JP7701607B2 - Method for controlling meandering of rolled material - Google Patents

Description

The present invention relates to a method for controlling the meandering of the tail end of a rolled material.

For example, when rolling a material to be rolled, such as steel, using a rolling stand, the center of the width of the material to be rolled may shift from the mill center (the center position of the rolling mill in the width direction, i.e., the center position in the direction of the rotation axis of the work roll), causing the material to move toward the end of the work roll, a phenomenon known as meandering. When meandering occurs, the flatness of the material to be rolled decreases, which may lead to a decrease in product quality. In addition, if the amount of meandering is large, the tail end of the material to be rolled may come into contact with the side guide and bend, causing the material to be bitten into the rolling mill in a double-folded state, a defect known as squeezing. When squeezing occurs, the surface of the work roll is damaged by the bent rolled material, so it is necessary to stop the production line and perform maintenance work such as inspection, maintenance, or replacement of the work roll, which may reduce the operating rate of the production line.

Control methods for suppressing meandering of the rolled material have been studied for some time. For example, Patent Document 1 discloses a method in which the load cell of any rolling stand (N-1) other than the final finishing mill among continuous strip finishing mills or a rolling material detector installed in front of the rolling stand detects the tail of the rolled material in the previous rolling stand, and the roll gap of the next rolling stand N to be controlled adjacent to the previous rolling stand is widened to thicken the tail of the rolled material, thereby preventing tail squeezing. In addition, Patent Document 2 discloses a method in which the roll bending device narrows the barrel length direction end of the work roll when the rear end of the rolled material passes, suppressing the movement of the rolled material toward the plate end, thereby preventing the rolled material from squeezing due to interference with the side guide.

Japanese Unexamined Patent Publication No. 55-161505 Japanese Unexamined Patent Publication No. 58-145303

Hiroe Nakajima and 5 others, "Study on the method of controlling meandering in hot strip rolling (first report)", Spring Lecture on Plastic Processing in 1980, pp. 61-64 The Iron and Steel Institute of Japan, "Theory and Practice of Plate Rolling (Revised Edition)", 2010, pp. 89-95

However, in the methods described in Patent Documents 1 and 2, which control the meandering by opening the roll gap or applying a bending force when the tail end of the rolled material passes through the rolling mill, there is a risk that the amount of control is too small, resulting in narrowing, or that the amount of control is too large, resulting in the tail end of the rolled material not being rolled to the desired thickness or shape, thereby reducing production yield.

The present invention has been made in consideration of the above problems, and the object of the present invention is to provide a method for controlling the meandering of a rolled material, which reduces the amount of meandering at the tail end of the rolled material, prevents the occurrence of constriction, and reduces yield loss due to poor thickness and shape at the tail end of the rolled material.

In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a method for controlling meandering of a rolled material in an M-th stand (1≦M≦N) in rolling of the rolled material by N rolling stands (N is a natural number), the method including a threshold setting step of setting in advance a threshold value E TH of a first type parallel stiffness at which the meandering amount of the rolled material in the M-th stand is less than an allowable value using at least one of a roll speed V, a lubricant supply amount Q, a roll cross angle θ, a roll shift amount L, and a roll crown _C as a control parameter, a first type parallel stiffness calculation step of calculating a first type parallel stiffness actual calculation value E _b in the M-th stand, and a step of not performing meandering control when the first type parallel stiffness actual calculation value E _b is equal to or less than the threshold value E _TH , and setting the first type parallel stiffness to the threshold value E _b based on the first type parallel stiffness actual calculation value E b when the first type parallel stiffness actual calculation value E _b is greater than the threshold value E _TH . The present invention provides a method for controlling the meandering of a rolled material, the method including a control step of calculating an amount of change in a control parameter of the Mth stand so as to make the tail end of the rolled material below _TH , and controlling the control parameter of the Mth stand corresponding to the amount of change based on the calculated amount of change in the control parameter while the tail end of the rolled material passes through the Mth stand.

At least one of the pressing position and bending force may be further used as a control parameter.

In the first type parallel stiffness calculation step, a first type parallel stiffness actual calculation value Eb at the M stand may be calculated based on the rolling load actual value _Pb and bending force actual value _Fb at the M stand, _which are simultaneously obtained during the period from when the leading end of the rolled material is bitten into the M stand until before the tail end of the rolled material is rolled by the M stand, and the actual values of the control parameters.

Alternatively, in the first type parallel stiffness calculation step, a rolling load set value _Pt and a bending force set value _Ft at the M stand and set values of the control parameters may be calculated by a setup calculation, an influence coefficient ∂E/ _∂P of the rolling load, an influence coefficient ∂E/∂F of the bending force and influence coefficients of the control parameters for the first type parallel stiffness set calculated value Et at the M stand may be calculated, and based on the rolling load actual value _Pb and bending force actual value _Fb at the M stand and the actual values of the control parameters which are simultaneously obtained during the period from when the front end of the rolled material is bitten into the M stand to before the tail end of the rolled material is rolled by the M stand, difference values between the set values and actual values may be calculated, and a first type parallel stiffness actual calculated value _Eb at the M stand may be calculated based on the difference value and the influence coefficient.

As described above, the present invention can reduce the amount of meandering at the tail end of the rolled material, prevent the occurrence of narrowing, and reduce yield loss due to poor thickness and shape at the tail end of the rolled material.

FIG. 2 is a schematic diagram showing a configuration example of a rolling stand according to an embodiment of the present invention. 1 is a graph showing an example of a correlation between first-type parallel stiffness immediately before the tail end portion of a rolled material and meandering of the tail end portion. 11 is a flowchart showing a process of a meandering control example 1. FIG. 13 is a schematic diagram showing an outline of a calculation process of a first type parallel stiffness actual calculation value _Eb in the meandering control example 1. 1 is a schematic diagram showing an image of calculating a first type parallel stiffness actual calculation value _Eb by first approximation from a rolling load actual value _Pb and a bending force actual value _Fb of a rolled material. FIG. FIG. 11 is an explanatory diagram for explaining a method for calculating an influence coefficient of a first type parallel stiffness on a rolling load. FIG. 11 is an explanatory diagram for explaining a method for calculating an influence coefficient of a first type parallel stiffness on a bending force. FIG. 11 is an explanatory diagram illustrating a method for calculating an influence coefficient of the first type parallel stiffness on a control parameter. 13 is a graph showing an example of a correlation between a first type parallel stiffness actual calculation value (using a model) and a first type parallel stiffness actual calculation value (using an influence coefficient). FIG. 2 is an explanatory diagram showing a rolling stand that is the control target of the method for controlling meandering of a rolled material according to the present embodiment, and the timing for measuring the rolling load and bending force at that time. 13 is a flowchart showing a modified example of the process of the meandering control example 1. 13 is a flowchart showing a modified example of the process of the meandering control example 1. 13 is a schematic diagram showing an outline of a calculation process of a first type parallel stiffness actual calculation value Eb in a meandering control example 2. FIG. 13 is a flowchart showing a process of a meandering control example 2.

The preferred embodiment of the present invention will be described in detail below with reference to the attached drawings. Note that in this specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals to avoid redundant description.

[1. Configuration of the rolling stand]
First, a schematic configuration of a rolling stand 10 according to one embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing one configuration example of the rolling stand 10 according to this embodiment. Fig. 1 shows the rolling stand 10 as viewed from the working side in the roll barrel length direction, and the passing direction (rolling direction) of the material S to be rolled is from right to left on the page.

Note that while FIG. 1 illustrates only one rolling stand 10, this rolling stand 10 may be, for example, one rolling mill that constitutes a finishing tandem rolling mill in hot rolling. A finishing tandem rolling mill is configured by arranging multiple rolling stands 10 in one direction. The material being rolled is gradually thinned as it passes through each rolling stand in succession, and is finally rolled to the desired thickness. Note that this technology can also be applied to a single-stand rolling mill equipped with one rolling stand 10.

As shown in FIG. 1, the rolling stand 10 according to this embodiment has a four-stage rolling mill having a pair of work rolls 1 and 2 and a pair of backup rolls 3 and 4 supporting the work rolls. The upper work roll 1 is supported by an upper work roll chock 5, and the lower work roll 2 is supported by a lower work roll chock 6. The upper work roll chock 5 and the lower work roll chock 6 are also provided on the rear side (drive side) of the paper in FIG. 1, and support the upper work roll 1 and the lower work roll 2, respectively. The upper backup roll 3 is supported by an upper backup roll chock 7, and the lower backup roll 4 is supported by a lower backup roll chock 8. The upper backup roll chock 7 and the lower backup roll chock 8 are also provided on the rear side (drive side) of the paper in FIG. 1, and support the upper backup roll 3 and the lower backup roll 4, respectively. The upper work roll chock 5, the lower work roll chock 6, the upper backup roll chock 7, and the lower backup roll chock 8 are held by a housing 9.

The housing 9 has an entry project block 9a and an exit project block 9b that protrude inward from the housing 9, where the roll chocks 5 to 8 are located. The entry project block 9a and the exit project block 9b support the work roll chocks 5 and 6 via increase bending devices 11a to 11d. Decrease bending devices 12a to 12d may also be provided between the work roll chocks 5 and 6 and the backup roll chocks 7 and 8.

The increase bending devices 11a to 11d are devices that apply a force to the work roll chocks 5 and 6 in a direction that increases the roll gap. The increase bending devices 11a to 11d are configured with a drive device such as a hydraulic cylinder. The decrease bending devices 12a to 12d are devices that apply a force to the work roll chocks 5 and 6 in a direction that decreases the roll gap. The decrease bending devices 12a to 12d are configured with a drive device such as a hydraulic cylinder.

The roll-down device 13 is installed above the upper back-up roll 3, which is the top roll, and adjusts the position of the upper back-up roll 3 and the upper work roll 1 in the roll-down direction (hereinafter also referred to as the "roll-down position") to adjust the gap between the upper work roll 1 and the lower work roll 2. The roll-down device 13 is composed of a drive device such as a hydraulic cylinder. Between the roll-down device 13 and the upper back-up roll chock 7, a rolling load detection device 14 is provided that detects the load in the roll-down direction (i.e., the rolling load). The rolling load detection device 14 may be, for example, a load cell.

The work rolls 1 and 2 rotate at a predetermined rolling speed and reduce the material S to a predetermined thickness from above and below, passing the material S in one direction. The reduction position (i.e., roll gap) of the work rolls 1 and 2 is appropriately adjusted by the reduction device 13 according to the rolling conditions such as the target thickness of the material S after rolling and the reduction rate. The roll speed of the work rolls 1 and 2 can be changed by a driving device such as a motor (not shown). In addition, a lubricant supplying device (not shown) that supplies lubricant to the material S during rolling may be installed on the entry side of the rolling stand 10.

The rolling stand 10 may be capable of changing the roll cross angle by moving the roll chocks 5 to 8, for example, as in a pair cross rolling mill. Alternatively, the rolling stand 10 may be capable of shifting the work rolls 1 and 2 or the intermediate rolls in the axial direction, for example, as in a CVC (continuous variable crown) rolling mill or a six-high rolling mill. Furthermore, the rolling stand 10 may be capable of changing the roll crowns of the work rolls 1 and 2, for example, as in a VC (variable crown) rolling mill. The roll crowns can be changed, for example, by using variable crown rolls having a hydraulic chamber for expansion inside the center of the roll body length as the work rolls 1 and 2.

In the rolling stand 10, the meandering control device 100 controls the meandering of the tail end of the rolled material S when it passes through the rolling stand 10. The meandering control device 100 changes at least one of the control parameters of the roll speed, the lubricant supply amount, the roll cross angle, the roll shift amount, and the roll crown according to the first-class parallel stiffness, which is an index of the ease of meandering at the tail end of the rolled material S. The roll shift amount includes not only the work roll shift amount but also the intermediate roll shift amount when there is an intermediate roll such as in a six-high rolling mill. In addition to these control parameters, the meandering control device 100 may further drive the increase bending devices 11a to 11d or the reduction device 13 to apply a bending force or change the reduction position by the required amount. This reduces the meandering amount at the tail end of the rolled material S and suppresses the occurrence of squeezing. The bending force may be applied by driving not only the increase bending devices 11a to 11d but also the decrease bending devices 12a to 12d.

The meandering control device 100 is configured with various processors, such as a CPU (Central Processing Unit) and a DSP (Digital Signal Processor), and the functions of the meandering control device 100 can be realized by the processors operating in accordance with a specified program.

As described above, whether or not to perform meandering control by the meandering control device 100 is determined based on the first type parallel stiffness actual calculation value. The first type parallel stiffness actual calculation value is calculated by an arithmetic processing device (the arithmetic processing device 200 in FIG. 4 or FIG. 12 described below). The arithmetic processing device is also composed of various processors such as a CPU and a DSP. The functions of the arithmetic processing device can be realized by operating the processor according to a specified program.

The meandering control device 100 only needs to have the function of controlling the operation of the rolling stand 10, and there are no limitations on its specific configuration. Similarly, the arithmetic processing device only needs to have the function of calculating the first type parallel stiffness actual calculation value, and there are no limitations on its specific configuration. For example, the meandering control device 100 and the arithmetic processing device may be various processors as described above, or may be a so-called microcomputer in which a processor and a storage device such as a memory are integrated. Alternatively, the meandering control device 100 and the arithmetic processing device may be various information processing devices such as a PC (Personal Computer) or a server.

[2. Controlling the wobble of the tail end]
The meandering control of the tail end of the rolled material by the meandering control device 100 of this embodiment is performed by calculating a first type parallel stiffness actual calculation value, and changing at least one of the control parameters of the roll speed, lubricant supply amount, roll cross angle, roll shift amount, and roll crown by the necessary amount when necessary, depending on the calculated first type parallel stiffness actual calculation value.

The first type parallel stiffness changes according to the change in the rolling load and bending force from the front end to the tail end of the rolled material. The first type parallel stiffness at the front end of the rolled material corresponds to the first type parallel stiffness obtained by the setting calculation before rolling, and has a relatively weak correlation with the meandering of the tail end of the rolled material. In contrast, the first type parallel stiffness just before the tail end of the rolled material shown in Figure 2 (measurement timing 2 in Figure 10) has a relatively high correlation with the meandering of the tail end of the rolled material compared to the front end. Therefore, in this embodiment, preferably, the first type parallel stiffness just before the tail end of the rolled material is calculated, and meandering control is performed based on this to suppress the meandering of the tail end of the rolled material.

Here, the meandering of the rolled material is caused by the difference in thickness between the left and right (width direction) of the rolled material at the exit of the rolling stand (i.e., the exit wedge amount h _df ). The exit wedge amount h _df is expressed by the following formula (1) (see, for example, Non-Patent Document 1).

In the above formula (1), _Sdf is the difference in roll gap between the left and right rolls, _Pdf is the difference in rolling load between the left and right rolls, a is the distance between the roll supports, and b is the plate width. In addition, E is the first parallel stiffness, D is the second parallel stiffness, and these are basic constants of the rolling mill related to the meandering phenomenon.

The equation for the amount of meandering of the rolled material ultimately reduces to the differential equation shown in Equation (2) below (see, for example, Non-Patent Document 1).

In addition, _v1 is the inlet speed of the rolled material, _yc is the amount of meandering, ξ is the forward constant, h is the outlet thickness, m is the plasticity coefficient, and Perturbation is an asymmetric disturbance term (for example, an influence term of an inlet wedge, a difference in deformation resistance between the left and right, leveling, etc.).

Here, the coefficients of each term in the above equation (2) are M and k as follows:

If we consider M to be the mass and k to be the spring constant, we can see that the above equation (2) has the same format as the equation of motion for a mass-spring system. Since the spring constant k is almost always a negative value, meandering is an inherently unstable phenomenon (divergent system). There are three main approaches to suppressing meandering:

(a) Minimize various asymmetric disturbances (i.e., minimize perturbations)
(b) Using steerable asymmetric disturbances (leveling) to cancel other disturbances
(i.e. minimize perturbation)
(c) Minimize the speed of meandering divergence when disturbance occurs
(i.e., minimize the absolute value of k)

The meandering control method according to this embodiment is based on the approach (c) above. However, it can also be used in combination with approaches (a) and (b). In addition, when evaluating the degree of meandering, it is physically appropriate to include not only the first parallel stiffness E but also the second parallel stiffness D, based on the above formula (1). However, the second parallel stiffness D does not change significantly during rolling, compared to the first parallel stiffness E, which fluctuates during rolling due to the rolling load and bending force. In other words, the second parallel stiffness D cannot be changed. For this reason, in the meandering control method according to this embodiment, the degree of meandering is evaluated based only on the first parallel stiffness E for practical simplicity.

Specifically, in rolling a material by N rolling stands (N is a natural number), when controlling the meandering of the material at the Mth stand (1≦M≦N), a first type parallel stiffness threshold value _ETH at which the amount of meandering of the material at the Mth stand is less than an allowable value is set in advance using control parameters for controlling the meandering of the material (threshold value setting step). In addition, before rolling, a first type parallel stiffness actual calculation value Eb at the Mth stand is calculated (first type parallel stiffness calculation step). Then, the first type parallel stiffness threshold value _ETH and the first type parallel stiffness actual calculation value _Eb are compared.

When the first type parallel stiffness actual calculation value _Eb is equal to or less than the threshold value _ETH , meandering control is not performed. On the other hand, when the first type parallel stiffness actual calculation value _Eb is greater than the threshold value _ETH , a change amount of the control parameter of the Mth stand is calculated based on the first type parallel stiffness actual calculation value _Eb in order to make the first type parallel stiffness equal to or less than the threshold value _ETH . Then, while the tail end of the rolled material passes through the Mth stand, the control parameter at the Mth stand is controlled based on the change amount of the control parameter (control step).

Here, the calculation of the first type parallel stiffness actual calculation value _Eb at the Mth stand may be performed, for example, by calculating an influence coefficient for the first type parallel stiffness set calculation value _Et of the material to be rolled calculated by the setup calculation and using the influence coefficient to calculate the first type parallel stiffness actual calculation value _Eb , or by using a model to calculate the first type parallel stiffness actual calculation value _Eb based on the rolling conditions. Hereinafter, the meandering control of the tail end of the material to be rolled according to this embodiment will be described in detail.

In this embodiment, the tail end of the material being rolled refers to the range from the tail end to a predetermined length. Here, the predetermined length refers to the length at which the effect of reducing meandering can be achieved when the method for controlling meandering of the material being rolled according to the present invention is applied to the range set as the tail end of the material being rolled. This length differs depending on the specifications of the rolling mill, the dimensions of the material being rolled, and the material of the material being rolled, so for example, the plate width of the material being rolled can be set as the initial value of the predetermined length, and adjustments can be made during actual operation to determine the length.

In the case of the second or subsequent stand in tandem rolling, the tail end of the rolled material may be, for example, "the range from the tail end of the rolled material when it leaves the rolling stand one upstream of the Mth stand that is the object of control (i.e., the (M-1)th stand) to the position where it is caught in the Mth stand that is the object of control." Alternatively, the tail end of the rolled material in the case of the second or subsequent stand in tandem rolling may be "the stand-to-stand distance between the (M-1)th stand and the Mth stand."

[2-1. Example 1 of meandering control (calculation of the first type parallel stiffness actual calculation value using the first type parallel stiffness setting calculation value and the influence coefficient in the setup calculation)]
First, based on Fig. 3 to Fig. 11B, a case where a first type parallel stiffness actual calculation value is calculated using a first type parallel stiffness set calculation value and an influence coefficient in the setup calculation, and meandering control of the tail end of the rolled material is performed will be described as a meandering control example 1. Fig. 3 is a flowchart showing the processing of the meandering control example 1. Fig. 4 is a schematic diagram showing an outline of the calculation processing of the first type parallel stiffness actual calculation value _Eb in the meandering control example 1. Fig. 5 is a schematic diagram showing an image of calculating the first type parallel stiffness actual calculation value _Eb by first-order approximation from the rolling load actual value _{Pb and} the bending force actual value Fb of the rolled material. Fig. 6 is an explanatory diagram explaining a calculation method of the influence coefficient of the first type parallel stiffness on the rolling load. Fig. 7 is an explanatory diagram explaining a calculation method of the influence coefficient of the first type parallel stiffness on the bending force. Fig. 8 is a graph showing an example of the correlation between the first type parallel stiffness actual calculation value (using a model) and the first type parallel stiffness actual calculation value (using an influence coefficient). 10 is an explanatory diagram showing the rolling stands to be controlled by the method for controlling the meandering of the rolled material according to the present embodiment, and the timing of measuring the rolling load and bending force at that time.

(S100: Selection of control parameters)
In the meandering control example 1, as shown in Fig. 3, first, at least one of the roll speed V, the lubricant supply amount Q, the roll cross angle θ, the roll shift amount L, and the roll crown C is used as the control parameter (S100). The control parameters can be selected based on the purpose to be emphasized in addition to the reduction of the meandering amount (prevention of the occurrence of the narrowing) in the meandering control at the tail end of the rolled material, and the constraints on the equipment configuration of the rolling stand 10, etc. The purpose to be emphasized in addition to the reduction of the meandering amount includes, for example, the reduction of the yield loss due to the thickness defect at the tail end of the rolled material, the reduction of the yield loss due to the shape defect, etc.

The control parameters may be selected, for example, by an operator who inputs the control parameters to the arithmetic processing device described below using an input device or the like. Alternatively, the arithmetic processing device may automatically select the control parameters based on the equipment configuration of the rolling stand 10. In this case, the priority of the objectives to be emphasized along with the reduction of the amount of meandering may be determined in advance for each rolling stand 10, and the combination of control parameters to be selected accordingly may be stored in the memory unit of the arithmetic processing device. In this way, if the operator inputs the priority of the objectives to be emphasized along with the reduction of the amount of meandering to the arithmetic processing device, the arithmetic processing device can automatically select the control parameters.

For example, when the roll speed V or the lubricant supply amount Q is used as a control parameter, it is effective in reducing the yield loss due to shape defects because it does not interfere with shape control. Control of the roll speed V or the lubricant supply amount Q has the advantage that it can be performed regardless of the type of rolling stand. In addition, when the roll cross angle θ, the roll shift amount L, or the roll crown C is used as a control parameter, it interferes with shape control, so yield loss due to shape defects is likely to occur, but it is effective in reducing the yield loss due to plate thickness defects. In addition, when the roll speed V or the lubricant supply amount Q is controlled, there are cases where it is difficult to achieve a sufficient effect of preventing the occurrence of narrowing depending on the rolling conditions, but when the roll cross angle θ, the roll shift amount L, or the roll crown C is controlled, there is the advantage that a stable effect of preventing the occurrence of narrowing can be obtained. The parameters that can be controlled for the roll cross angle θ, the roll shift amount L, and the roll crown C are limited depending on the type of rolling stand.

When the priority changes depending on the conditions, it is possible to use multiple control parameters in combination and adjust the balance of the control amount of the control parameters depending on the rolling conditions. In addition, the controllable range is expanded (the effect of suppressing shrinkage is increased) by using many control parameters. Therefore, for example, if it is desired to suppress the occurrence of shrinkage as much as possible while giving priority to reducing the yield loss due to defective shape, it is desirable to select both the roll speed V and the lubricant supply amount Q as control parameters. In addition, for example, if it is desired to prevent the occurrence of shrinkage as much as possible while giving priority to reducing the yield loss due to defective plate thickness, it is desirable to use all of the controllable control parameters among the roll cross angle θ, roll shift amount L, and roll crown C.

(S110: Threshold setting step)
When the control parameters are selected in step S100, a threshold value _ETH of the first type parallel stiffness at which the meandering amount of the rolled material becomes less than the allowable value is set in advance before rolling (S110). For example, based on past operational results, preferably, a correlation between the first type parallel stiffness immediately before the tail end and the tail end meandering amount as shown in Fig. 2 may be obtained in advance, and the value of the first type parallel stiffness at which the meandering amount becomes less than the allowable value may be set as the threshold value _ETH .

(S120 to S130: First type parallel stiffness calculation step)
Next, a first type parallel stiffness actual calculation value _Eb is calculated. In meandering control example 1, the first type parallel stiffness actual calculation value _Eb is calculated using the first type parallel stiffness set calculation value Et and the influence coefficient. To explain this together with the outline of the first type parallel stiffness calculation step shown in Fig. 4, first, a setup calculation using a model is performed for the Mth stand to be controlled, and the first type parallel stiffness set calculation value Et _and the influence coefficient are calculated (S120). This calculation is performed immediately before rolling.

As a model for calculating the first parallel stiffness setting calculation value E _t and the influence coefficient, for example, a mill stretch model can be used (see, for example, Non-Patent Document 2). The rolling load setting value P _t and bending force setting value F _t of the rolled material obtained by the setup calculation, the roll cross angle setting value θ _t , the roll shift amount setting value L _t , and the roll crown setting value C _t , among which the control parameter setting values selected in step S100, and other various rolling conditions are input to the calculation processing device 200. The roll speed setting value V _b and the lubricant supply amount setting value Q _b affect the first parallel stiffness via the rolling load, so that the influence is included in the rolling load setting value P _{t, and} therefore they are omitted from the values to be input. Here, the rolling load and bending force set as the rolling load setting value P _t and the bending force setting value F t are parameters that vary greatly online and affect the first parallel stiffness.

Then, the calculation processing device 200 performs a setup calculation using the mill stretch model, and calculates the first parallel stiffness setting calculation value E _t , and the influence coefficient ∂E/∂P of the rolling load P and the influence coefficient ∂E/∂F of the bending force F on the first parallel stiffness setting calculation value E _t . Furthermore, the calculation processing device 200 calculates the influence coefficients of the control parameters selected in step S100, that is, at least one of the influence coefficient ∂E/∂V of the roll speed V on the first parallel stiffness setting calculation value E _t , the influence coefficient ∂E/∂Q of the lubricant supply amount Q, the influence coefficient ∂E/∂θ of the roll cross angle θ, the influence coefficient ∂E/∂L of the roll shift amount L, and the influence coefficient ∂E/∂C of the roll crown C. Each influence coefficient is expressed by the following formulas (4-1) to (4-7).

The calculation in step S120 may be performed using a model other than the mill stretch model.

When the first type parallel stiffness setting calculation value _Et and the influence coefficient are calculated by the setup calculation, next, based on the rolling load actual value _Pb and bending force actual value _Fb of the rolled material, and the actual values of the control parameters selected in step S100 from the roll cross angle actual value _θb , the roll shift amount actual value _Lb , and the roll crown actual value _Cb , a first type parallel stiffness actual calculation value _Eb is calculated (S130) using the following linear approximation formula (5). In the linear approximation formula (5), X represents the control parameter selected in step S100 from the roll cross angle actual value _θb , the roll shift amount actual value _Lb , and the roll crown actual value Cb _. Here, the roll speed actual value _{Vb and} the lubricant supply amount actual value _Qb are omitted from X because they affect the first type parallel stiffness via the rolling load.

The rolling force actual value _Pb and the bending force actual value _Fb may use actual measured values. The rolling force actual value _Pb and the bending force actual value _Fb are simultaneously acquired during the period from when the leading end of the rolled material is bitten into the M stand until before the tail end of the rolled material is rolled by the M stand. The roll cross angle actual value _θb , the roll shift amount actual value _Lb , and the roll crown actual value _Cb may use currently set values. For example, when control starts, initial set values are used, and when the values are changed in step S150 described later, the changed values are used.

The linear approximation formula (5) can be regarded as a linear approximation of the change from the first parallel stiffness set calculation value _Et to the first parallel stiffness actual calculation value _Eb on a multidimensional curved surface representing the relationship between the first parallel stiffness E, the rolling load P, the bending force F, and the selected control parameters. For example, for the sake of simplicity, when considering a curved surface C representing the relationship between the first parallel stiffness E, the rolling load P, and the bending force F shown in Fig. 5, the linear approximation formula (5) can be regarded as a linear approximation of the change from the first parallel stiffness set calculation value _Et (point A) to the first parallel stiffness actual calculation value _Eb (point B) on the curved surface C. This can be said from the following.

First, the relationship between the first parallel stiffness E and the rolling load P is shown, for example, in Fig. 6. In this case, if it is considered that the rolling load set value _Pt of the rolled material has increased by an arbitrary value h _p , the increase in the first parallel stiffness E at that time can be divided by h _p to obtain the first-order approximation influence coefficient ∂E/∂P of the rolling load P on the first parallel stiffness E, as shown in the following formula (6). If the correlation between the first parallel stiffness E and the rolling load P is highly linear, such a first-order approximation is sufficient, but if it is highly nonlinear, the influence coefficient can be obtained more strictly by a second-order approximation or the like.

The relationship between the first parallel stiffness E and the bending force F is shown, for example, in FIG. 7. In this case, if it is assumed that the bending force setting value _Ft of the rolled material has increased by an arbitrary value _hF , the increase in the first parallel stiffness E at that time is divided by _hF , and the first-order approximation influence coefficient ∂E/∂F of the bending force F on the first parallel stiffness E can be expressed by the following formula (7). This is the influence coefficient ∂E/∂F. If the correlation between the first parallel stiffness E and the bending force F is highly linear, such a first-order approximation is sufficient, but if it is highly nonlinear, the influence coefficient can be obtained by a second-order approximation or the like.

The same is true for the control parameters X of the roll speed V, the lubricant supply amount Q, the roll cross angle θ, the roll shift amount L, and the roll crown C, and the relationship between the first parallel stiffness E and each control parameter X can be expressed as shown in FIG. 8. If it is considered that the set value _Xt of the control parameter has increased by an arbitrary value _hX , the increase in the first parallel stiffness E at that time is divided by _hX , and the influence coefficient ∂E/∂X of the first approximation of the control parameter X on the first parallel stiffness E can be expressed by the following formula (8). This is the influence coefficient ∂E/∂X. If the correlation between the first parallel stiffness E and each control parameter X is highly linear, such a first approximation is sufficient, but if it is highly nonlinear, the influence coefficient may be obtained by a second approximation or the like.

That is, the influence coefficient ∂E/∂P of the rolling load P on the first parallel stiffness E expressed by the above formula (6), the influence coefficient ∂E/∂F of the bending force F on the first parallel stiffness E expressed by the above formula (7), and the influence coefficient ∂E/∂X of the control parameter X on the first parallel stiffness E expressed by the above formula (8) represent the influence on the first parallel stiffness E of the changes in the rolling load P, the bending force F, and the control parameter X. By using these, the first parallel stiffness actual calculation value _Eb can be expressed by the above linear approximation formula (5).

FIG. 9 shows an example of the correlation between the first-kind parallel stiffness actual calculation value (using a model) calculated using a mill stretch model based on the actual values of the rolling conditions, and the first-kind parallel stiffness actual calculation value (using an influence coefficient) calculated using the above-mentioned linear approximation formula (5). Here, as shown in FIG. 10 (measurement timing 2), the actual values of the rolling conditions were measured just before the tail end _Sb of the rolled material S was rolled in the stand. As shown in FIG. 9, the correlation coefficient between the first-kind parallel stiffness actual calculation value (using a model) and the first-kind parallel stiffness actual calculation value (using an influence coefficient) is approximately 1.00, and the first-kind parallel stiffness actual calculation value (using a model) and the first-kind parallel stiffness actual calculation value (using an influence coefficient) are consistent. From this, it can be seen that, as in the meandering control example 1, by calculating the first-kind parallel stiffness actual calculation value _{Eb using the influence coefficient of linear approximation for the rolling load P, bending force F, and control parameter X} , the first-kind parallel stiffness can be calculated with the same accuracy as the strict solution calculated by the model calculation.

In this way, in meandering control example 1, a model calculation which is a high-load calculation is performed in advance before rolling to obtain the first type parallel stiffness setting calculated value _Et which represents the influence on meandering, the influence coefficient ∂E/∂P of the rolling load P on the first _type parallel stiffness setting calculated value Et, the influence coefficient ∂E/∂F of the bending force F, and the influence coefficient ∂E/∂X of the control parameters selected in step S100, and the first type parallel stiffness actual calculated value _Eb is obtained by a simple calculation from the actual changes in the rolling load P and bending force F during rolling. This makes it possible to reduce the calculation load during rolling and to easily realize application to an actual machine.

Here, as described above, the rolling force actual value _Pb and bending force actual value _Fb in step S130, as well as the actual values of the other control parameters, are acquired simultaneously from the time when the leading end of the rolled material is bitten into the Mth stand to be controlled until the tail end of the rolled material is rolled by the Mth stand. Specifically, the measurement timing of the rolling force actual value _Pb and bending force actual value _Fb is as shown in FIG.

First, in the case of a tandem rolling mill having N (N≧2) rolling stands, when the Mth stand is any one of the second stand to the Nth stand, the rolling load actual value _Pb and the bending force actual value _Fb are measured from the timing (measurement timing 1) when the leading end T of the material A to be rolled is bitten into the Mth stand (#M) until the tail end _Sb of the material S to be rolled is rolled by the Mth stand (#M) (measurement timing 2), as shown in the upper part of Fig. 10. The tail end _Sb is in the range from the tail end T to a predetermined length, as described above. Furthermore, when the first stand (#1) of the tandem rolling mill is the object to be controlled, as shown in the center of FIG. 10, the rolling force actual value _Pb and the bending force actual value _Fb are measured during the period from the timing when the leading end T of the material A to be rolled is bitten into the first stand (#1) (measurement timing 1) to the time before the tail end _Sb of the material S to be rolled is rolled by the first stand (#1) (measurement timing 2).

In the case of a single-stand rolling mill, as shown in the lower part of FIG. 10, the rolling force actual value _Pb and the bending force actual value _Fb are measured during the period from the timing when the leading end T of the rolled material A is bitten into the first stand (#1) (measurement timing 1) to the timing before the tail end _Sb of the rolled material S is rolled by the first stand (#1) (measurement timing 2).

If there is sufficient time for calculation, it is preferable to measure the rolling load actual value _Pb and the bending force actual value _Fb when a portion as close as possible to the tail end portion _Sb is rolled by the Mth stand, which is the object of control.

(S140 to S160: control steps)
When the first type parallel stiffness actual calculation value _Eb is calculated in step S130, the meandering control device 100 determines whether or not to perform meandering control of the tail end of the rolled material in the Mth stand by comparing the first type parallel stiffness actual calculation value _Eb with a threshold value _ETH (S140).

If the first type parallel stiffness actual calculation value _Eb is equal to or less than the threshold value _ETH (i.e., if _Eb ≦ _ETH ), the degree of meandering of the tail end of the rolled material is small, so meandering control is not performed and the process proceeds to step S170 described later.

On the other hand, when the first type parallel stiffness actual calculation value _Eb is greater than the threshold value _ETH (i.e., when _Eb > _ETH ), the tail end of the rolled material meanders to a large extent, so meandering control is performed. Therefore, first, the meandering control device 100 calculates the change amount ΔX of the control parameter selected in step S100 in the Mth stand in order to make the first type parallel stiffness actual calculation value _Eb equal to or less than the threshold value _ETH (S150).

Specifically, the meandering control device 100 calculates the control amount (change amount) according to the control parameters of the meandering control. The way in which meandering control is performed can be set arbitrarily within the range that satisfies the facility constraints and shape control constraints.

When meandering control is performed by changing the roll speed of the work rolls 1 and 2 using a driving device such as a motor, the roll speed change amount ΔV that satisfies the following formula (9) is calculated.

When the lubricant supply device performs meandering control by changing only the lubricant supply amount Q, the lubricant supply amount change amount ΔQ that satisfies the following formula (9) is calculated.

When meandering control is performed by moving the roll chocks to change only the roll cross angle θ, the roll cross angle change amount Δθ that satisfies the following formula (11) is calculated.

When meandering control is performed by shifting the work rolls in the axial direction and changing only the roll shift amount L, the roll shift amount change amount ΔL that satisfies the following formula (12) is calculated.

When meandering control is performed by changing only the roll crown C of the work roll, the roll crown change amount ΔC that satisfies the following formula (13) is calculated.

When a plurality of control parameters are selected as the control parameters from among the roll speed V, the lubricant supply amount Q, the roll cross angle θ, the roll shift amount L, and the roll crown C, as shown in the following formula (14), the change amount ΔX of each control parameter X is calculated as a control amount so that the sum of the products of the change amounts ΔX of the selected control parameters X and the influence coefficient ∂E/∂X is equal to or smaller than the difference between the first type parallel stiffness actual calculation value _Eb and the threshold value _ETH .

When the change amount is calculated in step S150, the meandering control device 100 controls the control parameter X based on the calculated change amount ΔX of the control parameter X (S160). This allows meandering control of the tail end of the rolled material in the Mth stand.

(S170: Check for change in controlled variable)
Thereafter, whether or not there is a change in the control amount (change amount) in the meandering control of the tail end portion is confirmed (S170). For example, if the steel plate temperature fluctuates while rolling the tail end portion of the rolled material in the Mth stand, which is the controlled object, the rolling load changes and the value of the first type parallel stiffness actual calculation value also changes. In such a case, it is desirable to recalculate the first type parallel stiffness actual calculation value _Eb and correct the control amount.

Therefore, in step S170, the meandering control device 100 checks whether the control amount has changed, and if the control amount has not changed, the process of FIG. 3 ends. On the other hand, if the control amount has changed, the meandering control device 100 instructs the calculation processing device 200 to execute the process from step S130 again. The process from step S130 again may be executed at any time, for example, between the time when the leading end of the rolled material bites into the Mth stand to be controlled and before the tail end of the rolled material is rolled by the Mth stand.

For example, first, steps S130 to S160 are performed when the tail end of the rolled material leaves the first stand, then steps S130 to S160 are performed when it leaves the second stand, and then steps S130 to S160 are performed when it leaves the third stand. In this way, the need for meandering control at stand M is checked multiple times between when the tip of the rolled material bites into stand M, which is the control target, and before the tail end of the rolled material is rolled at stand M, and meandering control is performed if the degree of meandering is large. This makes it possible to more reliably suppress the occurrence of meandering.

(Modification)
In the meandering control example 1 shown in Fig. 3, at least one of the roll speed V, the lubricant supply amount Q, the roll cross angle θ, the roll shift amount L, and the roll crown C is selected as the control parameter in step S100, but at least one of the rolling position S and the bending force F may be selected as the control parameter. Hereinafter, a process in which at least one of the roll speed V, the lubricant supply amount Q, the roll cross angle θ, the roll shift amount L, and the roll crown C and at least one of the rolling position S and the bending force F are selected as the control parameters will be described with reference to Figs. 11A and 11B. In the following description, detailed description of the same process as that in Fig. 3 will be omitted.

(S200: Selection of control parameters)
11A, first, at least one of the roll speed V, the lubricant supply amount Q, the roll cross angle θ, the roll shift amount L, and the roll crown C, and at least one of the rolling position S and the bending force F are used as the control parameters (S200). As described above, the control parameters can be selected based on the purpose to be emphasized in addition to the reduction of the amount of meandering in the meandering control at the tail end of the rolled material, constraints on the equipment configuration of the rolling stand 10, and the like. The control parameters may be selected by an operator, or the control parameters may be automatically selected by a calculation processing device.

For example, when the reduction position S is used as the control parameter, it does not interfere with shape control and is therefore effective in reducing yield loss due to poor shape. When the bending force F is used as the control parameter, it interferes with shape control and is therefore more likely to result in yield loss due to poor shape, but it is effective in reducing yield loss due to poor plate thickness. Control of the reduction position S or bending force F is generally provided in most rolling stands using a control device, and can be easily performed.

By combining at least one of the pressing position S or bending force F with at least one of the roll speed V, lubricant supply amount Q, roll cross angle θ, roll shift amount L, and roll crown C and using them as control parameters, it becomes possible to control the meandering by taking advantage of the characteristics of each control parameter.

For example, when three control parameters, roll speed V, lubricant supply amount Q, and roll down position S, are used, these are all control parameters that reduce the first parallel stiffness E by changing the rolling load P. Since the roll speed V, lubricant supply amount Q, and roll down position S do not affect the shape defects of the rolled material, they are more effective in reducing the yield loss due to shape defects than other parameters (roll cross angle θ, roll shift amount L, roll crown C, bending force F). In addition, the roll down position S can be controlled with high responsiveness when a hydraulic roll down device is provided, so it is more effective in preventing the occurrence of squeezing than the roll speed V or lubricant supply amount Q. On the other hand, the roll speed V and lubricant supply amount Q reduce the first parallel stiffness E without significantly changing the roll down amount, so they are more effective in reducing the yield loss due to plate thickness defects than the roll down position S.

For example, when considering the case where four control parameters, the roll cross angle θ, the roll shift amount L, the roll crown C, and the bending force F, are used, these are all control parameters that reduce the first type parallel stiffness E by increasing the sheet crown. The roll cross angle θ, the roll shift amount L, the roll crown C, and the bending force F do not affect the average sheet thickness of the rolled material, and therefore are more effective at reducing yield loss due to poor sheet thickness than the other parameters (roll speed V, lubricant supply amount Q, and reduction position S).

Furthermore, when other parameters (roll speed V, lubricant supply amount Q, rolling position S) are used, there are cases where the first parallel stiffness E does not change significantly even if the rolling load is changed. For example, there are cases where the effect on the first parallel stiffness E of the elongation deformation of the rolling stand caused by the change in rolling load P and the effect on the first parallel stiffness E of the bending deformation of the rolling stand caused by the change in rolling load P are offset. In this case, a sufficient effect of preventing the occurrence of squeezing cannot be obtained, but if the roll cross angle θ, roll shift amount L, roll crown C, and bending force F are used as control parameters and the sheet crown is controlled to be large, it is possible to reduce the first parallel stiffness E under most conditions, including the above-mentioned case. Therefore, the roll cross angle θ, roll shift amount L, roll crown C, and bending force F have a greater effect of preventing the occurrence of squeezing than other parameters (roll speed V, lubricant supply amount Q, rolling position S).

Most rolling stands are generally equipped with a control device, and the bending force F is a control parameter that can be used regardless of the equipment configuration of the rolling stand, so it can be controlled more easily than the roll cross angle θ, roll shift amount L, and roll crown C. On the other hand, the controllable range of the roll cross angle θ, roll shift amount L, and roll crown C is often relatively large, so they are slightly more effective at preventing the occurrence of squeezing than the bending force F.

In light of the above, it is possible to use control parameters such as the following cases a to f. In describing the priority of objectives, reduction of yield loss due to poor shape is described as "shape", reduction of yield loss due to poor thickness is described as "thickness", and prevention of reduction in thickness is described as "reduction in thickness". For cases c, d, and f, usable control parameters may be selected depending on the equipment configuration of the rolling stand.

(Case a: Shape > Plate thickness > Drawing) → Roll speed V, Lubricant supply amount Q
(Case b: Shape > Drawing > Plate thickness) → Pressing position S
(Case C: Plate thickness > Shape > Drawing)
→ Roll cross angle θ, roll shift amount L, roll crown C, bending force F
(Case d: Plate thickness > Drawing > Shape)
→ Roll cross angle θ, roll shift amount L, roll crown C, bending force F
(Case e: Drawing > Shape > Plate thickness) → Pressing position S
(Case F: Drawing > Plate thickness > Shape)
→ Roll cross angle θ, roll shift amount L, roll crown C, bending force F

In cases where the priority level changes depending on the conditions, for example, when there are cases a and b, it is possible to use a combination of the reduction position S and at least one of the roll speed V and the lubricant supply amount Q, and adjust the balance of the control amount of the control parameters according to the rolling conditions. In addition, by using many control parameters, the controllable range is expanded (the effect of preventing the occurrence of squeezing is increased). Therefore, for example, if it is desired to suppress the occurrence of squeezing as much as possible while giving priority to reducing the yield loss due to poor shape, it is desirable to select all of the reduction position S, roll speed V, and lubricant supply amount Q as control parameters. In addition, for example, if it is desired to prevent the occurrence of squeezing as much as possible while giving priority to reducing the yield loss due to poor plate thickness, it is desirable to use all of the controllable control parameters among the bending force F, roll cross angle θ, roll shift amount L, and roll crown C.

(S210: Threshold setting step)
When the control parameters are selected in step S200, a threshold value _ETH of the first type parallel stiffness at which the amount of meandering of the rolled material is less than the allowable value is set in advance before rolling (S210). Step S210 may be performed in the same manner as step S110 in FIG.

(S220 to S230: First type parallel stiffness calculation step)
Next, a first type parallel stiffness actual calculation value _Eb is calculated. In meandering control example 1, the first type parallel stiffness actual calculation value _Eb is calculated using the first type parallel stiffness set calculation value _Et and the influence coefficient. Basically, step S220 in FIG. 11A may be performed in the same manner as step S120 in FIG. 3. In this modified example, at least one of the pressing position S and the bending force F is also selected as a control parameter. Therefore, in step S220, the influence coefficient of the added control parameter is further calculated.

That is, in step S220, the calculation processing device 200 calculates the first parallel stiffness setting calculation value E _t , and the influence coefficient ∂E/∂P of the rolling load P and the influence coefficient ∂E/∂F of the bending force F on the first parallel stiffness setting calculation value E _t . Furthermore, the calculation processing device 200 calculates the influence coefficients of the control parameters selected in step S200, that is, at least one of the influence coefficient ∂E/∂V of the roll speed V on the first parallel stiffness setting calculation value E _t , the influence coefficient ∂E/∂Q of the lubricant supply amount Q, the influence coefficient ∂E/∂θ of the roll cross angle θ, the influence coefficient ∂E/∂L of the roll shift amount L, and the influence coefficient ∂E/∂C of the roll crown C. Furthermore, at least one of the influence coefficient ∂E/∂S of the rolling position S and the influence coefficient ∂E/∂F of the bending force F is calculated. The influence coefficient ∂E/∂S of the rolling position S is expressed by the following formula (15).

Step S230 in FIG. 11B may be performed in the same manner as step S130 in FIG. 3.

(S240 to S260: control steps)
When the first type parallel stiffness actual calculation value _Eb is calculated in step S230, the meandering control device 100 judges whether or not to perform meandering control of the tail end portion of the rolled material in the Mth stand by comparing the first type parallel stiffness actual calculation value _Eb with a threshold value _ETH (S240). Step S240 may be performed in the same manner as step S140 in FIG. 3.

If the first type parallel stiffness actual calculation value _Eb is equal to or less than the threshold value _ETH (i.e., if _Eb ≦ _ETH ), the degree of meandering of the tail end of the rolled material is small, so meandering control is not performed and the process proceeds to step S270 described later.

On the other hand, when the first type parallel stiffness actual calculation value _Eb is larger than the threshold value _ETH (i.e., when _Eb > _ETH ), the tail end of the rolled material meanders to a large extent, and so meandering control is performed. For this reason, the meandering control device 100 first calculates the change amount ΔX of the control parameter selected in step S200 in the Mth stand in order to make the first type parallel stiffness actual calculation value _Eb equal to or smaller than the threshold value _ETH (S250). Step S250 may basically be performed in the same manner as step S150 in Fig. 3, but in addition, the change amount of an added control parameter is calculated.

Specifically, for the amount of change in the additional reduction position S or bending force F, the meandering control device 100 calculates the control amount depending on whether the increase bending devices 11a to 11d (and further the decrease bending devices 12a to 12d) or the reduction device 13 is driven to perform the meandering control, as follows. The method of meandering control can be set arbitrarily within the range that satisfies the equipment constraints and shape control constraints.

First, when snaking control is performed by changing only the roll-down position using the roll-down device 13, a roll-down position change amount ΔS that satisfies the following formula (16) is calculated.

In addition, when meandering control is performed by changing only the bending force F using the increase bending devices 11a to 11d (and further the decrease bending devices 12a to 12d), a bending force change amount ΔF that satisfies the following formula (17) is calculated.

In addition, when a plurality of control parameters, including at least one of the roll speed V, the lubricant supply amount Q, the roll cross angle θ, the roll shift amount L, and the roll crown C, and at least one of the pressing position S or the bending force F, are selected as the control parameters, as shown in the above formula (14), the change amount ΔX of each control parameter X is calculated as a control amount so that the sum of the products of the change amount ΔX of the selected control parameter X and the influence coefficient ∂E/∂X is equal to or less than the difference between the first type parallel stiffness actual calculation value _Eb and the threshold value _ETH .

When the control amount is calculated in step S250, the meandering control device 100 controls the control parameter X based on the calculated control amount (change amount ΔX of the control parameter X) (S260). This allows meandering control of the tail end of the rolled material in the Mth stand. Step S260 can basically be performed in the same way as step S160 in FIG. 3, and furthermore, the change amount of an added control parameter (at least one of the rolling position S or bending force F) is calculated.

(S270: Check for change in control amount)
Thereafter, it is confirmed whether or not there is a change in the control amount in the meandering control of the tail end portion (S270). Step S270 may be performed in the same manner as step S170 in FIG.

The meandering control example 1 according to the present embodiment has been described above. In the meandering control example 1, the first type parallel stiffness set calculation value _Et and the influence coefficient for calculating the first type parallel stiffness actual calculation value _Eb are obtained before rolling, so that the calculation load during rolling can be reduced and application to an actual machine can be easily realized. In addition, since the calculated first type parallel stiffness actual calculation value _Eb is also estimated with high accuracy, it is possible to reduce the amount of meandering at the tail end of the rolled material and suppress the occurrence of reduction, and it is also possible to reduce thickness defects and shape defects of the rolled material after rolling.

[2-2. Example of meandering control 2 (calculation of first-class parallel stiffness actual value using model)]
Next, a case where a first type parallel stiffness actual calculation value is calculated using a model and meandering control of the tail end portion of the rolled material is performed will be described with reference to Figs. 12 and 13 as meandering control example 2. Fig. 12 is a schematic diagram showing an overview of the calculation process of a first type parallel stiffness actual calculation value _Eb in meandering control example 2. Fig. 13 is a flowchart showing the process of meandering control example 2.

As shown in Fig. 12, in meandering control example 2, a model is used to directly calculate a first type parallel stiffness actual calculation value _Eb from the rolling conditions of the tail end portion. That is, in meandering control example 2, calculation of a first type parallel stiffness set calculation value _Et and an influence coefficient on the first type parallel stiffness is not performed as in meandering control example 1, but a first type parallel stiffness actual calculation value _Eb is calculated from the rolling conditions of the tail end portion. Since calculation using a model is a high-load calculation, the calculation processing time may be longer than that of meandering control example 1, but it is possible to calculate a first type parallel stiffness actual calculation value _Eb in one calculation process. Hereinafter, meandering control example 2 will be described, but detailed description of the same processes as those in meandering control example 1 will be omitted.

(S300: Selection of control parameters)
As shown in Fig. 13, first, at least one of the roll speed V, lubricant supply amount Q, roll cross angle θ, roll shift amount L, and roll crown C is used as a control parameter (S300). As described above, the control parameters can be selected based on the purpose of the meandering control at the tail end of the rolled material, which is emphasized in addition to the reduction of the meandering amount, and the constraints on the equipment configuration of the rolling stand 10. The control parameters may be selected by an operator, or may be automatically selected by a calculation processing device. Step S300 may be performed in the same manner as step S100 in Fig. 3.

(S310: Threshold setting step)
In addition, a threshold value E _TH of the first type parallel stiffness at which the amount of meandering of the rolled material is less than the allowable value is set beforehand before rolling (S200). The threshold value E _TH may be set in the same manner as in step S110 of FIG.

(S320: First type parallel stiffness calculation step)
Next, a first type parallel stiffness actual calculation value _Eb is calculated. In meandering control example 2, the calculation processing device 200 calculates a first type parallel stiffness actual calculation value _Eb by using a model from the rolling conditions of the tail end of the rolled material in the Mth stand, which is the control target (S320). This calculation is performed based on the actual values of the control parameters selected in step S300 from the rolling load actual value _Pb , the bending force actual value _Fb , and the roll cross angle actual value _θb , the roll shift amount actual value _Lb , and _the roll crown actual value Cb.

The rolling force actual value _Pb and the bending force actual value _Fb are simultaneously acquired during the period from when the leading end of the rolled material is bitten into the Mth stand until before the tail end of the rolled material is rolled by the Mth stand. The currently set values may be used for the roll speed actual value _Vb , the lubricant supply amount actual value _Qb , the roll cross angle actual value _θb , the roll shift amount actual value _Lb , and the roll crown actual value _Cb . For example, when control starts, initial set values are used, and when the values are changed in step S350 described later, the changed values are used.

As a model for calculating the first type parallel stiffness actual calculation value _Eb , for example, a mill stretch model can be used (for example, see Non-Patent Document 2). Note that such calculation may be performed using a model other than the mill stretch model.

(S330 to S350: control steps)
When the first type parallel stiffness actual calculation value _Eb is calculated in step S320, the meandering control device 100 determines whether or not to perform meandering control of the tail end portion of the rolled material in the Mth stand by comparing the first type parallel stiffness actual calculation value _Eb with a threshold value _ETH (S330).

If the first type parallel stiffness actual calculation value _Eb is equal to or less than the threshold value _ETH (i.e., if _Eb ≦ _ETH ), the degree of meandering of the tail end of the rolled material is small, so meandering control is not performed and the process proceeds to step S360 described later.

On the other hand, when the first type parallel stiffness actual calculation value _Eb is larger than the threshold value _ETH (i.e., when _Eb > _ETH ), the tail end of the rolled material meanders to a large extent, so meandering control is performed. The meandering control may be performed in the same manner as steps S150 and S160 in FIG. 3. First, the meandering control device 100 calculates, as a control amount, a change amount ΔX of the control parameter selected in step S300 in the Mth stand for making the first type parallel stiffness actual calculation value _Eb equal to or smaller than the threshold value _ETH (S340). Then, when the change amount is calculated, the meandering control device 100 controls the control parameter X based on the calculated change amount ΔX of the control parameter X (S350). As a result, meandering control of the tail end of the rolled material in the Mth stand is performed.

(S360: Check for change in control amount)
Thereafter, whether or not there is a change in the control amount in the meandering control of the tail end is confirmed (S360). Step S360 may be performed in the same manner as step S170 in FIG. 3. That is, the meandering control device 100 confirms whether or not there is a change in the control amount, and if there is no change, ends the processing of FIG. 13 as it is. On the other hand, if there is a change in the control amount, the meandering control device 100 instructs the arithmetic processing device 200 to execute the processing from step S320 again. The processing of steps S320 to S350 may be repeated, for example, until the target value is not updated, or until the processing is repeated a predetermined number of times. This makes it possible to more reliably suppress the occurrence of meandering.

The above describes the meandering control example 2. In the above description, as shown in FIG. 3 of the meandering control example 1, at least one of the roll speed V, the lubricant supply amount Q, the roll cross angle θ, the roll shift amount L, and the roll crown C is selected as the control parameter in step S300. However, as shown in the modified example of the meandering control example 1 shown in FIG. 11A and FIG. 11B, at least one of the pressing position S or the bending force F may be selected as the control parameter.

The following verification was conducted to confirm the effectiveness of the tail meandering control of the rolled material according to this embodiment. In the verification, the occurrence rate of narrowing and the tail end yield loss rate were investigated when a steel plate was rolled in a finishing tandem rolling mill consisting of multiple rolling stands. The occurrence rate of narrowing represents the rate at which narrowing occurs due to meandering during tail end rolling. The tail end yield loss rate represents the rate at which the thickness of the steel plate after rolling deviates from the target thickness.

The verification was carried out for Comparative Examples 1 and 2 and an Example. Comparative Example 1 was a case where meandering control was not performed for the tail end of the steel plate, and Comparative Example 2 was a case where meandering control was performed for the tail end of the steel plate using the method of Patent Document 1. In addition, as an Example, meandering control was performed for the tail end of the steel plate based on meandering control example 1 of the meandering control method according to one embodiment of the present invention. The verification results are shown in Table 1 below.

As can be seen from Table 1 above, in Comparative Example 1, meandering control was not performed at the tail end of the steel plate, so meandering occurred and 0.100% narrowing occurred. In Comparative Example 2, meandering control was performed at the tail end of the steel plate, and as a result, the rate of meandering occurrence decreased compared to Comparative Example 1, and as a result, the rate of narrowing occurrence decreased. However, the plate thickness accuracy at the tail end deteriorated compared to Comparative Example 1.

On the other hand, in Examples 1 to 9, in which meandering control of the tail end of the steel plate was performed based on the meandering control example 1, the occurrence rate of meandering was reduced compared to Comparative Example 1, and as a result, the occurrence rate of squeezing was reduced. In addition, the thickness accuracy of the tail end was improved, and the yield loss rate of the tail end was also reduced. In Examples 1, 3, and 4, the reduction position, roll speed, and lubricant supply amount were used as control parameters, so it is believed that the thickness defect at the tail end was reduced and the yield loss rate at the tail end was reduced. In Examples 2, 5 to 8, the bending force, roll shift amount, roll cross angle, and roll crown were used as control parameters, so it is believed that the occurrence of squeezing was reduced. In Examples 8 and 9, a control parameter that is highly effective in reducing thickness defects was used in combination with a control parameter that is highly effective in preventing squeezing, so both the occurrence rate of squeezing and the yield loss rate at the tail end were reduced compared to other Examples.

The above describes in detail preferred embodiments of the present invention with reference to the attached drawings, but the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can conceive of various modified or revised examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

REFERENCE SIGNS LIST 1 Upper work roll 2 Lower work roll 3 Upper backup roll 4 Lower backup roll 5 Upper work roll chock 6 Lower work roll chock 7 Upper backup roll chock 8 Lower backup roll chock 9 Housing 9a Entry project block 9b Exit project block 10 Rolling stand 11a to 11d Increase bending device 12a to 12d Decrease bending device 13 Screw down device 14 Rolling load detection device 100 Meandering control device 200 Calculation processing device

Claims (4)

A method for controlling meandering of a rolled material, the method comprising the steps of: controlling meandering of the rolled material in an Mth stand (1≦M≦N) in rolling of the rolled material by N rolling stands (N is a natural number), the steps comprising:
The control parameter of the meandering control is at least one of a roll speed V, a lubricant supply amount Q, a roll cross angle θ, a roll shift amount L, and a roll crown C,
a threshold value setting step of setting in advance a threshold value E _TH of a first type parallel stiffness at which the tail end meandering amount of the rolled material in the Mth stand is less than a permissible value;
a first type parallel stiffness calculation step of calculating a first type parallel stiffness actual calculation value _Eb at the Mth stand;
When the first type parallel stiffness actual calculation value _Eb is equal to or smaller than the threshold value _ETH , the control parameter is not changed ,
When the first type parallel stiffness actual calculation value _Eb is greater than the threshold value _ETH ,
Calculating a change amount of the control parameter of the M stand for making the first type parallel stiffness equal to or less than the threshold value _ETH based on the first type parallel stiffness actual calculation value _Eb;
a control step of controlling a control parameter of the M stand corresponding to the calculated change amount of the control parameter based on the calculated change amount of the control parameter while the tail end portion of the rolled material passes through the M stand;
A method for controlling meandering of a rolled material, comprising: The method for controlling the meandering of a rolled material according to claim 1, further comprising using at least one of the rolling position and the bending force as the control parameter. 3. The method for controlling meandering of a rolled material according to claim 1 or 2, wherein in the first type parallel stiffness calculation step, a first type parallel stiffness actual calculation value Eb at the M stand is calculated based on a rolling load actual value _Pb and a bending force actual value _Fb at the M stand, which are simultaneously acquired during a period from when the leading end of the rolled material is bitten into the M stand until before the tail end of the rolled material is _rolled by the M stand, and actual values of the control parameters. In the first type parallel stiffness calculation step,
Calculate the rolling load set value _Pt and the bending force set value _Ft in the M stand and the set values of the control parameters by setup calculation;
Calculating the influence coefficient ∂E/∂P of the rolling load, the influence coefficient ∂E/∂F of the bending force, and the influence coefficients of the control parameters with respect to the first type parallel stiffness setting calculation value _Et in the M stand;
Calculating difference values between the set values and the actual values based on a rolling load actual value Pb and a bending force actual value _Fb at the M stand, which are simultaneously acquired during a period from when the leading end of the rolled material is bitten into the M stand until the tail end of the rolled material is rolled by the _M stand, and actual values of the control parameters;
3. The method for controlling meandering of a rolled material according to claim 1 or 2, further comprising the step of calculating the first type parallel stiffness actual calculation value _Eb at the Mth stand based on the difference value and the influence coefficient.

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