JP2906964B2 - Strip meandering prediction method and meandering monitoring method in strip continuous processing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a meandering prediction method and a meandering monitoring method for a strip in a continuous strip processing apparatus.

[0002]

2. Description of the Related Art In a continuous strip processing apparatus in which a strip such as a thin steel plate or a plastic film is continuously transported while being supported by a large number of transport rolls and subjected to heat treatment or surface treatment, a strip shape defect before treatment or treatment is performed. A meandering phenomenon in which the strip deviates from the center of the transport path line often occurs due to a poor shape of the strip occurring therein, and further, a poor connection of the strip. Such meandering hinders normal transport of the strip. If the meandering amount exceeds a certain value, various problems such as breakage of the strip may occur, and the transport may be impossible.

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

[0004] The first method is a method in which the meandering correction is performed using a transport roll generally called a crown roll, the radius of which is larger at the center of the transport roll than at the end. FIG. 9 is a diagram showing a meandering correction mechanism using a crown roll. As shown by a solid line in FIG. 9, when the strip 10 enters the crown roll 11 in a meandering state, the angle β of the strip with respect to the crown roll 11 becomes a right angle. No longer. For this reason,
As the strip 10 is conveyed, the meandering is corrected because the strip 10 is moved by the center of the roll 11 as shown by the broken line in the figure. In such a correction method, the meandering correction ability increases when the difference between the center radius and the end radius of the roll 11 is increased. However, when a wide and thin strip 10 is conveyed, the vicinity of the widthwise center of the strip 10 is reduced. There is a constraint that the difference in radius must be as small as possible, since buckling deformation is likely to occur and product quality is impaired. In this correction method, a large meandering correction ability cannot be expected with a single roll, but it is a method that can be realized at a relatively low cost. Can be expected.

[0005] The second method is a method of correcting the meandering using a strip meandering correction device comprising a combination of a transport roll generally called a steering roll and a function of rotating the transport roll. FIGS. 10 and 11 are diagrams each showing an example of the configuration of a steering roll. In these apparatuses, a roll 14 is fixed and supported on a gantry 13 that tilts about a fulcrum 12 as shown in FIG. 14
The gantry 13 is tilted in a state where the strip 10 is turned around, and the width of the strip 10 in the width direction is changed by the tilting operation. For example, in the overaging furnace of the continuous annealing line, as shown in FIG. 12, the steering rolls (upstream side 1 and downstream side 2) are provided at a ratio of one to every five to ten transport rolls together with the meandering detectors 3 and 4. Will be installed. In such a configuration, first, the actual meandering is detected by the meandering detectors 3 and 4, and the detected value of the meandering detectors 3 and 4 and the center of the pass line are determined for each of the steering rolls 1 and 2. The deviation is calculated by the computing devices 5 and 6, and the deviation is input to the steering roll tilting device 15, and feedback control is performed to tilt the steering rolls 1 and 2 so that the deviation becomes zero.

[0006]

By the way, the meandering amount of the strip usually increases as it goes downstream of the pass line. Therefore, when the meandering amount is small, the meandering correction can be performed by the downstream steering device, but when the meandering amount is large, the meandering correction capability of the downstream steering device is insufficient, and the meandering correction cannot be performed sufficiently. There were many. Furthermore, in the process of propagation of a certain meander to the downstream side, the meandering amount becomes excessive before the meander reaches the downstream steering device, so that the strip runs out of the roll between the upstream and downstream steering rolls, and the strip breaks. Accidents, etc., causing a significant decrease in productivity.

[0007] As an example of this, using the case of the continuous annealing line shown in FIG. 12, the thickness of the strip is 1.0 mm, the width is 1500 mm, the transport speed is 5 m / s,
Under the conditions of the maximum meandering correction amount of the steering roll of 100 mm and the roll width of 2000 mm, the meandering state of the strip is as shown in FIG. Note that, in FIG.
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 dashed line C is the meandering amount at which rollout occurs when the strip width is 1500 mm, and the two-dot chain line D is The meandering amount at which rollout occurs when the strip width is 1800 mm is shown, and the position of the steering roll 1 on the upstream side and the position of the steering roll 2 on the downstream side are shown. As shown, the meandering amount on the entry side of the steering roll 1 is as small as 40 mm. Looking at the meandering state when the upstream side steering roll 1 is not used, the meandering amount tends to increase toward the downstream side of the pass line as described above, and the meandering amount at the downstream side of the steering roll 2 enters. Is as large as 220 mm, and is in a dangerous state on the passing plate just before rollout occurs. Next, looking at the meandering situation when the upstream steering roll 1 is used in the same strip passing, the upstream steering roll 1 is seen.
The meandering amount on the entry side is 40 mm, and the maximum meandering correction capacity is 10 mm.
Since it is sufficiently small with respect to 0 mm, the strip is meander-corrected at the center of the pass line in the steering roll 1. However, on the downstream side of the upstream steering roll 1, the meandering amount tends to increase again, and the meandering amount on the entry 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 of the upstream side steering roll 2, the meandering correction ability is insufficient, and 80 m is required on the exit side of the steering roll 2.
m meandering has occurred.

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

In the case where the meandering exceeds the meandering correction capability of the steering roll as in the above-described example, the line operator takes measures such as increasing the line tension and decreasing the strip conveyance speed to increase the meandering. Work for prevention. However, the operator can only know the meandering state on the steering rolls where the meandering detector is installed, and has no means for knowing the meandering state 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 strip breakage often occurs.

To solve such a problem, the number of steering rolls is increased in the line to shorten the distance between the steering rolls, or the number of meandering detectors is increased in the line to reduce the meandering state between the steering rolls. Although it is conceivable to perform measurement, the number of steering rolls and meandering detectors are limited because they are expensive. In addition, when the above-mentioned facilities are newly added to an existing line, there are restrictions on the installation location and the like, and it is currently difficult to solve the above problems.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for predicting a meandering state between steering rolls which cannot be known at present, or preventing a rollout between steering rolls beforehand. It is intended to provide a monitoring method.

[0012]

In describing the present invention, a method for analyzing and predicting a meandering state between steering rolls in a strip continuous processing line composed of , for example, a vertical line and having a plurality of steering rolls will be described. . The analysis in the present invention is to determine the time-dependent change in the meandering of the strip at the position of a certain transport roll on the line, and this is a model formula representing the lateral elastic deformation of the strip running between the rolls. 1) The following equation (2), which is a model equation representing the lateral movement of the strip on a certain roll, and the following equation (3), which is a model equation representing a meandering correction mechanism using a crown roll in consideration of the strip shape: Is obtained by solving

[0013]

(Equation 4)

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

[0015]

(Equation 5)

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

[0017]

(Equation 6)

Where, H: length of the central flat portion of the crown roll [m] α: angle of the tapered portion of the crown roll [rad] m: constant M: difference in depth of ear waves present at the width direction ends of the strip [M] M = M _Dr −M _Op (when the meandering of the strip toward the processing device driving side is set to a positive value) M _Dr : Depth of ear wave existing at the end of the processing device driving side strip [m] M _Op : Depth of ear wave [m] existing at the strip end on the processing device operation side

That is, the above equation (1) is derived by regarding the strip traveling between the transport roll i and the transport roll i + 1 as an elastic body having a tension T in the longitudinal direction. The above equation (2) indicates that, for a roll having a slope of θ _{R in} the vertical direction of the pass line, the transport speed V and a strip entering the roll with a slope of dy / dx in the direction of the pass line. This is an expression representing a lateral movement. The above equation (3) is an equation representing a meandering correction mechanism using a crown roll, and a portion obtained by removing a shape defect portion such as an ear wave present at both ends of the strip from the width W of the strip is a virtual strip. as has been modeled as roll tilt angle theta _R virtual acting in the direction to correct this when the center of the virtual strip off the central pass line results. The constant m depends on the frictional force between the roll and the strip, and is a constant given by the roll surface roughness, the strip surface roughness, the friction coefficient between the roll and the strip, and the line tension.

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

[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) Where y _i : deviation of the strip on the roll i from the pass line [m] θ _Ri : tilt angle of the roll i [rad] y _{i + 1} : deviation of the strip on the roll i + 1 from the pass line [m] θ _{Ri + 1} : tilt angle of roll i + 1 [rad] L: distance [m] between roll i and roll i + 1

[0022]

(Equation 8)

Here, a _{1 to} a ₆ are T, E,
It is a function of W, h, V, L. When the above equation (5) is discretized with respect to time t and displacement y by a time difference Δt as a forward difference, 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) where y ₁ (j) is the deviation of the stop below the roll i from the pass line at time step j. In this equation, b _{1 to} b ₅ represent T, E, W,
h, V, L, θ _Ri , θ _{Ri + 1} , and time increment Δ during discretization
It is a function of t. Also, j, j + 1, j + 2 indicate time steps, and y _i (j) indicates time step j.
Shows the deviation of the strip on roll i from the center of the pass line.

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

[0026]

Y _OUT = y _IN + Δy (7) where y _IN : the position of the strip on the entrance side of the steering roll [m] y _OUT : the position of the strip on the exit side of the steering roll [m] Δy: the steering roll Therefore, the meandering of the strip is always measured on a certain roll i by a meandering detector, and y _i (j) and y _i (j +
1) is known and the downstream roll n (n = i +
1, i + 2, ...) in appropriate initial conditions y _n (j),
Given y _n (j + 1), using equations (6) and (7), meander y _n on the downstream roll n at time j + 2
(J + 2) can be sequentially calculated.

Further, if the depth and the position of a defective shape portion such as an ear wave existing at both ends in the width direction of the strip on the roll i or upstream thereof are measured and recorded, the roll n on the downstream side can be measured. Can be obtained, and a more accurate analysis can be performed.

In the strip meandering prediction method according to the present invention, the strip shape can be estimated only from the output of the meandering detector, and the method will be described below. As shown in FIGS. 12 and 13, the meandering of the strip increases once again on the downstream side even after being corrected by the upstream steering roll 1, and the meandering directions match. That is, when attention is paid to a part of the strip that is being conveyed, the part tends to meander in the same direction at all times on the conveying roll in the line. This is due to the fact that the strip is conveyed downstream of the line while maintaining the shape defect of the strip, which induces meandering at that site.

In consideration of the above points, by measuring the meandering condition on a certain roll, on the contrary, it is possible to estimate the depth and position of a shape-defective portion such as an ear wave present on the strip passing through the roll. is there. In the present invention, the depth and the position of the ear wave existing in the strip are estimated by the following equation (8). That is, when a meander 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 | is formed at the end of the strip in the same direction as the meander. Is modeled as existing at the site.

[0030]

M _Dr = | ky _i |, M _Op = 0 (0 < y _i ) (8) M _Dr = 0, M _Op = | ky _i | (0> y _i ) However, in the line drive side direction M _Dr : Depth of ear wave present at the end of the strip on the line drive side [m] M _Op : Depth of ear wave present at the end of the strip on the line operation side [m] k: Correction coefficient According to the above method, it is possible to estimate the time change of meandering occurring downstream 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. .

The above example predicts the depth and position of the ear wave of a strip based on the output of the meandering detector. However, a strip shape meter is provided upstream of the meandering detector, and thereby, the strip is more stripped. The depth and the position of the ear wave generated in the meandering detector are measured, and the time change of the meandering occurring downstream of the meandering detector can be estimated from the temporal change of the meandering detector output. Note that the analysis in the present invention may of course be configured to perform processing exclusively using an arithmetic unit. Further, the meandering state of the strip downstream of the meandering detector is predicted by the above-described meandering method of the strip, and when the predicted meandering amount exceeds a predetermined value, an alarm is issued and attention is paid to the equipment operator. Prompt.

[0032]

By using the above-mentioned method, it is possible to obtain a strip meandering state between the steering rolls, which could not be obtained until now. At this time, if the meandering amount of the strip between the steerings exceeds a certain value, a warning is issued and the line operator is alerted, so that the operator can increase the line tension more quickly than before, decrease the strip transport speed, etc. And appropriate measures can be taken to prevent the occurrence of accidents such as rollout and strip breakage. The measures for preventing the meandering from expanding, such as an increase in the line tension and a decrease in the strip conveyance speed, may be performed automatically by a computing device or the like simultaneously with the issuance of the alarm.

[0033]

An embodiment 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 configuration of an apparatus in a continuous annealing line overaging furnace to which a method according to one embodiment of the present invention is applied.
2 is a downstream steering roll, 3 and 4 are meandering detectors,
Numerals 5 and 6 denote arithmetic units for tilting the steering roll, 7 a transport roll, 9 an arithmetic unit for estimating the shape of the strip, meandering analysis and issuing an alarm according to the present invention, and 10 a strip.

The meandering detectors 3 and 4 are disposed on the exit sides of the upstream steering roll 1 and the downstream steering roll 2 respectively. The arithmetic unit 9 constantly collects information such as the amount of meandering on the exit 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 like, and the above equations (1) to (8). Is calculated to calculate the strip shape and the meandering condition between the steering rolls 1 and 2, and if the meandering amount exceeds the meandering correction capability of the downstream-side steering roll 2, an alarm is issued. Have been. 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 a meandering measured value and a meandering amount analysis value according to the embodiment of FIG. The implementation conditions are as follows: strip thickness 1.4 mm, width 900 mm, transport speed 2 m / sec, maximum meandering correction amount of steering roll 1
00 mm and a roll width of 2000 mm. In FIG. 2, the horizontal axis is time, and the vertical axis is the strip deviation from the center of the pass line, that is, the meandering amount. In the figure, the thin line E and the thick line F show the actual measurement value and the analysis value of the meandering amount at the entrance side of the downstream side steering roll 2, respectively.
Note that the actual measurement value of the meandering amount on the entrance side of the downstream side steering roll 2 can be obtained from Expression (7). It can be seen from the figure that the analysis of the meandering state of the present embodiment is performed accurately.

FIG. 3 is a schematic diagram showing an example of the configuration of one apparatus in a continuous annealing line overaging furnace to which a method according to another embodiment of the present invention is applied. In the present embodiment, the meandering detectors 3, 4
The strip shape meter 8 is disposed on the upstream side, and the strip shape meter 8 measures the depth and position of the ear wave of the strip. An operation to find its position,
That is, the arithmetic processing of the equation (8) is labor-saving, and otherwise operates in the same manner as the apparatus of FIG. 1, and the meandering amount measured value and meandering analysis value are as shown in FIG.

Next, FIGS. 5 to 7 show examples in which the meandering amount between the steering rolls 1 and 2 in the apparatus shown in FIG. 1 or 3 becomes excessive and an alarm is actually issued. This embodiment is an example of meandering generated by ear waves of the strip, and the conditions for the implementation are that the strip has a thickness of 0.8 mm and a width of 1600.
mm, the transport speed 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 meandering amount. 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 indicates a meandering state between the steering rolls 1 and 2 obtained according to the present embodiment. An alternate long and short dash line H indicates a meandering allowable value of 120 mm when the strip width is 1600 mm. When the meandering amount exceeds this value, an alarm is issued. The two-dot chain line I in the figure shows the meandering amount limit value of 200 mm that causes rollout when the strip width is 1600 mm. If the meandering amount exceeds this value, accidents such as rollout and strip breakage are expected. You. Further, the transport direction of the strip is the direction of the arrow in the figure.

FIG. 5 is a characteristic diagram showing a meandering situation at the moment when an alarm is issued. A meander between the steering rolls 1 and 2 was sharply expanded by ear waves generated halfway in the longitudinal direction of the strip, and an alarm was issued because the meandering wave exceeded the allowable meandering value of 120 mm. FIG. 6 is a characteristic diagram showing a meandering situation when no countermeasures are taken after an alarm is issued.
The meandering amount at the downstream steering roll 2 entrance side is 160 m
m, just before rollout. Even after the correction of the meandering, the meandering amount on the exit side of the downstream-side steering roll 2 still remains as 60 mm, which is extremely dangerous in operation. If this embodiment is not applied, the line operator performs operations such as an increase in line tension and a decrease in strip transport speed only in such a state. Accidents such as breakage often occur.

FIG. 7 is a characteristic diagram showing a meandering situation when the operator takes an operation of increasing the line tension and decreasing the strip transport speed after issuing the alarm. Since the operator took appropriate measures promptly, the meandering was reduced, and the meandering amount at the downstream side of the steering roll 2 was 110 mm, which was within the safe range for operation.

The above characteristics were observed not only in the overaging furnace of the continuous annealing line but also in other places. FIG. 8 is a schematic diagram of the continuous annealing line. As a result of the tests performed on the entrance loop tower portion, the heating zone portion, the cooling zone portion, and the exit loop tower portion in FIG. When changing the strip size, changing the line tension, changing the strip conveying speed, and changing the annealing temperature,
Accidents such as strip breakage can be reduced to about 1/4 of the conventional level, and the operating efficiency of the line has been improved by about 5%.

Further, the present invention is applicable to any equipment employing a plurality of steering rolls in controlling the meandering of the strip, so that the present invention is not limited to the continuous annealing line, and is not limited to the continuous annealing line. It can be applied to strip coating, printing line, etc.

[0042]

As described above, according to the present invention, the meandering condition between the steering rolls, which could not be known conventionally, can be easily grasped. In addition, since the meandering can be quickly prevented, occurrence of accidents such as rollout and strip breakage can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one apparatus 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 measured value on the downstream steering roll entrance side and a meandering amount analysis value according to the present embodiment in the configuration of FIG. 1;

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

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

FIG. 5 is a characteristic diagram showing a meandering state between steering rolls at the moment when an alarm is actually issued in the embodiment of FIG. 1 or FIG. 3;

FIG. 6 is a characteristic diagram showing a meandering situation in a case where an appropriate action is not taken despite a warning being issued in the embodiment of FIG. 1 or FIG. 3;

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

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

FIG. 9 is a diagram illustrating 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 one device configuration of a steering roll.

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

FIG. 13 is a characteristic diagram showing a strip meandering state in the configuration of FIG. 12;

[Explanation of symbols]

1: upstream steering roll 2: downstream steering roll 3, 4: meandering detector 5, 6: arithmetic unit for tilting the steering roll 7: transport roll 8: strip shape meter 9: arithmetic unit for meandering analysis and alarm issuance 10: Strip 11: Crown roll 12: Steering roll tilting fulcrum 13: Steering roll mount 14: Roll 15: Steering roll tilting device Solid line A: Meandering condition when using steering roll Dashed line B: Meandering when not using tearing roll Situation One-dot chain line C: The meandering amount at which rollout occurs when the strip width is 1500 mm. Two-dot chain line D: The meandering amount at which rollout occurs when the strip width is 1800 mm. Thin line E: Actual measurement value of the meandering amount at the steering roll 2 entrance Thick line F: at the side of the steering roll 2 Line amount analysis value Solid line G: Meandering condition between steering rolls 1 and 2 obtained by the present embodiment Single-dot chain line H: Allowable meandering value when strip width is 1600 mm Two-dot chain line I: Roll-out when strip width is 1600 mm Generated meandering amount

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-89757 (JP, A) JP-A-4-308040 (JP, A) JP-A-53-10311 (JP, A) JP-A-5-103 214449 (JP, A) JP-A-5-239556 (JP, A) JP-A-5-17831 (JP, A) JP-A-62-107821 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21D 9 / 56,11 / 00 B65H 23/038 B65H 23/18-23/192 B65H 26/04

Claims (4)

(57) [Claims] In a continuous strip processing apparatus comprising vertical lines, the following formula (1) representing the transverse elastic deformation of a strip running between rolls, and the following formula representing the lateral movement of a strip on a roll: Using the equation (2) and the following equation (3) representing a meandering correction mechanism using a crown roll in consideration of the shape of the strip, the meandering detector is used as a boundary condition using the output of the meandering detector arranged in the line as a boundary condition. A meandering state of the strip downstream of the strip. Note Where K ² = T / EI x: length in the pass line direction [m] y: meandering amount of the strip on the roll [m] E: Young's modulus of the strip T: line tension [N] I: secondary section of the strip moment ^{[m 4] I = hW 3} /12 h: thickness of the strip [m] W: strip width [m] [Equation 2] Here, t: time [sec] V: strip transport speed [m / sec] θ _R : roll tilt angle [rad] Where H is the length of the center flat portion of the crown roll [m] α is the angle of the tapered portion of the crown roll [rad] m is a constant M is the difference [m] between the depths of ear waves present at the width direction ends of the strip 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 [m] at the strip end on the operation side 2. The method according to claim 1, further comprising estimating a depth and a position of an ear wave of the strip based on a meandering amount and a meandering direction detected by the meandering detector. A meandering state of the strip in (1). 3. The method according to claim 1, wherein the depth and the position of an ear wave generated in the strip are measured by a strip shape meter arranged upstream of the meandering detector, and the strip meandering prediction method according to claim 1 is downstream of the meandering detector. A meandering state of the strip in (1). 4. A meandering state of a strip downstream of a meandering detector is predicted by the meandering predicting method for a strip according to any one of claims 1 to 3, and when the predicted meandering amount exceeds a predetermined value. A meandering monitoring method for a strip, wherein an alarm is issued to alert the operator of the apparatus.