A method and system for controlling the local wave shape of thin gauge strip rolling

Abstract

The application discloses a kind of thin gauge strip rolling local wave shape whole process control method and system, belong to metallurgical rolling automatic control technical field, comprising: S1, in heating and rough rolling stage, control slab same slab temperature difference, and control last pass steel temperature throwing;S2, in finishing rolling stage, according to strip rolling position dynamic adjustment side guide plate opening, S3, loop tension-angle collaborative control, F4-F6 rack loop angle is set to 15~20 °, loop tension is set to 12-15N / mm²;S4, rack level dynamic compensation, when finishing rolling single rack thickness deviation exceeds ±0.08mm or rolling force fluctuation exceeds ±100kN, limit AGC adjustment amplitude or lock roll gap;S5, cooling control, set finishing rolling F1-F7 outlet cooling water flow is 80~100m³ / h, water pressure is 0.8~1.0MPa.

Description

Technical Field

[0001] This invention belongs to the field of automatic control technology for metallurgical rolling, and in particular relates to a whole-process control method and system for local waviness in the rolling of thin strip steel. Background Technology

[0002] Currently, thin-gauge strip steel has become an important high-value-added product of hot rolling production lines. During its high-speed rolling process, due to factors such as fluctuations in rolling force, unstable tension between stands, uneven temperature field distribution, and improper matching of rolling parameters, strip steel is prone to irregular waviness defects in the middle, edge, or local areas, which seriously affect its flatness and subsequent processing.

[0003] Existing strip shape control mainly focuses on overall straightness adjustment, lacking the ability to finely control local waviness. Conventional bending rolls, shifting rolls, and tension adjustment have a lag in response, making it difficult to quickly suppress instantaneous local waviness. Some production lines rely on manual experience for adjustment, resulting in low control accuracy and poor stability, which can easily lead to accidents such as waviness expansion, strip deviation, and even steel piling, reducing yield and operational efficiency. Summary of the Invention

[0004] To address the above-mentioned technical deficiencies, this invention provides a full-process control method and system for local waviness in thin-gauge strip rolling. By constructing a full-process collaborative control model from heating, rough rolling to finish rolling and coiling, the local waviness defects that are prone to occur in thin-gauge strip during high-speed rolling are solved, thereby improving the straightness and yield of the strip.

[0005] To achieve the above-mentioned technical objectives, the present invention is implemented through the following technical solution: The first objective of this invention is to provide a method for controlling the local waviness of thin-gauge strip during the entire process of rolling, comprising: S1. During the heating and rough rolling stages, control the temperature difference between the slab and the slab to be ≤25℃, and control the temperature of the final pass of steel blasting to be 1030~1070℃. S2. During the finishing rolling stage, the opening degree of the side guide plates is dynamically adjusted according to the rolling position of the strip, specifically including: The opening of the head section for threading the strip is set to the target width of the strip + 10~20mm; The stabilization rolling section shrinks to the target strip width + 3~8mm; The tail section for steel stripping is slightly widened to the target strip width +5~12mm; S3, Loop tension-angle coordinated control, set the loop angle of F4–F6 frame to 15–20°, and the loop tension to 12–15 N / mm²; S4. Stand-level dynamic compensation: When the thickness deviation of a single stand in the finishing mill exceeds ±0.08mm or the rolling force fluctuation exceeds ±100kN, the AGC adjustment range is limited or the roll gap is locked. S5. Cooling control: Set the cooling water flow rate at the outlet of finishing mill F1-F7 to 80-100 m³ / h and the water pressure to 0.8-1.0 MPa.

[0006] Preferably, in S1, the air-fuel ratio is adjusted according to the fluctuation of the calorific value of the gas. The formula for calculating the air-fuel ratio is: gas: air = 1: [calorific value / 1000 + (0.05-0.15)], and the roughing descaling passes are closed and no less than 2 descaling passes are retained.

[0007] Preferably, in S2, the head strip entry section specifically refers to the range from the head of the strip entering the finishing mill to 10m, and the tail strip throwing section specifically refers to the range from the tail of the strip to the finishing mill exit to 10m.

[0008] Preferably, in S3, by reducing the looper angle and increasing the tension level, the tension coefficient of the strip between the F4 and F6 stands is increased by 20%-30%.

[0009] Preferably, in S4, when the trigger thickness or rolling force exceeds the threshold, the AGC adjustment range is limited to within 0.05mm, and the roll gap locking time is 0.3-0.8 seconds.

[0010] Preferably, in S5, the cooling water pressure is controlled by a variable frequency pump in a closed loop to maintain pressure fluctuations within ±0.05MPa.

[0011] Preferably, in S2, the opening of the guide plate before shearing in the head strip section is set to the target width of the strip + 15mm, and the opening of the guide plate between the finishing mill stands is set to the target width of the strip + 10mm.

[0012] Preferably, in S2, during the stable rolling section, the opening of the side guide plate is reduced to the target strip width + 5mm.

[0013] Preferably, in S2, the tail section for throwing steel has its opening slightly widened to the target width of the strip + 8mm.

[0014] The second objective of this invention is to provide a full-process control system for local waviness in the rolling of thin-gauge strip steel, comprising: The temperature control module is used to perform heating and roughing temperature control in S1; The side guide plate control module is used to perform the segmented adaptive opening adjustment in S2; The looper control module is used to execute the tension-angle coordinated setting in S3; The AGC protection module is used to execute the dynamic compensation strategy in S4. The cooling control module is used to perform flow and pressure control in S5.

[0015] The advantages and technical effects of this invention are: This invention addresses the localized waviness defects that easily occur in the high-speed rolling of thin-gauge strip by constructing a collaborative control model covering the entire process from heating, roughing, finishing, and coiling, thereby improving strip straightness and yield. Specifically: This invention covers the entire process chain from heating to cooling, and in particular proposes a specific side guide plate control strategy for the unsteady processes at the head and tail, realizing unsteady plate shape control.

[0016] This invention reduces the steel jamming rate at the head of the strip by about 60% and the waviness defect at the tail by more than 85% through the segmented control of the side guide plate and the coordinated action of the looper tension, significantly reducing local waviness.

[0017] This invention employs an AGC intervention mechanism, which effectively solves the problem of high sensitivity of thin strip steel to roll gap fluctuations, controlling thickness fluctuations within ±0.05mm and significantly improving strip shape stability. Detailed Implementation

[0018] To make the above-mentioned objectives, control system design, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] A method for controlling local waviness during the rolling of thin-gauge strip steel throughout the entire process includes the following steps: S1. Temperature uniformity control during heating and rough rolling stages.

[0020] Control the atmosphere inside the heating furnace and adjust the air-fuel ratio in real time according to the calorific value of the gas to ensure that the temperature difference between the slabs is ≤25℃; optimize the descaling passes in rough rolling, retain no less than 2 descaling passes to ensure surface quality, and at the same time control the steel-blasting temperature of the last pass at 1030-1070℃ to reduce unsteady temperature drop.

[0021] S2, Segmented adaptive control of the guide plate at the entrance of the finishing mill.

[0022] Based on the position of the strip along the rolling length, the opening of the side guide plates is dynamically adjusted to achieve stable alignment and stress release along the entire length of the strip. Head threading section: When the head of the strip enters the finishing mill within 10m, the opening of the side guide plate is set to the target width of the strip + 10mm~20mm to ensure smooth head alignment and prevent the strip from getting stuck and local waviness at the head. Stable rolling section: After the strip enters steady-state rolling, the opening of the side guide plate is reduced to the target width of the strip +3mm~8mm, which enhances the lateral constraint on the strip and suppresses deviation and edge waviness; Tail-end strip throwing section: When the tail of the strip is 10m away from the finishing mill exit, the opening of the side guide plate is slightly expanded to the target width of the strip +5mm~12mm to weaken the tail-end clamping force and eliminate the local instability wave caused by the sudden change in tail tension.

[0023] S3, Coordinated optimization control of intermediate billet tension and angle.

[0024] Between frames F4 and F6, the looper height setting is reduced to 15°–20°, while the looper tension is increased to 12–15 N / mm². By reducing the looper angle and increasing the tension level, the central waviness caused by insufficient rigidity of thin strip steel is suppressed.

[0025] S4, frame-level dynamic compensation for variable thickness and tension.

[0026] Real-time monitoring of the exit thickness and rolling force of each stand in the finishing mill; when the measured thickness deviation of a single stand exceeds ±0.08mm or the rolling force fluctuation exceeds ±100kN, the AGC (Automatic Thickness Control) adjustment range limit or short-term roll gap locking strategy is automatically triggered to avoid local extension differences caused by sudden changes in roll gap.

[0027] S5. Lateral uniformity control during the laminar flow cooling stage.

[0028] The cooling water flow rate at the outlet of the finishing mill F1-F7 stands is set to 80-100 m³ / h, and the water pressure is set to 0.8-1.0 MPa to ensure that the transverse cooling rate of the strip is consistent and to eliminate the temperature stress waviness caused by local rapid cooling.

[0029] To better understand the technical solution of this invention, the following is a non-limiting description: First, control the atmosphere inside the heating furnace. Adjust the air-to-coal ratio (gas:air = 1:[calorific value / 1000 + (0.05-0.15)]) according to the fluctuation of the gas calorific value. Clean the iron oxide scale inside the furnace in a timely manner to prevent clogging of the burners. Avoid local overheating or uneven burning of the slab and ensure that the temperature difference within the same slab is ≤25℃.

[0030] Secondly, while ensuring the quality of descaling on the strip surface, optimize the closure of roughing descaling passes (no less than 2 descaling passes) to reduce temperature drop and ensure the final pass steel-throwing temperature is 1030-1070℃.

[0031] This invention employs a segmented adaptive control strategy for the side guide plate, dynamically adjusting the opening degree based on the strip rolling position to achieve stable centering throughout the entire length. Head threading section (0-10m): The opening of the guide plate before shearing is set to the target width of the strip + 15mm, and the opening of the guide plate between the stands of the finishing mill is set to the target width of the strip + 10mm to ensure smooth threading of the head and prevent the strip from getting stuck or deviating, which could cause local stress concentration. Stable rolling section (10m to 10m from the tail): The opening of the side guide plate is reduced to the target width of the strip + 5mm, which strengthens the centering constraint of the strip, suppresses lateral offset, and ensures uniform rolling deformation of each stand. Tail section for steel throwing (10m from the tail to the tail): The opening is slightly widened to the target width of the strip + 8mm, which weakens the tail clamping constraint and avoids sudden tension changes and local instability caused by rigid tail clamping.

[0032] The looper tension-angle coordinated optimization control reduces the looper height setting value of F4–F6 stands to 15–20° and increases the looper tension to 12–15 N / mm², avoiding the problem of wavy formation caused by excessively high looper angle and low tension during rolling.

[0033] The thickness deviation threshold for each stand at the finish mill is set to ±0.08 mm, and the rolling force fluctuation threshold is set to ±100 kN. When either the measured thickness deviation or the rolling force fluctuation of a single stand exceeds the threshold, the system automatically limits the AGC adjustment range of that stand or locks the roll gap for a short time to avoid frequent AGC overshoot and sudden changes in roll gap causing uneven local reduction, thus eliminating local extension differences and waviness defects caused by dynamic deviations in the roll gap.

[0034] The cooling water flow rate for F1-F7 strip steel is controlled at 80-100 m³ / h, and the water pressure is 0.8-1.0 MPa to ensure uniform transverse cooling of the strip steel and avoid local rapid cooling that causes temperature differences and uneven deformation resistance, resulting in local stress concentration and wave formation.

[0035] Implementation Case: Heating and Rough Rolling: A thin strip steel (1.5mm x 1200mm) was heated in a walking beam furnace. The air-fuel ratio was adjusted in real time according to fluctuations in the calorific value of the gas to maintain a slightly oxidizing furnace atmosphere. The rough rolling stage employed five passes. Descaling water was activated in the first and third passes to ensure thorough removal of surface iron oxide scale. The final pass's polishing temperature was controlled at 1050℃ (target 1030-1070℃), with a measured temperature difference of 20℃ between the strip and the target plate.

[0036] Segmented control of side guide plates: Head (0-10m): The opening of the guide plate at the entry of the finishing mill is set to 1215mm (target width 1200mm + 15mm) to ensure unobstructed threading at the head.

[0037] Middle section (10m to the first 10m of the tail): The opening automatically shrinks to 1205mm (+5mm) to strongly center the strip.

[0038] Tail (last 10m): After the system detects the tail signal, the opening is widened to 1208mm (+8mm), releasing the tail tension.

[0039] Looping control: Between stands F4, F5, and F6, the looper angle was reduced from the conventional 25° to 18°, and the looper tension was increased from 8 N / mm² to 14 N / mm². This effectively suppressed the "bending" phenomenon in the middle of the strip.

[0040] AGC Dynamic Compensation: The thickness deviation threshold at the exit of stands F1-F7 is set to ±0.08mm. When the rolling force of stand F3 fluctuates instantaneously to 110kN, the system automatically limits the AGC adjustment to within 0.05mm and locks the roll gap for 0.5 seconds to avoid local thickness differences caused by instantaneous slippage.

[0041] Cooling control: The flow rate of the outlet manifolds of F1-F7 is uniformly set to 90 m³ / h, and the water pressure is stabilized at 0.9 MPa to ensure uniform transverse temperature drop of the strip steel and prevent edge waviness.

[0042] Results: The finished strip steel was tested and found to have a flatness that met the Class A standard, with no obvious local waviness. The yield rate increased from 92% to 98.5%.

[0043] A full-process control system for local waviness in thin-gauge strip rolling, comprising: The temperature control module is used to perform heating and roughing temperature control in S1; The side guide plate control module is used to perform the segmented adaptive opening adjustment in S2; The looper control module is used to execute the tension-angle coordinated setting in S3; The AGC protection module is used to execute the dynamic compensation strategy in S4. The cooling control module is used to perform flow and pressure control in S5.

[0044] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling the local waviness of thin-gauge strip during rolling throughout the entire process, characterized in that, include: S1. During the heating and rough rolling stages, control the temperature difference between the slab and the slab to be ≤25℃, and control the temperature of the final pass of steel blasting to be 1030~1070℃. S2. During the finishing rolling stage, the opening degree of the side guide plates is dynamically adjusted according to the rolling position of the strip, specifically including: The opening of the head section for threading the strip is set to the target width of the strip + 10~20mm; The stabilizing rolling section shrinks to the target strip width + 3~8mm; The tail section for steel stripping is slightly widened to the target strip width +5~12mm; S3, Loop tension-angle coordinated control, set the loop angle of F4–F6 frame to 15–20°, and set the loop tension to 12–15 N / mm²; S4. Stand-level dynamic compensation: When the thickness deviation of a single stand in the finishing mill exceeds ±0.08mm or the rolling force fluctuation exceeds ±100kN, the AGC adjustment range is limited or the roll gap is locked. S5. Cooling control: Set the cooling water flow rate at the outlet of finishing mill F1-F7 to 80-100 m³ / h and the water pressure to 0.8-1.0 MPa.

2. The method for controlling local waviness in thin-gauge strip rolling according to claim 1, characterized in that: In S1, the air-fuel ratio is adjusted according to the fluctuation of the calorific value of the gas. The formula for calculating the air-fuel ratio is: gas: air = 1: [calorific value / 1000 + (0.05-0.15)]. The descaling passes of the rough rolling mill are closed and no less than 2 descaling passes are retained.

3. The method for controlling local waviness in thin-gauge strip rolling according to claim 1, characterized in that: In S2, the head strip entry section specifically refers to the range from the head of the strip entering the finishing mill to 10m, and the tail strip throwing section specifically refers to the range from the tail of the strip to the finishing mill exit to 10m.

4. The method for controlling local waviness in thin-gauge strip rolling according to claim 1, characterized in that: In S3, by reducing the looper angle and increasing the tension level, the tension coefficient of the strip between F4 and F6 stands is increased by 20%-30%.

5. The method for controlling local waviness in thin-gauge strip rolling according to claim 1, characterized in that: In S4, when the trigger thickness or rolling force exceeds the threshold, the AGC adjustment range is limited to within 0.05mm, and the roll gap locking time is 0.3-0.8 seconds.

6. The method for controlling local waviness in thin strip rolling according to claim 1, characterized in that: In S5, the cooling water pressure is controlled by a variable frequency pump in a closed loop to maintain pressure fluctuations within ±0.05MPa.

7. The method for controlling local waviness in thin strip rolling according to claim 1, characterized in that: In S2, the opening of the guide plate before shearing in the head section is set to the target width of the strip + 15mm, and the opening of the guide plate between the stands of the finishing mill is set to the target width of the strip + 10mm.

8. The method for controlling local waviness in thin strip rolling according to claim 1, characterized in that: In S2, during the stable rolling section, the opening of the side guide plate is reduced to the target strip width + 5mm.

9. The method for controlling local waviness in thin strip rolling according to claim 1, characterized in that: In S2, the tail section for throwing steel has its opening slightly widened to the target width of the strip + 8mm.

10. A full-process control system for local waviness in thin-gauge strip rolling, characterized in that, include: Temperature control module, used to perform heating and roughing temperature control in S1 as described in any one of claims 1-9; The side guide plate control module is used to perform the segmented adaptive opening degree adjustment in S2 as described in any one of claims 1-9; The looper control module is used to perform the tension-angle coordinated setting in S3 as described in any one of claims 1-9; The AGC protection module is used to execute the dynamic compensation strategy in S4 as described in any one of claims 1-9; A cooling control module for performing flow and pressure control in S5 as described in any one of claims 1-9.