JP7440701B2 - Abnormality determination device, control device, rolling equipment, abnormality determination method, and control method - Google Patents

Description

The present invention relates to an abnormality determination device and an abnormality determination method for detecting an abnormality in the width of a metal strip that is a material to be rolled.

As an example of a tail end crop detection device that can appropriately detect a tail end crop with a suitable configuration in terms of cost and maintenance, Patent Document 1 describes a method for detecting a finishing end of a hot rolling line in addition to a hot rolling line. A camera is installed to continuously take images of the rolled material passing between rolling stands, and a tail end image of the rolled material is detected from the continuous images of the rolled material taken by the camera. By extracting the edge portion of the tail end of the material and then performing angle-of-view matching processing on the edge image, the edge image viewed diagonally to the rolling direction can be viewed from the direction perpendicular to the rolling direction. It is described that the tail end crop shape of the rolled material can be recognized by converting the image into a rolled image.

Japanese Patent Application Publication No. 2012-159431

In hot rolling, it is important to stably transport the tail end of the plate where no tension is applied. Normally, in order to transport the plate stably, the amount of meandering of the plate determined by imaging with a camera installed in the hot rolling line, and the load detected by a load detector (load cell) installed in the rolling mill. Leveling control is performed using the difference between left and right sides.

However, especially in plants that do not have a crop shear device on the entry side of the finishing rolling mill, if there is a bend or narrowing of the width at the tail end, detected values such as the amount of meandering of the plate and the difference in load between the left and right sides may change rapidly. This makes stable control difficult and tail end throttling more likely to occur. Similarly, stable conveyance is important when rolling not only the tail end but also the steady portion of the metal strip.

On the other hand, in order to perform appropriate rolling control, the above-mentioned patent document 1 extracts edge portions from the surface image of the rolled material taken by an imaging means, performs luminance information analysis, binarization processing, positioning, etc. It is disclosed that an operator can easily recognize the shape of a tail end crop by detecting a tail end image with high accuracy through correction or the like and displaying it on a monitor.

However, with the above-mentioned conventional technology, it is difficult for operators to uniformly judge the occurrence of cropping at the tail end of all board widths, and there is room for improvement in quality uniformity, and further technology is needed. Improvements were awaited.

The present invention provides an abnormality determination device, a rolling mill control device, and rolling equipment, which can uniformly determine abnormality in sheet width for metal strips of any width, and an abnormality determination method and control method. I will provide a.

The present invention includes a plurality of means for solving the above-mentioned problems, and one example thereof is an abnormality determining device for determining an abnormality in the width of a metal strip rolled by a rolling mill. The camera includes a camera that captures an image of the metal strip, and an image processing unit that determines an abnormality in the strip width based on the image captured by the camera, and the image processing unit includes a camera that captures an image of the metal strip. Among the portions imaged in , W ₀ is the plate width of the rolling steady portion, and W is the plate width of the metal strip in the portions sequentially imaged by the camera, then the rate of change in the plate width (W ₀ -W)/ _W0 becomes equal to or greater than a threshold value, it is determined that an abnormal portion where the board width is narrowed exists.

According to the present invention, it is possible to uniformly determine whether a strip width is abnormal for metal strips of any width. Problems, configurations, and effects other than those described above will be made clear by the description of the following examples.

1 is a schematic diagram showing the configuration of an abnormality determination device according to an embodiment of the present invention and a rolling facility equipped with the same. FIG. 3 is an image diagram of a control stop operation in the case of an abnormality in the control device of the embodiment. FIG. 3 is a diagram showing an example of a control operation by the control device of the embodiment. 5 is a control flowchart in the control device of the embodiment.

Embodiments of the abnormality determination device, control device, rolling equipment, abnormality determination method, and control method of the present invention will be described using FIGS. 1 to 4. In the drawings used in this specification, the same or corresponding components are given the same or similar symbols, and repeated description of these components may be omitted.

In addition, the metal strip that is the material to be rolled in the present invention is generally a strip of metal material that can be rolled, and its type is not particularly limited, and in addition to steel plates, it can be non-ferrous materials such as aluminum and copper. be able to.

First, the overall configuration of rolling equipment including an abnormality determination device, a control device, and a rolling mill will be explained using FIG. 1. FIG. 1 is a schematic diagram showing the configuration of an abnormality determination device according to the first embodiment and a rolling facility equipped with the same.

The rolling equipment 100 shown in FIG. 1 is equipment for rolling a material to be rolled 1, and includes an F1 stand 10, an F2 stand 20, an F3 stand 30, an F4 stand 40, an F5 stand 50, an F6 stand 60, and an F7 stand 70. , cameras 81 and 82, a control section 90, a display device 95, and the like.

Among these, the camera 81 and the image processing unit 91 of the control unit 90 constitute an abnormality determination device that determines an abnormality in the width of the rolled material 1 rolled by the rolling mill. Further, a control device is constituted by an abnormality determination device constituted by the camera 81 and the image processing unit 91 of the control unit 90, a command unit 92 of the control unit 90, and a tracking calculation unit 93 of the control unit 90.

Note that the rolling equipment 100 is not limited to the configuration in which seven rolling stands are provided as shown in FIG. 1, but may be any number as long as it has at least two or more stands.

Each of the F1 stand 10, F2 stand 20, F3 stand 30, F4 stand 40, F5 stand 50, F6 stand 60, and F7 stand 70 has an upper work roll and a lower work roll, and an upper work roll and a lower work roll, respectively. The upper backup roll, the lower backup roll, and the reduction cylinders 11, 21, 31, 41, 51, 61, 71 provided on the upper part of the upper backup roll and the load detectors 12, 22, 32, 42, which are supported by contact with each other. 52, 62, and 72. Note that a six-stage structure may be provided in which upper and lower intermediate rolls are further provided between each of the upper and lower work rolls and each of the upper and lower backup rolls.

The camera 81 is provided at a position where it can capture an image including the rolled material 1 on the entry side of the F1 stand 10, and for example, from directly above the rolled material 1 or diagonally above the rolled material 1. Images including the following are captured at 0.1 second intervals. Data of an image including the rolled material 1 captured by the camera 81 is transmitted to the control section 90 via the communication line 85.

The camera 82 is provided on the exit side of the F4 stand 40 and the entrance side of the F5 stand 50 at a position where it can capture an image including the rolled material 1, and, like the camera 81, for example, Images including the rolled material 1 are taken at 0.1 second intervals from directly above or diagonally above the rolled material 1. The data of the image captured by the camera 82 is also transmitted to the control unit 90 via the communication line 85.

Of these cameras 81 and 82, the camera 81 executes an imaging step of capturing an image including the rolled material 1.

In addition, although the case where the camera is provided in two places, the entrance side of the F1 stand 10 and the F4 stand 40 and the F5 stand 50, will be described, it is sufficient that the camera is provided in at least one place. There may be one, two or more, and they may be provided on the entrance side of all the stands.

The control unit 90 is a device that controls the operation of each device in the rolling facility 100, and includes an image processing unit 91, a command unit 92, and a tracking calculation unit 93.

The image processing unit 91 is a part that determines an abnormality in the board width based on the image captured by the camera 81.

FIG. 3 shows changes in the strip width, leveling amount, and gap at the camera position and the rolling mill position with respect to time. Here, if the shape changes as shown in FIG. 3(A) regardless of the meandering of the plate such as when the rolled material 1 moves toward the drive side, the metal strip of the part sequentially imaged by the camera The plate width may change suddenly as shown in FIG. 3(B).

In such a case, the plate width of the rolling steady part of the rolled material 1 imaged by the camera 81 is set as W ₀ , and the plate width at any position of the rolled material 1 of the part sequentially imaged by the camera 81 is set as W 0 Sometimes, when the rate of change in board width (W ₀ -W)/W ₀ becomes equal to or greater than the threshold W _th , the image processing unit 91 determines that an abnormal portion where the board width is narrowed exists. The image processing unit 91 executes an image processing step for determining an abnormality in board width based on the image taken in the imaging step.

There are no particular limitations on how to determine the width W of the rolled material 1, but for example, the brightness of a captured image containing the rolled material 1 is compared for each pixel with a threshold value to determine the width of the two ends of the rolled material 1 ( (driving side and working side), the number of pixels between the two ends is determined, and the determined number of pixels is regarded as the board width W.

There is no particular limitation on how to obtain the plate width W ₀ of the steady rolling part of the rolled material 1 captured by the camera 81, but for example, the work of the rolled material 1 determined from the image captured by the camera 81 at a certain time. The distance between the side end and the drive side end can be set to a value that is stable within a range that satisfies a predetermined standard in the rolling direction of the material to be rolled 1. Further, the distance between the working side end and the driving side end of the material to be rolled 1 may be a value that is stable within a range that satisfies a predetermined standard in the rolling direction for a certain period of time. Furthermore, the camera 81 detects the strip width of the rolled material 1 specified in the operating conditions at a time when the strip width is stably detected by the strip width meter installed on the exit side of the final finishing mill. The distance between the working side end and the driving side end of the rolled material 1, which is determined from the image taken in , can be used as the plate width W ₀ of the steady rolling part. The obtained plate width W ₀ of the steady rolling portion is saved as a reference value.

The threshold value W _th serving as a judgment criterion can be, for example, a rate of change of 3% in the plate width W ₀ of the steady rolling part, but is not particularly limited, and can be a larger value or a smaller value, It can be determined as appropriate depending on the type of material 1 to be rolled, the pass schedule, etc.

This image processing unit 91 can determine that an abnormal part of the board width exists when it is determined that the change rate of the board width was equal to or greater than a threshold value only once at a certain time A. Even if the rate of change in board width is greater than the threshold value, if the rate of change in board width at time B is less than the threshold value in an image captured by camera 81 after a certain time A, preferably at time B immediately after, , it can be determined that the plate width is in the normal range. In other words, the process may be such that it is determined that an abnormal portion exists only after it has been determined that the abnormal portion exists at least twice in a row. In this case, at time B, it is determined that an abnormal portion exists.

When the image processing unit 91 determines that an abnormal portion exists, the command unit 92 controls the leveling of the rolling mill provided downstream from the abnormal portion in the conveying direction of the rolled material 1 at the determined time. This is the part that stops after the judgment time. When the command unit 92 determines that an abnormality exists in the image processing step of the abnormality determination method, tracking is started from the determination time as a starting point, and tracking is started from the abnormality point to the downstream side in the conveyance direction of the rolled material 1. A command step is executed to stop the leveling control of the provided rolling mill at the timing when the abnormality reaches the rolling mill.

For example, as shown in FIGS. 1 and 2, when the camera 81 is on the entrance side of the F1 stand 10 and the image processing unit 91 determines that an abnormality exists, the command unit 92 As shown in (D), at the timing when the abnormality reaches the F1 stand 10, a control signal is sent to the rolling cylinder 11 to stop the leveling control of the rolling mill of the F1 stand 10 (controlled rolling mill (1)). Output.

In addition, as shown in FIG. 2 and FIG. Similarly to the F1 stand 10, the lowering cylinders 21, 31, 41 are set so that the leveling control is stopped at the timing when the abnormal part reaches each stand. , 51, 61, and 71.

Moreover, the command unit 92 can simultaneously stop the leveling control and open the gap between the rolls of the rolling mill whose leveling control has been stopped according to predetermined conditions.

In this embodiment, stopping the leveling control and opening the gap between the rolls are used together, but it is also possible to only stop the leveling control. In this case, at the timing when the abnormal portion reaches each stand, the leveling of the rolling mill provided on the downstream side in the conveyance direction of the material to be rolled 1 is stopped, and the roll gap is not opened. It is also possible to only open the roll gap. In this case, at the timing when the abnormal part reaches each stand, the gap between the rolls of the rolling mill provided on the downstream side in the conveyance direction of the material to be rolled 1 is opened according to predetermined conditions. , will continue to perform leveling control for all rolling mills.

The timing to open the roll gap may be the timing at which it is determined that the abnormal portion exists, but the tracking calculation unit 93, which will be described later, tracks the abnormal strip width portion, and the abnormal strip width portion reaches the target control rolling mill. It is desirable to set the timing.

For example, in the case of the F1 stand 10, as shown in FIG. 3E, the timing at which the abnormal part reaches the F1 stand 10 is determined from the time when it is determined that the abnormal part exists.

In the case of a rear-stage multiple rolling mill (at least one of the F2 stand 20, F3 stand 30, F4 stand 40, F5 stand 50, F6 stand 60, and F7 stand 70), the control is performed as shown in FIG. 3(H). This is the timing when the abnormal part reaches the stand of the rolling mill (2).

The "predetermined conditions" that determine the amount of gap opening when the position where the strip width narrows reaches each stand can be determined according to the type of material 1 to be rolled and the pass schedule, and the It is advisable to decide on each case in advance.

At this time, the roll gap of each stand is set so that it is smaller than the roll gap when the leveling control is stopped in the rolling mill installed one upstream in the conveyance direction, and the work rolls above and below the rolled material 1 are It can be a range of contact.

Note that depending on the "predetermined conditions", there may be a case in which the gap is not opened even if the sheet width becomes narrower, and the gap amount during steady rolling is maintained.

In addition _{, the} image processing unit 91 determines that during "stable rolling" as shown in _FIG . Either no particular signal is output, or a signal indicating that it is a normal section is output to the command section 92. In this case, the command unit 92 continues the leveling control and also continues the roll gap control.

The tracking calculation unit 93 is a part that calculates the amount of movement of the abnormal part in the transport direction based on the image captured by the camera 81, and determines the timing at which the abnormal part reaches the subsequent rolling mill (each stand). . This tracking calculation section 93 executes a tracking calculation step of calculating the amount of movement of the abnormal part in the transport direction.

In this tracking calculation unit 93, based on the image taken by the camera 82, the spot where the strip width is judged to be abnormal is displayed in each stand of the subsequent rolling mills (F5 stand 50, F6 stand 60, F7 stand 70). You can adjust the timing of your arrival.

In addition, although a case will be described in which a strip width abnormality is determined based only on the image captured by the camera 81, based on the image captured by the camera 82, subsequent rolling mills (F5 stand 50, F6 stand 60 , F7 stand 70).

The display device 95 is a display device such as a display or an audio device such as an alarm, and for example, when the control unit 90 determines that the board width is abnormal, it informs the operator of the occurrence of the board width abnormality and the work to be done to deal with it. It is a device for

During operation, the operator visually checks the display screen of the display device 95, each stand itself, and between each stand to confirm whether there is an abnormality in board width. For example, when the display device 95 displays an abnormal board width and an operation to be performed, the operator can control the abnormal board width by manually operating according to the instructions.

It should be noted that it is not necessary to inform the operator of the board width abnormality and wait for the operator to perform the operation; instead, it is possible to display the abnormality on the display device 95 and automatically perform operations in response to the board width abnormality on the control unit 90 side, or to automatically perform operations in response to the board width abnormality without displaying the information. It is desirable that the system be operated at

Next, an abnormality determination method for determining an abnormality in the width of the rolled material 1 in this embodiment and a flow of control using the method will be described below with reference to FIGS. 3 and 4.

The control unit 90 constantly executes the flow shown in FIG. 4 during operation.

First, as shown in FIG. 4, the control unit 90 sets a threshold value (W _th ) for the rate of change in the strip width on the entry side of the controlled rolling mill (1) (detection stand) (step S41).

Thereafter, the image processing unit 91 executes a process to determine whether there is an abnormality in the sheet width based on the images taken by the camera ₈₁ , and determines the sheet width of the rolling steady portion of the rolled material 1 by sequentially taking images with the camera 81. When the plate width of the rolled material 1 at the portion where the plate width is W is defined as W, it is determined whether the rate of change in plate width (W ₀ -W)/W ₀ is equal to or greater than a threshold value W _th (step S42).

For example, as shown in FIG. 3, when the rolled material 1 is in "stable rolling", there is no abnormal part where the strip width narrows, and the rate of change in strip width (W ₀ - W)/W ₀ is the threshold value W Since it becomes less than _th (No in step S42), the command unit 92 continues normal rolling control (step S43) and completes the process.

On the other hand, as shown in FIG. 3(A), when a change occurs in the shape of the rolled material 1 and the rate of change in the sheet width becomes equal to or greater than the threshold value W _th (Yes in step S42), the image processing unit 91 It is determined that there is an abnormal part where the plate width is narrowed, and the tracking calculation unit 93 starts tracking the abnormal part (step S44).

Thereafter, at the timing when the abnormality reaches each target stand, the leveling control is immediately stopped (step S45), and the roll gap is opened to the opening stop position according to predetermined conditions (step S46). , complete the process.

Next, the effects of this embodiment will be explained.

The above-described abnormality determination device of this embodiment is a device for determining abnormality in the width of the rolled material 1 rolled by a rolling mill, and includes a camera 81 that captures an image including the rolled material 1; an image processing unit 91 that determines an abnormality in the sheet width based on the image taken by the camera 81, and the image processing unit 91 determines the sheet width of the regular rolling portion of the portion of the rolled material 1 imaged by the camera 81. When W _{0 is W 0} and W is the strip width of the rolled material 1 in the portions sequentially imaged by the camera 81, when the rate of change in strip width (W ₀ −W)/W ₀ is equal to or greater than the threshold value, It is determined that there is an abnormality where the plate width is narrowed.

In this way, by determining the strip width from the captured image and making a judgment based on the rate of change in the strip width, changes in strip width can be detected using the same ratio index even if the absolute value of the strip width of the metal strip changes. This makes it possible to uniformly determine abnormalities in the width of metal strips of all widths. Therefore, even if a sudden decrease in the width of the strip occurs, for example at the tail end, it is possible to accurately and reliably judge the abnormality of the strip width for metal strips of any width.

Furthermore, even if it is detected that the strip width has become narrower at a certain time, if it is detected that the strip width has returned to a predetermined value or more at a later time, then the strip width may have become narrower due to some reason. In many cases, the shape should be judged to be normal, rather than a so-called tapered shape that causes unstable control, even if only the portion becomes thinner. Therefore, the camera 81 continuously captures images at different times A and B (A<B), and the image processing unit 91 determines that the rate of change in board width at time A is equal to or greater than a threshold value, and the board width at time B is If it is determined that an abnormal area exists two or more times in a row, such as when the rate of change in width also exceeds a threshold, false positives can be avoided by formally determining that an abnormal area exists at time B. It is possible to prevent the operation from being determined to be abnormal more than necessary, and to prevent the operation from being stopped due to the presence of an abnormality that does not require stopping the operation.

Furthermore, if there is an abnormality in the plate width, especially at the tail end, control becomes unstable, making meandering and tail end throttling more likely to occur. Therefore, when the abnormality determination device and the abnormality determination device determine that an abnormality exists, the control device is installed downstream of the abnormality in the conveyance direction of the rolled material 1 at the time of the determination. By including a command unit 92 that stops the leveling control of the rolling mill after the determined time, unstable control can be avoided and occurrence of abnormalities such as tail end throttling can be reduced. In order to quickly avoid unstable control, it is possible to stop the leveling control of the rolling mill provided on the downstream side of the abnormality in the conveyance direction of the material to be rolled at the same time as it is determined that the abnormality exists.

In addition, instead of or in addition to stopping the leveling control, the command unit 92 is configured to open the roll gap after the judgment time according to predetermined conditions, so that the roll gap such as the tail end throttle can be Even if a width defect that causes damage to the roll occurs, damage to the roll surface can be reduced.

In addition, the command unit 92 stops the leveling control and opens the gap between the rolls of the rolling mill according to predetermined conditions, so that the control unit 92 can prevent the plate, such as the tail end drawing, from damaging the rolls. Even if a width defect occurs, damage to the roll surface can be reduced.

Furthermore, it further includes a tracking calculation unit 93 that calculates the amount of movement of the abnormal part in the conveying direction, and the command unit 92 performs leveling at the timing when the abnormal part reaches the rolling mill based on the movement amount calculated by the tracking calculation unit 93. By stopping the control, it is possible to prevent rolling defects due to inappropriate leveling control at locations where the strip width is narrow. In addition, instead of stopping the leveling control, or in addition, the command unit 92 opens the gap between the rolls of the rolling mill according to predetermined conditions, thereby reducing the narrowing of the plate due to the abnormal part of the rolled material 1. It is possible to suppress the occurrence of damage to the surface of the work roll.

Further, the command unit 92 is configured such that the gap is smaller than the gap when leveling control is stopped in a rolling mill provided one upstream in the conveyance direction, and within a range that contacts the rolled material 1. As a result, the rolled material 1 passing through the rolling mill is conveyed while being lightly sandwiched between the upper and lower rolls, which reduces meandering of the rolled material 1 and prevents damage to the roll surface due to abnormal parts. can be reduced.

<Others>
Note that the present invention is not limited to the above-described embodiments, and various modifications and applications are possible. The embodiments described above are described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described.

1... Rolled material (metal strip)
10... First stand 11, 21, 31, 41, 51, 61, 71... Reduction cylinder 12, 22, 32, 42, 52, 62, 72... Load detector 20... Second stand 30... Third stand 40... Fourth stand 50...Fifth stand 60...Sixth stand 70...Seventh stand 81, 82...Camera (abnormality determination device)
85...Communication line 90...Control unit (control device)
91...Image processing unit (abnormality determination device)
92...Command unit 93...Tracking calculation unit 95...Display device 100...Rolling equipment

Claims (11)

An abnormality determination device for determining an abnormality in the width of a metal strip rolled by a rolling mill,
a camera that captures an image including the metal strip;
an image processing unit that determines an abnormality in the board width based on the image taken by the camera;
The image processing unit is configured to determine, among the portions of the metal strip imaged by the camera, a width of the rolling steady portion as W ₀ and a width of the metal strip of the portions sequentially imaged by the camera as W 0 . When the rate of change in the plate width (W ₀ -W)/W ₀ becomes equal to or greater than a threshold value, it is determined that an abnormal portion where the plate width narrows exists. The abnormality determination device according to claim 1,
The camera continuously captures the images at different times A and B (A<B),
The image processing unit determines that the abnormal portion exists when the rate of change in the plate width at time A is equal to or greater than the threshold value, and the rate of change in the plate width at time B is equal to or greater than the threshold value. An abnormality determination device characterized by: A control device equipped with the abnormality determination device according to claim 1 or 2,
When the abnormality determination device determines that the abnormality exists, the leveling control of the rolling mill provided on the downstream side of the abnormality in the conveyance direction of the metal strip is started at the determined time. A control device comprising: a command unit that stops the rolling mill later and/or opens a gap between rolls of the rolling mill after the time according to predetermined conditions. The control device according to claim 3,
further comprising a tracking calculation unit that calculates the amount of movement of the abnormal part in the transport direction,
The command unit may stop the leveling control at the timing when the abnormality reaches the rolling mill based on the movement amount calculated by the tracking calculation unit, and/or adjust the gap between the rolls of the rolling mill in advance. A control device that is characterized by opening according to predetermined conditions. The control device according to claim 3 or 4,
The command unit sets the gap so that it is smaller than the gap when the leveling control is stopped in the rolling mill provided one upstream in the conveying direction, and sets the metal strip so that upper and lower work rolls are attached to the metal strip. A control device characterized by having a contact range. A control device according to any one of claims 3 to 5,
A rolling facility comprising: a rolling mill that rolls a metal strip. An abnormality determination method for determining an abnormality in the width of a metal strip rolled by a rolling mill, the method comprising:
an imaging step of capturing an image including the metal strip;
an image processing step of determining an abnormality in the board width based on the image taken in the imaging step,
In the image processing step, W ₀ is the plate width at the rolling steady portion of the portion of the metal strip imaged in the imaging step, and the plate width of the portion of the metal strip imaged sequentially in the image capturing step is W 0 . An abnormality determination characterized in that when the rate of change in the plate width (W ₀ - W)/W ₀ becomes equal to or greater than a threshold value, it is determined that an abnormal part where the plate width narrows exists. Method. In the abnormality determination method according to claim 7,
In the imaging step, the images are continuously captured at different times A and B (A<B),
In the image processing step, it is determined that the abnormal portion exists when the rate of change in the plate width at time A is equal to or greater than the threshold value, and the rate of change in the plate width at time B is equal to or greater than the threshold value. An abnormality determination method characterized by: A control method comprising the abnormality determination method according to claim 7 or 8,
When it is determined that the abnormal portion exists in the image processing step of the abnormality determination method, a rolling mill installed downstream of the abnormal portion in the conveyance direction of the metal strip at the time of the determination is made. A control method comprising: a commanding step of stopping leveling control after the time and/or opening a gap between rolls of the rolling mill after the time according to predetermined conditions. The control method according to claim 9,
further comprising a tracking calculation step of calculating a movement amount of the abnormal part in the transport direction,
In the command step, the leveling control is stopped at the timing when the abnormality reaches the rolling mill based on the movement amount calculated by the tracking calculation step, and/or the gap between the rolls of the rolling mill is adjusted in advance. A control method characterized by opening according to predetermined conditions. The control method according to claim 10,
In the command step, the gap is made smaller than the gap when the leveling control is stopped in the rolling mill provided one upstream in the conveying direction, and upper and lower work rolls are attached to the metal strip. A control method characterized in that the area is a contact area.

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