A rolling control method for improving length direction washboard of a medium-thick steel plate
By dynamically adjusting the speed and torque balance of the rolling mill motor, the wavy defect of the washboard during the rolling of medium and heavy steel plates was solved, achieving precise control and efficient production, and improving product quality and production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUNAN VALIN XIANGTAN IRON & STEEL CO LTD
- Filing Date
- 2026-02-04
- Publication Date
- 2026-06-05
AI Technical Summary
Existing plate shape control technologies are insufficient to effectively address the wavy defects along the length direction caused by the mismatch between the speed and torque of the upper and lower motors of the rolling mill during the rolling process of medium and heavy steel plates, especially when rolling thin steel plates.
By dynamically adjusting the speed and torque balance of the upper and lower large motors of the rolling mill, monitoring and controlling the motor torque deviation in real time, and adjusting the speed in segments with linear increments, the motors work together to avoid equipment overload and achieve precise control of the washboard waviness.
It significantly improves the straightness of medium and heavy steel plates along the length direction, reduces the cold straightening rate, increases the yield and production efficiency, and reduces energy consumption and equipment interference.
Smart Images
Figure CN122142097A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of steel metallurgical rolling technology, specifically relating to a rolling control method for improving the wavy shape of medium-thick steel plates in the length direction. Background Technology
[0002] In the rolling process of medium and heavy plates, especially in the last few passes of the finishing rolling stage, a wavy defect that undulates periodically along the length of the steel plate often occurs, commonly known as "washboard wavy pattern". This defect seriously affects the final flatness, surface quality, and processing performance of the steel plate, reduces the product qualification rate and yield, and causes resource waste.
[0003] Long-term monitoring and data analysis of the production site revealed that the occurrence of such defects is closely related to the automated control strategy of the rolling mill. Research found that one root cause is a transient or continuous mismatch in the speed and torque control of the upper and lower large motors during the rolling process. This mismatch is particularly pronounced when rolling thin grades, such as finished passes for medium-thick plates with a thickness ≤35mm. This mismatch leads to inconsistent metal flow velocities on the upper and lower surfaces of the steel plate during plastic elongation, resulting in accumulated periodic fluctuations along the length direction.
[0004] Existing sheet shape control technologies mostly focus on adjusting bending roll force, adjusting roll crown, setting straightening rolls, or performing specific control during the widening stage. However, these methods primarily address sheet shape defects in the transverse width direction or specific problems in intermediate billets. They lack targeted, dynamic, and precise control methods for the washboard-like waviness that exists in the length direction, caused by precise and coordinated control of the motor drive system. These methods are difficult to adapt to the complex working conditions of different sheet specifications, varying rolling forces, and different pass numbers. This problem is particularly pronounced when rolling thinner sheet specifications.
[0005] Therefore, the industry urgently needs a rolling control method that can solve the rolling defects of the washboard pattern in the length direction of medium and heavy plates caused by the mismatch between the speed and torque of the upper and lower motors of the rolling mill in real time and dynamically. Summary of the Invention
[0006] To achieve the above objectives, this invention provides a rolling control method for improving the wavy texture along the length of medium-thick steel plates. By dynamically adjusting the speed and torque balance of the upper and lower large motors of the rolling mill, the wavy texture defect that appears along the length of the finished steel plate can be effectively improved.
[0007] The technical solution of the present invention is as follows: a rolling control method for improving the wavy shape of medium-thick steel plates in the length direction, comprising the following steps: Step S1: Based on the target thickness of the steel plate obtained from the rolling mill process automation system in the last loaded pass, determine whether the function is enabled. If the target thickness of the steel plate is not greater than the set threshold, the system automatically determines that it is suitable to enable the washboard wavy shape improvement function; otherwise, it is not enabled. Step S2: After the steel plate head is bitten into the rolling mill, within the sled action length L Ski Inside, the rolling mill is in sled control mode, the washboard ripple improvement function is paused, and no intervention is made to the rolling mill; Step S3: After the steel plate head passes the sled control area, immediately turn off the conventional torque balance control function between the upper and lower large motors of the rolling mill, and then start the speed adjustment program; Step S4: Monitor the torque deviation between the upper and lower motors in real time. When the deviation exceeds the preset safety threshold, stop the speed adjustment program and restore torque balance control.
[0008] Furthermore, before step S1, the method further includes: before the penultimate rolling pass of the finishing mill, determining whether the pass is the last loaded pass of the mill or the final pass is the last loaded pass of the mill based on the numerical state of the expected rolling force.
[0009] Furthermore, the threshold value in step S1 is 35 mm.
[0010] Furthermore, the working length of the sled in step S2 is a value between 0.1m and 1.5m.
[0011] Furthermore, the speed adjustment procedure in step S3 is specifically as follows: Step S3.1: Calculate the maximum allowable speed difference between the upper and lower large motors based on the current pass thickness of the medium-thick plate and the desired rolling force. The unit is %, and the value range is limited to 0~±5%. The calculation formula is as follows: ; in, The thickness of the medium-thick plate in the current pass is in mm; The expected rolling force for medium and heavy plates in the current pass is expressed in MN. Step S3.2: Calculate the remaining effective rolling length for the current pass. The calculation formula is as follows: ; in, This represents the remaining effective rolling length for the current pass. For the target rolling length; Divide the remaining effective rolling length N into equal parts and calculate the length of each part. The length unit is m; Step S3.3: Adjust the maximum speed difference It is also divided into N equal parts, and the velocity increment for each part is calculated. ; Step S3.4: Select the large motor at the bottom of the rolling mill to perform speed adjustment. During subsequent rolling, whenever the real-time integral position of the steel plate head reaches a certain value... When the lengths overlap, the speed of the selected motor is increased by one. The increment continues until the current rolling pass is completed.
[0012] Preferably, the working length of the sled in step S2 is 0.6m.
[0013] Furthermore, the number of equal divisions N is a positive integer between 10 and 50.
[0014] Preferably, the number of equal divisions N is 20.
[0015] Furthermore, the safety threshold in step S4 is a value between 1.5 and 3 times the rated torque of the large motor.
[0016] Preferably, the preset safety threshold is set to twice the rated torque of the large motor.
[0017] The beneficial effects of this invention are: (1) This invention directly addresses the root cause of the washboard-like waviness in the length direction of medium-thick plates: the mismatch between motor speed and torque; it actively intervenes and achieves precise control from the source. Compared with traditional methods of post-deformation compensation or lateral adjustment, the solution is more targeted.
[0018] (2) By automatically determining whether to enable the function based on the thickness of the pass, the method is ensured to operate only under necessary and effective conditions, avoiding unnecessary energy consumption and interference with the normal rolling process, and realizing intelligent condition matching.
[0019] (3) The cleverly designed "no intervention during the sled control phase" mechanism ensures the absolute stability of the starting point of the rolling process; at the same time, the equipped torque deviation real-time monitoring and forced recovery protection mechanism provides double safety protection for the equipment and effectively prevents equipment overload or damage caused by control intervention.
[0020] (4) This invention achieves smooth and precise dynamic compensation for the steel plate elongation process through a segmented, linearly increasing speed adjustment mode, significantly improving the straightness of the final product in the length direction, reducing the high cold straightening rate caused by plate shape defects, and greatly improving the yield and production efficiency. According to actual production data from the field application of this invention, the cold straightening rate of bridge steel is reduced by about 20%, the cold straightening rate of low alloy steel is reduced by about 18%, and the cold straightening rate of 36 grade steel for ship plates is reduced by about 14%, showing significant effects. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 This is a flow control diagram of the implementation method of the present invention; Figure 2 It is a diagram showing the correspondence between the speed difference increment and the rolling length position; The markings in the figure are: 1 - rolling length, 2 - speed increment. Detailed Implementation
[0023] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.
[0024] like Figure 1 As shown, the present invention provides a rolling control method for improving the wavy shape of medium-thick steel plates along their length, comprising the following steps: Step S1: Operating Condition Judgment and Function Activation: In the automated control system of the rolling process, the mill process automation control system synchronously sends setting parameters for three consecutive passes to the mill basic automation system, covering the process data of the currently executing pass, the next pass to be rolled, and the pass after that. Among them, the expected rolling force of each pass is the core process parameter, and its numerical status is the key basis for determining the last loaded pass of the finishing mill. A non-zero value indicates that the pass is under loaded rolling conditions, and a zero value indicates that the pass is in an unloaded state. Before the second-to-last pass of the finishing mill, a systematic judgment must be made based on the numerical status of the expected rolling force to determine whether the pass is the last loaded pass of the mill or the very last pass. Then, based on the target thickness of the steel plate obtained from the mill process automation system for the last loaded pass, the system judges whether the function should be activated: when the thickness is not greater than the set threshold, the system automatically judges that it is suitable to activate the washboard waviness improvement function, the preferred threshold is 35mm, otherwise it is not activated.
[0025] Step S2: Sled Control Stage: After the steel plate head is bitten into the rolling mill, the rolling mill is in sled control state within a preset head length area. During this initial stabilization stage, the improved method of the present invention remains in a suspended state and does not intervene in the rolling mill in any way, ensuring stable biting and initial rolling.
[0026] It should be noted that the preset head length range, i.e. the effective length of the sled, is a value between 0.1m and 1.5m, preferably 0.6m.
[0027] Step S3: Once the steel plate head has passed the sled control area, the conventional torque balance control function between the upper and lower main motors of the rolling mill is immediately and automatically shut down. Then, the speed adjustment program is started. The correspondence between the speed difference increment and the rolling length position is as follows: Figure 2 As shown.
[0028] It should be noted that the speed adjustment program is specifically as follows: Step S3.1: Calculate the maximum allowable speed difference between the upper and lower large motors based on the current pass thickness of the medium-thick plate and the desired rolling force. The unit is %, and the value range is limited to 0~±5%. The calculation formula is as follows: ; in, The thickness of the medium-thick plate in the current pass is in mm; The value represents the expected rolling force for medium and heavy plates in the current pass, in units of MN. The parameters 300, 0.25, and 1.03 in the formula are empirical coefficients, which can be fine-tuned according to the actual usage conditions on site. Step S3.2: Calculate the remaining effective rolling length for the current pass. The calculation formula is as follows: ; in, This represents the remaining effective rolling length for the current pass. For the target rolling length; Divide the remaining effective rolling length N into equal parts and calculate the length of each part. The length unit is m; Step S3.3: Adjust the maximum speed difference It is also divided into N equal parts, and the velocity increment for each part is calculated. ; Step S3.4: Select the large motor at the bottom of the rolling mill to perform speed adjustment. During subsequent rolling, whenever the real-time integral position of the steel plate head reaches a certain value... When the lengths overlap, that is, through , ,... At these positions, the speed of the selected motor is increased by one. The increment continues until the current rolling pass is completed.
[0029] It should be noted that the number of equal divisions N is a positive integer between 10 and 50, preferably N is 20.
[0030] Step S4: During the rolling process, continuously monitor the real-time output torque of the upper and lower large motors of the rolling mill. When the torque deviation between the upper and lower motors exceeds the set safety threshold, the system immediately and automatically terminates the improvement function of this invention and re-enables the normal torque balancing function of the upper and lower large motors of the rolling mill to protect the safety of the motors and frequency converter equipment, and ensure that the rolling of the current steel plate can be completed safely.
[0031] It should be noted that the set safety threshold is a value between 1.5 and 3 times the rated torque of the large motor, preferably 2 times.
[0032] On the human-machine interface (HMI) of the rolling mill main control system, a control interface for the present invention is provided to the operator, including at least: an activation / deactivation button for improving functions, a selection button for selecting the motor to perform speed adjustment (upper / lower large motor), and the maximum allowable speed difference calculated by the system.
[0033] The following examples provide further details.
[0034] Example 1: Take the most common rolling process of a medium-thick plate as an example.
[0035] Prerequisites: When the finishing mill reaches the penultimate pass, the last loaded pass of the mill is determined. Based on the pass information issued by the mill, the last pass for this steel plate is identified as the last loaded pass of the mill. After the mill completes the penultimate pass, it enters the final pass. The target thickness H of this pass is 30 mm ≤ 35 mm, meeting the activation conditions. Target rolling length L 总 = 30 m, the desired rolling force F is 35MN.
[0036] Preset parameters: Based on experience data and equipment capabilities, set the sled control length L. Ski = 0.6 m, according to the formula ΔV max =300 / H-0.25 F+1.03 calculates the maximum speed difference ΔV for the current track. max = 2.28%, and the large motor under the rolling mill was selected as the target for speed regulation.
[0037] The implementation steps are as follows: Step 1: The operator activates the improved function of this invention through the human-machine interface and selects the lower motor. When the steel plate for this pass begins to bite into the rolling mill, the system automatically detects a thickness of 30mm, and the improved function of this invention is activated.
[0038] Step 2: In the 0 to 0.6m range after the steel plate head is bitten in, the rolling mill executes its preset sled control strategy, and no adjustments are made within this range.
[0039] Step 3: Start the speed adjustment program. When the head of the steel plate passes the 0.6-meter mark, the system will automatically shut down the conventional torque balancing function of the upper / lower motors of the rolling mill.
[0040] Calculate the remaining rolling length L Remain = L Total – L Ski = 30 m - 0.6 m = 29.4 m; Determine the number of segments and the increment: Set N=20, then the length of each segment ΔL = L Remain / N = 29.4 m / 20 = 1.47 m; The speed difference increment per segment ΔV = ΔV max / N = 2.28% / 20 = 0.114%; The reference stacking points are set as follows: starting point 0.6 m, followed by 0.6 + 1.47 = 2.07 m, and 0.6 + 2... 1.47 = 3.54 m, ..., up to 30 m.
[0041] The rolling process continues, with the head position of the steel plate monitored in real time. Each time the head position reaches a preset overlapping point (e.g., successively reaching 2.07 m, 3.54 m, 5.01 m...), the operating speed of the lower motor increases by 0.114%. Through 20 such increases, by the end of the rolling pass, the speed of the lower motor has increased by a total of 2.28% relative to the initial stage.
[0042] Step 4: The monitoring unit continuously collects the output torque of the upper and lower motors. Assume the rated torque of the motor is T_rated. If at any time |T_rated is detected... 上 - T 下 | > 2 T 额 If the speed regulation program is stopped, the torque balancing function of the upper and lower motors will be restored to ensure that the remaining rolling in this pass is completed in a safe mode.
[0043] Through the aforementioned closed-loop "measurement-judgment-adjustment-protection" process, this invention achieves dynamic compensation for motor control mismatch by optimizing software control logic without requiring significant modifications to existing rolling mill hardware, thereby effectively suppressing the formation of washboard ripples.
[0044] In summary, the method of the present invention, through an automated control logic, intelligently judges and dynamically adjusts the upper and lower motors of the rolling mill during the stable rolling stage, ensuring that they work in the best matching state, thereby effectively eliminating or reducing the wavy pattern of the washboard and improving the shape quality of medium and heavy plates.
[0045] The application of this invention is not limited to the described embodiments, and those skilled in the art can make adjustments within the scope of the claims. For example, the number of equal divisions N and ΔV. max and L Ski The value of and the specific multiple of the trigger torque protection can be adjusted adaptively according to different steel grades and product specifications.
[0046] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present technical solution are within the protection scope of the present invention.
[0047] To facilitate understanding by those skilled in the art of the improvements of this invention over the prior art, some of the accompanying drawings and descriptions have been simplified, and for clarity, some other elements have been omitted from this application. Those skilled in the art should realize that these omitted elements may also constitute the content of this invention.
Claims
1. A rolling control method for improving the wavy pattern along the length of medium-thick steel plates, characterized in that, Includes the following steps: Step S1: Based on the target thickness of the steel plate obtained from the rolling mill process automation system in the last loaded pass, determine whether the function is enabled. If the target thickness of the steel plate is not greater than the set threshold, the system automatically determines that it is suitable to enable the washboard wavy shape improvement function; otherwise, it is not enabled. Step S2: After the steel plate head is bitten into the rolling mill, within the length of the sled action... Inside, the rolling mill is in sled control mode, the washboard ripple improvement function is paused, and no intervention is made to the rolling mill; Step S3: After the steel plate head passes the sled control area, immediately turn off the conventional torque balance control function between the upper and lower large motors of the rolling mill, and then start the speed adjustment program; Step S4: Monitor the torque deviation between the upper and lower motors in real time. When the deviation exceeds the preset safety threshold, stop the speed adjustment program and restore torque balance control.
2. The rolling control method for improving the wavy shape of medium-thick steel plates along the length direction as described in claim 1, characterized in that, Before step S1, the method further includes: before the penultimate rolling pass of the finishing mill, determining whether the pass is the last loaded pass of the mill or the last loaded pass, based on the numerical state of the expected rolling force.
3. The rolling control method for improving the wavy shape of medium-thick steel plates along the length direction as described in claim 2, characterized in that, The threshold value in step S1 is 35mm.
4. The rolling control method for improving the wavy shape of medium-thick steel plates along the length direction as described in claim 2, characterized in that, The working length of the sled in step S2 is a value between 0.1m and 1.5m.
5. The rolling control method for improving the wavy shape of medium-thick steel plates along their length as described in claim 2, characterized in that, The speed adjustment procedure in step S3 is as follows: Step S3.1: Calculate the maximum allowable speed difference between the upper and lower large motors based on the current pass thickness of the medium-thick plate and the desired rolling force. The unit is %, and the value range is limited to 0~±5%. The calculation formula is as follows: ； in, The thickness of the medium-thick plate in the current pass is in mm; The expected rolling force for medium and heavy plates in the current pass is expressed in MN. Step S3.2: Calculate the remaining effective rolling length for the current pass. The calculation formula is as follows: ； in, This represents the remaining effective rolling length for the current pass. For the target rolling length; Divide the remaining effective rolling length N into equal parts and calculate the length of each part. The length unit is m; Step S3.3: Adjust the maximum speed difference It is also divided into N equal parts, and the velocity increment for each part is calculated. ; Step S3.4: Select the large motor at the bottom of the rolling mill to perform speed adjustment. During subsequent rolling, whenever the real-time integral position of the steel plate head reaches a certain value... When the lengths overlap, the speed of the selected motor is increased by one. The increment continues until the current rolling pass is completed.
6. The rolling control method for improving the wavy shape of medium-thick steel plates along the length direction as described in claim 4, characterized in that, The working length of the sled in step S2 is 0.6m.
7. The rolling control method for improving the wavy shape of medium-thick steel plates along the length direction as described in claim 5, characterized in that, The number of equal divisions N is a positive integer between 10 and 50.
8. The rolling control method for improving the wavy shape of medium-thick steel plates along the length direction as described in claim 7, characterized in that, The number of equal divisions, N, is 20.
9. The rolling control method for improving the wavy shape of medium-thick steel plates along their length as described in claim 5, characterized in that, The safety threshold in step S4 is a value between 1.5 and 3 times the rated torque of the large motor.
10. The rolling control method for improving the wavy shape of medium-thick steel plates along their length as described in claim 9, characterized in that, The preset safety threshold is set to twice the rated torque of the large motor.