A method for controlling the camber defects at the beginning and end of hot-rolled thin steel strip

Abstract

This invention relates to the field of steel rolling technology, specifically to a method for controlling the camber defect at the beginning and end of hot-rolled thin steel strip. The method includes: increasing the slab heating time (hot slab heating time ≥ 200 min, cold slab heating time ≥ 220 min); using a three-pass (1, 3, 5 passes) steel plate centering method for rough rolling R2; increasing the R2DT temperature by 20-30℃ compared to slabs of the same steel grade with a thickness of 2.5 mm or more; maintaining the R2 exit slab thickness at 30-35 mm; controlling the offset between the steel strip and the mill centerline after rough rolling within ±30 mm; and using an insulation cover on the slab before finishing rolling and employing edge heaters for supplemental heating. This invention optimizes the slab heating, rough rolling, and finishing rolling processes, as well as roll period, strip shape settings, and surface inspection feedback. By adopting full-process quality control from the hot rolling inlet to the outlet, it effectively improves the camber defect at the beginning and end, reduces quality re-judgment and cutting losses, and is suitable for stable large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of steel rolling technology, specifically to a method for controlling the head and tail camber defects of hot-rolled thin steel strip. Background Technology

[0002] Hot-rolled camber is a common defect in hot-rolled steel strips, particularly pronounced within 50m of the beginning and end of thin-gauge strips. This severely impacts product quality and production efficiency. For hot-rolled finished products, camber defects cause misalignment and dimensional discrepancies in parts during reprocessing, leading to cutting losses and scrapping. For cold-rolled raw materials, the cold rolling process is prone to deviation, strip breakage, and steel piling, causing roll damage or shutdowns. This is especially true for pickling and continuous rolling mills, where the large number of loopers increases the risk of deviation and shutdowns, affecting the mill's production rhythm.

[0003] To prevent camber defects in hot-rolled steel strips, automatic correction technology and equipment for roughing and finishing mill camber have been developed. This involves measuring and controlling camber using anti-deviation detection and control equipment. However, the investment in detection instruments and equipment is high, and the control is mainly aimed at camber after roughing. Control measures and feedback methods are limited, resulting in limited improvement effects on camber after finishing.

[0004] CN 111318579 A discloses a data-driven method for controlling camber in roughing mills. The method includes: establishing a data-driven prediction model for the head and tail camber of the intermediate slab in roughing mills; collecting process data related to camber in roughing mills; forming multiple sets of input data by taking the leveling values ​​of the current pass operator within the allowable range of the leveling values ​​and using a set accuracy as the step size; predicting the head camber value YHc and the tail camber value YTc based on the input data and the established prediction model; determining the objective function value corresponding to each leveling value of the current pass operator based on the obtained YHc and YTc; and sending the sum of the leveling value of the current pass operator when the objective function reaches its minimum value and its intervention value as the comprehensive leveling value of the current pass operator to the basic automated control system of the roughing mill to perform roll tilt adjustment.

[0005] CN 106914495 A discloses a method and system for controlling the camber of hot-rolled strip steel, comprising the following steps: S1. Calculating the curvature ρ of the camber of the slab after rough rolling; S2. Calculating the roll gap wedge compensation amount ΔS of the finishing mill based on the curvature ρ; S3. Controlling the roll gap value of the finishing mill based on the roll gap wedge compensation amount ΔS. This invention provides a method and system for controlling the camber of hot-rolled strip steel.

[0006] CN 109877184 A discloses a method for improving the camber defect of steel strip, including step 1: when the steel strip is being leveled, ensuring that the deviation between the center position of the steel strip and the center position of the leveling equipment meets a first preset condition; step 2: after leveling and slitting, determining whether the steel strip has a camber defect; step 3: when the steel strip has a camber defect, obtaining the defect location of the steel strip; step 4: adjusting the pressing amount of the first straightening roller at the defect location according to a first adjustment mode, and / or adjusting the relative position between the support rollers distributed above the first straightening roller and the steel strip according to a second adjustment mode; step 5: repeating step 4 until the steel strip meets the second preset condition.

[0007] Based on this, existing methods for controlling the camber of hot-rolled strip mainly rely on theoretical calculations and process models, or on how to improve the hot-rolled coils that have already developed camber defects during the leveling process in reprocessing. There is a lack of methods to improve the camber defects at the beginning and end of hot-rolled thin steel strips from the perspective of controlling each stage of the hot rolling process. Summary of the Invention

[0008] To address the particularly prominent issue of camber within 50m of the beginning and end of hot-rolled steel strip, this invention provides a method for controlling camber defects at the beginning and end of hot-rolled thin steel strip. By optimizing production processes such as slab heating, roughing, and finishing rolling, as well as setting roll period, strip shape, and surface inspection feedback, and employing full-process quality control from the hot rolling inlet to the outlet, the method effectively improves camber defects at the beginning and end, reduces quality re-judgment and cutting losses, and is suitable for stable production in large-scale industries.

[0009] The technical solution of this invention is as follows:

[0010] A method for controlling the camber defects at the beginning and end of hot-rolled thin steel strip includes:

[0011] Optimize slab heating process: Increase slab heating time, hot slab heating time ≥200min, cold slab heating time ≥220min, to ensure sufficient heating, ensure uniform temperature from the surface to the core of the billet, and reduce the risk of camber caused by temperature fluctuations at the beginning and end;

[0012] Optimize the slab roughing process: R2 roughing uses a three-pass process of 1, 3, and 5 passes for steel plate centering, which ensures the head and tail shape of the rough-rolled slab while reducing the temperature drop during the process; the R2DT temperature is 20-30℃ higher than that of slabs of the same steel grade with a thickness of 2.5mm or more, which can compensate for the temperature drop during the rolling process of thin-gauge steel strips; the slab thickness at the R2 exit is 30-35mm, ensuring reasonable control of the rolling reduction rate; the offset between the steel strip and the centerline of the mill after roughing is controlled within ±30mm, providing good conditions for finishing rolling;

[0013] Optimize the slab finishing rolling process: before finishing rolling, the slab is covered with an insulation cover and the edge heater is used to supplement the temperature, so as to reduce the temperature difference between the head and tail of the intermediate slab and the edge, which is beneficial to the control of the slab shape.

[0014] Furthermore, the control methods also include controlling the slab specifications: the difference between the slab width and the width of the hot-rolled finished steel strip is ≤20mm, and the fixed-width press is not used to reduce the width, thereby reducing the process temperature drop of the slab.

[0015] Furthermore, the control methods also include optimizing the roll period: the roll period of the roughing R2 work roll is controlled at 7,000 to 50,000 tons, and the roll period of the finishing support roll is controlled at 7,000 to 150,000 tons, which is conducive to the reasonable matching of roll crown and steel strip shape.

[0016] Furthermore, the control method also includes optimizing the strip shape setting: the crown of the finished strip is controlled at 35~50μm, with a target of 40μm, |wedge|≤25μm, and crown -|wedge|>0μm, which is beneficial for controlling the camber defect of the steel strip.

[0017] Furthermore, the control method also includes surface inspection feedback: the side bending of the steel strip is detected by an online surface inspection instrument at the exit of the hot rolling finishing mill. If the side bending exceeds 30mm, feedback is given to optimize the centering direction of the finishing mill to form a closed-loop control and avoid the sickle bend defect from exceeding the standard.

[0018] Furthermore, the thickness H of the hot-rolled thin steel strip is less than 2.5 mm.

[0019] The beneficial effects of this invention are as follows:

[0020] The method for controlling the camber defects at the beginning and end of hot-rolled thin steel strip provided by this invention requires no investment in testing instruments and equipment, and the process is controllable, which is conducive to its promotion and application. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0022] Example 1

[0023] To control the camber defects at the beginning and end of SGC400 hot-rolled thin steel strip, with strip specifications of 2.3*1520mm, the process parameters during hot rolling are controlled as follows:

[0024] Optimize the slab heating process: The steelmaking slab adopts a hot delivery mode with a heating time of 232 minutes.

[0025] Slab specifications are controlled as follows: the slab size is 230*1530*92000mm, the difference between the slab width and the steel strip width is 10mm, and a fixed width press is not used.

[0026] Optimize the slab roughing process: The hot-rolled roughing R2 uses three passes of steel plate centering in passes 1, 3 and 5; the roughing R2DT temperature is 1105℃ (1080℃ for the same steel grade and thickness specification), the R2 exit slab thickness is 33.6mm, and the offset from the center line of the unit is 12mm.

[0027] Optimize the slab finishing rolling process: before finishing rolling, the slab is covered with an insulation cover and the edge heater is used for heat supplementation.

[0028] Optimize roll duration: Control the roll duration of the roughing mill R2 work rolls to 7650 tons and the roll duration of the finishing mill support rolls to 8900 tons.

[0029] Optimize the plate shape settings: the crown of the hot-rolled and finished plate is 42μm, the wedge shape is -16μm, and (crown shape - |wedge shape|) = 26μm > 0.

[0030] Inspection feedback: The online inspection instrument at the hot-rolled finishing mill exit measured a lateral bend of 8mm at the head 50m and a lateral bend of 7mm at the tail 50m of the steel strip.

[0031] The hot-rolled steel coils wound using the above method have good coil shape and no excessive camber defects at the beginning and end.

[0032] Example 2

[0033] To control the camber defects at the beginning and end of SGC400 hot-rolled thin steel strip, with a strip specification of 2.1*1340mm, the process parameters during hot rolling are controlled as follows:

[0034] Optimize the slab heating process: The steelmaking slab adopts a hot delivery mode with a heating time of 255 minutes.

[0035] Slab specifications are controlled as follows: the slab size is 230*1355*90000mm, the difference between the slab width and the steel strip width is 15mm, and a fixed width press is not used.

[0036] Optimize the slab roughing process: The hot-rolled roughing R2 uses three passes of steel plate centering in passes 1, 3 and 5; the roughing R2DT temperature is 1108℃ (1080℃ for the same steel grade and thickness specification), the R2 exit slab thickness is 34.5mm, and the offset from the centerline of the unit is 8mm.

[0037] Optimize the slab finishing rolling process: before finishing rolling, the slab is covered with an insulation cover and the edge heater is used for heat supplementation.

[0038] Optimize roll duration: Control the roll duration of the roughing mill R2 work rolls to 8560 tons and the roll duration of the finishing mill support rolls to 12750 tons.

[0039] Optimize the plate shape settings: the crown of the hot-rolled and finished plate is 37μm, the wedge shape is 9μm, and (crown shape - |wedge shape|) = 28μm > 0.

[0040] Inspection feedback: The online inspection instrument at the hot-rolled finishing mill exit measured a lateral bend of 12mm at the head 50m and 25mm at the tail 50m of the steel strip.

[0041] The hot-rolled steel coils wound using the above method have good coil shape and no excessive camber defects at the beginning and end.

[0042] Example 3

[0043] To control the camber defects at the beginning and end of SGC340 hot-rolled thin steel strip, with a strip specification of 2.1*1250mm, the process parameters during hot rolling are controlled as follows:

[0044] Optimize the slab heating process: The steelmaking slab adopts a hot delivery mode with a heating time of 276 minutes.

[0045] Slab specifications are controlled as follows: the slab size is 230*1255*93000mm, the difference between the slab width and the steel strip width is 5mm, and a fixed width press is not used.

[0046] Optimize the slab roughing process: The hot-rolled roughing R2 uses three passes of steel plate centering in passes 1, 3 and 5; the roughing R2DT temperature is 1090℃ (1070℃ for the same steel grade and thickness specification), the R2 exit slab thickness is 31.5mm, and the offset from the centerline of the unit is 22mm.

[0047] Optimize the slab finishing rolling process: before finishing rolling, the slab is covered with an insulation cover and the edge heater is used for heat supplementation.

[0048] Optimize roll duration: Control the roll duration of the roughing mill R2 work rolls to 9630 tons and the roll duration of the finishing mill support rolls to 23800 tons.

[0049] Optimize the plate shape settings: the crown of the hot-rolled and finished plate is 46μm, the wedge shape is 23μm, and (crown shape - |wedge shape|) = 23μm > 0.

[0050] Inspection feedback: The online inspection instrument at the hot-rolled finishing mill exit measured a lateral bend of 16mm at the head 50m and a lateral bend of 5mm at the tail 50m of the steel strip.

[0051] The hot-rolled steel coils wound using the above method have good coil shape and no excessive camber defects at the beginning and end.

[0052] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for controlling the camber defects at the beginning and end of hot-rolled thin steel strip, characterized in that, The hot-rolled thin steel strip is either SGC400 or SGC340 hot-rolled thin steel strip, and the thickness H of the hot-rolled thin steel strip is less than 2.5 mm. Control methods include: Optimize slab heating process: hot slab heating time ≥ 200 min, cold slab heating time ≥ 220 min; Optimize the slab roughing process: R2 roughing uses three passes of steel plate centering (passes 1, 3, and 5); the R2 DT temperature is increased by 20-30℃ compared to slabs of the same steel grade with a thickness of 2.5mm or more; the slab thickness at the R2 exit is 30-35mm; the offset between the steel strip and the centerline of the mill after roughing is controlled within ±30mm. Optimize the slab finishing rolling process: before finishing rolling, the slab is covered with an insulation cover and the edge heater is used for heat supplementation; Optimize the plate shape settings: control the crown of the fine-rolled plate to be 35~50μm, |wedge|≤25μm, and crown -|wedge|>0μm.

2. The control method as described in claim 1, characterized in that, The control methods also include controlling the slab specifications: the difference between the slab width and the width of the hot-rolled finished steel strip is ≤20mm, and the fixed-width press is not used to reduce the width.

3. The control method as described in claim 1, characterized in that, The control methods also include optimizing the roll period: the roll period of the roughing mill R2 work roll is controlled at 7,000 to 50,000 tons, and the roll period of the finishing mill support roll is controlled at 7,000 to 150,000 tons.

4. The control method as described in claim 1, characterized in that, The convexity target is 40 μm.

5. The control method as described in claim 1, characterized in that, The control method also includes surface inspection feedback: the side bending of the steel strip is detected by an online surface inspection instrument at the exit of the hot rolling finishing mill. If the side bending exceeds 30mm, feedback is given to optimize the centering direction of the finishing mill, forming a closed-loop control.