JPH11188416A - Rolling equipment and rolling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an equipment in which the meander of the rear end of a rolled material is eliminated and the squeezing does not arise. SOLUTION: In this method, the rotational speeds (rolling speed) of a rolling mill stand F1 through which a rear end of a plate material 6 is left unfinished and a work roll 2 of a following rolling mill stand F2 are identically controlled, and also the mutual tension between the rolling stand F1 and the rolling stand F2 is controlled to be zero. The tension difference between the working side and the drive side is made to be state of zero at the point between the rolling stand F1 and the rolling stand F2, and similarly the tension difference between the working side and the drive side is made to be zero at the point between the rolling mill F2 and the rolling mill Fn when the plate material 6 is left unfinished. Thus, the meander of the rear end of the plate material 6 is prevented and the squeezing does not arise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling mill in which a plurality of rolling mill stands are arranged and a rolling method in a rolling mill, which is intended to prevent a rear end of a material to be rolled from being narrowed.

[0002]

2. Description of the Related Art A conventional example of a rolling mill in which a plurality of rolling mill stands are arranged will be described with reference to FIG. FIG. 7 shows a schematic side view of a conventional rolling mill.

[0003] on a hot rolling line is provided with a plurality of rolling mill stands F ₁ to F _n, the rolling mill stand F is composed of four stages roll type rolling mill 1. The four-high rolling mill 1 includes a pair of upper and lower work rolls 2 and a pair of upper and lower backup rolls 3. The work rolls 2 are driven down by the hydraulic pressure reduction cylinder 4 via the backup rolls 3. The pair of upper and lower work rolls 2 are rotationally driven in a symmetrical direction with the same speed or a speed difference therebetween given by a drive motor (not shown).

The hydraulic pressure lowering cylinder 4 is driven by a driving device 5 provided for each rolling mill 1, and is driven by a pair of work rolls 2.
The material to be rolled (plate material) 6 passing through the gap is rolled. Each drive device 5 is connected to the hydraulic pressure reduction control device 7, and each drive device 5 is individually sent a drive command from the hydraulic pressure reduction control device 7. The front end position and the rear end position of the plate 6 are detected by the tracking device 8 based on the roll rotation speed, the rolling load, and the like.

[0005] A method of rolling the sheet material 6 by the rolling apparatus having the above configuration will be described with reference to FIG. FIG. 8 is a flowchart showing a conventional rolling method.

[0006] With the roll gaps of the work rolls 2 in each of the rolling mill stands F _{1 to} F _n kept “open” (S1), the plate material 6 on the rolling line is moved from the upstream of the hot rolling line to the rolling mill stand F. It is conveyed to _{1 ~F n} (S2). The monitoring of the tracking device 8, the work rolls 2 of the rolling mill stand F ₁ of the distal end of the plate material 6 is the most upstream
Detects immediately before biting between, In accordance with this, the hydraulic pressure cylinder 4 of the rolling mill stand F ₁ to F _n is extruded driven, is adjusted controlled roll gap set by the hydraulic roll gap control device 7 ( S3).

Next, the tracking device 8 is monitored to detect the timing at which the trailing end of the plate material 6 has come off from the most upstream rolling mill stand F ₁ , and in accordance with this, the hydraulic pressure reduction control device 7 controls the rolling mill stand. hydraulic pressure cylinder 4 F ₁ is the drive for bringing in the roll gap of the work rolls 2 in the rolling mill stand F ₁ is controlled to "open". Is roll stand F ₂ to F _n are sequentially controlled similarly the subsequent is repeated rolling operation until a operation end command (S4, S5).

[0008]

In the above-mentioned conventional rolling mill, as shown in FIG. 9 showing a state viewed from arrows IX-IX in FIG.
_{When 1} rear end 6b of the plate 6 is Shirinuke, rolling mill stands F ₂ immediately after is in a state of continued pressure the plate 6.
The work rolls 2 of the rolling mill stands F ₁ to the rear end 6b has Shirinuke, if the tension difference between the left and right of the plate 6 different rolling force to the plate material 6 acts have occurred in the working side Ws and the drive side Ds When the trailing end 6b comes off, the trailing end 6b of the plate material 6, which has become free due to a difference in tension, may meander like 6c.

When the rear end 6b of the plate material 6 is meandering like 6c, the rear end 6c comes into contact with a side guide or the like of the rolling line 10 and is folded back, and is doubled between the work rolls 2 of the succeeding rolling mill stand F. And so-called squeezing occurs. If the rear end portion of the narrowed sheet material 6 is rolled while being bitten, the surface of the work roll 2 of the rolling mill stand F is flawed, and the work roll 2 may be cracked or broken. Therefore, when the work roll 2 is damaged, it is necessary to immediately change the work roll assembly,
The number of rearrangements per time increases, and the downtime of the device increases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rolling apparatus and a rolling method that do not cause narrowing of a material to be rolled.

[0011]

According to the present invention, there is provided a rolling apparatus comprising a work roll which is driven to rotate and is driven down, and a plurality of rolling rolls in which a rolled material is sequentially fed between the work rolls. Machine stand, rotation speed adjusting means for adjusting the drive rotation speed of the work roll, roll gap adjusting means for adjusting the roll gap by adjusting the rolling state of the work roll, and the end of the material to be rolled on the hot rolling line Position detecting means for detecting the movement position of the portion, and the rolling mill stand at least immediately before the material to be rolled back when the rear end of the material to be rolled is detected by the position detecting means immediately before the rolling through the mill stand. In order to reduce the tension of the material to be rolled to the subsequent rolling mill stand to zero, the rotation speed adjusting means adjusts the work roll rotation speed or the roll gap adjustment means. A control device for sequentially executing at least one of the opening directions of the roll gap of the work roll by the step.

A rolling method according to the present invention for achieving the above object is a rolling method in which rolling is performed by sequentially feeding a material to be rolled to a plurality of rolling mill stands. When it is detected that the rolled material is just before the trailing edge is removed, the tension of the rolled material between the rolling mill stand immediately before the rolled material is removed and the subsequent rolling mill stand becomes zero. The rolling is performed by sequentially adjusting the rotation speed of the work roll.

[0013] The rolling method of the present invention for achieving the above object is a rolling method in which rolling is performed by sequentially feeding a material to be rolled to a plurality of rolling mill stands. When it is detected that it is just before the bottom of the rolling mill stand on the upstream side, the rolling speed is adjusted by adjusting the rotation speed of the work roll so that the tension of the material to be rolled between all the rolling mill stands becomes zero. Is performed.

A rolling method according to the present invention for achieving the above object is a rolling method in which rolling is performed by sequentially feeding a material to be rolled to a plurality of rolling mill stands, wherein a rear end of the material to be rolled is rolled. When it is detected that it is just before the bottom of the rolling stand from the mill stand, the tension of the material to be rolled between the rolling mill stand immediately before the bottom of the rolling material and the subsequent rolling mill stand is zero. Rolling is performed by sequentially adjusting the roll gap of the work roll in the opening direction.

Further, a rolling method according to the present invention for achieving the above object is a rolling method in which rolling is performed by sequentially feeding a material to be rolled to a plurality of rolling mill stands. Adjusting the roll gap of the work roll in the opening direction so that the tension of the material to be rolled between all the rolling mill stands becomes zero when it is detected that it is just before the trailing edge from the upstream rolling mill stand Rolling.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration of a rolling apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart showing a rolling method as an operation thereof, and FIG. 3 is a relation between tension and time. Is shown. Note that the same members as those of the rolling device shown in FIG. 7 are denoted by the same reference numerals, and redundant description is omitted.

As shown in FIG. 1, a plurality of rolling mill stands F _{1 to} F _n are constituted by a four-roll mill 1, and the four-roll mill 1 comprises a pair of upper and lower work rolls 2; A pair of upper and lower backup rolls 3 and a hydraulic pressure lowering cylinder 4
And In addition, a pair of upper and lower work rolls 2
The driving motor 11 gives the same speed or a speed difference therebetween, and is rotationally driven in a symmetric direction.

The hydraulic pressure lowering cylinder 4 is driven by a driving device 5 provided for each rolling mill 1, and a pair of work rolls 2 are provided.
The material to be rolled (plate material) 6 passing through the gap is rolled. Each drive device 5 is connected to the hydraulic pressure reduction control device 7, and each drive device 5 is individually sent a drive command from the hydraulic pressure reduction control device 7. The front end position and the rear end position of the plate 6 are detected by the tracking device 8 based on the roll rotation speed, the rolling load, and the like.

The drive motors 11 are driven based on commands from a motor control unit 12 provided for each rolling mill 1. Each motor control unit 12 is connected to a tension control unit 13 and individually receives a drive command. The tracking device 8 is provided to be connected to the hydraulic pressure reduction control device 7 and the tension control device 13, and the hydraulic pressure is controlled via the hydraulic pressure reduction control device 7 and the tension control device 13 in accordance with the state of the leading end position and the rear end position of the plate 6. The drive of the pressure reduction cylinder 4 and the drive motor 11 is controlled.

An embodiment of a rolling method using the above-described rolling device will be described with reference to FIG.

[0021] After starting the rolling line, while holding the roll gap of the work rolls 2 in each "open" in the rolling mill stand F ₁ ~F _n (S11), between the plate material 6 on the rolling line is hot-rolled is conveyed from the line upstream to the rolling mill stand F ₁ ~F _n (S12). The monitoring of the tracking device 8, before the front end of the plate material 6 is caught between the roll stand F ₁ of the work rolls 2 of the most upstream side, the hydraulic pressure of the rolling mill stand F ₁ to F _n by the hydraulic pressure control unit 7 The cylinder 4 is driven to be extruded and adjusted to the set roll gap (S13), and the rolling operation is performed sequentially. The plurality of rolling mill stands F _{1 to} F _n are configured to sequentially increase the rolling speed of the downstream rolling mill stand F,
The necessary tension is applied to the plate 6.

Next, by monitoring the tracking device 8, it is detected immediately before the trailing end of the plate 6 comes off from the most upstream rolling mill stand F ₁ , and at the same time, the motor control unit 12 and the tension control device 13 are simultaneously detected. the rotational speed of the drive motor 11 for driving the work rolls 2 of the rolling mill stand F ₁ on the most upstream side, i.e., to control the rolling speed, the self-rolling mill stand (the most upstream side rolling mill stand F ₁₎ following The tension between the rolling mill stands (the rolling mill stand F ₂ ) becomes zero (S14).

Adjustment of the rotation speed (rolling speed) of the drive motor 11 to a state where the tension is zero among the plurality of rolling mill stands F _{1 to} F _n is performed by driving one of the rolling mill stands F before and after. The speed of the motor 11 can be reduced or increased according to the speed of the drive motor 11 of the other rolling mill stand F. FIG. 3 shows an example of the embodiment. The control for reducing the tension of one rolling mill stand F starts adjustment of the rotation (rolling speed) of the work roll 2 a fixed time before the trailing edge of the rear end of the plate material 6 to gradually reduce the tension, At the time when the trailing edge of the rear end of the plate material 6 is removed, the tension between the rolling mill stands F is set to zero.
This makes it possible to prevent the rear end of the plate 6 from jumping up due to a sudden change in tension.

[0024] Then, by monitoring the tracking device 8, and detects the timing at which the rear end of the plate material 6 is Shirinuke from the rolling mill stand F ₁ on the most upstream side, in accordance with this, the roll stand by the hydraulic pressure control unit 7 hydraulic pressure cylinder 4 F ₁ is the drive for bringing in the roll gap of the work rolls 2 in the rolling mill stand F ₁ is controlled to "open". Is roll stand F ₂ to F _n are sequentially controlled similarly the subsequent is repeated rolling operation until a operation end command (S15, S16).

In the above-described rolling method, the rotation speeds of the work rolls 2 of the rolling mill stand F (rolling mill stand F ₁ ) where the rear end of the plate material 6 falls out and the succeeding rolling mill stand F (rolling mill stand F ₂ ). (Rolling speed) is controlled the same,
And because mutual tension between the rolling mill stand F ₁ and the rolling mill stand F ₂ is controlled to be zero, and the working side Ws between the rolling mill stand F ₁ and the rolling mill stand F ₂ drive The tension difference with the side Ds can be set to zero.
Similarly, it is possible to zero state tension difference also work side Ws when Shirinuke of the plate 6 and the driving side Ds between the rolling mill stands F ₂ to F _n. For this reason, there is no possibility that the meandering will occur at the rear end of the plate member 6, and the narrowing will not occur.

Next, a second embodiment of the rolling method using the rolling apparatus shown in FIG. 1 will be described. FIG. 4 is a flowchart showing the operation of the rolling method according to the second embodiment.

[0027] Similar to the embodiment shown in FIG. 2, after starting the rolling line, while holding the roll gap of the work rolls 2 in each "open" in the rolling mill stand F ₁ ~F _n (S11 ), plate material 6 on the rolling line is transported from the hot rolling line upstream to the rolling mill stand F ₁ ~F _n (S12), while the distal end of the plate material 6 on the most upstream side of the rolling mill stand F ₁ of the work rolls 2 before biting into the rolling mill stand F ₁ to F _n of the work roll 2 is adjusted controlled roll gap that has been set (S13), performs sequential reduction operation.

[0028] Then, by monitoring the tracking device 8 detects immediately before the rear end of the plate material 6 is Shirinuke from the rolling mill stand F ₁ on the most upstream side, in accordance with the detection, the motor control unit 12 and the tension controller by 13, the rotational speed of the drive motor 11 for driving the work rolls 2 of all the rolling mill stands F ₁ to F _n, i.e., to control the rolling speed, simultaneously the tension between the rolling mill stands F ₁ to F _n These are mutually set to zero (S21).

[0029] Then, similarly to the embodiment shown in FIG. 2, to detect the timing at which the rear end of the plate material 6 is Shirinuke from the rolling mill stand F ₁ on the most upstream side, in accordance with this, the rolling mill stand F The roll gap of the work roll 2 in ₁ is controlled to “open”. Subsequent rolling mill stand F ₂
It is to F _n are sequentially similarly controlled, is repeated rolling operation until a operation end command (S15, S16).

[0030] In the above-described rolling method, immediately before the rear end of the plate material 6 is Shirinuke the rolling mill stand F _1, the rotational speed of the work rolls 2 of all the rolling mill stands F ₁ to F _n (rolling speed)
Are controlled simultaneously at the same time, and all rolling mill stands F ₁ to
Since mutual tension between F _n is controlled to be zero, it is possible to tension difference between the drive side Ds and work side Ws zero state. For this reason, there is no possibility that meandering will occur at the rear end of the plate member 6 with simple control, and no narrowing will occur.

Next, a third embodiment of the rolling method will be described with reference to FIG. FIG. 5 is a flowchart showing the operation of the rolling method according to the third embodiment. As a rolling device that performs the rolling method according to the present embodiment, the rolling device illustrated in FIG. 7 is applied.

[0032] Similar operation as that shown in FIG. 8, while holding the roll gap of the work rolls 2 in each "open" in the rolling mill stand F ₁ ~F _n (S1), the plate material 6 on the rolling line is conveyed from the hot rolling line upstream to the rolling mill stand F ₁ ~F _n (S2). By monitoring the tracking device 8, it is detected immediately before the leading end of the plate 6 is caught between the work rolls 2 of the rolling mill stand F ₁ on the most upstream side, and accordingly, the rolling mill stand F is controlled by the hydraulic pressure reduction control device 7. ₁ to F _n hydraulic pressure cylinder 4 is extruded driven, it is adjusted controlled roll gap that is set (S3).

Then, by monitoring the tracking device 8, the rear end of the plate 6 is moved to the front rolling mill stands F _{1 to} F _n-1.
, And the roll gaps of the work rolls 2 of the front rolling mill stand F and the rear rolling mill stand F are opened by the hydraulic pressure reduction control device 7 and the tension control device 13, respectively. It is controlled so that the mutual tension becomes zero (S31). The rolling operation is repeated until an operation end command is issued (S5).

In the above-mentioned rolling method, the roll gap between the rolling mill stand F and the work roll 2 of the succeeding rolling mill stand F is controlled to “open” immediately before the trailing edge of the plate material 6 passes through, and the mutual gap is controlled. Since the tension between the rolling mill stands F is controlled to be zero, the tension difference between the working side Ws and the driving side Ds between the rolling mill stands F can be made zero. For this reason, there is no possibility that the meandering will occur at the rear end of the plate member 6, and the narrowing will not occur.

Next, a fourth embodiment of the rolling method will be described with reference to FIG. FIG. 6 is a flowchart showing the operation of the rolling method according to the fourth embodiment. As a rolling device that performs the rolling method according to the present embodiment, the rolling device illustrated in FIG. 7 is applied.

[0036] Similar operation as that shown in FIG. 8 holds each "open" the roll gap of the work rolls 2 in the rolling mill stand F ₁ ~F _n (S1), the plate material 6 is roll stand F ₁ ~ is conveyed to F _n (S2), detects immediately before the leading end of the plate material 6 is caught between the roll stand F ₁ of the work rolls 2 of the most upstream side, in accordance with this, the rolling mill stand F ₁ to F _n Is adjusted and controlled to the set roll gap (S3).

[0037] Then, by monitoring the tracking device 8 detects immediately before the rear end of the plate material 6 is Shirinuke from the rolling mill stand F ₁ on the most upstream side, in accordance with the detection, the hydraulic pressure control unit 7, and tension control the apparatus 13, roll gap of the work rolls 2 of all the rolling mill stands F ₁ to F _n are controlled to "open", and the rolling mill stand F ₁ to F _n
Are simultaneously set to zero simultaneously (S41). The rolling operation is repeated until an operation end command is issued (S5).

[0038] In the above-described rolling method, the rolling mill stand F ₁ at the rear end of the plate material 6 is the most upstream side just before Shirinuke, roll gap of the work rolls 2 of all the rolling mill stands F ₁ to F _n are simultaneously It is controlled to "open", and since the mutual tension between all the rolling mill stands F ₁ to F _n is controlled to be zero, and the working side Ws between the rolling mill stands F between the drive side Ds Can be set to zero. For this reason, there is no possibility that meandering will occur at the rear end of the plate member 6 with simple control, and no narrowing will occur.

[0039]

The rolling apparatus of the present invention has a plurality of rolling mill stands that are provided with a work roll that is driven and rotated and is driven down, and a plurality of rolling mill stands in which the rolled material is sequentially fed between the work rolls. Rotation speed adjusting means for adjusting, roll gap adjusting means for adjusting the rolling gap of the work roll to set the roll gap, and position detecting means for detecting the moving position of the end of the material to be rolled on the hot rolling line Between the rolling mill stand and the rolling mill stand immediately before the rolled material at least immediately before the trailing edge of the material to be rolled through the rolling mill stand is detected by the position detecting means. The rotation speed of the work roll is adjusted by the rotation speed adjusting means or the roll gap of the work roll is adjusted by the roll gap adjusting means so that the tension of the material to be rolled becomes zero. Since a control device for sequentially performing at least one of the opening direction adjustments is provided, the tension of the material to be rolled can be made zero by adjusting the rolling speed or adjusting the opening direction of the roll gap. As a result,
There is no risk of meandering at the rear end of the material to be rolled, and no narrowing occurs.

The rolling method of the present invention is a rolling method in which rolling is performed by sequentially feeding a material to be rolled to a plurality of rolling mill stands. When it is detected that the roll is just before, the work roll is rotated so that the tension of the rolled material between the rolling mill stand immediately before the rolled-out material and the succeeding rolling mill stand becomes zero. Since the rolling is performed by sequentially adjusting the speed, there is no possibility that meandering may occur at the rear end of the material to be rolled, and narrowing does not occur.

Further, the rolling method of the present invention is a rolling method in which rolling is performed by sequentially feeding a material to be rolled to a plurality of rolling mill stands, wherein the rear end of the material to be rolled is moved from the most upstream rolling mill stand. Since it was detected that it was just before the bottom of the roll, the rolling speed was adjusted by adjusting the rotation speed of the work roll so that the tension of the material to be rolled between all the rolling mill stands became zero, so that the rolling was performed. With the simple control, there is no possibility that meandering will occur at the rear end of the material to be rolled, and no narrowing will occur.

Further, the rolling method of the present invention is a rolling method in which rolling is performed by sequentially feeding a material to be rolled to a plurality of rolling mill stands, wherein the trailing end of the material to be rolled has a trailing edge from the rolling mill stand. When it is detected that it is just before, the work roll is rolled so that the tension of the material to be rolled between the rolling mill stand immediately before the material to be rolled out and the succeeding rolling mill stand becomes zero. Since the rolling is performed by sequentially adjusting the gap in the opening direction, there is no possibility that meandering may occur at the rear end of the material to be rolled, and narrowing does not occur.

Further, the rolling method of the present invention is a rolling method in which rolling is performed by sequentially feeding the material to be rolled to a plurality of rolling mill stands, wherein the rear end of the material to be rolled is moved from the most upstream rolling mill stand. When it is detected that it is just before the bottom of the work roll, the work gap is adjusted by adjusting the roll gap of the work roll in the opening direction so that the tension of the material to be rolled between all the rolling mill stands becomes zero. Therefore, there is no possibility that meandering will occur at the rear end of the material to be rolled, and narrowing will not occur.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a rolling device according to an embodiment of the present invention.

FIG. 2 is a control flowchart of a rolling method according to an embodiment of the present invention.

FIG. 3 is a graph showing a relationship between tension and time.

FIG. 4 is a control flowchart of a rolling method according to a second embodiment of the present invention.

FIG. 5 is a control flowchart of a rolling method according to a third embodiment of the present invention.

FIG. 6 is a control flowchart of a rolling method according to a fourth embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a conventional rolling device.

FIG. 8 is a control flowchart of a conventional rolling method.

FIG. 9 is a view taken along line IX-IX in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Four-stage rolling mill 2 Work roll 3 Backup roll 4 Hydraulic pressure reduction cylinder 5 Drive device 6 Rolled material (plate material) 7 Hydraulic pressure reduction control device 8 Tracking device 10 Rolling line 11 Drive motor 12 Motor control unit 13 Tension control device

Claims (5)

[Claims] 1. A plurality of rolling mill stands having a work roll which is driven to rotate and is driven down and a rolled material is sequentially fed between the work rolls; a rotation speed adjusting means for adjusting a drive rotation speed of the work roll; Roll gap adjusting means for adjusting the rolling state of the work roll to set the roll gap; position detecting means for detecting the moving position of the end of the material to be rolled on the hot rolling line; When the trailing end of the rolling mill stand is detected immediately before the bottom of the rolling mill stand is detected, the tension of the rolled material between the rolling mill stand immediately before the bottom of the rolling material and the subsequent rolling mill stand is at least zero. In this case, the rotation speed of the work roll is adjusted by the rotation speed adjusting means or the opening direction of the roll gap of the work roll is adjusted by the roll gap adjusting means. A rolling device, comprising: a control device that sequentially executes at least one of them. 2. A rolling method for performing rolling by sequentially feeding a material to be rolled to a plurality of rolling mill stands, wherein it is detected that the rear end of the material to be rolled is immediately before the trailing edge from the rolling mill stand. In this case, the rolling speed of the work rolls is sequentially adjusted so that the tension of the material to be rolled between the rolling mill stand immediately before the material rolls through and the subsequent rolling mill stand becomes zero. Rolling method. 3. A rolling method in which rolling is performed by sequentially feeding a material to be rolled to a plurality of rolling mill stands, wherein a rear end of the material to be rolled is immediately before the trailing edge from the most upstream rolling mill stand. Rolling is performed by adjusting the rotation speed of the work roll so that the tension of the material to be rolled between all the rolling mill stands becomes zero when this is detected. 4. A rolling method for rolling by sequentially feeding a material to be rolled to a plurality of rolling mill stands, wherein it is detected that the rear end of the material to be rolled is immediately before the trailing edge of the rolling mill stand. The work roll gap is sequentially adjusted in the opening direction so that the tension of the material to be rolled between the rolling mill stand immediately before the material rolls through and the subsequent rolling mill stand becomes zero. A rolling method characterized by performing rolling. 5. A rolling method in which rolling is performed by sequentially feeding a material to be rolled to a plurality of rolling mill stands, wherein a rear end of the material to be rolled is immediately before the trailing edge from the most upstream rolling mill stand. A rolling method comprising: adjusting the roll gap of a work roll in the opening direction so that the tension of the material to be rolled between all rolling mill stands is reduced to zero when the detection is made.