JP6673303B2 - Rolling apparatus, rolling method and method for manufacturing thick steel plate - Google Patents

Description

  The present invention relates to a thick plate rolling apparatus, a rolling method, and a method for manufacturing a thick steel plate, which can reduce a thickness deviation of a roll biting side end portion of the thick plate material.

2. Description of the Related Art Conventionally, end thickness control of a thick plate material has been performed by automatic thickness control (AGC). Here, the thick plate means a material to be rolled which is a material of the thick steel plate. “Thick steel plate” refers to a steel plate having a thickness of 4.5 mm or more.
In this AGC, the roll opening deviation from the set roll opening S ₀ is ΔS (ΔS = roll opening S−the set roll opening S ₀ ), and the rolling load deviation from the target rolling load F ₀ is ΔF (ΔF = Assuming that the detected rolling load F−target rolling load F ₀ ) and the mill constant are K, the thickness deviation ΔH from the target thickness H ₀ shown in the following (1) (ΔH = actually measured thickness H−target) The position of the roll-down cylinder (roll opening deviation ΔS, ie, roll opening S) is controlled so that the plate thickness H ₀ ) becomes zero.
ΔH = ΔS + ΔF / K (1)

However, even if this AGC is performed, there is a problem that the thickness of the end portion of the thick plate material on the roll biting side becomes too thin after the AGC is locked on.
In order to solve the problem that the thickness of the end portion of the thick sheet material that is engaged with the roll becomes excessively thin, a method of rolling a thick sheet material disclosed in Patent Document 1, for example, has conventionally been proposed.
In the method of rolling a thick plate material disclosed in Patent Document 1, a response delay of the AGC occurs due to a sudden change in the plastic constant of the thick plate material from when the thick plate material is caught in the roll and when the AGC locks on to when it moves to a steady portion. During the fixed target thickness correction period in which the unsteady portion is rolled, the roll opening degree by the automatic thickness control is corrected by the predetermined end target thickness correction amount based on the actual results.
As a result, the thickness deviation of the end portion of the thick plate on the roll biting side can be reduced, and the problem that the thickness of the end portion of the thick plate material on the roll biting side becomes excessively thin after the AGC is locked on can be solved. Can be.

JP-A-6-238313

However, the conventional method for rolling a thick plate disclosed in Patent Document 1 has the following problems.
That is, in the method of rolling a thick plate disclosed in Patent Document 1, the correction start timing of the end target thickness correction to be performed after the AGC locks on is set in advance by presetting constant values for each thickness and width of the thick plate. Was decided. That is, the correction start timing of the end portion target thickness correction is determined in advance by a constant value for each plate thickness and plate width. On the other hand, the rolling load at the end of the thick plate material varies variously for each pass and each material depending on the plate thickness, the amount of reduction, the biting speed, the equipment status, and the like. When the rolling load at the end of the thick plate material changes, the position of the unsteady portion changes due to the response delay of AGC, and the correction start timing of the end target thickness correction is uniformly determined in advance as in Patent Document 1. In such a case, the thickness deviation of the end of the thick plate material on the side of the roll biting may not be appropriately reduced.
Therefore, the present invention has been made to solve this conventional problem, and an object of the present invention is to appropriately and appropriately determine the correction start timing of the end portion target thickness correction for each thick plate material, and It is an object of the present invention to provide a thick plate rolling device, a rolling method, and a method of manufacturing a thick steel plate, which can surely reduce the thickness deviation of the inset side end.

  In order to solve the above-described problems, a rolling device for a thick plate according to one embodiment of the present invention is configured such that, after the thick plate is caught between rolls, based on a rolling load detected by a load detector, the thick plate is rolled. An automatic thickness control unit that performs an automatic thickness control that controls the position of the screw-down cylinder so that the thickness deviation from the target thickness becomes zero, and after the automatic thickness control by the automatic thickness control unit is started. A constant end aim thickness correction for rolling an unsteady portion in which an automatic thickness control response delay occurs due to a sudden change in the plastic constant of a thick plate material from the lock-on of the automatic thickness control to a steady portion. A rolling device for a thick plate material, comprising: an end portion aimed thickness correction portion that performs an end portion aimed thickness correction that corrects the position of the roll-down cylinder by the automatic thickness control to change the roll opening during the period. The start timing of the end target thickness correction is determined by the detected timing. And summarized in that a value obtained by differentiating the extended load time is a timing at which the first threshold value.

Further, the method of rolling a thick plate material according to another aspect of the present invention, after the thick plate material is caught between the rolls, based on the rolling load detected by the load detector, from the target plate thickness of the thick plate material Automatic thickness control for controlling the position of the screw-down cylinder so that the thickness deviation becomes zero, and after starting the automatic thickness control, the thick material from the lock-on of the automatic thickness control to the steady portion. During a constant target thickness correction period in which the unsteady portion where the response of the automatic thickness control is delayed due to a rapid change in the plastic constant of the roll is corrected by correcting the position of the rolling-down cylinder by the automatic thickness control. A method of rolling a thick plate material that performs end-point target thickness correction and changes the start timing of the end-point target thickness correction, wherein a value obtained by differentiating the detected rolling load with respect to time becomes a first threshold value. The gist is that
Further, a method of manufacturing a thick steel plate according to another aspect of the present invention includes a rolling step of rolling a thick steel plate by the above-described method of rolling a thick steel plate.

  According to the thick plate rolling apparatus, the rolling method and the thick steel plate manufacturing method according to the present invention, the correction start timing of the end portion aimed thickness correction is appropriately determined for each thick plate, and the roll biting side end of the thick plate is determined. It is possible to provide a rolling device, a rolling method, and a method for manufacturing a thick steel plate, which can surely reduce the thickness deviation of the portion.

It is a schematic structure figure of the rolling device of the thick board concerning one embodiment of the present invention. FIG. 2 is a diagram illustrating a flow of a calculation process of a controller in the rolling device illustrated in FIG. 1. FIG. 2 is a diagram illustrating a control example by a controller in the rolling device illustrated in FIG. 1. It is a figure which shows the example of the edge part target thickness correction | amendment by the controller in the rolling mill concerning a comparative example. 5 is a graph showing a sheet thickness defect rate by a rolling method according to a comparative example and a sheet thickness defect rate by a rolling method according to an example of the present invention in comparison.

  The embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is based on the material, shape, structure, arrangement, etc. of the components. Is not specified as: The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

Hereinafter, a rolling device, a rolling method, and a method for manufacturing a thick steel plate of a thick steel plate according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a rolling device for a thick plate material according to an embodiment of the present invention. Is provided. The rolling mill 2 includes a pair of upper and lower work rolls 3 for rolling the thick plate material 20 and a pair of upper and lower backup rolls 4 supporting the work rolls 3. The rolling mill 2 is attached to a load cell (load detector) 5 for detecting a rolling load attached to the work roll 3 and the backup roll 4, and to a hydraulic press-down cylinder 6a for moving the positions of the work roll 3 and the backup roll 4. And a cylinder position detector 6b for detecting the position of the screw-down cylinder 6a.

The controller 9 includes a waiting gap control unit 10 that performs a waiting gap control, an automatic thickness control unit 11 that performs an automatic thickness control (abbreviated as AGC), and an end portion target thickness correction that performs an end portion target thickness correction. And a computer system. The waiting gap control, the AGC, and the end portion target thickness correction performed by the controller 9 are performed in accordance with arithmetic processing executed in the controller 9, that is, software.
For waiting gap control, AGC, and end target thickness correction, the controller 9 sends a target rolling load F ₀ , a set roll opening S ₀ , and a target rolling load from a process computer (P / C) 8 connected to the host computer 7. The mill constant K, the tuning rate C, the correction amount γ of the waiting gap control are input, the rolling load F detected by the load cell 5, and the position of the rolling cylinder (roll opening S) detected by the cylinder position detector 6b. Is entered.

As shown in FIG. 3, the waiting gap control by the waiting gap control unit 10 is performed for a first predetermined time α before the thick plate material 20 is engaged with the work roll 3 of the rolling mill 2 and after being engaged with the work roll 3. There until elapses, a control roll angle S from preset roll angle S ₀ screwing by γ correction amount described above. In this waiting gap control, before the AGC lock-on, the thick plate material 20 is bitten into the work roll 3 by the metal-in, and the oil in the press-down cylinder sinks due to the impact, thereby increasing the roll opening degree. Since the thickness of the plate material 20 becomes larger than the target thickness and becomes excessively thick, in order to prevent the thick plate material 20 from becoming excessively thick, the roll opening degree S must be changed during the first predetermined time α from the metal-in. from preset roll angle S ₀ so that screwing by γ correction amount described above. As shown in FIG. 3, the wait gap control ends at the end timing t1 when the first predetermined time α has elapsed since the metal-in. The first predetermined time α may be, for example, zero.

Further, the AGC by the automatic thickness control unit 11 is based on the rolling load F detected by the load cell 5 so that the thickness deviation ΔH from the target thickness H ₀ of the thick plate material 20 becomes zero so that the reduction cylinder 6 a It controls the position. More specifically, in AGC, the roll opening deviation from the set roll opening S ₀ is ΔS (ΔS = roll opening S−set roll opening S ₀ ), and the rolling load deviation from the target rolling load F _0. Where ΔF (ΔF = detected rolling load (actual rolling load) F−target rolling load F ₀ ) and the mill constant are K, the plate thickness deviation ΔH from the target plate thickness H ₀ shown in the following (1) is The position of the rolling-down cylinder 6a (the roll opening deviation ΔS, ie, the roll opening S) is controlled so as to be zero.
ΔH = ΔS + ΔF / K (1)
Since ΔH is 0, from equation (1),
ΔS = S−S ₀ = −ΔF / K = − (F−F ₀ ) / K (2)
By transforming equation (2),
S = S ₀ − (F−F ₀ ) / K (3)
Accordingly, the roll opening S (the position of the rolling cylinder) is determined by the set roll opening S ₀ from the process computer 8, the detected rolling load (actual rolling load) F from the load cell 5, and the target rolling load from the process computer 8. Based on F ₀ and the mill constant K from the process computer 8, control is performed according to the above equation (3).

As shown in FIG. 3, the AGC locks on at a start timing t2 at which a second predetermined time β has passed since the thick plate material 20 was bitten by the work roll 3 of the rolling mill 2 (metal-in). Start), and lock-off (end) when the AGC end time elapses from a metal-in (not shown). Start timing t2 of the AGC, in this embodiment, is set to a time when the rolling load detected by the load cell 5 (actual rolling load) F becomes the size of about 80% of the target rolling force F _0. The second predetermined time β is set to, for example, 0.08 seconds.

  Further, as shown in FIG. 3, the end target thickness correction by the end target thickness correction unit 12 is performed by sharply increasing the plastic constant of the thick plate material 20 from the start of the AGC to the lock-on of the AGC to the steady part. A change in the response of the AGC to the change occurs. That is, in the unsteady portion, the operation of the screw-down cylinder 6a in the opening direction is delayed from the setting, and the position (actual) of the screw-down cylinder 6a detected by the cylinder position detector 6b is shown in FIG. As shown in FIG. 3, the position is shifted from the position (setting) of the screw-down cylinder 6a set by the AGC. As described above, when the operation in the opening direction of the screw-down cylinder 6a is delayed from the setting, the plate thickness becomes excessively thin at the unsteady portion at the end of the thick plate material 20.

Therefore, during a certain end portion target thickness correction period for rolling the unsteady portion (Δt from a start timing t3 to an end timing t4 described later), the position of the press-down cylinder 6a by the AGC is corrected in the opening direction and the roll opening S To change.
Here, the start timing t3 of the end portion target thickness correction is, as shown in FIG. 3, a value of dF / dt obtained by differentiating the rolling load (actual rolling load) F detected by the load cell 5 with respect to the time t. This is the timing at which one threshold a is reached. In the present embodiment, the first threshold a is set to zero. Accordingly, the end target thickness correction is started at a start timing t3 at which the value of dF / dt obtained by differentiating the rolling load F detected by the load cell 5 with respect to time becomes zero.

  In the conventional method of rolling a thick plate disclosed in Patent Document 1, the start timing of the correction of the target thickness at the end portion performed after the AGC is locked on is set in advance by presetting constant values for each thickness and width of the thick plate. Was decided. That is, the correction start timing of the end portion target thickness correction is determined in advance by a constant value for each plate thickness and plate width. On the other hand, the rolling load at the end of the thick plate material varies variously for each pass and each material depending on the plate thickness, the amount of reduction, the biting speed, the equipment status, and the like. When the rolling load at the end of the thick plate material changes, the position of the unsteady portion changes due to the response delay of AGC, and the correction start timing of the end target thickness correction is uniformly determined in advance as in Patent Document 1. In such a case, the thickness deviation of the end of the thick plate material on the side of the roll biting may not be appropriately reduced.

  On the other hand, in the present embodiment, the start timing t3 of the end portion target thickness correction is, as shown in FIG. 3, the dF / d obtained by differentiating the rolling load (actual rolling load) F detected by the load cell 5 with respect to time. Since the value of dt is the timing at which the first threshold value a is reached, it is possible to cope with a change in the rolling load at the end of the thick plate material 20, and the start timing t3 of the end target thickness correction is appropriately set for each thick plate material 20. , And the thickness deviation at the end of the thick plate material 20 on the side where the roll bites can be reliably reduced.

  Also, the end timing t4 of the end portion aimed thickness correction is determined by the difference between the position of the screw down cylinder 6a detected by the cylinder position detector 6b and the position of the screw down cylinder 6a corrected by the end portion aimed thickness correction is equal to the second threshold value b. The timing is as follows. In the present embodiment, the second threshold value b is set to zero. Accordingly, the end target thickness correction ends when the deviation between the position of the pressing cylinder 6a detected by the cylinder position detector 6b and the position of the pressing cylinder 6a corrected by the end target thickness correction is zero or less, that is, zero. The process ends at timing t4.

Then, the correction amount Δh in the opening direction of the position of the rolling-down cylinder 6a in the end portion target thickness correction is determined based on the actual result of the rolling load F during the previous pass. Specifically, the peak value of the rolling load F in the previous pass is P ', the average value is P, the reference value is c (for example, 1.2), and the reference correction value stored in advance in the process computer 8 is When Δh ′ is set, the correction amount Δh is determined by the following equation (4).
Δh = Δh ′ × (P ′ / P−c + 1) (4)
The roll opening degree S determined by the waiting gap control by the waiting gap control unit 10 of the controller 9, the AGC by the automatic thickness control unit 11, and the end target thickness correction by the end target thickness correction unit 12 is determined by the controller 9. Then, the servo valve 13 is controlled by the command of the servo amplifier 13 to control the position of the screw-down cylinder 6a by controlling the amount of pressure oil in the screw-down cylinder 6a from the hydraulic pressure source 15.

Next, with reference to FIG. 2, the flow of the arithmetic processing of the controller 9 in the rolling mill 1 shown in FIG. 1 will be described.
First, in step S101, the waiting gap control unit 10 of the controller 9 starts the above-described waiting gap control before the thick plate material 20 bites between the work rolls 3 of the rolling mill 2, and proceeds to step S102.
Next, in step S102, the waiting gap control unit 10 determines whether or not the thick plate material 20 has caught between the work rolls 3, that is, whether or not metal in has occurred.

If it is determined in step S102 that there is no metal-in, the wait gap control unit 10 repeats the determination. If it is determined that metal-in has occurred in step S102, the process proceeds to step S103.
Then, in step S103, the wait gap control unit 10 determines whether the first predetermined time α has elapsed since the metal-in.
Next, when determining in step S103 that the first predetermined time α has not elapsed since the metal-in, the wait gap control unit 10 repeats the determination. If it is determined that the predetermined time α has elapsed, the process proceeds to step S104, and the wait gap control is ended as the end timing t1 of the wait gap control.

Thereafter, in step S105, the automatic thickness control unit 11 of the controller 9 determines whether or not a second predetermined time β has elapsed since the metal-in.
Next, when the automatic thickness control unit 11 determines in step S105 that the second predetermined time β has not elapsed since the metal-in, the determination is repeated, and in step S105, the metal-in If it is determined that the second predetermined time β has elapsed, the process proceeds to step S106, and the above-mentioned AGC is started (locked on) as the AGC start timing t2.

Thereafter, in step S107, the end target thickness correction unit 12 of the controller 9 sets the value of dF / dt obtained by differentiating the rolling load (actual rolling load) F detected by the load cell 5 with respect to time to a predetermined first threshold value a ( In the case of the present embodiment, it is determined whether or not zero has been reached.
Then, when it is determined in step S107 that the value of dF / dt is not equal to the predetermined first threshold a in step S107, the end target thickness correction unit 12 repeats the determination. When it is determined that the value of / dt has reached the predetermined first threshold value a, the process proceeds to step S108, and the above-described target edge thickness correction is started as the start timing t3 of the target edge thickness correction.

Next, in step S109, the end aimed thickness correction unit 12 determines the deviation between the position of the screw down cylinder 6a detected by the cylinder position detector 6b and the position of the screw down cylinder 6a corrected by the end aim thickness correction in the second direction. It is determined whether or not the value is equal to or less than a threshold value b (zero in the present embodiment).
Then, when it is determined in step S109 that the above-described deviation is not smaller than or equal to the second threshold value b, the end portion target thickness correction unit 12 repeats the determination, and in step S109, the above-described deviation is reduced to the second threshold value b. If it is determined that the difference has become less than the above, the process proceeds to step S110, and the above-described target edge thickness correction is ended as end timing t4 of the target edge thickness correction.

Thereafter, in step S111, the automatic thickness control unit 11 of the controller 9 determines whether the AGC end time has elapsed since the metal-in.
When the automatic thickness control unit 11 determines in step S111 that the AGC end time has not elapsed since the metal-in, the automatic thickness control unit 11 determines that the AGC end time has elapsed since the metal-in in step S111. In this case, the process proceeds to step S112, and the above-mentioned AGC is ended as an AGC end timing.
Thereby, the arithmetic processing of the controller 9 ends.
Then, after passing through a rolling step of rolling the thick plate material 20 by the above-described method of rolling a thick plate material, a cutting step of cutting the thick plate material 20 to a predetermined length is performed, thereby manufacturing a thick steel plate. Here, “thick steel plate” refers to a steel plate having a thickness of 4.5 mm or more.

  As described above, according to the rolling device 1 for the thick plate material 20, the method for rolling the thick plate material, and the method for manufacturing the thick steel plate according to the embodiment of the present invention, the start timing t3 of the end portion target thickness correction is illustrated in FIG. As described above, since the value of dF / dt obtained by differentiating the rolling load (actual rolling load) F detected by the load cell 5 with respect to time is the predetermined first threshold value a, the rolling load at the end of the thick plate material 20 is obtained. Can be adapted to the change of the thickness, and the start timing t3 of the end portion aimed thickness correction is appropriately determined appropriately for each thick plate material 20 to reliably reduce the thickness deviation of the end portion of the thick plate material 20 on the side where the roll bites. Can be.

Further, since the first threshold value a is zero, when the rolling load (actual rolling load) F detected by the load cell 5 reaches a local maximum value, the end portion thickness correction is started, and the reduction cylinder 6a of the rolling cylinder 6a is started. An opening delay can be reliably avoided.
Also, the end timing t4 of the end portion aimed thickness correction is determined by the difference between the position of the screw down cylinder 6a detected by the cylinder position detector 6b and the position of the screw down cylinder 6a corrected by the end portion aimed thickness correction is equal to the second threshold value b. Since the timing is as follows, the thickness deviation at the roll-engaging side end of the thick plate material 20 can be reliably reduced by controlling the required minimum end thickness correction.

Further, since the correction amount Δh in the end portion target thickness correction is determined based on the actual result of the rolling load in the previous pass, the correction amount Δh in the end portion target thickness correction can be appropriately set.
The embodiments of the present invention have been described above, but the present invention is not limited thereto, and various changes and improvements can be made.
For example, the first threshold a is not limited to zero and may be 0 to 50t.
Also, the second threshold value b is not limited to zero, and may be 0 to 50 μm.

In order to verify the effects of the present invention, the sheet thickness defect rate was investigated between a case where a thick plate was rolled by the rolling method of the present invention and a case where a thick plate was rolled by the rolling method of the comparative example.
The rolling method of the example of the present invention is a rolling method shown in FIGS. 1 to 3, wherein a start timing t3 of the end portion target thickness correction is set to a dF / dt value obtained by differentiating the rolling load F detected by the load cell 5 with respect to time t. Is a timing at which a predetermined first threshold value a (zero) is reached.
On the other hand, the rolling method of the comparative example has the same basic configuration as the rolling method of the present invention example shown in FIGS. 1 to 3, but as shown in FIG. 'Is set as the timing immediately after the start timing t2 of the automatic thickness control.

FIG. 5 shows the results of the examination of the sheet thickness defect rate.
Referring to FIG. 5, the sheet thickness defect rate by the rolling method of the present invention is reduced to about 42% of the sheet thickness defect rate by the rolling method of the comparative example. This is because, in the rolling method of the comparative example, the start timing t3 ′ of the end portion target thickness correction is fixed as the timing immediately after the start timing t2 of the automatic thickness control in all the thick plates, and the thickness of the thick plate is fixed. Is often too thin. On the other hand, in the rolling method of the example of the present invention, the start timing t3 of the end portion target thickness correction is set to a dF / dt value obtained by differentiating the rolling load F detected by the load cell 5 with respect to time t by a predetermined first threshold value. The timing of a (zero) is varied for each thick plate material, and there are few cases where the thickness of the thick plate material becomes excessively thin.

DESCRIPTION OF SYMBOLS 1 Rolling device 2 Rolling machine 3 Work roll 4 Backup roll 5 Load cell (load detector)
6a Roll-down cylinder 6b Cylinder position detector 7 Host computer 8 Process computer 9 Controller 10 Wait gap control unit 11 Automatic thickness control unit 12 Edge target thickness correction unit 13 Servo amplifier 14 Servo valve 15 Hydraulic source 20 Thick plate material

Claims (7)

After the thick plate is caught between the rolls, based on the rolling load detected by the load detector, the position of the rolling-down cylinder is controlled so that the plate thickness deviation from the target plate thickness of the thick plate becomes zero. An automatic thickness control unit for performing automatic thickness control, and after starting the automatic thickness control by the automatic thickness control unit, the plastic constant of the thick plate material from the lock-on of the automatic thickness control to the steady part. The roll opening is changed by correcting the position of the rolling-down cylinder by the automatic thickness control during the fixed end aim thickness correction period in which the unsteady part where the response delay of the automatic thickness control occurs due to a sudden change is rolled. An end target thickness correction unit for performing end target thickness correction to
The start timing of the end portion target thickness correction is a timing at which a value obtained by differentiating the detected rolling load with respect to time becomes a first threshold value of 0 to 50 t ,
The end timing of the end portion aimed thickness correction is defined as a deviation between the position of the screw down cylinder detected by the cylinder position detector and the position of the screw down cylinder corrected by the end portion aimed thickness correction is equal to or less than a second threshold value. A thick plate rolling apparatus, wherein the timing is set to 50 μm . The said 1st threshold value is 0t , The rolling apparatus of the thick plate material of Claim 1 characterized by the above-mentioned. 3. The thick plate rolling apparatus according to claim 1, wherein a correction amount in the end portion target thickness correction is determined based on a result of a rolling load in a previous pass. After the thick plate is caught between the rolls, based on the rolling load detected by the load detector, the position of the rolling-down cylinder is controlled so that the plate thickness deviation from the target plate thickness of the thick plate becomes zero. Automatic thickness control and, after starting the automatic thickness control, a response delay of the automatic thickness control with respect to a sudden change in the plastic constant of the thick plate material from the lock-on of the automatic thickness control to a steady state. In a constant target thickness correction period for rolling the unsteady portion where the unsteady portion occurs, the target thickness correction is performed by correcting the position of the reduction cylinder by the automatic thickness control and changing the roll opening degree. So,
The start timing of the end portion target thickness correction is a timing at which a value obtained by differentiating the detected rolling load with respect to time becomes a first threshold value of 0 to 50 t ,
The end timing of the end portion aimed thickness correction is defined as a deviation between the position of the screw down cylinder detected by the cylinder position detector and the position of the screw down cylinder corrected by the end portion aimed thickness correction is equal to or less than a second threshold value. A method for rolling a thick plate material, wherein the timing is set to 50 μm . The method according to claim 4 , wherein the first threshold value is 0t . The method according to claim 4 or 5 , wherein the correction amount in the end portion target thickness correction is determined based on a result of a rolling load in a previous pass. A method for manufacturing a thick steel plate, comprising a rolling step of rolling a thick steel plate by the method for rolling a thick steel plate according to any one of claims 4 to 6 .

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