JP3273117B2 - Meandering control method for hot tandem rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a meandering control technique for preventing narrowing due to meandering generated when a tail end of a material to be rolled passes through a tandem rolling mill in a hot tandem rolling operation.

[0002]

2. Description of the Related Art In the operation of hot tandem rolling, when the tail end of a steel strip (hereinafter referred to as "rolled material") passes through a rolling mill of each stand, that is, at the time of so-called trailing end,
The rolled material is shifted laterally from the center of the rolling mill in the width direction, that is, from the mill center (hereinafter referred to as "meandering"), and as a result, the tail end of the rolled material is provided on the rolling mill entry side. A phenomenon called so-called drawing occurs in which the rolled material comes into contact with the side guide and is rolled in a folded state. When such a reduction occurs, an excessive rolling load is applied to the rolling mill, so that a large trouble occurs such as a flaw is formed in the rolling roll, and in some cases, the rolling roll is damaged and cannot be rolled.

A technique for avoiding such rolling troubles, that is, a control technique for preventing the meandering and passing the rolled material straight through the rolling line is generally referred to as a meandering control technique. Since there is a difference between the rolling loads on the working side and the driving side (hereinafter simply referred to as “left and right”) of the rolling mill, the difference between the left and right loads is regarded as a control amount that has a strong correlation with the meandering amount. There is a method of controlling the difference between the left and right rolling position of the rolling mill in the direction of eliminating. In the case of run-through rolling in hot tandem rolling, meandering control based on such a rolling load difference is performed by starting from the time when the tail end of the rolled material passes through the rolling mill in the previous stand, to the right and left of the rolling mill in the next stand. It has been a general method to perform the control of the rolling position difference, that is, the rolling leveling control until the rolling stand passes through the rolling mill of the next stand.

Further, as an improvement of this method, for example, as disclosed in Japanese Patent Publication No. 58-51771, rolling load detectors are provided on the left and right sides of a rolling mill to separately detect the rolling loads on the left and right sides.
A method of calculating the ratio of the left and right load difference to the right and left load sum (hereinafter referred to as “load difference ratio”), and performing a rolling leveling control based on the load difference ratio.
As disclosed in JP-A-160817, a method has been proposed in which a correction signal based on a rolling position difference signal is added to a load difference detection signal to correct a variation in the load difference when the rolling position difference is changed, and to perform a rolling leveling control. .

[0005]

However, the conventional meandering control method based on the difference between the left and right rolling loads (hereinafter simply referred to as a rolling load difference in the present invention) is as follows.
Applicable to single-stand rolling such as plate rolling and rough rolling, but can be applied to the entrance, exit, or exit side as in steady-state tandem rolling or tail-end rolling, such as continuous finishing rolling. In the case of rolling in which acts, there is a problem in that the rolling load difference changes due to a change in the tension distribution, and control delays and malfunctions occur. In particular, in the case of tandem run-out rolling, immediately after the tail end of the rolled material passes through the previous stand, the change in the rolling load due to meandering in the next stand and the change in the load difference due to the change in the outlet tension distribution are offset. Therefore, there is a time during which the rolling load difference does not appear despite the meandering (hereinafter referred to as the meandering load difference dead zone), and in this region, a change in the rolling load difference opposite to the meandering direction occurs. The inventors have found from experimental studies that there is a fatal defect such as a delay in meandering detection and an erroneous initial operation of control.

An object of the present invention is to improve the reliability of meandering control when the tail end of a rolled material passes through a front stand.

[0007]

According to the present invention, when the tail end of tandem rolling is removed, there is a possibility that a control malfunction may occur immediately after the tail end of the rolled material passes through the front stand,
In other words, by specifying the above-mentioned meandering load difference dead zone, setting a control holding time for avoiding the meandering load difference dead zone, and starting the rolling load detection and the rolling leveling control based on the control holding time, an accurate setting can be obtained. A rolling leveling control based on a rolling load difference is realized.

[0008] That is, the present invention relates to a hot tandem rolling mill, in which the tail end of the material to be rolled passes through the rolling mill of the (i-1) -th stand until passing through the rolling mill of the i-th stand. The rolling loads on the working side and the driving side of the rolling mill of the stand are respectively detected, and the rolling load difference or the rolling load difference ratio is obtained. Based on this value, the rolling reduction of the rolling mill on the i-th stand is controlled, In the meandering control method for preventing meandering of the tail end of the material, the rolling leveling control is started in the rolling mill of the i-th stand after the tail end of the material to be rolled passes through the rolling mill of the (i-1) -th stand. The first feature is that a control hold time until the control is performed is set, and after the control hold time, the pressure leveling control of the i-th stand is started.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment of the present invention,
The control hold time is determined based on the amount of change in the load difference at the i-th stand, which occurs when the tail end of the material to be rolled passes through the rolling mill at the (i-1) -th stand, and the sheet speed of the rolled material on the exit side of the i-th stand. Is calculated. More specifically, the rolling load and the roll peripheral speed on the working side and the driving side during tandem rolling are sampled at substantially the same point, and furthermore, at the entry and exit sides of the tandem rolling mill train at substantially the same point as the data collection time. The plate thickness is measured at two or more points in the width direction and the temperature of the rolled material at the entrance and / or exit side of the tandem rolling mill is measured at two or more points in the width direction. Based on these data, the equation system in the steady state of tandem rolling is determined. Is used to calculate the amount of deviation of the rolling leveling value at the i-th stand from the optimal rolling leveling value during steady rolling,
Based on this deviation amount and the sheet speed of the rolled material on the exit side of the i-th stand, the control hold time is calculated during steady rolling.

[0010] With this arrangement, the rolling leveling control is started in the next stand to avoid a malfunction in which the correlation between the meandering amount and the load difference after the removal of the previous stand does not clearly appear and a malfunction may occur. Accurate meandering control is realized.

This will be described more specifically below. First, the inventors used a tandem rolling mill including a three-stand rolling mill as shown in FIG. 2 to investigate in detail the meandering behavior at the time of butt removal in tandem rolling. In FIG. 2, 1a, 1
b, 1c are rolling mills; 2a, 2b, 2c are rolling leveling control devices provided in the rolling mill; 3a, 3b, 3c are rolling load detectors, 4a, 4b, Reference numeral 4c denotes a meandering detector, 8 denotes a looper roll, 7 denotes a rolled material, and 6a and 6b denote entrance and exit coilers.

In FIG. 2, a plurality of rolling mills 1a, 1b and 1c are arranged in tandem in the order of the rolling direction 9 of the rolled material 7 to constitute a tandem continuous rolling mill. Each rolling mill has a rolling leveling control device 2a, 2b, 2c, rolling loaders 3a, 3b, 3c and roll speed detectors 5a, 5c.
b, 5c (not shown) are provided, respectively. In addition, meandering detectors 4a, 4b, and 4c are provided on the entrance side of each rolling mill, respectively. Further, coilers 6a and 6b are provided on the entrance side and the exit side of the continuous rolling mill, respectively, and a looper roll is provided between the entrance-side and exit-side coilers 6a and 6b and the rolling mills and between the rolling mills. 8a, 8b, 8c,
8d are provided.

Rolled material 7 delivered from coiler 6a
Enters a rolling mill via a looper roll 8a, is rolled by rolling mills 1a, 1b, 1c, wound up by a coiler 6b, and tandem rolling is performed.

In the experiment, the value of the reduction leveling of the second stand was deliberately shifted from the optimum reduction leveling value from the state where steady rolling was performed under the conditions shown in Table 1 (the state where the rolling level was deviated from the optimum leveling value). referred to as "reduction leveling failure" to represent the displacement deviation amount [Delta] S _df), the effects caused by the operation was rolled by tandem until a steady state, then the rear from the first stand inlet side 60
The rolled material 7 was cut at the position of 0 mm, and the meandering behavior generated when the tail end of the cut rolled material 7 passed through the rolling mill of each stand of the tandem rolling mill was observed.

[0015]

[Table 1]

Note that the optimum value of the rolling leveling referred to here is a condition in which there is no left-right difference in elongation rate difference due to rolling, that is, a rolling reduction in which the left-right difference in tension acting on the rolled material between rolling mills becomes zero. Leveling value, which has been adjusted sufficiently before conducting this experiment. FIG. 3 shows the measurement results of the meandering amount on the inlet side, rolling difference, rolling position difference, and outlet side tension difference of the second stand at that time.

From this, it can be seen that in the case of tandem rolling in which the tail end of the rolled material passes through the first stand, the poor leveling of the second stand becomes apparent at a stretch and large meandering occurs after the tail end of the rolled material passes through the first stand. Further, a time Δτ during which the rolling load difference does not change despite the meandering occurring immediately after the tail end of the rolled material passes through the front stand, that is, the first stand (hereinafter referred to as a meandering load difference dead zone).
Is found to exist. This is a peculiar phenomenon in tandem rolling caused by a change in the tension distribution on the exit side of the second stand. This will be described below with reference to FIG.

The symbols in FIG. 4 are WS: working side, DS: driving side, X _C : meandering amount, P _WS , P _DS : load detected by the working side and driving side rolling load detectors. , P _t (x): linear load, x: distance in the width direction (plus the WS direction) from the center of the rolled material width.

From the state in which the right and left tensions on the inlet and outlet sides of the rolling mill are left and right due to poor rolling leveling of the second stand at the time of steady rolling in tandem rolling [FIG. After the end portion passes through the first stand, in the second stand, the line load distribution changes in accordance with the difference in tension due to the disappearance of the entrance side tension, and the gap changes accordingly [(b in FIG. 4). )]. Thereafter, meandering occurs due to the change in the gap. However, since the tension distribution on the exit side of the second stand gradually changes in a direction to offset the change in the load difference due to the meandering, the meandering occurs. No load difference appears, or a change in rolling load difference opposite to the meandering direction occurs [(c) in FIG. 4].

Therefore, immediately after passing through the front stand, there is a time Δτ in which the correlation between the meandering amount and the rolling load difference does not clearly appear, that is, a meandering load difference dead zone.
In a conventional control method that does not take this into account, that is, a method in which meandering control is performed immediately after the tail end of the front stand has passed, not only accurate detection of meandering is delayed, but also malfunction occurs.

FIG. 5 shows that in the above-mentioned experiment, the deviation amount ΔS _df ² of the rolling leveling of the second stand is represented by ΔS _df ² = + 20.
Δτ ^{2 of} the second stand when changed to ~ + 80 μm
7 shows the relationship between the variation ΔP _df ² of the rolling load difference at the second stand when the bottom of the first stand comes off. here,
Δτ ² and ΔP _df ² are obtained from experimental data, for example, time-series data as shown in FIG. 3, and Δτ ² is a difference between the right and left rolling loads in the second stand from the timing of the trailing edge of the first stand. Defined as the time until P _df ² once decreases (DS load increases) and starts to increase again, Δ
P _df ² includes a P _df ² at the time of steady rolling in the tandem rolling,
It is defined as a difference from P _df ² at the time of the first stand bottom missing. From this, the larger the [Delta] P _df, the value of Δτ it can be seen that the smaller. This is because the amount of meandering increases as the degree of leveling failure increases, and the change in the load difference caused by meandering is more overwhelming than the change in the rolling load in the opposite direction to the meandering direction caused by the change in the tension distribution on the outlet side. This is because it becomes larger in size.

[0022]

(Equation 1)

Therefore, in the present invention, as a method of realizing high-precision meandering control at the time of trailing-off based on the above knowledge, the correlation between the meandering amount after the rolled material passes through the front stand and the rolling load difference is described. The time at which the error may not appear clearly and a malfunction may occur, that is, the meandering load difference dead zone Δτ is specified, and this Δτ is set as the control hold time until the control is started at the next stand. By starting the control, accurate meandering control without causing a malfunction is performed.

Hereinafter, the meandering control method of the present invention based on the above concept will be described in detail with reference to the apparatus configuration shown in FIG. FIG. 1 shows an apparatus configuration for implementing the present invention. The rolling mill is a tandem rolling mill provided with three or more horizontal rolling mills. The horizontal rolling mills 10a to 10c of the (i-2) th to i-th stands are provided with a reduction leveling control device 12a.
To 12c, load detectors 13a to 13c, and roll speed detectors 15a to 15c (not shown).
Further, looper rolls 18a to 18b are arranged between the rolling mills. The rolled material 7 is moved in the direction of arrow 9 and rolled. Reference numeral 22 denotes an arithmetic processing device for calculating a control operation amount.

The case where the meandering control of the present invention is applied to the i-th stand will be described below. The timing at which the tail end of the rolled material passes through the rolling mill at the (i-1) -th stand is detected. That is, the timing at this time can be obtained from a change in the load detection value of the load detector 13b since the rolling load of the (i-1) th stand becomes zero.
At that timing, the load detector 13c of the i-th stand changes the rolling load difference.

[0026]

(Equation 2)

The left and right rolling loads are detected by the load detector 13c of the i-th stand, and the load difference or the load difference ratio is calculated in the arithmetic processing unit 22 based on the detected load difference. The calculated load difference or load difference ratio is calculated. , The operation amount of the rolling-down leveling control device 12c of the i-th stand is calculated, and the rolling-down leveling control device 12c is operated based on this operation amount. The control based on the load difference or the load difference ratio is repeatedly performed until the tail end of the rolled material passes through the rolling mill of the i-th stand to prevent meandering of the rolled material.

As described above, using the equation system at the time of steady rolling of tandem rolling, the rolling leveling value at the i-th stand during steady rolling is calculated from the optimum leveling value.

[0029]

(Equation 3)

The control hold time can be determined. Note that the steady-state equation system of the tandem rolling is as follows.
The present inventors have already used the following equations (3) to (10) for a tandem rolling mill train composed of N-based rolling mills disclosed in JP-A-6-198323.

[0031]

(Equation 4)

[0032]

(Equation 5)

[0033]

(Equation 6)

[0034]

【Example】

Example 1 The meandering control method of the present invention was carried out using a tandem rolling mill composed of a three-stand rolling mill as shown in FIG. That is, from the state where steady rolling is performed under the conditions shown in Table 1, rolling level failure of the second stand is given, and rolling is performed in tandem until the influence caused by the operation becomes a steady state. 60 on the entry side
The rolled material 7 is cut at the position of 0 mm, and the meandering generated when the tail end of the cut rolled material 7 passes through the rolling mill of each stand of the tandem rolling mill is controlled by the rolling loader 3b in the second stand. Based on the detected rolling load difference, the rolling leveling control was performed by the rolling leveling control device 2b, and the conventional method and the method of the present invention were compared. Table 2 shows the control conditions at that time.

[0035]

[Table 2]

FIGS. 6 and 7 show the measurement of the amount of meandering on the inlet side, the difference in rolling load, the leveling reduction and the difference in tension on the outlet side when the meandering control is performed by the method of the present invention and the conventional method, respectively. The results are shown.

First, immediately after the first stand is disengaged, the rolling load difference of the second stand is locked on, and based on the change in the rolling load difference from this lock-on value, the rolling level control is performed to remove the rolled material from the second stand. In the conventional method performed as described above, as shown in FIG. 7, the rolling load difference fluctuated in the direction opposite to the meandering direction immediately after the first stand was disengaged, so that the rolling leveling control was performed in the direction opposite to the direction in which the meandering was suppressed. As a result, the meandering amount increased when no control was performed.

On the other hand, in the method of the present invention, immediately after the first stand is removed, the variation ΔP _df ² of the rolling load difference of the second stand is detected, and the ΔP _df ² and the sheet speed V ² on the exit side of the second stand are detected.
Based on the equation (1), the meandering load difference dead zone Δτ ² of the second stand is calculated, and after Δτ ² hours, the load difference of the second stand is locked on and the fluctuation of the load difference from this lock-on value is calculated. Based on this, the rolling leveling control was performed until the rolled material came off the second stand. As a result, as shown in FIG. 6, the maximum meandering amount could be reduced to about half as compared with the case of no control, and the effectiveness of the present invention could be confirmed.

[Embodiment 2] An embodiment in which the meandering control method of the present invention is applied to a hot tandem rolling mill facility including a seven-stand rolling mill as shown in FIG. 8 will be described. The rolling equipment shown in FIG.
Tandem rolling mill provided with two horizontal rolling mills, each rolling mill having a rolling leveling control device 2a-2g, a load detector 3a-3g, and a roll speed measuring device 5a-5g.
(Not shown) is provided. Further, looper rolls 8a to 8f are arranged between the rolling mills, and inlet and outlet temperature measuring devices 17a and 17b and inlet and outlet thickness measuring devices 19a and 19b are arranged on the inlet and outlet sides of the tandem rolled material. I have. Rolled material 7
Moves in the direction of arrow 9 and is rolled. Reference numeral 22 denotes an arithmetic processing device for calculating a control operation amount.

Among the rolling mills of the seven stands, among the rolling mills of the sixth and seventh stands, in which narrowing is particularly likely to occur,
The meandering control based on the rolling load difference ratio was performed, and the conventional method and the method of the present invention were compared.

First, immediately after the removal of the previous stand, the rolling load difference ratio of the next stand is locked on, and based on the change of the rolling load difference ratio from this lock-on value, rolling leveling control is performed and the rolled material exits the next stand. In the conventional method performed up to this point, when a thin material having a delivery side plate thickness of 1.2 mm and a width of 1200 mm was rolled, narrowing occurred in the rolling mill at the seventh stand.

On the other hand, in the method of the present invention, the rolling loads on the working side and the driving side of each stand of the tandem rolling mill during steady tandem rolling are determined by the load detectors 3a to 3g, and the roll peripheral speed is determined by the roll speed detectors 5a to 5g. 5g (not shown), and the wedge amounts on the inlet and outlet sides of the tandem rolling mill are detected by the inlet and outlet plate thickness measuring devices 19a and 19b, and the inlet and outlet temperature measuring devices 17a and 17b. The temperature difference between the rolled materials at each stand is estimated based on the temperature difference between the left and right of the rolled material at the entrance and exit of the tandem rolling mill measured by
Estimate the deformation resistance difference of each stand, and determine the tandem of formulas (3) to (10) based on the rolling load, roll peripheral speed, deformation resistance difference, and plate wedges on the inlet and outlet sides of the tandem rolling mill. Using the constant equation and equation (11), the reduction leveling value at the sixth and seventh stands is
The deviation amounts ΔS _df ⁶ and ΔS _df ⁷ from the optimum rolling leveling value are calculated, and the sheet speeds V ⁶ and V ⁷ of the rolled material on the exit side of the ^sixth and ^seventh stands are detected by the roll speed measuring devices 5f and 5g. The meandering load difference dead zones Δτ ⁶ and Δτ ⁷ of the ^sixth and ^seventh stands were calculated from Expression (2). These [Delta] [tau] ⁶ and [Delta] [tau] ⁷ were set to the control suspension time at the ^sixth and ^seventh stands, and after the control suspension time, meandering control based on the rolling load difference ratio was performed at the ^sixth and ^seventh stands.

As a result, even when a thin material with a thickness of 1.2 mm and a width of 1200 mm, which has been narrowed down by the conventional method, is rolled, the rolled material can be passed straight through the rolling line. Stable rolling operation without any accidents during bottom rolling was realized.

As described above, even when the meandering control method of the present invention is applied to actual hot tandem rolling equipment, meandering that occurs when the tail end of the rolled material passes through the tandem rolling mill is prevented. It was verified that accurate control was possible and that narrowing down could be prevented.

[0045]

As described above, according to the present invention, the meandering that occurs when the tail end of the rolled material passes through the tandem rolling mill can be accurately controlled, and as a result, the roll-through rolling of the rolled material can be performed. There is almost no accident at the time, and the work efficiency and yield of the rolling operation can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of a part of a rolling facility for implementing the present invention.

FIG. 2 is a block diagram showing an outline of a tandem rolling mill used for investigating meandering behavior at the time of trailing end of tandem rolling.

FIG. 3 shows the amount of meandering on the entry side of the second stand in the tandem rolling mill shown in FIG.
It is a graph which shows the measurement result of the rolling load difference, the rolling position difference, and the output side tension difference with respect to elapsed time.

FIG. 4 shows three stands # 1 of the tandem rolling mill shown in FIG.
3A to 3C are explanatory views showing a plan view and a front view of a second stand # 1, wherein (a), (b) and (c) are respectively
The state where the rolled material passes through the first stand constantly, the first
FIGS. 3A and 3B show a state immediately after the stand bottom has been removed and a state in which meandering has occurred after the first stand bottom has been removed, wherein FIG.

FIG. 5 is a second stand # of the tandem rolling mill shown in FIG.
2 is a graph showing the relationship between the meandering load difference dead zone Δτ and the amount of change ΔP _df of the load difference at the second stand # 2 when the first stand # 1 has come off the tail when the value ΔS _df of the leveling failure 2 is changed. It is.

FIG. 6 is a diagram illustrating the meandering control, rolling load difference, rolling-down position difference, and exit-side tension difference of the second stand when the meandering control of the present invention is applied when the first stand of the tandem rolling mill shown in FIG. 7 is a graph showing the measurement results of FIG.

FIG. 7 is a graph showing the relationship between the amount of meandering on the side of the second stand, the difference in rolling load, the difference between the rolling position, and the difference in tension on the side of the outside of the tandem rolling mill when the conventional meandering control is applied when the first stand comes off. It is a graph which shows a measurement result with respect to elapsed time.

FIG. 8 is a block diagram showing an outline of a rolling facility for carrying out the present invention.

[Explanation of symbols]

1a to 1g: Horizontal rolling mill of 1st to 7th stands 2a to 2g: Rolling down leveling control device of 1st to 7th stands 3a to 3g: Load detector of 1st to 7th stands 4a to 4c: 1st to 1st 7th stand meandering detector 7: Rolled material 8a to 8f: Looper roll between 1st to 2nd to 7th stand 5a to 5g: Roll speed detector of 1st to 7th stand 9: Rolling direction 6a, 6b: Coilers on the inlet and outlet sides of the tandem rolling mill 10a to 10c: Horizontal rolling mills on the (i-2) th to i-th stands 12a to 12c: Rolling-down leveling control devices for the (i-2) to i-th stands 13a to 13c: Load detectors 18-2 to i-th stand 18a to 18c: Looper rolls on exit side of i-2 to i-th stand 15a to 15c: Looper speedometer 17a on exit side of i-2 to i-th stand 17b: Tande Temperature measuring apparatus 19a of the rolling mill input and output side, 19b: tandem mill input and exit side of the plate thickness measuring apparatus 22: processing unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-267117 (JP, A) JP-A-60-170519 (JP, A) JP-A-6-198323 (JP, A) JP-A-3-1983 165913 (JP, A) JP-A-61-17318 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 37/00-37/78

Claims (3)

(57) [Claims] 1. In a hot tandem rolling mill, between the time when the tail end of the material to be rolled passes through the rolling mill in the (i-1) -th stand and the time when the tail end passes through the rolling mill in the i-th stand,
The rolling loads on the working side and the driving side of the rolling mill of the stand are respectively detected, the load difference or the load difference ratio is obtained, and based on this value, the rolling reduction control of the rolling mill on the i-th stand is performed, and In a meandering control method for preventing meandering of a tail end, from the time when the tail end of the material to be rolled passes through the rolling mill of the (i-1) -th stand until the start of the rolling leveling control in the rolling mill of the i-th stand The control mean time of the hot tandem rolling mill is characterized by setting the control hold time of the tandem type and starting the rolling leveling control of the i-th stand after the control hold time. 2. A meandering control method for a hot tandem rolling mill according to claim 1, wherein the load difference at the i-th stand generated when the tail end of the material to be rolled passes through the rolling mill at the (i-1) -th stand. A meandering control method for a hot tandem rolling mill, wherein a control hold time is calculated based on a variation amount and a sheet speed of a rolled material on an exit side of an i-th stand. 3. A meandering control method for a hot tandem rolling mill according to claim 1, wherein a rolling load and a roll peripheral speed on a working side and a driving side during tandem rolling are sampled at substantially the same point. Measure the sheet thickness at the entrance and exit of the tandem rolling mill row at two or more points in the width direction at substantially the same time as the data collection point, and measure the temperature of the rolled material at the entrance and / or exit side of the tandem rolling mill row at two or more points in the width direction. Then, based on these data, a deviation value of the rolling leveling value at the i-th stand during the steady rolling from the optimum rolling leveling value is calculated using an equation system in a steady state of tandem rolling, and this deviation amount is calculated. And the speed of the rolled material on the exit side of the i-th stand,
A meandering control method for a hot tandem rolling mill, wherein a control hold time is calculated.