JPH07188780A - Method for predicting meandering of strip in strip continuous treatment device and method for observing meandering - Google Patents

Abstract

PURPOSE:To sound the alarm in the case of exceeding the preset meandering value and to correct to the normal position on by using the specific formulas to a meandering condition the downstream side of a detector from the detected depth of edge wave of a strip with the meandering detector and this estimated position and predicting. CONSTITUTION:In a continuous treatment apparatus of the strip, the formula I showing an elastic deformation in the traversing direction of the strip running between rolls, the formula II showing a shifting in the traversing direction of the strip on the roll and the formula III showing the meandering correcting mechanism with a crown roll under consideration of the shape of the strip are used. Then, the meandering condition of the strip on the downstream side of the meandering detector is predicted by using the output of the meandering detector placed in the line as the boundary condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip meandering prediction method and a meandering monitoring method in a continuous strip processing apparatus.

[0002]

2. Description of the Related Art In a continuous strip processing apparatus for carrying out heat treatment and surface treatment by continuously transporting strips of thin steel plates, plastic films, etc. by a number of transport rolls, strip shape defects and treatments before treatment are performed. A meandering phenomenon in which the strip deviates from the center of the transport path line often occurs due to a defective shape of the strip, a defective connection of the strip, and the like. Such meandering interferes with the normal conveyance of the strip, and if the meandering amount exceeds a certain value, various problems such as breakage of the strip may occur and the conveyance may become impossible.

Therefore, various methods for correcting the meandering of the strip have been conventionally devised in a continuous strip processing apparatus. The two typical methods are as follows.

The first method is a method of correcting meandering by using a transport roll, which is generally called a crown roll, in which the radius of the central portion of the transport roll is larger than that of the end portion. FIG. 9 is a view showing a meandering correction mechanism by a crown roll. As shown by a solid line in the figure, when the strip 10 enters the crown roll 11 in a meandering state, the entering angle β of the strip with respect to the crown roll 11 is a right angle. No longer. For this reason,
As the strip 10 is conveyed, the meandering is corrected because the strip 10 is brought by the central portion of the roll 11 as shown by a broken line in the drawing. In such a correction method, when the difference between the radius of the center of the roll 11 and the radius of the end is increased, the meandering correction capability is increased. Since there is a tendency for buckling deformation to occur and product quality to be impaired, there is a constraint that the difference in radius should be as small as possible. This correction method cannot be expected to have a large meandering correction ability with one roll, but since it is a method that can be realized at a relatively low cost, it is effective when applied to a continuous processing apparatus having a large number of transfer rolls such as a continuous annealing line. Can be expected.

The second method is a method of performing meandering correction using a strip meandering correcting device which is a combination of a conveying roll generally called a steering roll and a function of rotating the conveying roll. FIG. 10 and FIG. 11 are views showing one configuration example of the steering roll. In these devices, the roll 14 is fixed and supported on a pedestal 13 that tilts around a fulcrum 12 as shown in the drawing, and the roll is 14
The strip 10 is tilted together with the pedestal 13 in a state of being orbited, and the tilting operation changes the width-direction passing position of the strip 10. For example, in the over-aging furnace of the continuous annealing line, as shown in FIG. 12, the steering rolls (upstream side 1, downstream side 2) are arranged at a ratio of 1 to 5 to 10 conveyance rolls together with the meandering detectors 3 and 4. Is installed. In such a configuration, first, the actual meandering is detected by the meandering detectors 3 and 4, and the detection values of the meandering detectors 3 and 4 and the center of the pass line are detected for each steering roll 1 and 2. Feedback control is performed in which the deviations are calculated by the calculation devices 5 and 6 and the deviations are input to the steering roll tilting device 15, and the steering rolls 1 and 2 are tilted so that the deviation becomes zero.

[0006]

By the way, the meandering amount of the strip normally increases as it goes downstream of the pass line. Therefore, when the amount of meandering is small, it is possible to correct the meandering by the steering device on the downstream side, but when the amount of meandering is large, the capability of correcting the meandering by the steering device on the downstream side is insufficient and the meandering correction cannot be performed sufficiently. There were many. Furthermore, in the process of a certain meander propagating to the downstream side, the meandering amount becomes excessive before the meandering reaches the steering device on the downstream side, and the strip rolls out from the roll between the upstream and downstream steering rolls or the strip breaks. An accident such as the above occurred, which was a cause of greatly reducing productivity.

As an example of this, the case of the continuous annealing line shown in FIG. 12 will be described. The strip thickness is 1.0 mm, the width is 1500 mm, and the conveying speed is 5 m / s.
Under the condition that the maximum steering meandering correction amount of the steering roll is 100 mm and the roll width is 2000 mm, the meandering condition of the strip is as shown in FIG. In the figure, the solid line A
Is the meandering condition when the steering roll is used, the dotted line B is the meandering condition when the steering roll is not used, the one-dot chain line C is the amount of meandering that rolls out when the strip width is 1500 mm, and the two-dot chain line D is In the case where the strip width is 1800 mm, the meandering amount at which roll-out occurs is indicated by, the position of the steering roll 1 on the upstream side, and the position of the steering roll 2 on the downstream side. As shown in the figure, on the entrance side of the steering roll 1, the meandering amount is as small as 40 mm. Looking at the meandering situation when the steering roll 1 on the upstream side is not used, the meandering amount tends to increase toward the downstream side of the pass line as described above, and the meandering amount on the entrance side of the steering roll 2 on the downstream side tends to increase. Is as large as 220 mm, which is in a dangerous state on the threaded plate just before the rollout occurs. Next, looking at the meandering situation when the upstream steering roll 1 is used in the passing of the same strip, the upstream steering roll 1
The meandering amount on the entrance side is 40 mm, and the maximum meandering correction ability is 10
In the steering roll 1, the strip is meandered in the center of the pass line because it is sufficiently smaller than 0 mm. However, the meandering amount tends to increase again on the downstream side of the upstream steering roll 1, and the meandering amount on the inlet side of the downstream steering roll 2 is 180 mm. Since the maximum meandering correction amount of the downstream side steering roll 2 is 100 mm, which is the same as that on the upstream side, its meandering correction capacity is insufficient, and the steering roll 2 has an output side of 80 m.
There is a meandering of m.

Further, in the above example, the strip width is 1
When it is 800 mm, the strip meandering amount between the steering rolls 1 and 2 is the roll-out limit of 10 regardless of whether the upstream steering roll 1 is used or not.
Since it exceeds 0 mm, rollout occurs.

When the meandering exceeding the meandering correction capability of the steering roll as in the above example occurs, the line operator takes measures such as increasing the line tension and decreasing the strip conveying speed to expand the meandering. To prevent the However, the operator can only know the meandering condition on the steering rolls on which the meandering detector is installed, and has no means for knowing the meandering condition between the steering rolls. Therefore, the rollout occurs between the steering rolls. When such a large meandering occurs, the above-described operation for preventing the meandering expansion cannot be performed, and an accident such as a strip breakage often occurs.

To solve such a problem, a large number of steering rolls are installed in the line to shorten the distance between the steering rolls, and a large number of meandering detectors are installed in the line to check the meandering condition between the steering rolls. Although it may be possible to measure, the steering rolls and the meandering detectors are expensive, so that the number of installations is limited. Further, when the above-mentioned equipment is newly added to the existing line, there are restrictions on the installation location and the like, and it is currently difficult to solve the above problem.

The present invention predicts a meandering condition between steering rolls, which cannot be known at present, or prevents a rollout between steering rolls from occurring, and a strip meandering prediction method and meandering. It is intended to provide a monitoring method.

[0012]

In describing the present invention, a method for analyzing and predicting the meandering condition between the steering rolls in a strip continuous processing line having a plurality of steering rolls will be described. The analysis in the present invention is to obtain the temporal change of the meandering of the strip at a position of a certain transport roll on the line, which is a model equation representing the lateral elastic deformation of the strip traveling between rolls. 1), the following equation (2), which is a model equation representing the lateral movement of the strip on a certain roll,
Also, it is obtained by solving the following equation (3), which is a model equation representing the meandering correction mechanism by the crown roll in consideration of the strip shape.

[0013]

[Equation 4]

Where K ² = T / EI x: length in the pass line direction [m] y: meandering amount of strip on roll [m] E: Young's modulus of strip T: line tension [N] I: of strip second moment ^{[m 4] I = hW 3} /12 h: thickness of the strip [m] W: strip width [m]

[0015]

[Equation 5]

However, t: time [sec] V: strip transport speed [m / sec] θ _R : roll tilt angle [rad]

[0017]

[Equation 6]

However, H: central flat portion length of the crown roll [m] α: taper portion angle of the crown roll [rad] m: constant M: depth difference of the ear waves existing at the widthwise end portions of the strip [M] M = M _Dr −M _Op (when the meandering of the strip toward the processing device driving side is a positive value) M _Dr : depth of the ear wave existing at the processing device driving side strip end [m] M _Op : Depth of the ear wave existing at the end of the strip on the processor side [m]

That is, the above formula (1) is derived by regarding the strip running between the transport roll i and the transport roll i + 1 as an elastic body having tension T in the longitudinal direction. Further, the above formula (2) is applied to a roll having a strip having a transport speed V and a strip having a slope of dy / dx in the pass line direction when the roll has a slope of θ _{R in} the vertical direction of the pass line. It is an expression representing a lateral movement. Further, the above formula (3) is a formula representing a meandering correction mechanism by a crown roll, and a portion excluding shape-defective portions such as ear waves existing at both ends of the strip from the width W of the strip is a virtual strip. Is modeled as an imaginary roll tilt angle θ _R that acts in a direction that corrects this when the center of the imaginary strip deviates from the center of the pass line. The constant m depends on the frictional force between the roll and the strip and is a constant given by the surface roughness of the roll, the surface roughness of the strip, the coefficient of friction between the roll and the strip, and the line tension.

When the rolls i and i + 1 are defined as shown in the following equation (4), the equation of motion for lateral movement of the strip shown in the following equation (5) is obtained from the above equations (1) to (3). .

[0021]

Y (x = 0) = y _i θ _R (x = 0) = θ _Ri y (x = L) = y _{i + 1} θ _R (x = L) = θ _{Ri + 1} (4) However, y _i : deviation from the pass line of the strip in roll i [m] θ _Ri : tilt angle of the roll i [rad] y _{i + 1} : deviation from the pass line of the strip in roll i + 1 [m] θ _{Ri + 1} : Tilt angle [rad] of roll i + 1 L: Distance [m] between roll i and roll i + 1

[0022]

[Equation 8]

Here, a _{1 to} a ₆ are T, E, and
It is a function of W, h, V, and L. When the above equation (5) is discretized with the forward difference by the time increment Δt with respect to the time t and the displacement y, the following equation (6) is obtained.

[0024]

Y _{i + 1} (j + 2) = b ₁ y _{i + 1} (j + 1) + b ₂ y _{i + 1} (j) + b ₃ y _i (j + 1) + b ₄ y _i (j) + B ₅ (6) However, y ₁ (j): deviation from the pass line of stop at roll i or less at time step j In this equation, b _{1 to} b ₅ are T, E, W, respectively.
h, V, L, θ _Ri , θ _{Ri + 1} , and time increment Δ during discretization
It is a function of t. Further, j, j + 1, j + 2 indicate time steps, and y _i (j) is at time step j,
The deviation from the pass line center of the strip on roll i is shown.

Further, the strip positions y _IN and Y _OUT on the entrance side and the exit side of the steering roll are expressed by the following equation (7) when the meandering correction amount given by the steering roll is Δy.

[0026]

[Mathematical formula-see original document] y _OUT = y _IN + Δy (7) where y _IN : strip position on steering roll entry side [m] y _OUT : strip position on steering roll exit side [m] Δy: steering roll Therefore, the meandering correction amount [m] given by is always measured on the certain roll i by the meandering detector, and y _i (j) and y _i (j +
1) is known, and the roll n (n = i +) on the downstream side is known.
1, i + 2, ...), appropriate initial conditions y _n (j),
Given y _n (j + 1), using equations (6) and (7), meandering y _n on the downstream roll n at time j + 2
(J + 2) can be calculated sequentially.

Further, by measuring and recording the depth and position of the shape-defective portion such as an ear wave existing at both ends in the width direction of the strip on the roll i, or on the upstream side thereof, on each roll n on the downstream side. The shape of the strip at can be obtained, and an even more accurate analysis can be performed.

In the strip meandering prediction method according to the present invention, since the strip shape can be estimated only from the output of the meandering detector, the method will be described below. As shown in FIGS. 12 and 13, the strip meandering is once corrected by the upstream side steering roll 1 and then increases again at the downstream side, and the meandering directions coincide. That is, when paying attention to a certain portion of the strip being conveyed, that portion tends to always meander in the same direction on the conveying rolls in the line. This is due to the fact that the strip is conveyed downstream in the line while the shape defect of the strip that induces meandering is maintained.

In consideration of the above points, conversely, by measuring the meandering condition on a certain roll, it is possible to estimate the depth and the position of a defective shape portion such as an ear wave existing in the strip passing through the roll. is there. In the present invention, the depth and position of the ear wave existing in the strip are estimated by the following equation (8). That is, when a meandering value of y _i is observed when a certain portion of the strip passes over a certain roll, an ear wave having a depth of | k _yi | at the end of the strip in the same direction as the meandering. Is modeled as existing at that site.

[0030]

[Equation 11] M _Dr = | ky _i |, M _Op = 0 (0 < y _i ) ... (8) M _Dr = 0, M _Op = | ky _i | (0> y _i ) However, the line drive side direction Is a positive value, and M _{Dr is} the depth of the ear wave existing at the strip end on the line driving side [m] M _{Op is} the depth of the ear wave existing at the strip end on the line operating side [m] k: Correction coefficient By the above method, it is possible to estimate the time change of the meandering occurring on the downstream side of the meandering detector from the time change of the meandering detector output without adding a new device such as a strip shape meter in the line. .

Although the above example predicts the depth and position of the strip's ear waves based on the meander detector output, a strip profilometer is placed upstream of the meander detector, which results in more strip. It is possible to measure the depth and the position of the ear wave that occurs in the, and to estimate the time change of the meandering occurring on the downstream side of the meandering detector from the time change of the meandering detector output. It should be noted that the analysis in the present invention may of course be performed by using a processing device exclusively. In addition, the strip meandering prediction method described above is used to predict the strip meandering condition downstream of the meandering detector, and when the predicted meandering amount exceeds a specified value, an alarm is issued and the operator is alerted. Urge.

[0032]

By using the above-mentioned method, it is possible to obtain a strip meandering state between the steering rolls, which has not been obtained so far. At this time, when the amount of strip meandering between steering wheels exceeds a certain value, an alarm is issued and the line operator is alerted to increase the line tension and decrease the strip transport speed more quickly than before. Therefore, it becomes possible to prevent accidents such as rollout and strip breakage from occurring. It should be noted that the measures for preventing the meandering expansion, such as the increase of the line tension and the decrease of the strip transport speed, may be automatically performed by the arithmetic unit or the like at the same time as the alarm is issued.

[0033]

Embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following examples. FIG. 1 is a schematic diagram showing an example of a device configuration in a continuous annealing line overaging furnace to which a method according to an embodiment of the present invention is applied, in which reference numeral 1 is an upstream side steering roll,
2 is a downstream steering roll, 3 and 4 are meandering detectors,
Reference numerals 5 and 6 are arithmetic devices for tilting the steering rolls, 7 is a transport roll, 9 is an arithmetic device for estimating the shape of the strip, meandering analysis and issuing an alarm according to the present invention, and 10 is a strip.

The meandering detectors 3 and 4 are disposed on the output side of the upstream side steering roll 1 and the downstream side steering roll 2, respectively. The arithmetic unit 9 constantly collects information such as the amount of meandering on the output side of the steering roll 1 and the amount of steering operation, as well as the dimensions of the strip, the line tension, the strip transport speed, and the above equations (1) to (8). Is calculated to analyze the shape of the strip and the meandering condition between the steering rolls 1 and 2, and when the meandering amount exceeds the meandering correction capability of the downstream side steering roll 2, a warning is issued. Has been done. The steering rolls 1 and 2 and the transport roll 7 are all crown rolls, and their shapes are known.

FIG. 2 is a characteristic diagram showing the meandering measurement value and the meandering amount analysis value according to the embodiment of FIG. The implementation conditions are: strip thickness 1.4 mm, width 900 mm, transport speed 2 m / sec, maximum amount of steering roll meandering correction 1
The width is 00 mm and the roll width is 2000 mm. In FIG. 2, the horizontal axis represents time, and the vertical axis represents strip deviation from the center of the pass line, that is, the amount of meandering. In the figure, the thin line E and the thick line F indicate the measured value and the analyzed value of the meandering amount on the entrance side of the downstream side steering roll 2, respectively.
The measured value of the meandering amount on the entrance side of the downstream side steering roll 2 can be obtained from the equation (7). According to the figure, it can be seen that the analysis of the meandering condition of this embodiment is performed accurately.

FIG. 3 is a schematic view showing an example of the construction of an apparatus in a continuous annealing line overaging furnace to which a method according to another embodiment of the present invention is applied. In this embodiment, the meandering detectors 3, 4
A strip shape meter 8 is disposed upstream of the strip shape meter 8. Since the strip shape meter 8 measures the depth of the ear wave of the strip and its position, the arithmetic unit 9 determines the depth of the ear wave of the strip and Operation to find its position,
That is, the calculation process of the equation (8) is omitted, and other than that, the device operates similarly to the device of FIG. 1, and the meandering amount actual measurement value and the meandering analysis value are as shown in FIG.

5 to 7 show examples in which the meandering amount between the steering rolls 1 and 2 in the apparatus of FIG. 1 or FIG. 3 becomes excessive and an alarm is actually issued. The present embodiment is an example of meandering generated by the seismic waves of the strip, and its implementation conditions are a strip thickness of 0.8 mm and a width of 1600.
mm, the conveying speed thereof is 5 m / sec, the maximum meandering correction amount of the steering roll is 100 mm, and the roll width is 2000 mm. 5 to 7, the horizontal axis represents the length in the pass line direction, and the vertical axis represents the deviation from the center of the pass line, that is, the amount of meandering. The symbol Δ in the figure indicates the position of the transport roll, and the symbol indicates the position of the steering roll. A solid line G in the figure shows the meandering state between the steering rolls 1 and 2 obtained in this embodiment. The alternate long and short dash line H indicates the meandering allowable value of 120 mm when the strip width is 1600 mm, and an alarm is issued when the meandering amount exceeds this value. The chain double-dashed line I in the figure shows the mean value of meandering amount of 200 mm that causes rollout when the strip width is 1600 mm. If the meandering amount exceeds this value, an accident such as rollout or strip breakage is expected. It The strip transport direction is the direction of the arrow in the figure.

FIG. 5 is a characteristic diagram showing the meandering situation at the moment when the alarm is issued. An alarm was issued because the meandering between the steering rolls 1 and 2 drastically expanded due to an ear wave generated in the middle of the strip longitudinal direction and exceeded the allowable meandering value of 120 mm. FIG. 6 is a characteristic diagram showing the meandering situation when no countermeasure is taken after the alarm is issued.
The meandering amount on the downstream side of the steering roll 2 is 160 m
It has expanded to m and is on the verge of rollout. Further, after the meandering correction, the amount of meandering on the output side of the downstream side steering roll 2 is still 60 mm, which is a very dangerous state in operation. When the present embodiment is not applied, the line operator performs an operation such as an increase in the line tension and a decrease in the strip transfer speed only in such a state, so that the operation is too late, and the rollout and the strip are performed. It often causes accidents such as breakage.

FIG. 7 is a characteristic diagram showing a meandering situation when an operator operates to increase the line tension and decrease the strip transport speed after the alarm is issued. Since the operator quickly took appropriate measures, the meandering was reduced, and the meandering amount at the inlet side of the downstream side steering roll 2 was 110 mm, which is within the safe operating range.

The above characteristics were similarly recognized not only in the overaging furnace of the continuous annealing line but also in other places. FIG. 8 is a schematic diagram of a continuous annealing line, but as a result of testing the inlet side loop tower portion, the heating zone portion, the cooling zone portion, and the outlet side loop tower portion in the same figure, regardless of the strip conveying speed, Rollout due to the meandering of the strip during strip size change, line tension change, strip transfer speed change, and annealing temperature change,
Accidents such as strip breaks can be reduced to about 1/4 of the conventional level, and the line operating efficiency has improved by about 5%.

Further, the present invention can be applied to all equipment adopting a plurality of steering rolls in the meandering control of the strip. Therefore, the present invention is not limited to the continuous annealing line, and the continuous molten zinc plating line, It can be applied to strip coating and printing lines.

[0042]

As described above, according to the present invention, it is possible to easily grasp the meandering condition between the steering rolls, which could not be known in the past, and to monitor the condition so that the meandering condition can be improved. Since it is possible to quickly prevent the meandering expansion, it is possible to prevent the occurrence of accidents such as roll-out and strip breakage.

[Brief description of drawings]

FIG. 1 is a schematic view showing a device configuration in a continuous annealing line overaging furnace to which a method according to an embodiment of the present invention is applied.

FIG. 2 is a characteristic diagram showing a meandering amount actual measurement value and a meandering amount analysis value according to the present embodiment on the downstream steering roll entrance side in the configuration of FIG.

FIG. 3 is a schematic view showing one device configuration in a continuous annealing line overaging furnace to which a method according to another embodiment of the present invention is applied.

4 is a characteristic diagram showing a meandering amount actual measurement value and a meandering analysis value according to the present embodiment on the downstream steering roll entrance side in the configuration of FIG. 3. FIG.

5 is a characteristic diagram showing a meandering condition between the steering rolls at the moment when an alarm is actually issued in the embodiment of FIG. 1 or FIG.

FIG. 6 is a characteristic diagram showing a meandering situation when an appropriate measure is not taken in spite of an alarm being issued in the embodiment of FIG. 1 or FIG. 3.

FIG. 7 is a characteristic diagram showing a meandering situation in a case where an appropriate measure is taken immediately after an alarm is issued in the embodiment of FIG. 1 or FIG.

FIG. 8 is a schematic view showing the entire continuous annealing line.

FIG. 9 is a diagram showing a meandering correction mechanism using a crown roll.

FIG. 10 is a diagram showing one device configuration of a steering roll.

FIG. 11 is a diagram showing a device configuration of a steering roll.

FIG. 12 is a schematic diagram showing the arrangement of conventional steering rolls in a continuous annealing line overaging furnace.

13 is a characteristic diagram showing a strip meandering condition in the configuration of FIG.

[Explanation of symbols]

1: Upstream side steering roll 2: Downstream side steering roll 3,4: Meandering detector 5,6: Steering roll tilting computing device 7: Conveying roll 8: Strip shape meter 9: Meandering analysis and alarm issuing computing device 10: Strip 11: Crown roll 12: Steering roll tilting fulcrum 13: Steering roll stand 14: Roll 15: Steering roll tilting device Solid line A: Meandering situation when steering roll is used Broken line B: Meandering when the tearing roll is not used Situation One-dot chain line C: Meandering amount that rolls out when the strip width is 1500 mm Two-dot chain line D: Meandering amount that rolls out when the strip width is 1800 mm Fine line E: Meandering amount measured value on the steering roll 2 entry side Thick line F: On the entry side of steering roll 2 Line analysis value Solid line G: Meandering state between the steering rolls 1 and 2 obtained in the present example Dash-dotted line H: Permissible meandering when strip width is 1600 mm Two-dot chain line I: Rollout when strip width is 1600 mm The amount of meandering that occurs

Claims (5)

[Claims] 1. A continuous strip processing apparatus, an expression representing a lateral elastic deformation of a strip running between rolls,
Using the formula that represents the lateral movement of the strip on the roll and the formula that represents the meandering correction mechanism by the crown roll that considers the shape of the strip, the output of the meandering detector arranged in the line is used as the boundary condition. , A strip meandering prediction method characterized by predicting a strip meandering condition downstream of a meandering detector. 2. An equation representing the lateral elastic deformation of the strip traveling between the rolls is the following equation (1), and an equation representing the lateral movement of the strip on the roll is the following equation (2):
3. The strip meandering prediction method according to claim 1, wherein the equation representing the meandering correction mechanism by the crown roll in consideration of the shape of the strip is the following equation (3). [Equation 1] However, K ² = T / EI x: length in the pass line direction [m] y: meandering amount of strip on roll [m] E: Young's modulus of strip T: line tension [N] I: cross section of strip moment ^{[m 4] I = hW 3} /12 h: thickness of the strip [m] W: strip width [m] [Equation 2] However, t: time [sec] V: strip transport speed [m / sec] θ _R : roll tilt angle [rad] However, H: central flat portion length of the crown roll [m] α: taper portion angle of the crown roll [rad] m: constant M: difference in depth of ear waves existing at the widthwise end portions of the strip [m] M = M _Dr −M _Op (when the meandering of the strip toward the processing device driving side is a positive value) M _Dr : Depth of ear wave existing at the end of the processing device driving side strip [m] M _Op : Processing device Depth of ear wave existing at the end of the operating strip [m] 3. The depth of the ear wave of the strip and its position are estimated based on the meandering amount and the meandering direction detected by the meandering detector, and the meandering prediction method of the strip according to claim 1 downstream of the meandering detector. A method of predicting the meandering of a strip, characterized by predicting the meandering condition of the strip in. 4. The depth of an ear wave generated in the strip and its position are measured by a strip shape meter disposed upstream of the meandering detector, and the downstream of the meandering detector is determined by the strip meandering prediction method according to claim 1. A method of predicting the meandering of a strip, characterized by predicting the meandering condition of the strip in. 5. The strip meandering prediction method according to any one of claims 1 to 4 is used to predict the strip meandering condition downstream of the meandering detector, and when the predicted meandering amount exceeds a predetermined value. A method of monitoring meandering of a strip, which is characterized by issuing an alarm and calling attention to an operator of the apparatus.