Method for reducing the length of the head and tail thickness deviation of cold-rolled strip steel

Abstract

The application discloses a method for reducing the length of the thickness deviation of the head and tail of a cold-rolled strip steel. The stable operation of the cold-rolled tension rolling is ensured by improving the installation precision of the tension roller, and the thickness fluctuation is reduced. The thickness control response time is shortened by improving the hydraulic system of the main rolling mill and upgrading the motor transmission cabinet, so that the thickness control precision is improved. The type of the main motor encoder of the acid continuous rolling mill is innovated, and the main motor and the encoder are connected in a buffer mode, so that the rolling precision of the motor is realized, and the thickness control precision is improved. The response speed of the flying shear motor and the accurate positioning of the shearing position are controlled, so that the stability and accuracy of shearing are ensured, the welding seam passing speed is improved, and the thickness control precision of the head and tail is effectively improved.

Description

Technical Field

[0001] This invention relates to a method for reducing the length of thickness deviation at the beginning and end of cold-rolled strip steel. Background Technology

[0002] In 2022, cold-rolled products accounted for 1,385 tons, representing 37.9% of all defects. Among these, the thickness deviation defects at the beginning and end of the strip accounted for 98.6%. Direct economic losses amounted to 1.77 million yuan, and due to the sluggish steel industry, the company was essentially operating at a loss. Therefore, addressing the thickness deviation defects at the beginning and end of the strip is urgently needed. While the application of fully automated intelligent control technology and high-efficiency energy-saving technology in cold rolling has continuously improved the precision control capabilities of cold-rolled products, the control precision of the thickness at the beginning and end varies significantly among steel mills. Furthermore, customers are increasingly demanding higher control precision for cold-rolled sheets to ensure better yields.

[0003] Literature search results: "Improvement of Head and Tail Thickness Jump in Cold-Rolled Strip" by Chen Guang and Huang Peijie. This literature mainly improves the thickness deviation of cold-rolled strip caused by head and tail thickness jump by adjusting the AGC feedback at the No. 1 stand exit, the feedforward amplification factor of the AGC at the No. 1 stand exit, and adjusting the tension by the stand speed under constant rolling force mode at the No. 5 stand. This is unrelated to the present invention patent. "Dimensional Accuracy and Surface Quality Control of Cold-Rolled Plate for High-Precision Chemical Drums" by Hu Honglin, Xiang Hua, Ma Xiaojuan, and Lu Pengcheng. This literature, based on the process equipment characteristics of Baosteel's production of cold-rolled raw materials for chemical drums, mainly analyzes the welding defects and causes of the drum body. It focuses on optimizing the hot rolling, cold rolling, and annealing processes, analyzing and summarizing the key points of each process from steelmaking to hot rolling and finally cold rolling. However, it does not analyze in detail how to control thickness accuracy. The literature "Thickness Quality Control and Improvement of Cold-Rolled Strip Steel" by Cai Guoqing and Chen Hai mainly focuses on eliminating thickness gauge detection errors, controlling raw material quality to reduce the impact of incoming materials on thickness accuracy, measuring the mill stiffness coefficient, regressing the bounce curve, and calculating the mill stiffness online to increase the accuracy of roll gap control. Through a series of improvements in process, operation, and management, the thickness quality control is significantly improved, but it is not strongly related to this invention. Summary of the Invention

[0004] The purpose of this invention is to provide a method for reducing the thickness deviation length at the beginning and end of cold-rolled strip steel. By organically combining the control precision of existing process equipment with the characteristics of cold-rolled products, and through continuous breakthroughs, innovations, and improvements in equipment functional precision and process precision, the goal of continuously improving the thickness precision of cold-rolled products can be achieved.

[0005] The technical solution adopted in this invention is a method for reducing the thickness deviation length at the beginning and end of cold-rolled strip steel, implemented according to the following steps: the thickness variation of hot-rolled coils does not exceed 0.5 mm, and the maximum thickness deviation at the beginning and end is 10% of the nominal thickness; the hydrochloric acid temperature of pickling tanks 1-4 is controlled at 65-75℃, the process section operating speed is controlled at 60-130 m / min, and the pickling unit ensures that the HCl content of the acid solution in pickling tank 1 is ≥50 g / L and the iron ion content is ≤100 g / L, preventing the occurrence of under-pickling of steel coils; the outlet temperature of the filter in rinsing tanks 1-4 of the pickling unit is 60℃-80℃, the conductivity of rinsing water in rinsing tank 2 is ≤100 μS / cm, and the opening of the rinsing water replenishment valve is increased by 25%-40% compared with ordinary steel grades; pickling... The installation accuracy of the entrance and exit looper roller system should be improved, including the installation accuracy of the roller system, swing arm gate, trolley wheels, guide wheels, and guide rails. The parallelism of the swing arm gate should be controlled to <±3mm, the wear deviation of the looper wheels and guide wheels to <1mm, and the track gauge change of the guide rails to <1mm. The alignment instrument should be checked monthly, and the automatic alignment calibration control accuracy should reach ±3mm. The alignment filter element should be replaced quarterly, and the oil cleanliness should be <NSA6. The alignment mechanical bolts should be tightened monthly. The roughness of the alignment rollers should be tested quarterly, and the alignment rollers should be replaced annually to maintain a working sleeve quantity of over 80%. The pickling process section should maintain an operating speed of 80-150m / min, eliminating defects such as under-pickling and over-pickling. The installation accuracy of the tension rollers in the rolling mill should be such that the maximum horizontal tilt of the tension rollers does not exceed 0.5mm / m, and the maximum vertical tilt of the bearing housing does not exceed 0. 0.5mm, the maximum horizontal tilt of the bearing seat does not exceed 1mm, the perpendicularity of the tension roll axis to the rolling center line is less than 0.2mm / m; the main mill servo hydraulic system lifting: system pressure ≥220bar, AGC back pressure 50±3bar, balance cylinder pressure 170±5bar, bending roll back pressure 50±3bar, on-load step response speed less than 30ms, cleanliness level reaches NAS5 level, oil filtration accuracy 10μm, improving the strip thickness response control accuracy; for the main motor encoder model of the acid continuous rolling mill, the main motor and encoder adopt a buffer connection method to reduce the axial swing of the coupling, the encoder installation accuracy is controlled to ±3μm, and the encoder fluctuation range is controlled to ±1rpm; the 6RA70 transmission cabinet is upgraded to the 6RA80 series, the calculation speed is controlled to within 9ms, and the acceleration and deceleration response time of each main motor is controlled to below 120ms; the thickness compensation coefficient of the No. 5 mill acceleration and deceleration is adjusted from 0.4 to 0.45 after several tests, and the welding seam tracking flying shear shear position is calibrated, with a correction coefficient of 0. The value was adjusted from 0.2 to 0.1 to precisely position the flying shear. The response speed of the flying shear motor was controlled to below 2ms, ensuring precise positioning of the shearing position and guaranteeing the stability and accuracy of the shearing. This increased the speed of thin-gauge weld seams from 160m / min to 180m / min and thick-gauge weld seams from 100m / min to 120m / min. The monitoring and distribution coefficient of the No. 5 rolling mill was controlled to 0.45. Increase the thickness correction amount of the front stand and increase the correction coefficient of the No. 1 mill feedforward feedback and No. 5 mill feedback control during the tailing process; optimize the parameters of the thickness gauge at the rear of the No. 4 mill to ensure measurement accuracy and improve the AGC control function: increase the amplification factor of F4 feedback and F5 feedforward by 25%; maintain the angle of the emulsion blowing beams before and after the thickness gauge at 45-60°, and the blowing pressure not lower than 0.5 MPa; when the speed of the No. 5 mill reaches 260±30 m / min, stabilize the speed for 10-15 seconds before further acceleration; thickness gauge management: perform calibration every shift, clean the transmitting and receiving electrode surfaces before calibration to ensure no contaminants, and use an external standard template for calibration once per quarter, controlling the error to within ±0.03%*standard template thickness range to ensure the thickness gauge measurement accuracy is 1 μm.

[0006] This invention first achieves stable operation of the pickling process by innovating and improving the precision of the pickling process parameters and the inlet / outlet looper equipment, thus providing the primary condition for stable rolling in the rolling mill process. By improving the installation precision of the tension rolls, stable operation of cold rolling tension rolling is ensured, reducing thickness fluctuations. Upgrading the main rolling mill's hydraulic system and motor drive cabinet shortens the strip thickness control response time, thereby improving thickness control precision. An innovative buffered connection method is adopted between the main motor encoder and the main motor of the continuous pickling mill, improving motor rolling precision and thickness control precision. By precisely controlling the response speed and shearing position of the flying shear motor, the stability and accuracy of shearing are ensured, increasing the speed through the weld seam and effectively improving the thickness control precision at both ends. By effectively implementing measures affecting the control and measurement accuracy of the thickness gauge, measurement accuracy errors are reduced, effectively improving thickness control precision. Using this method, the thickness deviation of the strip head and tail with a finished thickness of less than 0.6mm was reduced from 45m to 20m, and the thickness accuracy control was improved by 33.3%; the thickness deviation of the strip head and tail with a finished thickness of more than 1.5mm was reduced from 35m to 10m, and the thickness accuracy control was improved by 28.5%. Detailed Implementation

[0007] A method for reducing the thickness deviation length at the beginning and end of cold-rolled strip steel is implemented according to the following steps: the thickness variation of hot-rolled coils does not exceed 0.5 mm, and the maximum thickness deviation at the beginning and end is 10% of the nominal thickness; the hydrochloric acid temperature of pickling tanks 1-4 is controlled at 65-75℃, the process section operating speed is controlled at 60-130 m / min, and the pickling unit ensures that the HCl content of acid solution in pickling tank 1 is ≥50 g / L and the iron ion content is ≤100 g / L, preventing the occurrence of under-pickling of steel coils; the outlet temperature of the filter in rinsing tanks 1-4 of the pickling unit is 60-80℃, the conductivity of rinsing water in rinsing tank 2 is ≤100 μS / cm, and the opening degree of the rinsing water replenishment valve is increased by 25%-40% compared with ordinary steel grades; the installation accuracy of the pickling inlet and outlet looper roller system is improved, and the roller system, swing arm door, trolley wheels, guide wheels, etc. are improved. The installation accuracy of the guide rails, the parallelism of the swing arm of the swing arm door is controlled to <±3mm, the wear deviation of the looper wheels and guide wheels is <1mm, the track gauge change due to guide rail loosening is <1mm, the alignment instrument is checked monthly, and the automatic alignment calibration control accuracy reaches ±3mm; the alignment filter element is replaced quarterly, and the oil cleanliness is <NSA6; the alignment mechanical bolts are tightened monthly; the roughness of the alignment roller is tested quarterly, and the alignment roller is replaced annually to maintain the working sleeve quantity at more than 80%, ensuring that the pickling process section runs at a speed of 80-150m / min, and eliminating defects such as under-pickling and over-pickling; the installation accuracy of the tension rollers of the rolling mill unit is such that the maximum horizontal tilt of the tension rollers does not exceed 0.5mm / m, and the maximum vertical tilt of the bearing seat does not exceed 0. 0.5mm, the maximum horizontal tilt of the bearing seat does not exceed 1mm, and the perpendicularity of the tension roll axis to the rolling center line is less than 0.2mm / m; the main mill servo hydraulic system lifting: system pressure ≥220bar, AGC back pressure 50±3bar, balance cylinder pressure 170±5bar, bending roll back pressure 50±3bar, on-load step response speed less than 30ms, cleanliness level reaches NAS5 level, oil filtration accuracy 10μm, improving the strip thickness response control accuracy; for the main motor encoder model of the acid continuous rolling mill, the main motor and encoder adopt a buffer connection method to reduce the axial swing of the coupling, the encoder installation accuracy is controlled to ±3μm, and the encoder fluctuation range is controlled to ±1rpm; the 6RA70 transmission cabinet is upgraded to the 6RA80 series, the calculation speed is controlled to within 9ms, and the acceleration and deceleration response time of each main motor is controlled to below 120ms; the thickness compensation coefficient of the No. 5 mill acceleration and deceleration is adjusted from 0.4 to 0 after several tests. 0.45, the shearing position of the welding seam tracking flying shear was calibrated, and the correction coefficient was adjusted from 0.2 to 0.1 to accurately position the flying shear. The response speed of the flying shear motor was controlled to less than 2ms, ensuring the stability and accuracy of the shearing. This increased the speed of thin-gauge weld seams from 160m / min to 180m / min and thick-gauge weld seams from 100m / min to 120m / min. The monitoring and distribution coefficient of the No. 5 rolling mill was controlled to 0.45. Increase the thickness correction amount of the front stand and increase the correction coefficient of the No. 1 mill feedforward feedback and No. 5 mill feedback control during the tailing process; optimize the parameters of the thickness gauge at the rear of the No. 4 mill to ensure measurement accuracy and improve the AGC control function: increase the amplification factor of F4 feedback and F5 feedforward by 25%; maintain the angle of the emulsion blowing beams before and after the thickness gauge at 45-60°, and the blowing pressure not lower than 0.5 MPa; when the speed of the No. 5 mill reaches 260±30 m / min, stabilize the speed for 10-15 seconds before further acceleration; thickness gauge management: perform calibration every shift, clean the transmitting and receiving electrode surfaces before calibration to ensure no contaminants, and use an external standard template for calibration once per quarter, controlling the error to within ±0.03%*standard template thickness to ensure the thickness gauge measurement accuracy is 1 μm.

[0008] Example:

[0009] The thickness variation of hot-rolled coils shall not exceed 0.5 mm, and the maximum thickness deviation at the beginning and end shall be 10% of the nominal thickness.

[0010] The hydrochloric acid temperature in pickling tanks 1-4 should be controlled at 65-75°C, and the operating speed of the process section should be controlled at 60-130 m / min. If the speed drops below 60 m / min under special circumstances, corrosion inhibitor should be added immediately.

[0011] The pickling unit ensures that the HCl content of the acid solution in the No. 1 pickling tank is ≥50g / L and the iron ion content is ≤100g / L, and prevents the occurrence of under-pickling of steel coils.

[0012] The outlet temperature of the filter in the pickling unit's No. 1-4 rinsing tanks is 60℃~80℃; the conductivity of the rinsing water in the No. 2 rinsing tank is ≤100us / cm; and the opening of the rinsing water supply valve is increased by 25%~40% compared to ordinary steel grades.

[0013] Improve the installation accuracy of the pickling inlet and outlet looper roller system, and enhance the installation accuracy of the roller system, swing arm door, trolley wheels, guide wheels, and guide rails. Control the parallelism of the swing arm door to <±3mm, the wear deviation of the looper trolley wheels and guide wheels to <1mm, and the track gauge change of the guide rail to <1mm. Check the alignment instrument monthly, and ensure that the automatic alignment calibration control accuracy reaches ±3mm. Replace the alignment filter element quarterly, and ensure that the oil cleanliness is <NSA6. Tighten the alignment mechanical bolts monthly. Test the roughness of the alignment rollers quarterly, and replace the alignment rollers annually to maintain the working sleeve quantity at more than 80%. Ensure that the pickling process section operates at a speed of 80-150m / min, and eliminate defects such as under-pickling and over-pickling.

[0014] The installation accuracy of the tension rolls in the rolling mill unit is as follows: the maximum horizontal tilt of the tension rolls shall not exceed 0.5 mm / m, the maximum vertical tilt of the bearing housing shall not exceed 0.5 mm, the maximum horizontal tilt of the bearing housing shall not exceed 1 mm, and the perpendicularity of the tension roll axis to the rolling center line shall be less than 0.2 mm / m.

[0015] The main mill servo hydraulic system is improved as follows: system pressure ≥220 bar, AGC back pressure 50±3 bar, balance cylinder pressure 170±5 bar, bending roll back pressure 50±3 bar, on-load step response speed less than 30 ms, cleanliness level reaches NAS5, oil filtration accuracy 10 μm, improving the strip thickness response control accuracy; for the main motor encoder model of the acid continuous rolling mill, the main motor and encoder adopt a buffer connection method to reduce the axial swing of the coupling, the encoder installation accuracy is controlled to ±3 μm, and the encoder fluctuation range is controlled to ±1 rpm.

[0016] The 6RA70 drive cabinet has been upgraded to the 6RA80 series, with the calculation speed controlled to within 9ms and the acceleration and deceleration response time of each main motor controlled to below 120ms.

[0017] After several tests, the thickness compensation coefficient for acceleration and deceleration of the No. 5 rolling mill was adjusted from 0.4 to 0.45. The shearing position of the flying shear tracking weld was calibrated, and the correction coefficient was adjusted from 0.2 to 0.1. The flying shear position was accurately positioned, and the response speed of the flying shear motor was controlled to less than 2ms. The precise positioning of the shearing position ensured the stability and accuracy of the shearing, increasing the speed of thin specifications through the weld from 160m / min to 180m / min; and the speed of thick specifications from 100m / min to 120m / min.

[0018] The L2 multi-point strategy setting coefficient, AGC thickness control gain coefficient, dynamic variable specification parameters (rolling force, tension, bending force, roll gap), AGC thickness control gain coefficient, and the monitoring allocation coefficient of No. 5 mill were controlled to 0.45. The thickness correction amount of the front stand was increased, and the feedforward feedback of No. 1 mill and the feedback control correction coefficient of No. 5 mill during the tailing process were increased to minimize the impact of incoming material thickness fluctuations on finished product thickness. The test results showed a significant improvement in thickness accuracy control by 0.2%.

[0019] Optimize the parameters of the thickness gauge at the back of the No. 4 mill to ensure measurement accuracy, improve the AGC control function (increase the amplification factor of F4 feedback and F5 feedforward by 25%), keep the angle of the emulsion blowing beams before and after the thickness gauge at 45-60°, and keep the blowing pressure at no less than 0.5 MPa. When the speed of the No. 5 mill is increased to 260±30 m / min, stabilize the speed for 10-15 seconds before increasing the speed again.

[0020] Thickness gauge management: Calibration is performed every shift. Before calibration, the surfaces of the transmitting and receiving electrodes are cleaned to ensure they are free of contaminants. An external standard template is used for calibration once per quarter, and the error is controlled within ±0.03% of the standard template thickness to ensure that the thickness gauge measurement accuracy is 1μm.

Claims

1. A method for reducing the length of thickness deviation at the beginning and end of cold-rolled strip steel, characterized in that... Implement the following steps: For hot-rolled coils, the thickness variation should not exceed 0.5mm, and the maximum thickness deviation at the beginning and end should be 10% of the nominal thickness; the hydrochloric acid temperature in pickling tanks 1-4 should be controlled at 65-75℃; the pickling unit should ensure that the HCl content in the acid solution of tank 1 is ≥50g / L and the iron ion content is ≤100g / L, preventing under-pickling of steel coils; the outlet temperature of the filters in rinsing tanks 1-4 should be 60℃-80℃; the conductivity of the rinsing water in tank 2 should be ≤100us / cm; the opening of the rinsing water supply valve should be increased by 25%-40% compared to ordinary steel grades; improve the installation accuracy of the pickling inlet and outlet looper roller system, and improve the roller... The installation accuracy of the system, swing arm door, looper wheel, guide wheel, and guide rail is as follows: the parallelism of the swing arm door is controlled to <±3mm; the wear deviation of the looper wheel and guide wheel is <1mm; the track gauge change of the guide rail is <1mm; the alignment instrument is checked monthly, and the automatic alignment calibration control accuracy reaches ±3mm; the alignment filter element is replaced quarterly, and the oil cleanliness is <NAS6; the alignment mechanical bolts are tightened monthly; the roughness of the alignment roller is tested quarterly, and the alignment roller is replaced annually to maintain the working sleeve quantity at more than 80%; the pickling process section operating speed is maintained at 80-150m / min, and defects such as under-pickling and over-pickling are eliminated; the installation accuracy of the tension roller of the rolling mill unit: the maximum horizontal tilt of the tension roller is not... For rolling mills, the vertical tilt of the bearing housing should not exceed 0.5 mm / m, the horizontal tilt should not exceed 1 mm, and the perpendicularity of the tension roll axis to the rolling centerline should be less than 0.2 mm / m. The main mill servo hydraulic system lifting system should have a system pressure ≥220 bar, AGC back pressure 50±3 bar, balance cylinder pressure 170±5 bar, bending roll back pressure 50±3 bar, on-load step response speed less than 30 ms, cleanliness level reaching NAS5, oil filtration accuracy 10 μm, and strip thickness response control accuracy. The main motor and encoder of the acid continuous rolling mill adopt a buffered connection to reduce axial sway of the coupling, and the encoder installation accuracy is controlled to... ±3μm, the encoder fluctuation range is controlled to ±1rpm; the 6RA70 drive cabinet is upgraded to the 6RA80 series, the calculation speed is controlled to within 9ms, and the acceleration and deceleration response time of each main motor is controlled to below 120ms; the thickness compensation coefficient for acceleration and deceleration of the No. 5 rolling mill is adjusted from 0.4 to 0.45 after several tests; the shearing position of the weld seam tracking flying shear is calibrated, and the correction coefficient is adjusted from 0.2 to 0.1, accurately positioning the flying shear position, controlling the response speed of the flying shear motor to below 2ms, and accurately positioning the shearing position to ensure the stability and accuracy of shearing, thereby increasing the speed of thin-gauge weld seams from 160m / min to 180m / min; The speed for thicker specifications has been increased from 100m / min to 120m / min; The monitoring allocation coefficient of No. 5 mill was controlled to 0.45, the thickness correction amount of the front stand was increased, and the feedback control correction coefficients of No. 1 mill and No. 5 mill were increased during the tailing process. The parameters of the thickness gauge after No. 4 mill were optimized to ensure measurement accuracy, and the AGC control function was improved: the amplification factor of F4 feedback and F5 feedforward was increased by 25%, the angle of the emulsion blowing beams before and after the thickness gauge was kept at 45-60°, the blowing pressure was not less than 0.5Mpa, and when the speed of No. 5 mill was increased to 260±30m / min, it was stabilized for 10-15s before further speed increase. Thickness gauge management: calibration was carried out every shift. Before calibration, the surfaces of the transmitting and receiving electrodes were cleaned to ensure that there were no contaminants. The external standard template was used for calibration once every quarter, and the error was controlled within ±0.03%*the thickness of the standard template to ensure that the thickness gauge measurement accuracy was 1μm.