CN105834224A - Method for preventing cool roller bed of hot rolling layer from steel rear-end collision - Google Patents

Abstract

A method for preventing the hot-rolled layer from chasing steel on the cold roller table. Through the hot metal detector, in cooperation with the basic automatic control machine and the process control machine, according to the requirements of the process setting, the front and rear two adjacent strips are processed according to different steel types. and specifications to realize the control of the rolling rhythm. Under the premise of ensuring the rolling rhythm, avoiding the layer cold area chasing steel caused by the difference in steel type and specification, including: 1. Theoretical calculation of the tail of the previous strip and the rear strip The time gap value T between the steel heads; 2. The actual detection calculates the actual time gap T′ between the tail of the previous strip and the head of the next strip; 3. Compare T and T′, and according to the comparison results Issue the instruction of swinging in situ or moving forward to the last piece of steel strip. The present invention can reduce the estimation of long gap time in the process of personnel control, reduce unnecessary time waste, and avoid chasing in the layer cooling area due to differences in steel types and specifications under the premise of ensuring the fastest rolling rhythm. steel accident.

Description

A method for preventing hot-rolled layer from chasing steel in cold roller table

technical field

The invention belongs to the field of steel strip control in hot rolling, and in particular relates to a method for preventing hot rolling layers from chasing steel on cold roller tables.

Background technique

To give full play to the production capacity advantages of hot rolling mills, it is required to maximize the production efficiency within the effective rolling time, and finally achieve high-efficiency production with the highest efficiency and the lowest consumption while ensuring product quality. The key link is the rolling line. Hourly output, and the specific parameter is the rolling rhythm.

In order to increase the hourly output of the rolling line, it is necessary to increase the rolling rhythm of the strip steel, but the premise is to ensure that the strip steel does not chase steel on the rolling line, so as to ensure the accuracy of tracking and normal setting.

The tracking of strip steel on the hot rolling production line needs to go through several major areas: heating furnace, rough rolling, finishing rolling and coiling. In order to ensure that the strip steel does not chase head-to-tail in the rolling line area and track errors, it must be controlled with a certain rolling rhythm. When the steel meets a certain gap time and is rolled separately, it can be guaranteed that the head and tail will not chase each other, and the tracking error will not occur.

In view of the great difference in the rolling speed of steel types of different varieties and specifications in the rolling process of hot continuous rolling, if the front and rear strips are pulled out from the heating furnace with a fixed gap time and then rolled , the following two situations may occur:

(1) Long intervals before and after:

The rhythm gap time between the front and rear strips is too long, resulting in waste of waiting time, affecting hourly output and energy consumption;

(2) Short intervals before and after:

The rhythmic gap between the front and rear strips is relatively short, and the front and rear strips chase each other head to tail in a certain physical area.

Usually, the rolling rhythm of the strip steel is guaranteed by the control. From the extraction of the heating furnace to the entrance area of the finish rolling, since the rolling speed of the rough rolling and the speed of the roller table are relatively fixed, so In terms of gap time, personnel are relatively easy to control, and the rhythm is more accurate; but for the finishing rolling and coiling area, due to the process of rising speed rolling in finishing rolling and slowing down coiling in coiling process, and even for strips of the same specification, due to different process control requirements, there are certain differences in the acceleration of the rising speed and the deceleration rate of the falling speed, so it is difficult for personnel to accurately control the gap time, and often When the gap between rolling rhythms is short, the front and rear strips chase each other head to tail on the layer cooling roller table, resulting in accidents such as strip scrapping and production line shutdown, which have brought great harm to normal production and organization. Impact.

In view of the above objective factors, in order to improve the rolling rhythm of the production line, accurately control the rolling gap time, and avoid the accident of strip steel chasing steel in the layer cooling, it is necessary to develop a method to prevent the front and rear ends of the strip steel on the layer cooling roller table. The automatic control function of tail-to-tail pursuit, and at the same time accurately control the gap time between the front and rear strips to ensure the maximum production capacity of the rolling line to meet the needs of normal and stable production on site.

Contents of the invention

In order to solve the above problems, the present invention provides a method for preventing the hot-rolled layer from chasing steel in the cold roller table, which can determine the minimum gap time required by the front and rear strips according to the specific time when the front and rear strips reach the coiling area under different specifications and varieties , the position of the strip is controlled through the interlocking conditions of the rolling line to ensure that the strip does not have an accident of chasing steel on the layer cooling roller table; at the same time, it no longer depends on the rough time estimation of the operator, reducing the gap time in the process of personnel control Longer estimates reduce unnecessary waste of time, and avoid steel chasing accidents in the layer cooling area caused by differences in steel types and specifications under the premise of ensuring the fastest rolling rhythm. The technical plan is as follows:

A method for preventing hot-rolled layer from chasing steel in the cold roller table, characterized in that: through the hot metal detector, in cooperation with the basic automatic control machine and the process control machine, according to the requirements of the process setting, the front and rear two adjacent strips are controlled according to the Different steel types and specifications realize the control of the rolling rhythm, so as to avoid the accident of chasing steel in the layer cooling area caused by the difference in steel types and specifications under the premise of ensuring the rolling rhythm. The steps are as follows:

S1: When the steel grade of the same specification enters the last rough rolling pass, the process computer calculates the time from the finish rolling entrance to the coiler entrance for the tail of the previous strip according to the process setting value At the same time, calculate the time for the last piece of strip head from the entrance of finishing rolling to the entrance of coiler according to the process setting value

S2: The process computer sets the requirements according to the process, and according to the calculated Calculate the minimum gap time T between the two strips before and after, and send the T value to the basic automatic control machine;

S3: Set the detection point of the actual position of the strip in the finish rolling entrance area, and the detection points respectively record the arrival time point t1 of the tail of the previous piece of steel strip and the arrival time point t2 of the head of the next piece of steel strip, and send the recorded values of t1 and t2 To the basic automation control machine;

S4: The basic automatic control machine calculates the actual interval time T′ of the two strips before and after according to the difference between t2 and t1;

S5: The basic automatic control machine compares the size of T′ and T,

When T′≥T, issue a forward command to the next piece of strip steel and start rolling.

When T′<T, issue an instruction to swing the steel in situ for T′-T seconds to the next strip steel, and move forward to rolling after the steel swing action is completed.

According to a method of preventing hot-rolled layer cold roller table chasing steel according to the present invention, it is characterized in that: in step S1, the said "the head of the last piece of strip steel is from the finish rolling entrance to the coiler entrance" is specifically "after A piece of strip steel head from the finishing entrance to the penultimate set of roller tables in front of the coiler".

According to a method of preventing hot-rolled layer cold roller table chasing steel according to the present invention, it is characterized in that: in step S1 follow:

in: $V_0=\frac{h_7*V_7}{h_0},$

The time (s) for the tail of the nth strip from the flying shear to the coiler,

Lcs: constant, the distance from the flying shear to the F1 rack (m),

L: constant, the distance between racks (m),

L _dc : constant, distance from F7 frame to coiler (m),

V ₀ : variable, strip speed before F1 (m/s),

V ₁ ~ V ₇ : variable, the strip speed (m/s) at the exit of F1 ~ F7,

V _out : variable, strip throwing speed (m/s),

V _coiling : variable, the speed of the tail of the strip into the coiler (m/s),

h ₇ : variable, finished product thickness (mm),

h ₀ : variable, intermediate billet thickness (mm).

According to a method of preventing hot-rolled layer cold roller table chasing steel according to the present invention, it is characterized in that: in step S1 follow:

In the formula:

The time (s) of the n+1 strip head from the entrance of the finishing flying shear to the Ki (the penultimate group) roller table in front of the coiler,

L _cs : constant, the distance from the flying shear to the F1 frame (m),

L: constant, the distance between racks (m),

_{Before L dc} : constant, the distance from the F7 frame to the Ki roller table in front of the coiler (m),

V _descaling : variable, the speed of the strip head through the flying shear area at the entrance of finishing rolling (m/s),

V ₁ ~ V ₇ : variable, the strip speed (m/s) at the exit of F1 ~ F7.

According to a method of preventing hot-rolled layer cold roller table chasing steel according to the present invention, it is characterized in that: in step S2, the $T=t+t_1^{\mathrm{no}}-t_2^{\mathrm{no}+1},$

Among them, t: constant, the minimum rhythm time (s) of the front and rear strips.

The present invention provides a method for preventing cold rollers chasing steel in the hot-rolled layer, and provides a calculation method for the gap time between the front and rear strips, which can be judged according to the specific time when the front and rear strips reach the coiling area under different specifications and varieties. The minimum gap time required for the front and rear strips, the position of the strips is controlled by the interlocking conditions of the rolling line to ensure that the strips do not have accidents of chasing steel on the layer cooling roller table; at the same time, no longer rely on the operator's rough time estimation , to reduce the estimation of long gap time in the process of personnel control, reduce unnecessary waste of time, and avoid chasing steel accidents in the layer cooling area caused by differences in steel types and specifications under the premise of ensuring the fastest rolling rhythm . It can effectively avoid the accident that the front and rear strips collide with scrap steel on the layer cooling roller table due to the difference in rolling speed between the front and rear strips, and thus cause unnecessary downtime and affect normal production. ; At the same time, the hourly output of the rolling line is improved and the energy consumption is reduced.

Description of drawings

Fig. 1 is the control flowchart of the present invention.

detailed description

In the following, a method for preventing hot-rolled layer from chasing steel on the cold roller table of the present invention will be further described in detail according to the accompanying drawings and specific implementation methods.

A method for preventing hot-rolled layer from chasing steel in the cold roller table, characterized in that: through the hot metal detector, in cooperation with the basic automatic control machine and the process control machine, according to the requirements of the process setting, the front and rear two adjacent strips are controlled according to the Different steel types and specifications realize the control of the rolling rhythm, so as to avoid the accident of chasing steel in the layer cooling area caused by the difference in steel types and specifications under the premise of ensuring the rolling rhythm. The steps are as follows:

S1: When the steel grade of the same specification enters the last rough rolling pass, the process computer calculates the time from the finish rolling entrance to the coiler entrance for the tail of the previous strip according to the process setting value At the same time, calculate the time for the last piece of strip head from the entrance of finishing rolling to the entrance of coiler according to the process setting value

S2: The process computer sets the requirements according to the process, and according to the calculated Calculate the minimum gap time T between the two strips before and after, and send the T value to the basic automatic control machine;

S3: Set the detection point of the actual position of the strip in the finish rolling entrance area, and the detection points respectively record the arrival time point t1 of the tail of the previous piece of steel strip and the arrival time point t2 of the head of the next piece of steel strip, and send the recorded values of t1 and t2 To the basic automation control machine;

S4: The basic automatic control machine calculates the actual interval time T′ of the two strips before and after according to the difference between t2 and t1;

S5: The basic automatic control machine compares the size of T′ and T,

When T′≥T, issue a forward command to the next piece of strip steel and start rolling.

When T′<T, issue an instruction to swing the steel in situ for T′-T seconds to the next strip steel, and move forward to rolling after the steel swing action is completed.

Further, in step S1, the "the head of the next piece of strip from the entrance of the finish rolling to the entrance of the coiler" is specifically "the head of the next piece of strip goes from the entrance of the finish rolling to the penultimate group of rolls before the coiler" road".

Further, in step S1 follow:

in: $V_0=\frac{h_7*V_7}{h_0}$

The time (s) for the tail of the nth strip from the flying shear to the coiler,

Lcs: constant, the distance from the flying shear to the F1 rack (m),

L: constant, the distance between racks (m),

L _dc : constant, distance from F7 frame to coiler (m),

V ₀ : variable, strip speed before F1 (m/s),

V ₁ ~ V ₇ : variable, the strip speed (m/s) at the exit of F1 ~ F7,

V _out : variable, strip throwing speed (m/s),

V _coiling : variable, the speed of the tail of the strip into the coiler (m/s),

h ₇ : variable, finished product thickness (mm),

h ₀ : variable, intermediate billet thickness (mm).

Further, in step S1 follow:

In the formula:

The time (s) of the n+1 strip head from the entrance of the finishing flying shear to the Ki (the penultimate group) roller table in front of the coiler,

L _cs : constant, the distance from the flying shear to the F1 frame (m),

L: constant, the distance between racks (m),

_{Before L dc} : constant, the distance from the F7 frame to the Ki roller table in front of the coiler (m),

V _descaling : variable, the speed of the strip head through the flying shear area at the entrance of finishing rolling (m/s),

V ₁ ~ V ₇ : variable, the strip speed (m/s) at the exit of F1 ~ F7.

Further, in step S2, the

Among them, t: constant, the minimum rhythm time (s) of the front and rear strips.

Example

Since the main control is that the front and rear strips do not collide in the layer cooling roller table area, the main control is the minimum running time of the front and rear strips from the finish rolling entrance to the coiling area: that is, the front After the tail of a piece of steel strip leaves the finish rolling F7 stand, it meets the conditions for the latter piece of steel strip to enter the finish rolling stand for rolling, but it must be ensured that the tail of the previous piece of strip steel can be coiled smoothly before the latter piece of steel strip can reach the coiling The position of the machine, and at this time the function of the coiler has met the coiling conditions.

1. Selection of the judgment point of the finish rolling entrance

In order to control the front and rear strips from colliding in the interlayer cooling area, if the head of the latter strip enters the finish rolling stand for rolling, it is difficult to recover when making a comparison and judgment at this time, so it must be selected in the finish rolling entrance area. Judgments and calculations are made within.

Usually the strip steel entrance area is equipped with a hot metal detector to track the actual area position of the strip steel, and at the same time, the signal of the hot metal detector stimulates the calculation of the relevant control unit program.

Since the front and rear strips cannot appear in the same tracking area to avoid physical tracking errors, from the position distribution of photoelectric cells arranged in the finish rolling entrance area, generally the entrance judgment point can be selected to be separated from the finish rolling tracking area by two At the tracking area, that is, at HMD 1 in the H1 tracking area, it is ensured that the front and rear strips do not appear in the same tracking area, and there is also a certain time margin for calculation.

Assume that the time required for the tail of the previous strip to leave HMD1 until the coiling is completed smoothly is The time required for the head of the latter piece of strip to reach HMD1 until it is smoothly bitten into by coiling is The minimum safety time required for the front and rear strips is T, then the minimum safety time T for each strip can be calculated every time the rough rolling is rolled for the last time, and the timing starts when the tail of the previous strip leaves HMD1. If the head of a strip arrives at HMD1 within time T, the pendulum steel will not enter the tracking area of H1 until the time meets the requirement of T before moving forward; if the head of the next strip arrives at HMD1 after time T, it means There will be no front-rear rear-end collision accidents, and you can directly move forward and enter H1 tracking for rolling.

2. Calculation of the running time of the tail of the previous strip

The tail of the previous piece of strip steel is coiled from the finish rolling entrance to the coiler, and its speed characteristics are: the strip steel is thrown at a constant speed and leaves the end stand F7 at a speed V _out , and starts to decelerate on the layer cooling roller table from F7 until it reaches the coil. When the machine is taken up, it is _coiled into the coiler at a certain coiling speed V, and the speed characteristic diagram is as follows:

The specific time for the tail of the previous piece of strip from the entrance of the finish rolling to the entrance of the coiler Calculated as:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}}{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}$

in:

The time from the flying shear to the coiler at the end of the strip steel (s)

L _cs : constant, the distance from the flying shear to the F1 frame (m)

L: constant, distance between racks (m)

L _dc : constant, distance from F7 frame to coiler (m)

V ₀ : variable, strip speed before F1 (m/s),

V ₁ ~ V ₇ : variable, strip speed at the exit of F1 ~ F7 (m/s)

V _out : variable, strip throwing speed (m/s)

V _coiling : variable, the speed of the tail of the strip into the coiler (m/s)

h ₇ : variable, finished product thickness (mm)

h ₀ : variable, intermediate billet thickness (mm)

3. Calculation of running time of the last strip head

The head of the last strip is from the finish rolling entrance to the coiler entrance. The speed characteristics are: the strip passes through the finish rolling entrance and the flying shear area at a certain speed V _descaling . The different speeds of the racks pass through the F1～F7 racks. When the head leaves the last rack F7, the speed is increased with a certain acceleration. When the speed is increased to V ₁ , it just reaches the coiler. The speed characteristic diagram is as follows:

Since the acceleration of the speed-up process after the general strip exits F7 is very small, the speed operation mode from the exit of F7 to the coiler can be approximated as a uniform speed process, V _coiling ≈ V ₇ . At the same time, in order to ensure that when the next piece of strip steel arrives at the coiler, the coiler has already met the conditions for coiling the strip steel of this specification, so when the head of the next piece of strip steel reaches a certain set of roller tables before coiling, the coiler The machine needs to judge whether the coiling function has been satisfied at this time. When the coiling function is not satisfied, the automatic quick stop of the coiling roller table will occur. Therefore, the running time of the next strip head needs to be calculated from the finish rolling entrance to the coiler. Running time of the ex-Ki roller table.

The specific running time of the last strip head from the finish rolling entrance to the Ki roller table in front of the coiler Calculated as:

In the formula:

The time of n+1 strip head from the entrance of the finishing flying shear to the Ki roller table in front of the coiler (s)

L _cs : constant, the distance from the flying shear to the F1 frame (m)

L: constant, distance between racks (m)

_{Before L dc} : constant, the distance from the F7 frame to the Ki roller table in front of the coiler (m)

V _descaling : variable, the speed of the strip head through the flying shear area at the entrance of finishing rolling (m/s)

V ₁ ~ V ₇ : variable, strip speed at the exit of F1 ~ F7 (m/s)

4. Calculation of the minimum gap time between the front and rear strips

The specific time of the tail of the previous piece of strip from the finishing entrance to the coiler is known The specific running time of the last strip head from the finish rolling entrance to the Ki roller table in front of the coiler At the same time, considering that the front and rear strips cannot appear in the same tracking area, that is, they cannot appear in the H1 tracking at the entrance of the finish rolling (between HMD2 and HMD1), this is defined as the minimum rhythm time t, due to the length of the tracking area, roller table Speed is a constant value, so t is a constant value. Then the minimum gap time between the front and back strips is:

$\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}$

In the formula:

T: variable, minimum gap time (s)

t: constant, the minimum rhythm time of the front and rear strips (s)

The time from the flying shear to the coiler at the end of the strip steel (s)

The time of n+1 strip head from the entrance of the finishing flying shear to the Ki roller table in front of the coiler (s)

5. Judgment on whether the last strip runs or not

According to the above formula, the running time of the tail of the nth strip from the flying shear to the coiler when it is finished rolling It has been determined that when the n+1th piece of strip is rolled in the last pass of rough rolling, the time for its head to go from the entrance of the finishing rolling flying shear to the Ki roller table in front of the coiler Also determined, the minimum gap time of the front and rear strips can be calculated

The cumulative timing starts from the tail of the current strip n leaving HMD1. If the head of the next strip arrives at HMD1 within time T, if the head of the next n+1 strip arrives at HMD1 within time T, then n+1 strips The steel stays in the steel swing before MHD1, and does not enter the H1 tracking area, until the accumulated steel swing time before MHD1 meets the requirement of T, then cancels the steel feeding chain and allows the strip to move forward.

If the time t when the head of the next n+1 strip arrives at HMD1 is greater than the required T time, it means that there will be no front and rear rear-end collision accidents, and you can directly move forward and enter H1 to track and then roll.

Example application

In the current control practice, when the thickness of the previous strip n strip is 3.2mm, its threading speed on each frame is as follows:

V0 V1 V2 V3 V4 V5 V6 V7 0.68 1.19 1.94 3.16 4.40 5.65 6.68 7.50

Since V _out = 8.24 m/s, the steel throwing speed of each frame is calculated as follows:

V0 V1 V2 V3 V4 V5 V6 V7 0.75 1.30 2.13 3.47 4.84 6.21 7.33 8.24

According to the existing situation, _Lcs =10.4m, L=5.8m, V _coiling =4m/s, _Ldc =144.04m, then according to the running time formula of n-strip tail:

When the thickness of the last strip n+1 strip is 2.03mm, the required strip threading speed of each frame is:

V0 V1 V2 V3 V4 V5 V6 V7 0.59 1.29 2.42 4.27 6.11 8.08 9.25 10.20

The value of V _descaling is 1.1 m/s, L _{dc front} = 114.64 m, then according to the formula for the running time of n+1 strip head:

Taking the minimum rhythm time of the front and rear strips as 14 seconds, the minimum gap time is

When the end of the n-strip (thickness 3.2mm) leaves HMD1, the timer starts,

(1) If the head of the next n+1 strip (thickness 2.0mm) arrives at HMD1 in 20 seconds, and the time interval is less than 31.97 seconds, then n+1 strip (thickness 2.0mm) is at The front of HMD1 swings automatically for 11.97 seconds, until the total time reaches 31.97 seconds before steel is allowed to enter and roll.

The present invention provides a method for preventing cold rollers chasing steel in the hot-rolled layer, and provides a calculation method for the gap time between the front and rear strips, which can be judged according to the specific time when the front and rear strips reach the coiling area under different specifications and varieties. The minimum gap time required for the front and rear strips, the position of the strips is controlled by the interlocking conditions of the rolling line to ensure that the strips do not have accidents of chasing steel on the layer cooling roller table; at the same time, no longer rely on the operator's rough time estimation , to reduce the estimation of long gap time in the process of personnel control, reduce unnecessary waste of time, and avoid chasing steel accidents in the layer cooling area caused by differences in steel types and specifications under the premise of ensuring the fastest rolling rhythm . It can effectively avoid the accident that the front and rear strips collide with scrap steel on the layer cooling roller table due to the difference in rolling speed between the front and rear strips, and thus cause unnecessary downtime and affect normal production. ; At the same time, the hourly output of the rolling line is improved and the energy consumption is reduced.

Claims (5)

1. A method for preventing the hot-rolled layer cold roller table from chasing steel, characterized in that: through the hot metal detector, cooperate with the basic automatic control machine and the process control machine, according to the requirements of the process setting, the front and rear two adjacent strips According to different steel types and specifications, steel can realize the control of rolling rhythm, including the following steps: S1: When the steel grade of the same specification enters the last rough rolling pass, the process computer calculates the time from the finish rolling entrance to the coiler entrance for the tail of the previous strip according to the process setting value At the same time, calculate the time for the last piece of strip head from the entrance of finishing rolling to the entrance of coiler according to the process setting value S2: The process computer sets the requirements according to the process, and according to the calculated Calculate the minimum gap time T between the two strips before and after, and send the T value to the basic automatic control machine; S3: Set the detection point of the actual position of the strip in the finish rolling entrance area, and the detection points respectively record the arrival time point t1 of the tail of the previous piece of steel strip and the arrival time point t2 of the head of the next piece of steel strip, and send the recorded values of t1 and t2 To the basic automation control machine; S4: The basic automatic control machine calculates the actual interval time T′ of the two strips before and after according to the difference between t2 and t1; S5: The basic automatic control machine compares the size of T′ and T, When T′≥T, issue a forward command to the next piece of strip steel and start rolling. When T′<T, issue an instruction to swing the steel in situ for T′-T seconds to the next strip steel, and move forward to rolling after the steel swing action is completed. 2. A method for preventing the cold roller table of the hot-rolled layer from chasing steel according to claim 1, characterized in that: in step S1, the head of the "last piece of strip steel" is from the entrance of the finish rolling to the entrance of the coiler. "Specifically, it is "the head of the last piece of strip steel is from the entrance of finishing rolling to the penultimate group of roller tables in front of the coiler". 3. A kind of method for preventing hot-rolled layer cold roller table chasing steel according to claim 1, it is characterized in that: in step S1 follow: in: $V_0=\frac{h_7*V_7}{h_0},$ The time (s) for the tail of the nth strip from the flying shear to the coiler, Lcs: constant, the distance from the flying shear to the F1 rack (m), L: constant, the distance between racks (m), L _dc : constant, distance from F7 frame to coiler (m), V ₀ : variable, strip speed before F1 (m/s), V ₁ ~ V ₇ : variable, the strip speed (m/s) at the exit of F1 ~ F7, V _out : variable, strip throwing speed (m/s), V _coiling : variable, the speed of the tail of the strip into the coiler (m/s), h ₇ : variable, finished product thickness (mm), h ₀ : variable, intermediate billet thickness (mm). 4. A method for preventing hot-rolled layer cold roller table chasing steel according to claim 2, characterized in that: in step S1 follow: In the formula: The time (s) of the n+1 strip head from the entrance of the finishing flying shear to the Ki (the penultimate group) roller table in front of the coiler, L _cs : constant, the distance from the flying shear to the F1 frame (m), L: constant, the distance between racks (m), Before L _dc : constant, the distance from the F7 frame to the Ki roller table in front of the coiler (m), V _descaling : variable, the speed of the strip head through the flying shear area at the entrance of finishing rolling (m/s), V ₁ ~ V ₇ : variable, the strip speed (m/s) at the exit of F1 ~ F7. 5. A method for preventing hot-rolled layer from chasing steel in cold roller table according to claim 1, characterized in that: in step S2, the $T=t+t_1^{\mathrm{no}}-t_2^{\mathrm{no}+1},$ Among them, t: constant, the minimum rhythm time (s) of the front and rear strips.