A method for controlling the head and tail thickness fluctuation of a cold continuous rolling wide gauge tin-plated substrate

Abstract

The present application relates to the technical field of metal material rolling, and particularly relates to a method for controlling head and tail thickness fluctuation of wide specification tin-plated substrate in cold continuous rolling, which solves the thickness overproof problem through multi-link collaborative control of hot rolling and cold rolling. In the hot rolling stage, U-shaped laminar cooling is adopted to ensure uniform temperature of the strip steel full length, the thickness compensation is carried out by optimizing the finishing rolling model, and the roll gap accuracy is ensured by the zero compensation of the portal and the pre-control of the hot crown of the work roll. In the cold rolling stage, the S-shaped speed-up curve and the advance speed-down pre-adjustment are adopted for the pickling and rolling unit, and the gradient control strategy of extending the tension lifting time is adopted, and the laser speed measurement is used for real-time feedback fine adjustment. Through these collaborative measures, the head and tail thickness fluctuation of the wide specification tin-plated substrate can be controlled within ±3 mu m, and the product precision and the yield are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of metal material rolling technology, and in particular to a method for controlling the thickness fluctuation of the head and tail of cold continuous rolling wide-gauge tin-plated substrates, especially a method for synergistic control of thickness fluctuation in the head and tail regions of strip steel. Background Technology

[0002] Tin-plated substrates, as a key material in the food packaging industry, have extremely stringent requirements for thickness precision. Especially for tin-plated substrates with a width ≥1000mm, the difficulty of thickness control during the production process is significantly higher than for products of ordinary specifications. In actual cold continuous rolling production, thickness deviations are commonly found in the head and tail areas (typically referring to the head 50 meters and tail 30 meters) of wide-specification tin-plated substrates, with fluctuations often exceeding ±5μm. This problem directly leads to products in this area becoming scrap or downgraded due to non-compliance with precision requirements, severely impacting production efficiency and economic benefits. In-depth analysis reveals the following main reasons for this phenomenon: 1. Temperature Inhomogeneity and Microstructure Differences in Hot Rolling: During hot rolling, the heat dissipation conditions at the head and tail of the strip differ from those in the middle, resulting in significant temperature fluctuations. Traditional laminar flow cooling, employing a uniform cooling strategy, cannot specifically compensate for these temperature differences, further exacerbating the microstructure inhomogeneity between the head / tail and the middle sections. This leads to inconsistent deformation resistance during subsequent cold rolling, ultimately manifesting as thickness fluctuations.

[0003] 2. Insufficient adaptability of hot-rolled finishing models: Existing hot-rolled finishing thickness control models are mostly designed based on steady-state rolling conditions. For the unsteady rolling stages at the beginning and end of the strip, the models cannot compensate for thickness deviations caused by temperature changes and rolling force fluctuations in real time and accurately, making it difficult to guarantee the thickness accuracy at the beginning and end.

[0004] 3. Instability during the acceleration and deceleration processes of cold rolling and pickling mills: During the acceleration and deceleration stages of cold rolling and pickling mills, changes in rolling speed can cause drastic fluctuations in key parameters such as rolling force and tension. Traditional control strategies are not quick or precise enough to respond to such dynamic changes, and are prone to producing significant thickness deviations at the head (acceleration stage) and tail (deceleration stage) of the strip.

[0005] Therefore, how to effectively control the thickness fluctuations at the beginning and end of the hot and cold rolling processes of wide-specification tin-plated substrates, and improve product accuracy and yield, is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for controlling the thickness fluctuation of the beginning and end of the cold continuous rolling wide-specification tin-plated substrate. This method, through the coordinated optimization control of multiple stages of hot rolling and cold rolling, can stably control the thickness fluctuation of the beginning and end of the wide-specification tin-plated substrate within ±3μm, significantly improving product accuracy and yield.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for controlling the thickness fluctuation at the beginning and end of a wide-gauge tin-plated substrate produced by cold continuous rolling includes the following steps: Hot rolling stage control steps: S1: The hot-rolled strip is cooled using a U-shaped laminar flow cooling mode; S2: In the hot rolling finishing process, a head and tail thickness compensation model optimized for wide-specification tin-plated substrates is applied to dynamically adjust the roll gap compensation amount according to the temperature deviation at the head of the strip and the tension change at the tail. S3: Before rolling the first steel coil after changing rolls on the finishing mill, perform dynamic zero-position calibration and pre-compensate the thermal expansion of the finishing mill stand based on historical data and steel strength. S4: Before rolling wide-gauge tin-plated substrates, the temperature of the work rolls is pre-controlled to ensure that they reach a stable thermal crown state in the early stage of rolling. Cold rolling stage control steps: S5: During the speed-up phase of the cold rolling and pickling mill, an S-shaped speed-up curve is adopted to control the acceleration between 0.5 and 1.0 m / s², and the initial tension setting is set to be 5-10% lower than the steady-state value and gradually increased to the target tension. S6: During the deceleration phase of the cold rolling and pickling mill, the deceleration begins 100 meters before the end of the strip reaches the mill, and thickness pre-adjustment is carried out simultaneously. S7: After the pickling and rolling mill bites the steel, a gradual tension increase strategy is adopted to extend the time for the tension to rise from 0 to the target value to 8-10 seconds; S8: A laser velocimeter is installed at the exit of the pickling and rolling mill to measure the strip speed in real time. When the measured speed deviates from the set speed by more than 0.5%, the rolling force of the upstream stand is immediately adjusted in a stepwise manner by 1%-3%, and the roll gap of the corresponding stand is simultaneously corrected in a closed loop by 0.005-0.02mm to offset the influence of speed fluctuations on the rolling deformation zone and realize the dynamic correction of strip thickness.

[0008] As a further preferred option, in S1, the cooling water volume for the 0-30 meter section at the head of the strip is increased by 15-20% compared to the middle section; and the cooling water volume for the 0-20 meter section at the tail of the strip is increased by 10-15% compared to the middle section, ensuring that the temperature fluctuation of the strip along its entire length is controlled within ±15℃.

[0009] As a further preferred option, in S2, during the first 0-50 meters of rolling, the roll gap is dynamically adjusted according to the strength of the steel grade; during the last 0-30 meters of rolling, the rolling force is gradually reduced starting 50 meters in advance.

[0010] As a further preferred option, thickness pre-adjustment during the rolling tail: the rolling force is gradually reduced by 1-2%, and the roll gap is correspondingly raised by 0.02-0.04 mm.

[0011] As a further preferred option, in S2, the roll gap preload is reduced by 0.03-0.05 mm for low carbon steel and by 0.05-0.08 mm for medium carbon steel.

[0012] As a further preferred option, in S3, the compensation value ranges from 0.01 to 0.03 mm to ensure the roll gap accuracy in the initial stage of rolling.

[0013] As a further preferred option, in S6, the thickness pre-adjustment includes a roll gap pre-lift of 0.01-0.02 mm, while the tension is gradually reduced by 3-5%.

[0014] This invention combines U-shaped cooling, head and tail thickness compensation, and equipment status pre-control in the hot rolling stage with acceleration / deceleration curve optimization, tension gradient control, and real-time laser feedback in the cold rolling stage to form a control scheme covering the entire process. This scheme specifically addresses the problem of thickness deviations caused by uneven head and tail temperatures, poor model adaptability, and unstable dynamic processes in the production of wide-specification tin-plated substrates. It can significantly improve head and tail thickness accuracy, reduce cutting losses, and increase product yield and economic benefits. Attached Figure Description

[0015] Figure 1 To improve the previous thickness fluctuation state (there is thickness fluctuation); Figure 2 To improve the thickness fluctuation state (no thickness fluctuation). Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0017] The parameters of each step in the method of the present invention can be adjusted and optimized within a certain range according to the specific unit equipment capacity, steel type (such as SPCC, MRT-4, etc.) and specifications (width, thickness).

[0018] Hot rolling stage: 1. The laminar flow cooling mode has been adjusted to U-shaped cooling. After hot rolling and finishing, the traditional laminar flow cooling mode is changed to U-shaped cooling.

[0019] Head control: In the 0-30m section at the head of the strip, open 80% of the cooling nozzles, increasing the cooling water flow by 15-20% compared to the middle section; Mid-section control: The middle section of the strip is cooled using conventional processes to ensure the target coiling temperature; Tail section control: In the 0-20m section at the tail of the strip, 75% of the cooling nozzles are opened, and the cooling water volume is increased by 10-15% compared to the middle section; Ensure that the temperature fluctuation of the strip is controlled within ±15℃ along its entire length to provide a uniform microstructure and properties basis for subsequent cold rolling.

[0020] 2. Hot-rolled finishing model control optimization Establish a thickness compensation model for the beginning and end of the steel, and preset compensation values ​​according to the steel type and specifications; Head compensation: When rolling the head 0-50m, dynamically adjust the roll gap according to the strength of the steel grade; Low carbon steel: roll gap preload reduction of 0.03-0.05mm; Medium carbon steel: roll gap preload reduction of 0.05-0.08mm; Tail compensation: When rolling the tail section from 0-30m, thickness pre-adjustment should begin 50m in advance; The rolling force is gradually reduced by 1-2%, and the roll gap is correspondingly raised by 0.02-0.04 mm.

[0021] 3. Zero-position compensation of the finishing mill stand After each roll change, dynamic zero-position calibration is performed before rolling the first steel coil.

[0022] Before rolling the head, the thermal expansion of the archway is pre-compensated based on historical data and the strength of the steel grade; The compensation value range is 0.01-0.03mm, ensuring the roll gap accuracy in the initial stage of rolling.

[0023] 4. Pre-control of thermal crown of work rolls Before rolling wide-gauge tin-plated substrates, the work rolls are preheated or precooled.

[0024] Based on the target rolling temperature and coil length, the temperature distribution of the work rolls is preset; this ensures that the work rolls reach a stable thermal crown state in the early stages of rolling, reducing the impact of head shape fluctuations on thickness.

[0025] 5. Optimization of pickling and rolling speed and thickness control Acceleration phase: When the speed increases from 0 to the target speed (1200-1500m / min); an S-shaped speed curve is adopted, and the acceleration is controlled at 0.5-1.0m / s2; the rolling force increases synchronously and linearly to avoid impact changes; the tension set value is 5-10% lower than the steady-state value, and gradually transitions to the target tension; Deceleration phase: Deceleration begins 100m before the tail reaches the destination; thickness pre-adjustment is performed in advance, and the roll gap is pre-raised by 0.01-0.02mm; tension is gradually reduced by 3-5% to compensate for the impact of speed reduction.

[0026] 6. Cold rolling inlet tension gradient control After the pickling and rolling mill bites the steel, a gradual tension increase strategy is adopted; the time for the tension to rise from 0 to the target value is extended from the conventional 5 seconds to 8-10 seconds; to avoid sudden changes in rolling force and thickness deviation caused by a sudden increase in tension.

[0027] 7. Laser velocimetry and feedback control A high-precision laser velocimeter is installed at the outlet of the pickling and rolling mill. The measured speed is compared with the set speed in real time. When the deviation exceeds 0.5%, the rolling force and roll gap are immediately finely adjusted to form a closed-loop control.

[0028] Take the MR T-4 steel grade tin-plated substrate with a width of 1050mm as an example.

[0029] Head thickness compensation: When the rolling head is 0-50m, it is determined to be low carbon steel grade according to the model, and the roll gap of the last stand (F7) of the finishing mill is preloaded with 0.04mm.

[0030] Tail thickness compensation: When rolling reaches 80m from the tail (i.e. 50m ahead), the model triggers tail compensation, and the rolling force of the F7 stand begins to decrease linearly at a slope of 0.02% per meter, for a total reduction of about 1.5%, while the roll gap increases by 0.03mm simultaneously.

[0031] Work roll preheating: Two rolls of this width specification are rolled before the work roll preheating mode is activated, so that the temperature in the middle of the work roll is slightly higher than that at the edge, thus forming a suitable thermal crown in advance.

[0032] Cold rolling stage: Pickling and rolling mill: The target speed of the mill is set at 1350 m / min. After the steel bites, the mill accelerates smoothly to the target speed within 20 seconds using an S-curve, with an acceleration of approximately 0.8 m / s². Simultaneously, the inlet tension linearly increases from 0 to the target value (starting at 95% of the steady-state value) within 9 seconds. The rolling force increases smoothly with the speed.

[0033] Speed ​​reduction and pre-adjustment: When 100m of strip remains, the speed reduction begins. At the same time, the roll gap of the last stand immediately rises by 0.015mm, and the tension setpoint begins to decrease from 100% to 96% at a slope of 0.05% per meter.

[0034] Laser feedback: The exit laser velocimeter monitors the strip speed in real time. When the instantaneous speed of the unit drops below the set value by 0.6% due to disturbance, the control system immediately increases the rolling force of the last stand by 0.3% and adjusts the roll gap accordingly, correcting the speed deviation to within 0.2% within 1 second.

[0035] By implementing the above-mentioned synergistic control, the thickness fluctuation of the strip within the first 50 meters and the last 30 meters is strictly controlled within +2.5μm / -2.8μm, which fully meets the thickness tolerance requirements of high-quality tin-plated substrates. The excess parts at the beginning and end are greatly reduced, effectively improving the product yield.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling the thickness fluctuation at the beginning and end of a cold-rolled wide-gauge tin-plated substrate, characterized in that... This includes the following steps: Hot rolling stage control steps: S1: The hot-rolled strip is cooled using a U-shaped laminar flow cooling mode; S2: In the hot rolling finishing process, a head and tail thickness compensation model optimized for wide-specification tin-plated substrates is applied to dynamically adjust the roll gap compensation amount according to the temperature deviation at the head of the strip and the tension change at the tail. S3: Before rolling the first steel coil after changing rolls on the finishing mill, perform dynamic zero-position calibration and pre-compensate the thermal expansion of the finishing mill stand based on historical data and steel strength. S4: Before rolling wide-gauge tin-plated substrates, the temperature of the work rolls is pre-controlled to ensure that they reach a stable thermal crown state in the early stage of rolling. Cold rolling stage control steps: S5: During the speed-up phase of the cold rolling and pickling mill, an S-shaped speed-up curve is adopted to control the acceleration between 0.5 and 1.0 m / s², and the initial tension setting is set to be 5-10% lower than the steady-state value and gradually increased to the target tension. S6: During the deceleration phase of the cold rolling and pickling mill, the deceleration begins 100 meters before the end of the strip reaches the mill, and thickness pre-adjustment is carried out simultaneously. S7: After the pickling and rolling mill bites the steel, a gradual tension increase strategy is adopted to extend the time for the tension to rise from 0 to the target value to 8-10 seconds; S8: A laser velocimeter is installed at the exit of the pickling and rolling mill to measure the strip speed in real time. When the measured speed deviates from the set speed by more than 0.5%, the rolling force of the upstream stand is immediately adjusted in a stepwise manner by 1%-3%, and the roll gap of the corresponding stand is simultaneously corrected in a closed loop by 0.005-0.02mm to offset the influence of speed fluctuations on the rolling deformation zone and realize the dynamic correction of strip thickness.

2. The method for controlling the thickness fluctuation at the beginning and end of a cold-rolled wide-gauge tin-plated substrate according to claim 1, characterized in that: In S1, the cooling water volume for the 0-30 meter section at the head of the strip is increased by 15-20% compared to the middle section; and the cooling water volume for the 0-20 meter section at the tail of the strip is increased by 10-15% compared to the middle section, ensuring that the temperature fluctuation of the strip along its entire length is controlled within ±15℃.

3. The method for controlling the thickness fluctuation at the beginning and end of a cold-rolled wide-gauge tin-plated substrate according to claim 1, characterized in that: In S2, during the first 0-50 meters of rolling, the roll gap is dynamically adjusted according to the strength of the steel grade; during the last 0-30 meters of rolling, the rolling force is gradually reduced starting 50 meters in advance.

4. The method for controlling the thickness fluctuation at the beginning and end of a wide-gauge tin-plated substrate in cold continuous rolling according to claim 3, characterized in that: Thickness pre-adjustment during the rolling tail: The rolling force is gradually reduced by 1-2%, and the roll gap is raised accordingly by 0.02-0.04mm.

5. The method for controlling the thickness fluctuation at the beginning and end of a cold-rolled wide-gauge tin-plated substrate according to claim 1, characterized in that: In S2, for low carbon steel, the roll gap preload is reduced by 0.03-0.05 mm; for medium carbon steel, the roll gap preload is reduced by 0.05-0.08 mm.

6. The method for controlling the thickness fluctuation at the beginning and end of a cold-rolled wide-gauge tin-plated substrate according to claim 1, characterized in that: In S3, the compensation value ranges from 0.01 to 0.03 mm to ensure the roll gap accuracy in the initial stage of rolling.

7. The method for controlling the thickness fluctuation at the beginning and end of a cold-rolled wide-gauge tin-plated substrate according to claim 1, characterized in that: In S6, the thickness pre-adjustment includes a roll gap pre-lift of 0.01-0.02mm, while the tension is gradually reduced by 3-5%.

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