Step S4: Dynamically adjust the edge shielding range and the number of edge shielding devices activated in the laminar flow cooling zone according to the strip specifications; Step S5: Increase the winding temperature and install a waterproof device between the pinch roller and the winding machine to prevent cooling water from flowing into the winding area.
[0007] Furthermore, the grading of strip steel specifications in step S1 includes: dividing the strip steel into several specification categories based on its width and thickness, with different specification categories corresponding to different width and thickness ranges.
[0008] Furthermore, the specification categories include: Category 1: Width 950~1200 mm, thickness 2.2~2.7 mm; Category 2: Width 950~1200 mm, thickness 2.7~3.5 mm; Category 3: Width 1200~1400 mm, thickness 2.2~2.7 mm; Category 4: Width 1200~1400 mm, thickness 2.7~3.5 mm.
[0009] Furthermore, the classification of the waviness at the finishing mill exit in step S1 includes: dividing it into several waviness levels according to the magnitude of the waviness value, with different waviness levels corresponding to different waviness value ranges, where positive values represent edge waviness and negative values represent middle waviness; The wave pattern is divided as follows: Large edge waves: ≥60 IU; Edge waves: [30, 60) IU; Micro edge waves: [0, 30) IU; Slight to medium wave: (-30, 0] IU; Medium wave: (-60, -30] IU; Large to medium wave: ≤-60 IU.
[0010] Furthermore, the method for dynamically adjusting the target convexity value in step S2 is as follows: determine the convexity correction amount according to the wave level, and then superimpose the reference convexity set by the model with the convexity correction amount to obtain the corrected target convexity value.
[0011] Furthermore, the convexity correction amount has a monotonic correspondence with the wave shape level. When the wave shape level is biased towards the edge wave, the convexity correction amount is negative, and when the wave shape level is biased towards the middle wave, the convexity correction amount is positive.
[0012] Furthermore, in step S3: reducing the cooling intensity of the ultra-fast cooling section includes: reducing the number of ultra-fast cooling section activation groups to a preset low group range; the sparse cooling mode includes: in the front cooling zone after the finishing mill exit, the cooling manifold is activated at intervals; the rear auxiliary cooling device includes rear side spray water and rear fine adjustment water.
[0013] Furthermore, the method for dynamically adjusting the edge blocking range and the number of edge blocking devices activated in step S4 is as follows: the edge blocking ratio and the number of activated groups are determined according to the width and thickness of the strip steel, wherein the edge blocking ratio is positively correlated with the strip steel width and negatively correlated with the strip steel thickness, and the number of activated groups is positively correlated with the edge blocking ratio.
[0014] Furthermore, the step S5 of raising the winding temperature includes raising the winding temperature to a preset high temperature range; the waterproof device is a baffle structure set between the pinch roll exit side and the winding machine inlet, used to block the cooling water flowing along the strip surface.
[0015] The present invention has the following beneficial effects: This invention optimizes the cross-sectional shape of the strip from the rolling source by classifying the strip specifications and the waviness at the finishing mill exit, and dynamically adjusting the target crown value accordingly. This lays a solid foundation for shape control during subsequent cooling. In the post-rolling cooling stage, reducing the cooling intensity of the ultra-fast cooling section, adopting a sparse cooling mode, and shutting down the auxiliary cooling devices in the later stages effectively reduces the temperature gradient and thermal stress during cooling, avoiding waviness defects caused by over-cooling or uneven cooling. Simultaneously, dynamically adjusting the edge shielding range and the number of devices activated in the laminar flow cooling zone according to the strip specifications can specifically improve the cooling conditions at the strip edges, reducing edge over-cooling. Furthermore, increasing the coiling temperature and installing a waterproof device not only helps alleviate the internal stress of the strip during coiling but also prevents cooling water from entering the coiling area and adversely affecting coiling quality. By comprehensively applying these measures, the plate shape quality of hot-rolled DP980 duplex steel during the post-rolling cooling process can be significantly improved, effectively reducing the generation of plate shape defects such as double-sided waves, improving the surface quality and pass rate of products, reducing the risk of quality objections from downstream customers, and thus enhancing the company's market competitiveness and economic benefits. Attached Figure Description
[0016] 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.
[0017] Figure 1 This is a process flow diagram of the present invention; Figure 2 Schematic diagram of front-end sparse cooling and front-end concentrated cooling modes; Figure 3 To produce DP980 post-rolling cooling plate shape for comparative production; Figure 4 The DP980 post-rolling cooling plate shape was produced for Example 1.
[0018] The purpose, features, and advantages of this accompanying drawing will be further explained in conjunction with the embodiments and with reference to the accompanying drawing. Detailed Implementation
[0019] 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.
[0020] 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.
[0021] The first aspect of this application provides a method for controlling the shape of hot-rolled DP980 duplex steel after cooling, including the following steps: Step S1: Obtain the specifications and finishing mill exit bevel data of the strip steel, and classify the strip steel specifications and finishing mill exit bevel according to the preset classification rules; Step S2: Based on the grading results, dynamically adjust the target convexity value of the strip. Step S3: Adjust the cooling path and cooling intensity during the post-rolling cooling process, including reducing the cooling intensity of the ultra-fast cooling section, switching the cooling mode of the conventional cooling section to the sparse cooling mode, and turning off the auxiliary cooling device in the later stage. Step S4: Dynamically adjust the edge shielding range and the number of edge shielding devices activated in the laminar flow cooling zone according to the strip specifications; Step S5: Increase the winding temperature and install a waterproof device between the pinch roller and the winding machine to prevent cooling water from flowing into the winding area.
[0022] In this embodiment, the grading of strip steel specifications in step S1 includes: dividing the strip steel into several specification categories according to its width and thickness, with different specification categories corresponding to different width and thickness ranges.
[0023] In this embodiment, the specification categories include: Category 1: Width 950~1200 mm, thickness 2.2~2.7 mm; Category 2: Width 950~1200 mm, thickness 2.7~3.5 mm; Category 3: Width 1200~1400 mm, thickness 2.2~2.7 mm; Category 4: Width 1200~1400 mm, thickness 2.7~3.5 mm.
[0024] In this embodiment, the classification of the waviness at the finishing mill exit in step S1 includes: dividing it into several waviness levels according to the size of the waviness value, with different waviness levels corresponding to different waviness value ranges, where positive values represent edge waviness and negative values represent middle waviness; Wave shape is evaluated using I-units (IU) and divided into six levels: Large edge waves: ≥60 IU; Edge waves: [30, 60) IU; Micro edge waves: [0, 30) IU; Slight to medium wave: (-30, 0] IU; Medium wave: (-60, -30] IU; Large to medium wave: ≤-60 IU.
[0025] In this embodiment, the method for dynamically adjusting the target convexity value in step S2 is as follows: A convexity correction amount is determined based on the wave level, and the corrected target convexity value is obtained by superimposing the baseline convexity set by the model with the convexity correction amount. The convexity correction amount has a monotonic correspondence with the wave level; the convexity correction amount is negative when the wave level is biased towards the edge wave and positive when the wave level is biased towards the middle wave.
[0026] According to the wave shape level, the model setting crown change amount is modified sequentially from large edge wave to large and medium wave to -12μm, -9μm, -6μm, -3μm, 0μm, and 3μm. The corresponding wave shape level is divided for four different specifications of strip steel, thereby modifying the crown target value for each specification of rolled strip steel.
[0027] The corrected convexity target = model-defined baseline convexity + correction amount.
[0028] The determination of this correction amount is based on the following mechanism: edge waviness (positive waviness) indicates that the edge of the strip has excessive elongation relative to the center. The fundamental reason is that the excessively rapid cooling rate at the edge leads to premature martensitic transformation and restricted volume expansion, resulting in compressive stress. By reducing the crown target, the cross-sectional shape of the rolled strip can be made flatter, reserving deformation space for phase transformation expansion during the cooling process. The magnitude of the correction amount is linearly related to the severity of the waviness, with approximately 2~3μm crown correction for every 10 IU of waviness. Experiments have verified that this ratio has the best compensation effect on DP980 steel.
[0029] In this embodiment, step S3: reducing the cooling intensity of the ultra-fast cooling section includes: reducing the number of ultra-fast cooling section activation groups to a preset low group range; preferably, the number of ultra-fast cooling section activation groups is reduced from 5 groups in the conventional process to 2~3 groups, and the specific number of groups is determined according to the strip thickness: 2 groups are activated when the thickness is ≤2.7 mm, and 3 groups are activated when the thickness is >2.7 mm. The sparse cooling mode includes: in the front cooling zone after the finishing mill exit, the cooling manifolds are opened at intervals; preferably, the conventional cooling section mode switching adopts the "front sparse cooling" mode instead of the "front concentrated cooling" mode. The "front concentrated cooling" refers to the complete opening of all cooling manifolds in a dense manner of "1 group open, 0 groups closed" in the first 1 / 3 of the cooling zone after the finishing mill exit, resulting in high cooling intensity and a short cooling zone. The "front sparse cooling" refers to the intermittent opening of cooling manifolds in a sparse manner of "1 group open, 1 group closed" or "1 group open, 2 groups closed" in the first 1 / 3 of the cooling zone after the finishing mill exit, resulting in reduced cooling intensity and a longer cooling zone, thereby reducing the peak transverse temperature difference of the strip. In this embodiment, DP980 adopts the "1 group open, 1 group closed" sparse mode.
[0030] The shut-off auxiliary cooling device includes rear-section side spray water and rear-section fine-tuning water. Shutting off the side spray water and fine-tuning water of the laminar flow cooling rear section prevents residual cooling water at the tail end from causing localized overcooling before winding.
[0031] In this embodiment, the method for dynamically adjusting the edge blocking range and the number of edge blocking devices activated in step S4 is as follows: the edge blocking ratio and the number of activated groups are determined according to the width and thickness of the strip steel, wherein the edge blocking ratio is positively correlated with the strip steel width and negatively correlated with the strip steel thickness, and the number of activated groups is positively correlated with the edge blocking ratio.
[0032] As the strip width increases and the thickness decreases, the edge occlusion area becomes larger, and the number of opening groups also increases. The specific matching relationship is as follows: (1) For the first type of strip steel specifications, the edge shading range accounts for 7% of the width specification, and 5 sets are put into use.
[0033] (2) For the second type of strip steel specifications, the edge shading range accounts for 5% of the width specification, and 3 sets are put into use.
[0034] (3) For the third category of strip steel specifications, the edge shading range accounts for 10% of the width specification, and 6 sets are put into use. (4) For the fourth category of strip steel specifications, the edge shading range accounts for 8% of the width specification, and 4 sets are put into use.
[0035] The matching principle between the edge occlusion ratio and the number of enabled groups follows: The wider the strip, the greater the shading ratio (wider strips have a larger heat dissipation area at the edges, requiring a larger shading range to suppress overcooling at the edges). The smaller the thickness, the greater the shielding ratio (thinner specifications have smaller heat capacity and faster cooling rate, requiring stronger shielding). The number of groups that can be activated increases as the occlusion ratio increases (ensuring that the occlusion effect covers the entire length of the cooling zone).
[0036] In this embodiment, the step S5 of increasing the winding temperature includes: increasing the winding temperature to a preset high temperature range; increasing the winding temperature from 545°C in the conventional process to 560~575°C. The selection of this temperature range is based on the following: below 560°C, the martensite transformation rate is still too high, and the residual stress is difficult to be fully released; above 575°C, excessive bainite is generated in the microstructure, affecting the mechanical properties of the finished product.
[0037] The waterproof device is a baffle structure installed between the exit side of the pinch roll and the inlet of the coiler, used to block the cooling water flowing along the surface of the strip. The waterproof baffle is made of stainless steel, with a width matching the width of the strip, and is installed between the exit side of the pinch roll and the inlet of the coiler, 10-15 mm away from the upper surface of the strip, extending downstream at an angle of 15°-30°, to block the cooling water flowing along the surface of the strip and prevent it from entering the coiling area and causing localized rapid cooling.
[0038] Example The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight. Unless otherwise stated, all reagents used in the examples are available commercially or synthesized using conventional methods and are ready for use without further processing. Unless otherwise stated, all instruments used in the examples are available commercially.
[0039] See Figure 1 A method for controlling the shape of hot-rolled DP980 duplex steel after cooling includes the following steps: Step S1: Ensuring that all equipment is in good working order and strip rolling is stable, collect DP980 duplex steel production rolling data, and classify the strip specifications and finishing mill exit waviness as follows: DP980 strip steel specifications are divided into four categories: Category 1: Width 950~1200 mm, thickness 2.2~2.7 mm; Category 2: Width 950~1200 mm, thickness 2.7~3.5 mm; Category 3: Width 1200~1400 mm, thickness 2.2~2.7 mm; Category 4: Width 1200~1400 mm, thickness 2.7~3.5 mm.
[0040] Step S2: The classification of the waviness at the finish rolling mill exit is shown in Table 1 below. Negative values represent intermediate waviness, and positive values represent edge waviness.
[0041] The rolled DP980 duplex steel specification is taken as 2.5mm thick, 1100mm wide, with a target crown value of 45μm. According to the specification classification, it belongs to the first category. The average waviness value of the finished roll exit of this type of strip steel is 25IU, which is classified as micro-edge waviness according to the waviness level. The model sets the baseline convexity to 45 μm. Based on the wave level "micro-edge wave", the correction amount is found to be -6 μm according to the table. Therefore, the target convexity value after correction is 39 μm. Step S3: Adjust the cooling path and cooling intensity during the post-rolling cooling of DP980 duplex steel. The specific steps are as follows: (1) For thicknesses of 2.5 mm ≤ 2.7 mm, the number of ultra-fast cooling groups activated in laminar flow cooling is reduced from 5 groups to 2 groups; (2) The conventional cooling section adopts a front-end sparse cooling mode instead of a front-end centralized cooling mode, that is, an interval of "one group on, one group off", as shown in the schematic diagram. Figure 2 As shown; (3) Turn off the side spray water and the fine-tuning water in the rear section of the laminar flow cooling system; Step S4: Adjust the edge shielding range and number of opening groups of the laminar flow cooling section according to the strip specifications. The rolled strip specifications belong to category b, the edge shielding ratio is 5%, and 3 sets of edge shielding are put into use, with a shielding range of 55mm (1100 mm × 5% = 55 mm). Step S5: Increase the coiling temperature from 545℃ to 560℃. Install a waterproof baffle between the pinch rolls and the coiler. The baffle's width should match the strip steel, and it should extend downstream at a 20° angle, 12 mm from the top surface of the strip steel, to prevent cooling water from flowing into the coiler. See [link to post-rolling cooling plate shape] for details. Figure 4 .
[0042] result: Finished plate shape wave value: 8 IU (slight edge wave); Residual stress: edge compressive stress -12 MPa, middle tensile stress +8 MPa, uniformly distributed; Return rate: 5.8% (8.5% for the same specifications and original process).
[0043] Example 2 This embodiment is basically the same as Embodiment 1, except that the DP980 duplex steel rolled in step S2 is 3.0 mm thick and 1100 mm wide. Classified by specifications, it belongs to the second category. Statistically, the average waviness value at the finishing mill exit of this type of strip steel is 25 IU, which is classified as micro-edge waviness according to the waviness level. The model is set with a baseline convexity of 50 μm. According to the wave level "micro-edge wave", the correction amount is -6 μm. Therefore, the target convexity value after correction is 44 μm. Step S3: Adjust the cooling path and cooling intensity during the post-rolling cooling of DP980 duplex steel. The specific steps are as follows: (1) The number of ultra-fast cooling groups activated in laminar flow cooling is 3; (2) The conventional cooling section adopts the front-end sparse cooling mode instead of the front-end centralized cooling mode, that is, the interval method of "opening 1 group and closing 1 group". (3) Turn off the side spray water and the fine-tuning water in the rear section of the laminar flow cooling system; Step S4: Adjust the edge shielding range and number of opening groups of the laminar flow cooling section according to the strip specifications. The rolled strip specifications belong to category b, the edge shielding ratio is 5%, and 3 sets of edge shielding are put into use, with a shielding range of 65mm (1300 mm × 5% = 65 mm). Step S5: The winding temperature is 570℃. A waterproof baffle is installed between the pinch roll and the winding machine. The width matches the strip steel, and it extends downstream at an angle of 20° from the upper surface of the strip steel to block the cooling water from flowing into the winding machine.
[0044] result: Finished plate shape wave value: 6 IU (slight edge wave); Residual stress: edge compressive stress -8 MPa, middle tensile stress +5 MPa, uniformly distributed; Return rate: 4.5% (6.2% for the same specifications and original process).
[0045] Example 3 This embodiment is basically the same as Embodiment 1, except that the DP980 duplex steel rolled in step S2 is 2.3mm thick and 1350mm wide. Classified by specifications, it belongs to the third category. Statistically, the average waviness value at the finishing exit of this type of strip steel is 35IU, which, according to waviness level, belongs to edge waviness. The model sets the baseline convexity to 50μm. According to the wave level "edge wave", the correction amount is -9μm according to the table. Therefore, the target convexity value after correction is 41μm. Step S3: Adjust the cooling path and cooling intensity during the post-rolling cooling of DP980 duplex steel. The specific steps are as follows: (1) The number of ultra-fast cooling groups activated in laminar flow cooling is 2; (2) The conventional cooling section adopts the front-end sparse cooling mode instead of the front-end centralized cooling mode, that is, the interval method of "opening 1 group and closing 1 group". (3) Turn off the side spray water and the fine-tuning water in the rear section of the laminar flow cooling system; Step S4: Adjust the edge shielding range and number of opening groups of the laminar flow cooling section according to the strip specifications. The rolled strip specifications belong to category C, the edge shielding ratio is 10%, and 6 groups of edge shielding are put into use. Step S5: The winding temperature is 560℃. A waterproof baffle is installed between the pinch roll and the winding machine. The width matches the strip steel, and it extends downstream at an angle of 20° from the upper surface of the strip steel to block the cooling water from flowing into the winding machine.
[0046] result: Finished plate corrugation value: 12 IU; Residual stress: edge compressive stress -18 MPa, middle tensile stress +12 MPa, uniformly distributed; Return rate: 7.2% (12.3% for the same specifications and original process).
[0047] Comparative Example 1 This comparative example is basically the same as Example 1, except that the DP980 duplex steel rolled in step S2 is 2.5mm thick and 1300mm wide. Classified by specifications, it belongs to the third category. Statistically, the average waviness value at the finishing exit of this type of strip steel is 52 IU, which, according to waviness level, belongs to edge waviness. The model is set to a baseline convexity of 50 μm, and no convexity correction is performed. Step S3: Adjust the cooling path and cooling intensity during the post-rolling cooling of DP980 duplex steel. The specific steps are as follows: (1) The number of ultra-fast cooling groups activated in laminar flow cooling is 5; (2) A front-end centralized cooling mode is adopted; (3) Turn off the side spray water and the fine-tuning water in the rear section of the laminar flow cooling system; Step S4: Do not perform edge occlusion; Step S5: Coiling temperature is 545℃, without a waterproof baffle. See the image for the post-rolling cooling plate shape. Figure 3 .
[0048] result: Finished plate corrugation value: 48 IU; Residual stress: edge compressive stress -58 MPa, middle tensile stress +35 MPa, uniformly distributed; Return rate: 12.3%.
[0049] Comparative Example 2 This comparative example is basically the same as Example 1, except that the DP980 duplex steel rolled in step S2 is 2.5mm thick and 1300mm wide. Classified by specifications, it belongs to the third category. Statistically, the average waviness value at the finishing exit of this type of strip steel is 50 IU, and according to the waviness level, it belongs to the edge waviness category. The model sets the baseline convexity to 50μm. According to the wave level "edge wave", the correction amount is -9μm according to the table. Therefore, the target convexity value after correction is 41μm. Step S3: Adjust the cooling path and cooling intensity during the post-rolling cooling of DP980 duplex steel. The specific steps are as follows: (1) The number of ultra-fast cooling groups activated in laminar flow cooling is 5; (2) A front-end centralized cooling mode is adopted; (3) Turn off the side spray water and the fine-tuning water in the rear section of the laminar flow cooling system; Step S4: Do not perform edge occlusion; Step S5: Winding temperature is 545℃, without waterproof baffle.
[0050] result: Finished plate wave value: 35 IU (edge waves are still obvious); Residual stress: edge compressive stress -42 MPa, middle tensile stress +25 MPa, uniformly distributed; Return rate: 9.5%.
[0051] Comparative Example 3 This comparative example is basically the same as Example 1, except that the DP980 duplex steel rolled in step S2 is 2.5mm thick and 1300mm wide. Classified by specifications, it belongs to the third category. Statistically, the average waviness value at the finishing exit of this type of strip steel is 48 IU, which, according to waviness level, belongs to edge waviness. Step S3: Adjust the cooling path and cooling intensity during the post-rolling cooling of DP980 duplex steel. The specific steps are as follows: (1) The number of ultra-fast cooling groups activated in laminar flow cooling is 2; (2) Employ front-end sparse cooling; (3) Turn off the side spray water and the fine-tuning water in the rear section of the laminar flow cooling system; Step S4: Do not perform edge occlusion; Step S5: Winding temperature is 545℃, without waterproof baffle.
[0052] result: Finished plate corrugation value: 32 IU; Residual stress: edge compressive stress -38MPa, middle tensile stress +22MPa, uniformly distributed; Return rate: 8.8%.
[0053] 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 controlling the shape of hot-rolled DP980 duplex steel after cooling, characterized in that, Includes the following steps: Step S1: Obtain the specifications and finishing mill exit bevel data of the strip steel, and classify the strip steel specifications and finishing mill exit bevel according to the preset classification rules; Step S2: Based on the grading results, dynamically adjust the target convexity value of the strip. Step S3: Adjust the cooling path and cooling intensity during the post-rolling cooling process, including reducing the cooling intensity of the ultra-fast cooling section, switching the cooling mode of the conventional cooling section to the sparse cooling mode, and turning off the auxiliary cooling device in the later stage. Step S4: Dynamically adjust the edge shielding range and the number of edge shielding devices activated in the laminar flow cooling zone according to the strip specifications; Step S5: Increase the winding temperature and install a waterproof device between the pinch roller and the winding machine to prevent cooling water from flowing into the winding area.
2. The method for controlling the shape of hot-rolled DP980 duplex steel after cooling according to claim 1, characterized in that, The grading of strip steel specifications in step S1 includes: dividing the strip steel into several specification categories based on its width and thickness, with different specification categories corresponding to different width and thickness ranges.
3. The method for controlling the shape of hot-rolled DP980 duplex steel after cooling according to claim 2, characterized in that, The specification categories include: Category 1: Width 950~1200 mm, thickness 2.2~2.7 mm; Category 2: Width 950~1200 mm, thickness 2.7~3.5 mm; Category 3: Width 1200~1400 mm, thickness 2.2~2.7 mm; Category 4: Width 1200~1400 mm, thickness 2.7~3.5 mm.
4. The method for controlling the shape of hot-rolled DP980 duplex steel after cooling according to claim 1, characterized in that, The classification of the waviness at the finishing mill exit in step S1 includes: dividing it into several waviness levels according to the size of the waviness value, with different waviness levels corresponding to different waviness value ranges, where positive values represent edge waviness and negative values represent middle waviness; The wave pattern is divided as follows: Large edge waves: ≥60 IU; Edge waves: [30, 60) IU; Micro edge waves: [0, 30) IU; Slight to medium wave: (-30, 0] IU; Medium wave: (-60, -30] IU; Large to medium wave: ≤-60 IU.
5. The method for controlling the shape of hot-rolled DP980 duplex steel after cooling as described in claim 1, characterized in that, The method for dynamically adjusting the target convexity value in step S2 is as follows: determine the convexity correction amount according to the wave level, and then superimpose the reference convexity set by the model with the convexity correction amount to obtain the corrected target convexity value.
6. The method for controlling the shape of hot-rolled DP980 duplex steel after cooling according to claim 5, characterized in that, The convexity correction amount has a monotonic correspondence with the wave shape level. When the wave shape level is biased towards the edge wave, the convexity correction amount is negative, and when the wave shape level is biased towards the middle wave, the convexity correction amount is positive.
7. The method for controlling the shape of hot-rolled DP980 duplex steel after cooling as described in claim 1, characterized in that, In step S3: reducing the cooling intensity of the ultra-fast cooling section includes: reducing the number of ultra-fast cooling section activation groups to a preset low group range; the sparse cooling mode includes: in the front cooling zone after the finishing mill exit, the cooling manifold is activated at intervals; the rear auxiliary cooling device includes rear side spray water and rear fine adjustment water.
8. The method for controlling the shape of hot-rolled DP980 duplex steel after cooling according to claim 1, characterized in that, The method for dynamically adjusting the edge blocking range and the number of edge blocking devices activated in step S4 is as follows: determine the edge blocking ratio and the number of activated groups based on the width and thickness of the strip steel, wherein the edge blocking ratio is positively correlated with the strip steel width and negatively correlated with the strip steel thickness, and the number of activated groups is positively correlated with the edge blocking ratio.
9. The method for controlling the shape of hot-rolled DP980 duplex steel after cooling according to claim 1, characterized in that, The step S5 of raising the winding temperature includes raising the winding temperature to a preset high temperature range; the waterproof device is a baffle structure set between the exit side of the pinch roll and the inlet of the coiler, used to block the cooling water flowing along the surface of the strip.