Method for solving middle rolling breakage in finish rolling thin gauge rolling process in hot rolling procedure

Abstract

The invention discloses a method for solving middle rolling breakage in the finish rolling thin gauge rolling process in the hot rolling procedure, and belongs to the technical field of hot rolling. The method comprises the steps that the opening degree of a side guide plate before shearing and the opening degree of a side guide plate between finish rolling racks are subjected to segmented control through strip steel head threading, body rolling and tail steel throwing; in a finish rolling area, strip steel output by each rolling mill is detected, and when a detection result and a theoretical parameter exceed threshold values, AGC of the corresponding rolling mill is closed; the maximum accelerated speed of speed-increasing rolling is reduced; the height set value of the loop before and after the middle rolling rack is reduced, and the tension of the loop is increased. According to specific conditions, by adaptively adjusting the opening degree of the guide plate, the AGC, the maximum acceleration of accelerated rolling, the height of the loop and the tension of the loop, the defect that the middle is rolled to be broken in the finish rolling thin-specification rolling process in the hot rolling process can be reduced or even avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of hot rolling, and in particular relates to a method for solving the problem of middle rolling failure during the hot rolling process of finishing thin-gauge rolling. Background Art

[0002] In hot rolling production, the rolling of thin strip steel is always a complex and challenging process. This is not only because of the material characteristics of the strip steel itself and the high requirements of the rolling process, but also because when the equipment accuracy is slightly reduced, the entire rolling process may be in trouble. In particular, when a specific rolling mill encounters the phenomenon of running and waving during the finishing process, the consequences are often catastrophic. At the least, it may cause rolling defects in the middle of the strip steel, seriously affecting the product quality; at the worst, it may cause steel piling accidents, causing the entire production line to be paralyzed.

[0003] In order to cope with this problem, the hot rolling production line has adopted a series of sophisticated control strategies in the finishing rolling stage. Among them, speed-up rolling is a crucial link. After the strip is threaded, in order to ensure that the final rolling temperature of the product is in the optimal state, the finishing mill will quickly increase the rolling speed. However, during this process, the temperature of the intermediate billet will gradually decrease, resulting in a significant increase in the rolling force of each finishing rolling stand. The change in rolling force further affects the actual loaded roll gap of the rolling mill. In order to keep the thickness deviation of the finished strip within the standard range over the entire length, the automatic thickness control (AGC) function of the rolling force is put into use. This function ensures that the strip thickness at the exit of each stand remains constant by adjusting the loaded roll gap of each stand in real time.

[0004] However, in actual operation, the lack of equipment accuracy often becomes a bottleneck restricting the rolling quality. In particular, during the adjustment process, the hydraulic cylinders (HGC cylinders) on both sides of the rolling mill need to be adjusted synchronously according to the precise calculation amount. However, due to equipment wear, poor lubrication or other factors, the actual effective adjustment amount of the HGC cylinders on both sides often differs. This difference leads to deviations on both sides of the actual loaded roll gap, which in turn causes serious accidents such as lateral bending and wave shape. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for solving the problem of middle-portion crushing during the hot rolling process of finishing thin-gauge rolling. By adaptively adjusting multiple parameters such as guide plate opening, AGC, maximum acceleration of speed-up rolling, looper height and looper tension, the defect of middle-portion crushing during the hot rolling process of finishing thin-gauge rolling can be reduced or even avoided.

[0006] The technical solution adopted by the present invention is:

[0007] A method for solving the problem of middle rolling failure during the hot rolling process of finishing thin gauge rolling, comprising:

[0008] The opening degree of the side guide plate before shearing and the side guide plate between the finishing mill stands is controlled in sections by strip head threading, main body rolling and tail throwing;

[0009] In the finishing area, the strip steel output from each rolling mill is tested. When the test result and the theoretical parameter exceed the threshold, the AGC of the corresponding rolling mill is turned off;

[0010] Reduce the maximum acceleration of the speed-up rolling;

[0011] The setting value of the looper height before and after the middle crushing frame will be reduced, and the looper tension will be increased.

[0012] In a feasible technical solution, when rolling 1500mm strip steel, the actual width of the intermediate billet in the hot state is 1535mm; at this time, the opening of the side guide plate before shearing and the side guide plate between the finishing mill stands is:

[0013]

[0014] In a feasible technical solution, detecting the steel strip outputted from each rolling mill refers to detecting the thickness difference between two sides of the steel strip.

[0015] In a feasible technical solution, the maximum acceleration of the speed-up rolling is set to 1.5%.

[0016] In a feasible technical solution, the looper height setting value before and after the middle rolling stand is reduced by 10%, and the looper tension is increased by 10%.

[0017] Compared with the prior art, the advantages and positive effects of this application are:

[0018] The present invention analyzes the causes of middle-part rolling failure during the hot rolling process of finishing thin-gauge rolling, finds out several factors that affect the rolling failure, such as the guide plate opening, AGC, the maximum acceleration of speed-up rolling, the looper height and the looper tension, and then according to the specific actual situation, adaptively adjusts the guide plate opening, AGC, the maximum acceleration of speed-up rolling, the looper height and the looper tension. Through the above adjustment, the defect of middle-part rolling failure during the hot rolling process of finishing thin-gauge rolling can be reduced or even avoided. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention generally described and shown herein can be arranged and designed in various configurations. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0020] A method for solving the problem of middle rolling failure during the hot rolling process of finishing thin gauge rolling, comprising:

[0021] The opening degree of the side guide plate before shearing and the side guide plate between the finishing mill stands is controlled in three sections: strip head threading, main body rolling and tail steel throwing; taking the rolling of 1500mm strip steel as an example, the width of the intermediate billet in the actual hot state is 1535mm; the setting parameters of each side guide plate are as shown in Table 1;

[0022] Table 1 shows the setting parameters of each side guide plate

[0023]

[0024] In the prior art, after the rough rolling process, the intermediate billet often has the phenomenon of excessive width at the head and tail, and often has sickle bend defects at the head and tail. In order to ensure stable threading and steel throwing, the present application adopts a strategy of dynamically adjusting the width of the side guide plate. Specifically, during the head and tail rolling, the width of the side guide plate is appropriately widened to reduce the lateral constraints on the billet and ensure stable threading and steel throwing. During the steady rolling process of the main body, the width of the side guide plate is gradually reduced to increase the control over the billet and improve the rolling stability. This strategy not only effectively reduces the defects at the head and tail, but also makes the entire rolling process more stable and controllable.

[0025] In the finishing area, the strip steel output from each rolling mill is tested. Once the test result and the theoretical parameter exceed the preset threshold, the AGC of the corresponding rolling mill is turned off;

[0026] Turn off the rolling force AGC function of individual rolling mills in the finishing rolling area. The reason for the middle rolling failure during the finishing rolling process is that during the rolling process, as the temperature of the intermediate billet decreases and the rolling mill speed increases, the rolling force of the rolling mill increases, and the loaded roll gap of the rolling mill increases. In order to ensure that the thickness of the finished product meets the standard requirements, the rolling force AGC adjusts the roll gap of the rolling mill online. If there is a deviation in the stiffness on both sides of the rolling mill, the effective adjustment amount of the roll gap on both sides is different, resulting in a deviation in the actual loaded roll gap on both sides of the rolling mill, and the strip appears wavy, resulting in the failure of the middle rolling;

[0027] In order to ensure that the final rolling temperature of the product reaches the target value, the finishing rolling adopts the control strategy of increasing the speed of rolling. Excessive acceleration will bring greater variables to the rolling process, so the maximum acceleration is adjusted from 2% to 1.5% to stabilize the rolling state.

[0028] The looper height setting value before and after the middle rolling frame will be reduced by 10%, and the looper tension will be increased by 10%. By lowering the looper height and increasing the looper tension, the rolling state can be stabilized by utilizing the adjustment function of the looper.

[0029] This application conducts an in-depth analysis of the problem of middle rolling failure that may occur during the finishing rolling process. It is found that the root cause lies in the deviation of the roll gap caused by factors such as the increased speed of the rolling mill, the increased rolling force, and the deviation of the stiffness on both sides of the rolling mill during the rolling process. To this end, the present invention has taken a number of measures: first, adjusting the parameters of the side guide plate; second, limiting the upper limit of the acceleration of the frame to avoid the instability caused by too fast speed changes; third, stabilizing the rolling state by adjusting the height and tension of the looper. Specifically, the setting value of the looper height before and after the frame where the middle rolling failure occurs is reduced by 10%, and the looper tension is increased by 10%. This can not only effectively prevent the strip from waving and rolling failure during the rolling process, but also make full use of the adjustment function of the looper to optimize the rolling process.

[0030] The present application performs three-stage control on the opening of the finishing side guide plate, which can not only meet the requirements of stable strip threading and rolling at the head and tail, but also reduce the set value during the main rolling to limit the lateral movement of the strip in the frame to improve the stability of rolling. By turning off the rolling force AGC function of the frame where the plate shape is prone to change during finishing rolling, when various factors cause the rolling force of the frame to change, the roll gap will remain unchanged due to the closure of the function, thus avoiding the deviation change of the loaded roll gap on both sides caused by the roll gap change. Limiting the upper limit of the acceleration of the frame can avoid variables caused by rapid speed changes and improve rolling stability. By reducing the height of the looper and increasing the tension of the looper, the adjustment function of the looper in the finishing rolling process can be effectively exerted, avoiding the occurrence of strip damage accidents caused by excessively high looper height.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A method for solving the problem of middle rolling failure during hot rolling thin gauge finishing rolling, characterized in that: include: The opening degree of the side guide plate before shearing and the side guide plate between the finishing mill stands is controlled in sections by strip head threading, main body rolling and tail throwing; In the finishing area, the strip steel output from each rolling mill is tested. When the test result and the theoretical parameter exceed the threshold, the AGC of the corresponding rolling mill is turned off; Reduce the maximum acceleration of the speed-up rolling; The setting value of the looper height before and after the middle crushing frame will be reduced, and the looper tension will be increased.

2. The method for solving the problem of middle rolling failure during the hot rolling process of thin gauge finishing rolling according to claim 1, characterized in that: When rolling 1500mm strip steel, the actual width of the intermediate billet in the hot state is 1535mm; at this time, the opening of the side guide plate before shearing and the side guide plate between the finishing mill stands is:

3. The method for solving the problem of middle rolling failure during the hot rolling process of thin gauge finishing rolling according to claim 1, characterized in that: Testing the strip output from each rolling mill means testing the thickness difference on both sides of the strip.

4. The method for solving the problem of middle rolling failure during the hot rolling process of thin gauge finishing rolling according to claim 2, characterized in that: The maximum acceleration of the accelerated rolling was set to 1.5%.

5. The method for solving the problem of middle rolling failure during the hot rolling process of thin gauge finishing rolling according to claim 2, characterized in that: The looper height setting value before and after the middle crushing frame will be reduced by 10%, and the looper tension will be increased by 10%.

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