Methods for controlling the rhythm of hot strip mill after finishing rolling

Abstract

This invention relates to a rhythm control method after the hot strip enters the finishing mill, belonging to the technical field of control methods specifically applicable to metal rolling mills. This method, by setting the dynamic distance between the lower strip and the finishing mill F7, can avoid abnormal coiling settings or insufficient coiling equipment response time. Specifically, it controls the overall speed reduction of the lower strip during finishing mill rolling by comparing the time t1 (when the tail of the preceding strip reaches the first coiling pinch roll) and the time t2 (when the head of the lower strip completes the dynamic distance) once per second in real time. The time difference between t1 and t2 is compared with a known time safety margin constant to determine the optimal time for the lower strip to slow down until normal rolling resumes. Therefore, it precisely controls the two strips during finishing mill coiling to prevent tail-end collisions and insufficient coiling equipment response time, reducing wasted interval time and improving production efficiency.

Description

Technical Field

[0001] This invention relates to a rhythm control method after the finishing mill of a hot continuous rolling mill, belonging to the field of hot continuous rolling rhythm control technology. Background Technology

[0002] A hot strip mill production line typically consists of equipment arranged sequentially, including a heating furnace, roughing mills (R1-R2), intermediate insulation hood, finishing mills (F1-7), laminar flow cooling, and a coiler. Automatic control of the hot strip mill's rhythm can effectively improve production efficiency and reduce the time wasted due to manual control. Currently, the types of steel billets on hot strip mills change frequently; the type of steel rolled from one billet to the next often differs. If the rhythm is not properly controlled when the next billet enters the finishing mill, it can easily cause strip collisions between the finishing and coiling areas, equipment delays in setting up, or other abnormalities, thus affecting the production efficiency of the hot strip mill production line.

[0003] Chinese patent application No. 201510014316 discloses a method for preventing steel chasing on the cold roll table of a hot-rolled strip. This method calculates the difference in time required for the tail of the preceding strip and the head of the following strip to reach the coiling entrance before the finishing mill begins rolling. This time difference is used to adjust the minimum gap time, thereby controlling whether the following strip needs to wait at the finishing mill entrance. However, this method does not address the rhythm control of the two strips during the rolling process after the finishing mill begins rolling. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: how to avoid tail-end collision and shorten the interval time when two strips of steel that have already been tapped are rolled after entering the finishing mill.

[0005] The technical solution proposed by this invention to solve the above-mentioned technical problems is: a rhythm control method after hot strip mill finishing, for the period when the head of the lower strip has been rolled by the finishing mill and the tail of the front strip has not yet entered the coiler, including the following steps:

[0006] 1) Calculate the dynamic distance S required for the lower strip to travel on the finishing mill F7 according to the following formula (1). j ,

[0007] Sj = S f -V h 7×(tj+t0) (1),

[0008] In equation (1), S f It is the distance from the finishing mill F7 to the No. 1 coiling side guide plate, t0 is the time protection correction margin; t j This is the time required for the winding machine to complete its movement; V h 7 is the exit speed of the next strip at the finishing mill F7;

[0009] 2) After the next strip is bitten by F7 of the finishing mill, the time t1 for the tail of the previous strip to reach the No. 1 coiling pinch roll is calculated in real time according to the following formula (2), and the time t2 for the head of the next strip to complete the dynamic distance is calculated in real time according to the following formula (3).

[0010]

[0011]

[0012] In equation (2), L q 7 is the distance from the tail of the preceding strip to the take-up pinch roll after leaving the finishing mill F7, V q 7 is the speed of the front strip after it leaves the F7 mill;

[0013] In equation (3), S h 7 is the length of the lower strip after it exits the finishing mill F7, V h 7 is the speed of the lower strip head after it leaves the finishing mill F7;

[0014] 3) Calculate t1 and t2 once per second, and make the following judgments and controls:

[0015] (A) If t2-t1>a or t1=0, then normal rolling is performed;

[0016] (B) If t2-t1≤a, then control the finishing mills F1-F7 to reduce the overall speed by the same percentage until condition (A) is met and then stop reducing the speed.

[0017] (C) This step stops after the tail of the current strip passes the No. 1 take-up pinch roll;

[0018] Where 'a' is the time safety margin constant, which is generally configured as 3-6 seconds.

[0019] The beneficial effects of this invention are as follows: By setting the dynamic distance between the lower strip and the finishing mill F7, abnormal coiling settings or insufficient coiling equipment operation can be avoided. In particular, the head of the lower strip has been rolled by the finishing mill while the tail of the preceding strip has not yet entered the coiler. By calculating the time t1 when the tail of the preceding strip reaches the No. 1 coiling pinch roll and the time t2 when the head of the lower strip completes the dynamic distance in real time, the difference between t1 and t2 is compared with a known time safety margin constant to control the overall slowdown rolling of the lower strip in finishing mills F1-F7 until normal rolling resumes. Therefore, the risk of tail-end collision and insufficient coiling equipment operation during finishing rolling is precisely controlled, enabling the finishing mill to dynamically control the rolling speed of the lower strip in finishing mills F1-F7 at any time. This achieves precise control of the finishing rhythm of adjacent strips, minimizing wasted interval time and avoiding abnormalities such as strip tail-end collision, insufficient equipment settings or operation, thus improving production efficiency.

[0020] Furthermore, the time protection correction margin t0 is 1-3 seconds, the time tj required for the winding machine to complete its operation is 7-12 seconds, and the percentage is 3-5%. Attached Figure Description

[0021] The rhythm control method after hot continuous rolling milling of the present invention will be further explained below with reference to the accompanying drawings.

[0022] Figure 1 This is a schematic diagram of the rhythm control method after hot continuous rolling and finishing steel feeding in the embodiment. Detailed Implementation

[0023] Example 1

[0024] The rhythm control method after the hot strip mill finishes entering the steel in this embodiment is illustrated using two strips of steel on the front and back of the rolling line as an example. The rolling specifications of the front strip are 2.62*1155mm, and the rolling specifications of the back strip are 2.47*1143mm. For the period when the head of the back strip has been rolled by the finishing mill and the tail of the front strip has not yet entered the coiler, the method includes the following steps:

[0025] 1) The dynamic distance Sj required for the lower strip to travel on the finishing mill F7, calculated according to the following formula (1),

[0026] S j =S f -V h 7×(t j +t0) (1),

[0027] In equation (1), S f This is the distance from the finishing mill F7 to the No. 1 coiling side guide plate, in this embodiment, S f =130m;

[0028] t0 is the time protection correction margin, which is generally 1-3 seconds. In this embodiment, t0 is 1 second.

[0029] t j This refers to the time required for the winding machine to complete its movement, typically 7-12 seconds. In this embodiment, t... j Take 10 seconds;

[0030] V h 7 represents the exit speed of the lower strip at the finishing mill F7. In this embodiment, the V of the lower strip is collected. h 7 = 10.8 m / s;

[0031] Substitute the above values ​​to calculate S j =130-10.8×(10+1)=11.2 meters.

[0032] The purpose of setting a dynamic distance is to ensure that the coiler has enough time to operate before the head of the next strip arrives at the coiler.

[0033] 2) After the next strip is bitten by F7 of the finishing mill, the time t1 for the tail of the previous strip to reach the No. 1 coiling pinch roll is calculated in real time according to the following formula (2), and the time t2 for the head of the next strip to complete the dynamic distance is calculated in real time according to the following formula (3).

[0034]

[0035]

[0036] In equation (2), L q 7 is the distance from the tail of the preceding strip to the coiling pinch roll after leaving the finishing mill F7. This value is provided by the hot strip rolling control system and is a dynamic variable. In this embodiment, L is read as the distance. q 7 = 0;

[0037] V q 7 is the speed of the strip tail after it leaves the F7 mill, also provided by the hot strip control system. In this embodiment, V is read... q 7 = 13.14 m / s; Substitute the values ​​into the calculation.

[0038] In equation (3), S h 7 represents the length of the next strip after it exits the finishing mill F7, provided by the hot strip rolling control system. This value is a dynamic variable; in this embodiment, it reads S... h 7 = 1 meter; V h 7 is the speed of the lower strip head after it exits the F7 mill (i.e., leaves the finishing mill F7). In this embodiment, V is read as... h 7 = 10.8 m / s; Substitute the values ​​into the calculation.

[0039] 3) Calculate t1 and t2 once per second, and make the following judgments and controls:

[0040] (A) If t2-t1>a or t1=0, then normal rolling is performed;

[0041] (B) If t2-t1≤a, then control the finishing mill F1-F7 to reduce the overall rolling speed until condition (A) is met and then stop reducing the speed.

[0042] (C) This step stops after the tail of the current strip passes the No. 1 coiling pinch roll (i.e., the tail of the previous strip enters the coiler);

[0043] Where 'a' is the time safety margin constant, which is generally configured as 3-6 seconds. In this embodiment, it is set as 3 seconds.

[0044] In this embodiment, since t1 = 0, normal rolling is performed without the need to reduce the speed.

[0045] Example 2

[0046] The method in this embodiment is basically the same as that in Embodiment 1, except that:

[0047] 1) The front strip is rolled to a specification of 6.0*1050mm; the lower strip is rolled to a specification of 3.8*1190mm; collect the V-value of the lower strip. h 7 = 9.0 m / s;

[0048] 2)S j =S f -V h 7×(t j +t0)=130-9×(10+1)=31 meters;

[0049] 3) The L read in this embodiment q 7 = 8 meters, V read q 7 = 6 m / s, the reading of S h 7 = 1 meter, V read h 7 = 9 m / s

[0050] In this embodiment, a is set to 3 seconds; since t2-t1=3.3-1.3=2≤3, the lower strip steel is controlled to reduce speed by the same percentage across the seven mills of finishing mills F1-F7; in this embodiment, F1-F7 gradually reduce speed synchronously by 3-5%.

[0051] Continue calculating t1 and t2 every second until the next strip speed decreases to 6.8 m / s, then read L. q 7 = 5 meters, V read q7 = 6 m / s, the reading of S h 7 = 4.9 meters, V read h 7 = 6.8 m / s; then the calculation at this time is

[0052] Since t2-t1=3.84-0.83=3.01>3 at this time, condition (A) in step (3) is satisfied, so the speed reduction is stopped and the normal rolling speed is restored.

[0053] The above description is only a preferred embodiment of the present invention, but the present invention is not limited thereto. All equivalent substitutions or modifications made to the concepts and technical solutions of the present invention should be covered within the protection scope of the present invention.

Claims

1. A rhythm control method after hot strip mill finishing, for the period when the head of the lower strip has been rolled by the finishing mill and the tail of the upper strip has not yet entered the coiler, includes the following steps: 1) Calculate the dynamic distance S required for the lower strip to travel on the finishing mill F7 according to the following formula (1). j , S j =S f -V h 7×(t j +t0) (1), In equation (1), S f It is the distance from the finishing mill F7 to the No. 1 coiling side guide plate, t0 is the time protection correction margin; t j This is the time required for the winding machine to complete its movement; V h 7 is the exit speed of the next strip at the finishing mill F7; 2) After the next strip is bitten by F7 of the finishing mill, the time t1 for the tail of the previous strip to reach the No. 1 take-up pinch roll is calculated in real time according to the following formula (2), and the dynamic distance S for the head of the next strip to travel is calculated in real time according to the following formula (3). j Time t2, （2）， （3）， In equation (2), L q 7 is the distance from the tail of the preceding strip to the first take-up pinch roll after leaving the finishing mill F7. q 7 is the speed of the front strip after it leaves the finishing mill F7; In equation (3), S h 7 is the length of the lower strip after it exits the finishing mill F7, V h 7 is the speed of the lower strip head after it leaves the finishing mill F7; 3) Calculate t1 and t2 once per second, and make the following judgments and controls: (A) If t2-t1>a or t1=0, then normal rolling is performed; (B) If t2-t1≤a, then control the finishing mills F1-F7 to reduce the overall speed by the same percentage until condition (A) is met and then stop reducing the speed; (C) This step stops after the tail of the current strip passes the No. 1 take-up pinch roll; Where 'a' is the time safety margin constant, configured to be 3-6 seconds.

2. The rhythm control method after hot continuous rolling mill finishing steel feeding according to claim 1, characterized in that: The time protection correction margin t0 is 1-3 seconds, the time tj required for the winding machine to complete its operation is 7-12 seconds, and the percentage is 3-5%.

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