A method for preventing rear-end collisions in a hot-rolled coiler

Abstract

This invention relates to the field of hot rolling technology, and more particularly to a method for preventing tail-end collisions in hot rolling coilers. The method comprises: S1, calculating the strip head speed when the final stand of the finishing mill bites the strip; S2, calculating the time it takes for the strip head to reach coiler #1; S3, calculating in real-time the minimum coiler speed required to avoid tail-end collisions or jamming due to untimely coiler switching; and S4, using this minimum coiler speed as the lower limit of the tail speed of the preceding strip coiler to limit the coiler speed. The advantages of this invention are: by accurately calculating the head-to-tail interval between two strips before the coiler and controlling the lower limit of the coiling speed at the tail of the coiler, the time interval between the head and tail of the preceding and following strips is maintained greater than the coiler switching time. This effectively avoids tail-end collisions or jamming caused by insufficient time to switch coilers, and the calculation is accurate without affecting the rolling rhythm, resulting in good application performance.

Description

Technical Field

[0001] This invention relates to the field of hot rolling technology, and in particular to a method for preventing tail-end collisions in hot rolling coilers. Background Technology

[0002] In the hot rolling mill production process, after the finishing mill rolls the strip into shape, it needs to be coiled into coils by a coiler for subsequent transportation and processing. Typically, a hot rolling mill has two to three coilers to perform this task. A central roller conveyor and laminar flow cooling system are installed between the finishing mill and the coiler, which transports and cools the strip to ensure it reaches the appropriate temperature and properties before coiling.

[0003] After the strip is rolled out of the finishing mill, the PLC (Programmable Logic Controller) program tracks and calculates the head and tail positions of the strip on the central roller conveyor in real time to ensure that the strip can smoothly enter the coiler and complete the coiling operation. After the tail of the previous strip enters the coiler, a coiler switching operation is required. This includes opening and closing the coiler gate and raising and lowering the pinch rolls. The entire switching process usually takes a few seconds.

[0004] When the rolling interval is large, the tail of the previous strip enters the coiler before the head of the next strip has been rolled out, or the time between their entry into the coiler is long enough, preventing tail-end collisions and allowing the coiler sufficient time to complete the switching operation. However, as production increases and the rolling pace accelerates, the interval between two strips becomes shorter. In this situation, the coiler may not have enough time to complete the switching operation after the tail of the previous strip enters, while the head of the next strip has already reached the coiler, leading to a jamming accident. In more serious cases, tail-end collisions between two strips on the roller conveyor may occur, which not only affects production efficiency but may also damage equipment, increasing maintenance costs and safety risks. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preventing tail-end collisions in hot-rolled coilers. By accurately calculating the time when the head of the next strip arrives at the coiler and the time when the tail of the previous strip enters the coiler in real time, the minimum interval between the two strips is controlled by dynamically controlling the lower limit of the coiler speed. This provides the coiler with sufficient switching time, prevents strip tail-end collisions and steel jamming accidents, and improves production safety.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preventing rear-end collisions in a hot-rolled coiler includes:

[0008] S1. Calculate the strip head speed when the final stand of the finishing mill bites the strip;

[0009] S2. Calculate the time it takes for the strip head to reach the No. 1 coiler;

[0010] S3. Real-time calculation of the minimum speed of the coiler to avoid accidents such as rear-end collisions or steel jamming due to untimely switching of the coiler.

[0011] S4. The minimum speed of the coiler to avoid rear-end collisions or steel jams due to untimely coiler switching shall be used as the lower limit of the tail speed of the previous strip coiler to limit the coiler speed.

[0012] In S1, the strip head speed is calculated when the final stand of the finishing mill bites the strip, using the following formula:

[0013] v H =v0(1+f0)①

[0014] In formula ①, v0 represents the linear velocity of the last effective stand in the finishing mill, in m / s; f0 represents the forward slip ratio of the last effective stand in the finishing mill, in %; v H This indicates the strip head speed when the final stand of the finishing mill bites the strip, and the unit is m / s.

[0015] In S2, the time for the strip head to reach the No. 1 coiler is calculated using the following formula:

[0016]

[0017] In formula ②, 'a' represents the acceleration rate of the strip head, in m / s. 2 ; s0 represents the distance from the acceleration point to the No. 1 coiler, in meters; s1 represents the distance from the last effective stand of the finishing mill to the acceleration point, in meters; t H This indicates the time it takes for the strip head to reach the No. 1 coiler, expressed in seconds.

[0018] In S3, the minimum coiling speed required for real-time calculation to avoid rear-end collisions or steel jams due to untimely coiling machine switching is calculated using the following formula:

[0019]

[0020] In formula ③, t q ds represents the safe switching time of the winding machine, in seconds. t dv represents the distance from the tail of the strip to the coiler, in seconds (s); L This indicates the minimum speed of the coiler required to avoid rear-end collisions or steel jams caused by untimely coiler switching, and is expressed in m / s.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] By accurately calculating the head-to-tail interval between two strips in front of the coiler and controlling the lower limit of the coiling speed at the tail of the coiler, the head-to-tail interval of the front and rear strips is kept greater than the coiler switching time. This can effectively prevent accidents such as strips colliding in front of the coiler or being unable to switch coilers in time, which can cause steel jamming. The calculation is accurate and does not affect the rolling rhythm, resulting in good application effects. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the anti-rear-end collision control process for a hot-rolled coiler.

[0024] Figure 2 It is a speed curve at the tail end of the winding machine.

[0025] Figure 3 This is a schematic diagram of the anti-rear-end collision control principle for a hot-rolled coiler. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0027] The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the methods used in the following embodiments are conventional methods.

[0028] Example 1

[0029] Currently, two common control methods for preventing rear-end collisions are used in hot rolling production lines:

[0030] One approach is to limit the range of rolled product types to be too large and to rely on the experience of finishing mill operators to control the steel feeding interval;

[0031] Another method is to automatically control the steel feeding interval of the finishing mill by calculating and predicting the steel throwing and feeding times, thereby controlling the interval between the two steel pieces to prevent rear-end collisions.

[0032] Because the winding time and speed at the tail end of the coiler are highly variable, and speed prediction itself has a large error, the above two methods have significant calculation errors and are not very effective. Excessive safety margin affects the rolling rhythm, while insufficient margin cannot prevent tail-end collisions. This invention provides a tail-end collision prevention control method for hot-rolled coilers, enabling more precise control.

[0033] See Figure 1 ,See Figure 3 Taking the coiler of a hot-rolled 1780 production line in a steel plant as an example, the previous strip is coiled by coiler #2. The finishing rolling speed at the tail end of the coil is 10 meters per second. When there are 40 meters left at the tail end of the previous strip, the next strip is finished rolled out. The anti-tailgating control method for the hot-rolled coiler is as follows:

[0034] Step 1: The final effective stand speed of the last strip finishing mill is 10 m / s, and the slip ratio before rolling on the last stand is 10%. When the last stand bites the strip, the strip head speed is calculated using the following formula:

[0035] v H =v0(1+f0)①

[0036] In formula ①, v0 represents the linear velocity of the last effective stand in the finishing mill, in m / s; f0 represents the forward slip ratio of the last effective stand in the finishing mill, in %; v H This indicates the speed of the strip head when it bites the steel at the final stand of the finishing mill, in m / s.

[0037] According to formula ①, v H =10(1+10%)=11m / s.

[0038] Step 2: Taking a strip acceleration rate of 10% as an example, the distance from the last effective stand of the finishing mill to the No. 1 coiler is 130 meters, and the distance from the last effective stand of the finishing mill to the acceleration point is 20 meters. Calculate the time for the strip head to reach the No. 1 coiler using the following formula:

[0039]

[0040] In formula ②, 'a' represents the strip head acceleration rate, in m / s², a = 0.1 (given by the host computer according to the steel grade layer); 's0' represents the distance from the acceleration point to coiler #1, s0 = 130 - 20 = 110 in meters; 's1' represents the distance from the last effective stand of the finishing mill to the acceleration point in meters; t H This indicates the time it takes for the strip head to reach the No. 1 coiler, in seconds.

[0041] According to formula ②,

[0042] Step 3: The safe switching time of the coiler is 7 seconds. Taking the distance between the tail of the upper strip and the No. 2 coiler as 40m and the coiling speed as 7m / s, the minimum speed of the coiler is calculated in real time according to the following formula to avoid tail-end collisions or steel jamming accidents due to untimely switching of the coiler.

[0043]

[0044] In formula ③, t q ds represents the safe switching time of the winding machine, in seconds. t dv represents the distance from the tail of the strip to the coiler, in meters (m). L This indicates the minimum speed of the coiler required to avoid rear-end collisions or steel jams caused by untimely coiler switching, and is expressed in m / s.

[0045] According to formula ③,

[0046] Step 4: Calculate the speed dv l =9.1 m / s is used as the lower limit of the tail speed of the previous strip coiler to limit the speed of coiler #2 when coiling the strip tail. That is, coiler #2 increases its speed from the current 7 m / s to 9.1 m / s for coiling. See Figure 2 Increase the running speed of the tail section of the preceding steel piece to prevent rear-end collisions and ensure safe switching between the two coilers.

[0047] Example 2

[0048] See Figure 1 Taking the coiler of a hot-rolled 1780 production line in a steel plant as an example, the previous strip is coiled by coiler #2. The finishing rolling speed at the tail end of the coil is 10 meters per second. When there are 25 meters left at the tail end of the previous strip, the next strip is finished rolled out. The anti-tailgating control method for the hot-rolled coiler is as follows:

[0049] Step 1: The final effective stand speed of the last strip finishing mill is 10 m / s, and the slip ratio before rolling on the last stand is 10%. When the last stand bites the strip, the strip head speed is calculated using the following formula:

[0050] v H =v0(1+f0)①

[0051] In formula ①, v0 represents the linear velocity of the last effective stand in the finishing mill, in m / s; f0 represents the forward slip ratio of the last effective stand in the finishing mill, in %; v H This indicates the speed of the strip head when it bites the steel at the final stand of the finishing mill, in m / s.

[0052] According to formula ①, v H =10(1+10%)=11m / s.

[0053] Step 2: Taking a strip acceleration rate of 10% as an example, the distance from the last effective stand of the finishing mill to the No. 1 coiler is 130 meters, and the distance from the last effective stand of the finishing mill to the acceleration point is 20 meters. Calculate the time for the strip head to reach the No. 1 coiler using the following formula:

[0054]

[0055] In formula ②, 'a' represents the strip head acceleration rate, in m / s², a = 0.1 (given by the host computer according to the steel grade layer); 's0' represents the distance from the acceleration point to coiler #1, s0 = 130 - 20 = 110 in meters; 's1' represents the distance from the last effective stand of the finishing mill to the acceleration point in meters; t HThis indicates the time it takes for the strip head to reach the No. 1 coiler, in seconds.

[0056] According to formula ②, we get:

[0057]

[0058] Step 3: The safe switching time of the coiler is 7 seconds. Taking the distance between the tail of the upper strip and the No. 2 coiler as 40m and the coiling speed as 7m / s, the minimum speed of the coiler is calculated in real time according to the following formula to avoid tail-end collisions or steel jamming accidents due to untimely switching of the coiler.

[0059]

[0060] In formula ③, t q ds represents the safe switching time of the winding machine, in seconds. t dv represents the distance from the tail of the strip to the coiler, in meters (m). L This indicates the minimum speed of the coiler required to avoid rear-end collisions or steel jams caused by untimely coiler switching, and is expressed in m / s.

[0061] According to formula ③, we get:

[0062]

[0063] Step 4: Calculate the speed dv l =5.7 m / s is used as the lower limit of the tail speed of the previous strip coiler to limit the speed of coiler #2 when coiling the strip tail. That is, when coiler #2 decelerates from the current speed of 7 m / s to 5.7 m / s, it will not decelerate further and will maintain a coiling speed of 5.7 m / s. Figure 2 The winding process is shown in the curve in Example 2; ensure a safe switching time between the two winding machines.

[0064] See Figure 2 During normal production, after the strip is thrown out of the finishing mill, the tail of the strip runs at the throwing speed before the calculated deceleration point, and then moves at 1m / s after reaching the deceleration point. 2 The strip is decelerated at a fixed deceleration rate, and the crawling speed is reduced to 3m / s before entering the coiler. Tail positioning control is started before the strip enters the coiler, and the strip is decelerated and stopped after entering the coiler. When the anti-collision control is activated, if the head of the next strip reaches the coiler too fast, in order to avoid the coiler not having enough time to switch, the tail of the previous strip does not decelerate or even accelerates until it reaches the tail positioning control point in front of the coiler and then directly performs tail positioning operation. This method is used to increase the interval between the front and rear strips.

[0065] This invention precisely calculates the head-to-tail interval between two steel strips in front of the coiler and controls the lower limit of the coiling speed at the tail of the coiler to ensure that the head-to-tail interval between the front and rear strips is greater than the coiler switching time. This effectively avoids accidents such as strip collision in front of the coiler or steel jamming due to insufficient time to switch coilers. The calculation is accurate and does not affect the rolling rhythm, resulting in good application effects.

Claims

1. A method for preventing rear-end collisions in a hot-rolled coiler, characterized in that, include: S1. Calculate the strip head speed when the final stand of the finishing mill bites the strip; S2. Calculate the time it takes for the strip head to reach the No. 1 coiler; S3. Real-time calculation of the minimum speed of the coiler to avoid accidents such as rear-end collisions or steel jamming due to untimely switching of the coiler. S4. The minimum speed of the coiler to avoid rear-end collisions or steel jams due to untimely coiler switching is used as the lower limit of the tail speed of the previous strip coiler to limit the coiler speed. The formula for calculating the time it takes for the strip head to reach the No. 1 coiler is as follows: ② In formula ②, This indicates the acceleration rate of the strip head, in m / s. 2 ; This represents the distance from the acceleration point to the No. 1 winding machine, in meters. This represents the distance from the last effective stand of the finishing mill to the acceleration point, in meters (m). This indicates the time it takes for the strip head to reach the No. 1 coiler, in seconds. This indicates the strip head speed when the final stand of the finishing mill bites the strip, and the unit is m / s; The formula for calculating the minimum coiling speed in real time to avoid accidents such as rear-end collisions or steel jams due to untimely coiling machine switching is as follows: ③ In formula ③, This indicates the safe switching time of the winding machine, in seconds. This indicates the distance from the tail end of the strip to the coiler, in seconds (s). This indicates the minimum speed of the coiler required to avoid rear-end collisions or steel jams caused by untimely coiler switching, and is expressed in m / s.

2. The anti-tailgating control method for a hot-rolled coiler according to claim 1, characterized in that, In S1, the formula for calculating the strip head speed during the bite of the final stand in the finishing mill is as follows: ① In formula ①, This indicates the linear speed of the last effective stand in the finishing mill, in m / s. This represents the forward slip ratio of the last effective stand in the finishing mill, expressed in percent.

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