JPH07299510A - Method for controlling sheet crown and sheet shape in continuous rolling mill - Google Patents

Abstract

PURPOSE:To obtain a method for controlling sheet crown and sheet shape in a continuous rolling mill by which a sheet is rolled while maintaining good sheet crown and sheet shape. CONSTITUTION:A sheet crown schedule 11 in the downstream direction which has the optimum manipulated variable and allowable manipulated variable from the operating condition and capacity of equipment at each stand based on a crown value on the inlet side of the continuous rolling mill is connected with a sheet crown schedule 12 in the upstream direction which has the optimum manipulated variable and allowable manipulated variable for making the target sheet crown and sheet shape on the outlet side of the final rolling mill into desired values. This is a pass schedule by which respective manipulated variables are changed from the sheet crown schedule 11 in the downstream direction to the sheet crown schedule 12 in the upstream direction so that the respective variables are mutually satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate crown / plate shape control method for a continuous rolling mill for rolling while maintaining a good plate crown / plate shape.

[0002]

2. Description of the Related Art In a continuous rolling mill equipped with plate crown / plate shape control capability, it is only necessary to secure the plate crown and plate shape (flatness of plate surface) of a material to be rolled such as a steel plate at target values. First, from the standpoint of the passing plate, it is important to maintain the plate shape between stands or between passes within an allowable range and make it as flat as possible. In order to effectively perform such shape control from the tip of the material to be rolled, a pass schedule that initially sets the control operation amounts of the plate crown and plate shape to optimal values is necessary. In order to achieve such an object, conventionally, the preset calculation of the strip crown and strip shape in the hot rolling mill has been set by a predetermined table or manually by an operator. However, the plate crown and the plate shape have the property of interfering with each other. Therefore, it is the current situation that ordinary manual setting by an operator or setting by a table cannot easily cope with fluctuations in rolling conditions. That is, it is difficult to achieve the target plate crown and plate shape at the same time because the plate shape is deteriorated in an attempt to control the plate crown, or the opposite phenomenon occurs. In addition, Japanese Patent Publication No. 3-3304
No. 1 gazette calculates the maximum and minimum plate crown ratio of each stand that can be achieved under the shape allowable range in each stand and the shape control operation amount allowable range, and based on this, with respect to the target product plate crown ratio. , In order to reduce the change in plate crown ratio between stands in the downstream stand,
That is, the target crown ratio of each stand is determined so that the inter-stand plate shape is constant in the downstream stand,
It is described that the shape control operation amount of each stand is determined based on this. Specifically, the shape control operation amount is determined by determining the maximum and minimum crown ratios of the i-th stand that can be achieved under the control conditions (shape control allowable range, plate shape allowable range) from the first stand to the i-th stand. , The first stand to the n-th stand (final stand) are sequentially calculated. Based on this, a stand capable of achieving a plate crown ratio equal to the product target plate crown ratio is obtained from the downstream side.
For the stands upstream of these stands, the previously determined maximum or minimum plate crown ratio is set as the target plate crown ratio, and the downstream stand sets a value close to the product plate crown ratio as the target plate crown ratio.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
According to Japanese Patent Publication No. 41-41, line 21 in FIG. 6 showing the relationship between the stand number and the plate crown ratio (ratio between plate crown and plate thickness).
As described above, in the downstream stand, since the change in the plate crown ratio between the stands is small, the plate flatness between the stands becomes small, but between the downstream stand and the stands whose maximum or minimum plate crown ratio is the target plate crown ratio,
Also, regarding the stand upstream of this stand, the change in the plate crown ratio between the stands becomes large, and the plate flatness becomes large. Therefore, if the plate shape of the downstream stand is uniformly small, there is a problem that the plate flatness of the upstream stand becomes large, and depending on the conditions, the line 2 shown in FIG.
As described in No. 2, there is a problem that the number of downstream stands that aims to reduce the plate flatness decreases. As described above, with the conventional control method, it has been difficult to deteriorate the plate shape of the specific stand or reliably control the plate crown on the delivery side of the final rolling stand. Further, there is a drawback that the allowable limit of the obtained result is unknown and the range that can cope with the sudden situation change cannot be determined, so that the possible limit cannot be determined. Further, although the prior art can be used in the case of having only one plate crown shape operation means, it cannot be applied to a rolling mill having a plurality of plate crown shape control means. In view of the above problems, the present invention optimizes the plate crown at each stand, and is also applicable to a rolling mill having a plurality of plate crown shape control means, a plate crown / plate shape control method for a continuous rolling mill. The purpose is to provide.

[0004]

According to the present invention, the optimum operation amount and the allowable operation amount are determined from the operating conditions and equipment capacity of each stand based on the plate crown value on the inlet side of the continuous rolling mill. The downstream direction crown crown schedule, the target plate crown on the exit side of the final rolling mill, and the upstream direction crown crown schedule with the optimum and allowable operation amounts for setting the plate shape to the desired value. And a pass schedule that changes from the downstream direction plate crown schedule to the upstream direction plate crown schedule so that the respective operation amounts are satisfied with each other.
That is, the downstream plate crown schedule, with the plate crown on the inlet side of the continuous rolling mill as an initial value, in each stand from the upstream stand, optimal from operating conditions and rolling conditions,
Determine the stand-out side plate crown and the allowable range of the stand-out side plate crown. This is sequentially calculated until the final stand. The upstream direction plate crown schedule uses the target product plate crown on the delivery side of the continuous rolling mill as an initial value, determines the optimum stand entry side plate crown from the downstream stand to each stand from operating conditions and rolling conditions, and determines the allowable stand. Determine the range of the entry side crown. This is sequentially calculated up to the first stand. The plate crown on the delivery side of the final stand calculated by the downstream plate crown schedule does not always match the target product plate crown. By combining the calculated upstream direction plate crown schedule and the downstream direction plate crown schedule with an intermediate stand where the allowable widths overlap, various conditions are satisfied in each stand, and a target product plate crown on the exit side of the final stand is obtained. As a result, it is possible to determine a pass schedule having an excellent plate crown and plate shape.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for controlling a strip crown and strip shape of a continuous rolling mill according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a demonstration example to which the present invention is applied. In the figure,
A rolling condition input means 1 inputs rolling conditions such as a plate thickness, a plate width, a rolling load, a roll crown, and an entering side plate crown. 2 is a model parameter calculation means, which will be described later (1),
The model parameters of the plate crown ratio and flatness represented by the equation (2) are calculated. 11 is a downstream direction plate crown calculation means, with the plate crown on the entrance side of the continuous rolling mill as an initial value,
In each of the stands from the upstream stand, the optimum stand exit side plate crown is determined from the operating conditions and rolling conditions, the allowable range of the stand exit side plate crown is determined, and this is sequentially calculated up to the final stand. The downstream direction plate crown calculating means 11 includes an evaluation function J1 _i calculating means 3, an evaluation function J2 _i calculating means 4, an evaluation function JU _i calculating means 5, and a crown target C _i calculating means 6. Reference numeral 12 is an upstream-direction plate crown schedule calculation means, which determines an optimum stand-in side plate crown from operating conditions and rolling conditions in each stand from the downstream stand with the target product plate crown on the delivery side of the continuous rolling mill as an initial value. , Determine the allowable range of the stand-in side plate crown, and calculate sequentially up to the first stand. The upstream direction plate crown calculating means 12 comprises an evaluation function J1 _i calculating means 7, an evaluation function J2 _i calculating means 8, an evaluation function JU _i calculating means 9, and a crown target C _i calculating means 10. In the downstream direction plate crown schedule calculated by the downstream direction plate crown calculating means 11, the plate crown on the delivery side of the final stand does not always become the target product plate crown. Reference numeral 18 denotes a connecting means which is an intermediate stand in which the widths of both the upstream direction plate crown schedule calculated by the upstream direction plate crown schedule calculation means 12 and the downstream direction plate crown schedule calculated by the downstream direction plate crown schedule calculation means 11 overlap. In order to determine a plate crown schedule that satisfies various conditions in each stand and can obtain a target product plate crown on the delivery side of the final stand. The connection means 18 includes a determination means 13, an evaluation function JC _i calculation means 14, an evaluation function JS calculation means 15, each stand target plate crown determination means 16, and each stand operation amount determination means 1.
It consists of 7. The crown shape manipulated variable of each stand to achieve the plate crown schedule determined by the above procedure is calculated and set. Next, a model formula representing the relationship between the plate crown, the plate shape, and the crown control operation amount and the method for determining the crown control operation amount will be described. The same applies to a multi-pass rolling mill.
That is, the i-th stand outlet side of the strip crown C _i in the continuous rolling mill, flatness f _i is given by the following equation.

C _i = a 0 (P _i , CR _i ) + a 1 _i · C _i−1 + a 2 _i · x _{1 i} + a 3 _i · x 2 _i (1) f _i = b _i · (C _i / h _i −C _{i -1} / h _{i -1} ) (2) However, in the formulas (1) and (2), i: stand number (i = 1 to n, n is the final stand number) P: rolling load CR: roll crown x1 : Crown shape operation amount (operation means 1) x2: Crown shape operation amount (operation means 2) h: Delivery side plate thickness a0, a1, a2, a3: Plate crown influence coefficient b: Shape change coefficient

It should be noted that a1 to a3 and b are determined from rolling conditions such as plate thickness, plate width, roll dimension, tension, etc., and are determined by model calculation or experimentally. Further, in the formula (1), the crown shape operation amount indicates two places, but if there are three or more operation means, the same term may be added, and only one operation means may be added. If there is only that, it is sufficient to consider only x1. Therefore, if the rolling conditions and the plate crown C0 on the inlet side of the continuous rolling mill are given, the plate crown C _i on the outlet side of each stand can be obtained, and the flatness can also be obtained from the equation (2). On the contrary, if the plate crown C _i is determined, the crown shape operation amount is determined from the equation (1). However, when there are a plurality of operating means, the respective operating amounts cannot be uniquely determined. Based on the above formulas (1) and (2) as basic formulas, the product target plate crown C _n based on the rolling conditions such as plate thickness, plate width, rolling load, roll crown, and incoming plate crown of the continuous rolling mill. *, Product target flatness f _n
It is intended to obtain the crown-shaped manipulated variables x1 and x2 such that * is secured and the flatness on the delivery side of the first to (n-1) th stand is made as small as possible. Further, although the crown-shaped manipulated variables x1 and x2 cannot be uniquely determined, as a guideline for determining these, an attempt is made to obtain an manipulated variable that matches the operator's sense by incorporating an empirical value. The method for determining the crown shape manipulated variable for the above purpose will be described in detail below. First, the rolling conditions such as the plate thickness, the plate width, the rolling load, and the roll crown are input to the rolling condition input means 1, and then the model parameter calculation means 2 inputs the plate crown influence coefficient a0 in the above equations (1) and (2). ~ A
3 and the shape change coefficient b are calculated. The calculation result here is a calculation under a fixed condition, and is synonymous with the determination of the shape dead zone. Then, the downstream direction plate crown schedule calculation unit 11 calculates the downstream direction plate crown schedule. Here, based on the plate crown on the first stand entry side,
The target value of the plate crown at each stand is sequentially calculated until the final stand. First, the evaluation function J1 _i calculating means 3 calculates the next evaluation function J1 _i at the i-th stand in order to minimize the flatness of each stand.

J1 _i = f (C _i-1 , C _i , h _i-1 , h _i ) (3)

Equation (3) is expressed by the i-1th stand entry side plate crown C _i-1 , the plate thickness h _i-1 , and the i-th stand exit side plate thickness h _i.
Is given, the i-th stand outgoing side plate crown C _i
Is given to the evaluation function J1 _i . The evaluation function is normalized so that the maximum value is 1 and the minimum value is 0.
In Equation (2), the maximum value is given at the i-th stand outgoing side plate crown C _i where the flatness is the smallest (f _i = 0). However, this is a case where the flatness between the stands is reduced, and if there is a target of the flatness between the stands, J1 _i takes the maximum value in C _i which gives the target from the equation (2). May be determined as follows. The value of the evaluation function is set to 0 when C _i 1 is such that the plate shape is not good. FIG. 2 is a diagrammatic representation of this evaluation function. Next, the evaluation function J2 _i calculation means 4
Then, the weighting function for each operation amount is calculated so as to optimize the crown-shaped operation amount in each stand. I-th
The weighting function for each manipulated variable x1 _i , x2 _i in the stand is given by the following equation.

W1 _i = f (x1 _i ) (4) W2 _i = f (x2 _i ) (5)

In each case, the magnitude of the weighting function is given to the operation amount. The weighting function is set to the maximum value in the most desirable operation amount in the i-th stand. In addition, the upper and lower limits of the manipulated variable are determined based on the equipment-like operation range of each manipulated variable and the operator's request. Then, the evaluation function JD _i calculation means 5 calculates the i-th value from the equations (4) and (5).
Calculate the following cost function in the stand.

J2 _i = f (C _i ) (6)

C _{i in the} equation (6) is calculated by the equation (1) from X1 _i and X2 _i . The magnitude of J2 _i with respect to C _i is calculated by the following formula.

J2 _i = (W1 · W1 _i + W2 · W2 _i ) / J2 _maxi (7)

Since this evaluation function corresponds to the weighting function of each operation amount, the evaluation function is set to have the maximum value in the most desirable operation amount. Further, J2 _i is normalized as shown in equation (7), and the maximum value is 1. FIG. 3 schematically shows an example of the calculation of the weighting function and the calculation of the evaluation function in the evaluation function calculating means 4. In this example, the cross angle of the pair cross rolling mill and the bending force of the roll bender are considered as the crown shape operation amount. The following method is one example of the method of calculating the cross angle setting weight function. That is, when the rolls are thermally expanded by the subsequent rolling and a so-called heat crown is formed, the plate crown tends to become smaller, so the cross angle needs to be made smaller. The expected value Δθ ⁻ of the cross angle in the rolling cycle in the decreasing direction is calculated. Next, the expected value Δθ ⁺ in the increasing direction that increases the cross angle due to the increase of the rolling load in the rolling cycle in the subsequent rolling is calculated. Next, the upper and lower limits of the cross angle θ
Calculate min and θmax. Using these, the cross angle θopt at which the weighting function becomes maximum is calculated by the following equation.

[0016] ^{θopt = θmin + | Δθ - |} · (θmax -θmin) / (| Δθ - | + | Δθ + |) ... (8)

As another example, the previous set value can be selected as the cross angle that maximizes the weight function. In this case, the aim is to reflect the requirement that the cross angle is not frequently changed. Next, the evaluation function JDi
In _calculation detecting means 5 combines the evaluation function J1 _i and J2 _i, to calculate the evaluation function JD _i. FIG. 4 is a diagrammatic representation of this.

JD _i = f (C1) = J1 _i × W1 + J2 _i × W2 (when J1 _i ≠ 0 and J2 _i ≠ 0) = 0 (when J1 _i = 0 or J2 _i = 0) (9)

Here, the plate crown C1 having the maximum evaluation function JD _i is set as the target plate crown C _i D on the delivery side of the i-th stand. Further, the crown shape manipulated variables x1 _i and x2 _i are calculated from C _i D using the equations (6) and (7). With the above calculation, the target value C _i D of the stand outlet side plate crown is calculated from the _i- th stand inlet side plate crown C _i-1 . Next, for the (i + 1) th stand, the target plate crown C _{i + 1} D on the stand exit side is calculated in the same manner as above with the entrance side plate crown as C _i D. Similarly, the evaluation function of each stand and the target plate crown C _i D are calculated until the final stand. In this way, C _i D to C _n D of all stands are calculated. In this way, the plate crown target C _n D on the delivery side of the final stand is also calculated, but this does not always match the product target plate crown. Therefore, the upstream direction plate crown schedule means 12
Calculate the upstream direction plate crown schedule by. That is, based on the product target plate crown on the delivery side of the final stand, the evaluation function J1 _n-1 corresponding to the equation (3) is calculated in the preceding stand of the final stand, that is, the n-1 stand. Similarly, the evaluation function J2 _n-1 corresponding to the equation (6)
To calculate. Then, the evaluation function JU _n-1 corresponding to the equation (8) is calculated from J1 _n-1 and J2 _n-1, and the plate crown target value C _n-1 U at the n-1 stand is calculated. next,
Based on C _n-1 U, each evaluation function of the n-2 stand is calculated, and the target plate crown value C _n-2 U of the n-2 stand is calculated. This is sequentially calculated toward the upstream stand, and the calculation is continued up to the first stand. In this way, C ₁ U
~ Cn _- 1U is calculated. Next, the connecting means 18 connects the downstream direction plate crown schedule and the upstream direction plate crown schedule. The determining means 13 checks, for each stand, whether or not there is a non-zero area for both the evaluation function JD _i of the downstream direction plate crown schedule and the evaluation function JU _i of the upstream direction plate crown schedule, and downstream in such an area. The evaluation function JD _i of the direction plate crown schedule and the evaluation function JU _i of the upstream direction plate crown schedule are combined, and the evaluation function JC _i calculation means 14 calculates the evaluation function JC _i .

JC _i = JD _i + JU _i (10)

Then, each stand target plate crown determining means 16 determines a plate crown CC _i having the maximum evaluation function JC _i , and sets it as a target plate crown of the stand. The stand on the upstream side of the stand that can be connected in this way adopts the downstream direction plate crown schedule CD _i ,
By adopting the upstream plate crown schedule CU _i for the stands downstream of the connected stands, the plate crown target values of all the stands are determined. The plate crown target value determined in this way has a good flatness by considering the evaluation function J1 _i , and the evaluation function J2 _i
By taking into consideration, it is possible to satisfy the range of manipulated variables, operator requirements, and operational constraints. As described above, the manipulated variables x1 _i and x2 _i are calculated from the plate crown target using the evaluation function J2 _i . A schematic representation of this is shown in FIG. If the determining means 13 determines the evaluation function JD _i of the downstream plate crown schedule.
If there is no region in which the evaluation function JU _i and the upstream direction plate crown schedule are not 0, the evaluation function JS calculating means 15 selects the stand where the two regions are closest to each other, and the stand (k stand) Do)
Before and after, the shape evaluation function J represented by the following equation from the equation (2)
The crown having the minimum S is set as the target plate crown.

[0022]

[Equation 1]

In the above-mentioned embodiment, the case where the first to the last stands have the crown shape control means has been described. However, in the case where the arbitrary shape has the crown shape control means, when the evaluation function J2 is calculated for the stand having no crown shape control means,
Both the upper and lower limit values of the set weighting function may be set to 0. Also,
Needless to say, the crown shape control means may be any one capable of changing the crown shape such as the cross angle of the pair cross mill, the roll bending force, and the intermediate roll shift amount of the 6-step mill.

[0024]

According to the present invention, the plate crown on the delivery side of the final stand can be set as the target, the plate shape between the stands is good, and the setting schedule can be easily handled by the operator.

[Brief description of drawings]

FIG. 1 is a view showing a plate crown of a continuous rolling mill according to the present invention.
It is a block diagram which shows one verification example of the plate shape control method.

FIG. 2 is an explanatory diagram showing an example of determining an evaluation function J1 _{i according to} the present invention.

FIG. 3 is an explanatory diagram showing an example of determining an evaluation function J2 _{i according to the} present invention.

FIG. 4 is an explanatory diagram showing an example of determining an evaluation function J _{i according to the} present invention.

FIG. 5 is an explanatory diagram showing a relationship between a stand number and a plate crown for determining a pass schedule according to the present invention.

FIG. 6 is a graph showing a relationship between a stand number and a plate crown ratio according to a conventional technique.

[Description of Reference Signs] 1 rolling condition input means 2 model parameter calculation means 11 downstream path schedule calculation means 12 upstream path schedule calculation means 18 connection means

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[Procedure amendment]

[Submission date] June 7, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for controlling a strip crown and strip shape of a continuous rolling mill according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a demonstration example to which the present invention is applied. In the figure,
A rolling condition input means 1 inputs rolling conditions such as a plate thickness, a plate width, a rolling load, a roll crown, and an entering side plate crown. 2 is a model parameter calculation means, which will be described later (1),
The model parameters of the plate crown ratio and flatness represented by the equation (2) are calculated. 11 is a downstream direction plate crown calculation means, with the plate crown on the entrance side of the continuous rolling mill as an initial value,
In each of the stands from the upstream stand, the optimum stand exit side plate crown is determined from the operating conditions and rolling conditions, the allowable range of the stand exit side plate crown is determined, and this is sequentially calculated up to the final stand. The downstream direction plate crown calculating means 11 comprises an evaluation function J1 _i calculating means 3, an evaluation function J2 _i calculating means 4, an evaluation function JD _i calculating means 5, and a crown target C _i calculating means 6. Reference numeral 12 is an upstream-direction plate crown schedule calculation means, which determines an optimum stand-in side plate crown from operating conditions and rolling conditions in each stand from the downstream stand with the target product plate crown on the delivery side of the continuous rolling mill as an initial value. , Determine the allowable range of the stand-in side plate crown, and calculate sequentially up to the first stand. The upstream direction plate crown calculating means 12 comprises an evaluation function J1 _i calculating means 7, an evaluation function J2 _i calculating means 8, an evaluation function JU _i calculating means 9, and a crown target C _i calculating means 10. In the downstream direction plate crown schedule calculated by the downstream direction plate crown calculating means 11, the plate crown on the delivery side of the final stand does not always become the target product plate crown. Reference numeral 18 denotes a connecting means which is an intermediate stand in which the widths of both the upstream direction plate crown schedule calculated by the upstream direction plate crown schedule calculation means 12 and the downstream direction plate crown schedule calculated by the downstream direction plate crown schedule calculation means 11 overlap. In order to determine a plate crown schedule that satisfies various conditions in each stand and can obtain a target product plate crown on the delivery side of the final stand. The connection means 18 includes a determination means 13, an evaluation function JC _i calculation means 14, an evaluation function JS calculation means 15, each stand target plate crown determination means 16, and each stand operation amount determination means 1.
It consists of 7. The crown shape manipulated variable of each stand to achieve the plate crown schedule determined by the above procedure is calculated and set. Next, a model formula representing the relationship between the plate crown, the plate shape, and the crown control operation amount and the method for determining the crown control operation amount will be described. The same applies to a multi-pass rolling mill.
That is, the i-th stand outlet side of the strip crown C _i in the continuous rolling mill, flatness f _i is given by the following equation.

Front Page Continuation (72) Inventor Yoichi Yashiki House 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (1)

[Claims] 1. Based on the operating condition and equipment capacity of each stand based on the inlet side plate crown value of the continuous rolling mill,
A downstream plate crown schedule having an optimum operation amount and an allowable operation amount, a target plate crown on the delivery side of the final rolling mill, and an optimum operation amount for setting the plate shape to a desired value are allowed. It is characterized in that it is combined with an upstream direction plate crown schedule having an operation amount, and is a pass schedule that changes from the downstream direction plate crown schedule to the upstream direction plate crown schedule so that each operation amount is satisfied with each other. Method for controlling strip crown and strip shape of continuous rolling mill.