Control method for eliminating edge cracks of cold-rolled base stock after rolling

Abstract

The invention relates to a control method for eliminating edge cracks of a cold-rolled base material after rolling, which comprises the following steps of: S1, additionally arranging a set of water baffles on two side areas of a rolling line vertical roller; s2, a strip steel cooling water collecting pipe between the F4 finishing mill frame and the F5 finishing mill frame is specially designed; s3, a side water spraying header is arranged at the front end of the F2-F7 rack; s4, data acquisition and analysis; s5, rolling process parameters are preset; s6, dynamic regulation and control; and S7, laminar cooling. Through accurate control over the hot rolling process, the quality of the edge of the cold-rolled low-carbon steel base material is effectively improved, the edge crack defect after rolling is eliminated or remarkably reduced, and the yield and quality of products are improved.

Description

Technical Field

[0001] The invention relates to the technical field of hot-rolled plate and strip rolling, and in particular to a control method for eliminating edge cracks of a cold-rolled base material after rolling. Background Art

[0002] In the steel production process, cold-rolled low-carbon steel is widely used in industries such as automobiles and home appliances due to its excellent overall performance. However, edge cracks often occur in cold-rolled low-carbon steel base material after rolling on the cold rolling mill, seriously affecting product quality and subsequent processing performance. Edge cracks not only increase the probability of strip breakage during the cold rolling process, resulting in low production efficiency and reduced product yield, but also damage certain equipment during the subsequent operation of the continuous annealing unit. For example, pinch rollers often suffer increased wear due to jagged edge cracks, leading to unplanned replacement and increased production costs. They can also affect the performance and safety of the final product.

[0003] Existing research indicates that edge cracking in cold-rolled low-carbon steel is closely related to various factors during the hot rolling process. For example, uneven temperature distribution at the strip edge during hot rolling can lead to differences in microstructure and properties, which can cause edge cracking during cold rolling. Improper control of process parameters such as rolling force and rolling speed during hot rolling can also cause stress concentration at the strip edge, further inducing edge cracking. While some measures have been implemented to mitigate edge cracking, such as adjusting hot rolling process parameters and optimizing roll geometry, these methods have been less than ideal and cannot fundamentally eliminate the problem. Summary of the Invention

[0004] In response to the above problems, the purpose of the present invention is to provide a control method for eliminating edge cracks of cold-rolled base material after rolling. By precisely controlling the hot rolling process, the quality of the edge of the cold-rolled low-carbon steel base material can be effectively improved, the edge crack defects after rolling can be eliminated or significantly reduced, and the yield and quality of the product can be improved.

[0005] The technical solution adopted in the present invention is as follows:

[0006] The present invention proposes a control method for eliminating edge cracks of cold-rolled base material after rolling, which specifically includes the following steps:

[0007] S1. Add a set of water retaining plates on both sides of the vertical rollers of the rolling line;

[0008] The strip cooling water headers between the S2, F4 and F5 finishing mill stands are specially designed: there are 11 rows of branch pipes, with 4 branch pipes in each row welded to the main pipe body;

[0009] S3. Side water spray headers are installed at the front ends of the F2-F7 stands. The side water spray headers at the front ends of the F6 and F7 stands have the same structure and spray the entire cross-section of the strip; the side water spray headers at the front ends of the F3 and F5 stands have the same structure and spray both sides of the strip; the side water spray headers at the front ends of the F2 and F4 stands have the same structure and spray the middle area of the strip; each set of side water spray headers is equipped with an independent electrically controlled on / off valve;

[0010] S4. Data Collection and Analysis: Before the workpiece enters the finishing mill, the temperature monitoring system collects real-time longitudinal and cross-sectional temperature distribution data and transmits it to the central processing unit. The central processing unit pre-processes the data and uses it as the basis for subsequent control settings.

[0011] S5. Presetting of rolling process parameters: The rolling process parameter optimization system generates optimized rolling process parameters according to the initial parameters of the rolled piece, and the rolling mill control system starts rolling according to the optimized parameters;

[0012] S6. During the rolling process, the temperature monitoring system continuously monitors the temperature changes of the rolled product at the outlet of the final finishing stand, transmitting updated data to the central processing unit several times per second. Once the central processing unit determines that the temperature of a certain area of the rolled product cross-section deviates from the preset uniform temperature range, it immediately issues a command to the side spray header adjustment system. The rolling mill control system dynamically adjusts the rolling speed or the number of cooling water headers in use and the valve opening between stands based on the longitudinal temperature deviation to meet the target temperature control accuracy in the longitudinal direction of the finished product outlet.

[0013] S7, laminar cooling.

[0014] Furthermore, in step S2, the spray holes of the branch pipe are distributed non-parallel to the running direction of the strip, and the water spraying angle is 15° to the left and right sides of the strip; water is sprayed in the opposite direction of the running direction of the strip, and the longitudinal angle is 15°.

[0015] Furthermore, the aperture size of each branch pipe varies symmetrically according to its distance from the center line of the rolling line, that is, the aperture in the middle is the largest and the two sides are the smallest, and the upper and lower surfaces are arranged symmetrically; the cooling water flow forms a uniform fan-shaped cooling area on the surface of the strip.

[0016] Furthermore, in step S5, the pre-set parameters include: rough rolling outlet temperature 1020-1070°C; finishing rolling inlet temperature 990-1030°C; final rolling temperature 880-920°C; cross-sectional temperature difference 0-15°C; coiling temperature 680-720°C, inter-stand strip cooling water headers F4 and F5 are used; speed adjustment is selected as automatic; laminar cooling mode is sparse in the rear section; hot rolled slab thickness is 230 mm, heating furnace in-furnace time is 160-200 minutes, and intermediate slab thickness is 36-41 mm.

[0017] Furthermore, in step S1, the water retaining plate is composed of a base plate and a sealing plate fixedly connected to the upper portion of the base plate.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. Significantly Improve Product Quality: The method of this invention effectively eliminates or significantly reduces edge cracking defects in cold-rolled low-carbon steel base material. Practical application statistics show that the edge crack shear loss rate in hot rolling has been reduced from 0.0047% to 0.001%, the edge crack rate in cold rolling has been reduced from 8.63% to 1.45%, and the incidence of cold-rolled strip breaks due to edge cracking has been reduced by approximately 75%. This effectively improves product surface quality and dimensional accuracy, meeting the stringent material quality requirements of high-end products.

[0020] 2. Improve the yield rate: Reducing edge crack defects means fewer products are scrapped due to quality problems, and at the same time reduces the probability of strip breakage during the cold rolling process, thereby improving the yield rate of products in each process of hot rolling and cold rolling, reducing production costs and improving economic benefits.

[0021] 3. Enhanced production stability: The present invention makes the rolling process more stable through precise control of the hot rolling process, reduces production interruptions and equipment failures caused by edge cracking problems, and improves production efficiency and equipment utilization.

[0022] 4. Wide applicability: The present invention is applicable to the hot rolling production process of cold-rolled low-carbon steel base materials of different specifications and materials, and has good versatility and promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a simplified structural diagram of the cooling water header in the finishing rolling area;

[0024] Figure 2 This is a schematic diagram of the structure of the cooling water header between the F4-F5 finishing mill stands;

[0025] Figure 3 This is a structural diagram of the water spray header at the front end of the finishing mill stand;

[0026] Figure 4 It is a schematic diagram of laminar cooling;

[0027] Figure 5 This is a schematic diagram of the conventional hot rolling production process. DETAILED DESCRIPTION

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Continuous annealing production process of cold rolled steel coil: (steelmaking) molten iron pretreatment → converter smelting → refining outside the furnace → continuous casting → hot rolling heating → rough rolling, finishing rolling → controlled cooling → coiling → (cold rolling) uncoiling, welding → pickling, cold rolling → continuous annealing → flattening → surface and performance inspection → packaging → delivery; among them, the hot rolling production process is as follows Figure 1 shown.

[0030] The present invention proposes a control method for eliminating edge cracks of cold-rolled base material after rolling, which specifically includes the following steps:

[0031] S1. A set of water baffles is added on both sides of the vertical rollers of the rolling line. The water baffles are mainly composed of a base plate and a sealing plate fixed above the base plate. The combination of the two can effectively block the cooling water generated during the operation of the rolling line.

[0032] Before the water baffle is installed, cooling water easily splashes onto the surface of the workpiece, causing the temperature at the edge of the workpiece to drop rapidly. This localized temperature drop can lead to uneven temperature distribution across the cross-section of the workpiece, which in turn causes strength variations and affects product quality. However, with the addition of the water baffle, the present invention successfully avoids the problem of cooling water splashing onto the workpiece surface, fundamentally preventing problems such as uneven cross-section temperature and strength variations caused by cooling the workpiece. This provides a strong guarantee for stable production on the rolling line and the output of high-quality intermediate billets.

[0033] The strip cooling water headers between the S2, F4 and F5 finishing mills are specially designed: there are 11 rows of branch pipes, with 4 branch pipes in each row welded to the main pipe body to ensure the firmness and sealing of the connection; the nozzles of each branch pipe are distributed non-parallel to the running direction of the strip, and the spray angle is 15° to the left and right sides of the strip. Water is sprayed in the opposite direction of the strip running, with a longitudinal angle of 15°. The aperture size of each branch pipe changes symmetrically from the middle to the sides according to its distance from the center line of the rolling line. The aperture of the middle branch pipe is the largest, and the aperture of the branches on both sides is the smallest. They are arranged symmetrically along the upper and lower surfaces of the strip, such as Figure 2 The cooling water flow forms a uniform fan-shaped cooling area on the strip surface, reducing the temperature drop at the edge of the strip and ensuring that the cross-section temperature of the strip gradually increases from the middle to the sides.

[0034] S3. Side water spray headers are installed at the front end of the F2-F7 racks. The side water spray headers at the front end of the F6 and F7 racks have the same structure and spray the entire cross section of the strip; the side water spray headers at the front end of the F3 and F5 racks have the same structure and spray both sides of the strip; the side water spray headers at the front end of the F2 and F4 racks have the same structure and spray the middle area of the strip; each set of side water spray headers is equipped with an independent electric control switch valve, such as Figure 3 As shown; the electronically controlled switch valve switches according to the instructions of the central processor, thereby achieving differentiated adjustment of the transverse temperature of the rolled piece, ensuring that the temperature on both sides of the cross section of the rolled piece is not lower than the middle temperature.

[0035] S4. Data Collection and Analysis: Before the workpiece enters the finishing mill, the temperature monitoring system collects real-time longitudinal and cross-sectional temperature distribution data and transmits it to the central processing unit. The central processing unit pre-processes the data and uses it as a basis for subsequent control settings.

[0036] S5. Presetting of rolling process parameters: The rolling process parameter optimization system generates optimized rolling process parameters according to the initial parameters of the rolled piece, and the rolling mill control system starts rolling according to the optimized parameters;

[0037] For cold-rolled low-carbon steel, the pre-set parameters include: rough rolling outlet temperature 1020-1070℃; finishing rolling inlet temperature 990-1030℃; final rolling temperature 880-920℃; cross-sectional temperature difference 0-15℃; coiling temperature 680-720℃, F4 and F5 strip cooling water manifolds between stands; automatic speed adjustment; laminar cooling mode with sparse rear section; hot-rolled slab thickness 230mm, heating furnace time 160-200 minutes, and intermediate slab thickness 36-41mm.

[0038] Rolling Process Parameter Optimization System: This system incorporates a rolling process model for hot-rolled low-carbon steel and cold-rolled stock, built based on extensive experimental data and numerical simulations. This model accounts for the complex relationships between multiple variables, including material properties, rolling speed, reduction, and cooling strategies. Operators input initial rolling material parameters into the system, which automatically generates optimized rolling process parameters, such as the optimal rolling speed range and appropriate reduction allocation, and transmits these to the mill control system.

[0039] S6. Dynamic Control: During the rolling process, temperature changes of the rolled product (HR-TB) at the exit of the finishing mill stand are continuously monitored using temperature monitoring point pyrometers (FDTs) and multi-function detectors (MFDIs). Updated data is transmitted several times per second to the central processing unit (CPU). If the CPU determines that the temperature of a region of the rolled product cross-section deviates from the preset uniform temperature range, it immediately issues a command to the side spray water header (ISSW) control system. For example, in the production of hot-rolled mild steel DC01, the cross-sectional temperature difference is set to 0-15°C (edge-to-center). During normal operation, side spray water is used on F6 and F7. When the cross-sectional temperature difference falls below 0°C (edge-to-center), the front spray water on F2 and F4 is activated. When the cross-sectional temperature difference exceeds 15°C (edge-to-center), the front spray water on F2 and F4 is shut off. Based on the longitudinal temperature deviation, the mill control system dynamically adjusts the rolling speed, the number of active interstand cooling water headers (ISC), and the valve opening to coordinately balance the cross-sectional temperature of the rolled product. For example, when the longitudinal temperature (FDT) at the finishing exit of hot-rolled low-carbon steel DC01 product is detected to be 8°C higher or lower than the target of 900°C, the amount of cooling water sprayed between the stands will be increased or decreased accordingly; when it deviates from the target by more than 15°C, the speed of the rolling mill will participate in temperature regulation, increasing or decreasing the speed to adjust the longitudinal temperature change of the product to meet the target temperature value.

[0040] S7, laminar cooling. The laminar cooling equipment mainly consists of a high-level water tank, brackets, platforms, ladders, upper and lower headers, etc.; 21 sets of upper and lower headers, 23 sets of side water spray devices, and 2 sets of compressed air purge devices; the process diagram of the laminar cooling equipment is as follows Figure 4 shown.

[0041] Matters not described in detail in this invention are all known technologies.

[0042] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A control method for eliminating edge cracks of cold-rolled base material after rolling, characterized in that: The method comprises the following steps: S1. Add a set of water retaining plates on both sides of the vertical rollers of the rolling line; The strip cooling water headers between the S2, F4 and F5 finishing mill stands are specially designed: there are 11 rows of branch pipes, with 4 branch pipes in each row welded to the main pipe body; S3. Side water spray headers are installed at the front ends of the F2-F7 stands. The side water spray headers at the front ends of the F6 and F7 stands have the same structure and spray the entire cross-section of the strip; the side water spray headers at the front ends of the F3 and F5 stands have the same structure and spray both sides of the strip; the side water spray headers at the front ends of the F2 and F4 stands have the same structure and spray the middle area of the strip; each set of side water spray headers is equipped with an independent electrically controlled on / off valve; S4. Data Collection and Analysis: Before the workpiece enters the finishing mill, the temperature monitoring system collects real-time longitudinal and cross-sectional temperature distribution data and transmits it to the central processing unit. The central processing unit pre-processes the data and uses it as the basis for subsequent control settings. S5. Presetting of rolling process parameters: The rolling process parameter optimization system generates optimized rolling process parameters according to the initial parameters of the rolled piece, and the rolling mill control system starts rolling according to the optimized parameters; S6. During the rolling process, the temperature monitoring system continuously monitors the temperature changes of the rolled product at the outlet of the final finishing stand, transmitting updated data to the central processing unit several times per second. Once the central processing unit determines that the temperature of a certain area of the rolled product cross-section deviates from the preset uniform temperature range, it immediately issues a command to the side spray header adjustment system. The rolling mill control system dynamically adjusts the rolling speed or the number of cooling water headers in use and the valve opening between stands based on the longitudinal temperature deviation to meet the target temperature control accuracy in the longitudinal direction of the finished product outlet. S7, laminar cooling.

2. A control method for eliminating edge cracks of cold-rolled base material according to claim 1, characterized in that: In step S2, the spray holes of the branch pipe are distributed non-parallel to the running direction of the strip, and the water spraying angle is 15° to the left and right sides of the strip; water is sprayed in the opposite direction of the running direction of the strip, and the longitudinal angle is 15°.

3. The method for eliminating edge cracks of cold-rolled base material according to claim 2, characterized in that: The aperture size of each branch pipe changes symmetrically according to its distance from the center line of the rolling line, that is, the aperture in the middle is the largest and the two sides are the smallest, and the upper and lower surfaces are arranged symmetrically; the cooling water flow forms a uniform fan-shaped cooling area on the surface of the strip.

4. The method for eliminating edge cracks of cold-rolled base material according to claim 1, characterized in that: In step S5, the preset parameters include: roughing outlet temperature 1020-1070°C; finishing inlet temperature 990-1030°C; finishing temperature 880-920°C; cross-sectional temperature difference 0-15°C; coiling temperature 680-720°C, inter-stand strip cooling water headers F4 and F5 in use; speed adjustment selection automatic; laminar cooling mode with rear-stage sparse; hot-rolled slab thickness 230 mm, heating furnace in-furnace time 160-200 minutes, and intermediate slab thickness 36-41 mm.

5. The method for eliminating edge cracks of cold-rolled base material according to claim 1, characterized in that: In step S1, the water retaining plate is composed of a base plate and a sealing plate fixedly connected to the base plate.

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