JP2011147957A - Method of controlling cold tandem rolling mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform decoupling control between sheet thickness and a shape by furthermore correcting work roll bending force which is calculated from a shape evaluation model by the sheet thickness/shape decoupling control theory. <P>SOLUTION: In a method of controlling the sheet thickness and the shape of the sheet simultaneously with a cold tandem rolling mill, by detecting or estimating the variation of a sheet crown ratio, sheet width and rolling load, the deviation between the target value and an estimated value of the sheet thickness on the outlet side is determined and a temporary screw-down location control target value is set from that deviation. On the other hand, a shape evaluating parameter is calculated on the basis of the detected value or the estimated value of the variation of the sheet crown ratio or the like is determined, by determining the deviation between the calculated value and the target value of the shape evaluating parameter, the work roll bending force by which that deviation is canceled is taken as a temporary controlled variable of the work-roll bending force, that controlled variable and a temporary controlled variable of the screw-down location for controlling the sheet thickness are corrected on the basis of the sheet thickness/shape decoupling control theory and the screw-down location and a work-roll bender are simultaneously controlled on the basis of corrected control variable of the work-roll bending force and the screw-down location. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control method for a cold tandem rolling mill that uses a mechanical plate crown model and a plate thickness / shape non-interference control theory to obtain a steel plate having excellent plate thickness and shape accuracy.

  In a cold tandem rolling mill, the reduction control is generally performed at the first stand, and the thickness after the second stand is controlled by tension control based on the final stand outlet side thickness gauge. In the first stand, the method of estimating and controlling the thickness immediately below the roll bite and the monitor control by the first stand outlet side thickness gauge are often used together. In many cases, a system or a BISRA system is employed. The mass flow method is a method for estimating the plate thickness from the plate thickness meter on the inlet side, the plate speed meter, and the plate speed meter on the outlet side according to the constant mass flow rule. Since the thickness gauge is affected by the thickness gauge filter, there is a limit to catching a sudden change in thickness, but the thickness estimation method is simple and stable thickness estimation is stable. It is often used because of its high accuracy.

  The BISRA method is a method for obtaining a mill constant in advance and estimating a mill stretch from a load during rolling. Since the nonlinearity of mill stretch is not considered, the plate thickness cannot be estimated in absolute value, but this method is also simple in the plate thickness estimation method. It is often used because it allows accurate estimation. However, when the plate thickness changes greatly across the joint, the influence of the non-linearity of the mill stretch increases, so that the accuracy is worse compared to the mass flow method.

  In Patent Document 1, plate thickness control is performed by a rolling operation at the final stand of the cold tandem rolling mill or at the first stand and the final stand, and at other rolling stands, the plate thickness is controlled by tension control using the roll peripheral speed. A sheet thickness control method is disclosed in which the rolling position of the rolling mill is controlled while keeping the tension constant based on the deviation from the target sheet thickness.

In Patent Document 2, the thickness of the rolling mill exit side is estimated in mass flow AGC, and when the rolling position is changed using this, the load change becomes large, and the shape change is induced. A control method for changing the work roll bending force so as to be kept constant is disclosed.
On the other hand, Patent Document 3 discloses a method of calculating the outlet plate crown c from the mechanical plate crown, the inlet plate crown C, and the crown genetic coefficient.

Japanese Patent No. 3984490 JP 2007-16787A Japanese Patent Publication No. 3-072364

Theory and practice of sheet rolling, edited by Japan Iron and Steel Institute (published on September 1, 1984) "Theory on sheet crown and flatness", pages 89-102

However, in the method described in Patent Document 1, if the reduction position is changed, the load change becomes large, and there is a risk of inducing the shape disturbance.
The method described in Patent Document 2 aims to keep the mechanical plate crown constant. At this time, the mechanical plate crown is a rolling mill exit side plate crown derived when the rolling mill entry side plate crown is 0 on the assumption that the load distribution between the plate and the work roll is uniform. However, in a cold rolling mill with a work roll diameter of 400 to 600 mm and a cylinder length of about 2000 mm, the work roll bender is such that the load distribution between the plate and the work roll is strong and the mechanical plate crown is constant. There is a problem that the plate shape does not become constant even when the force is controlled.

  The present invention has been made in view of the above circumstances, and based on a shape evaluation model using a mechanical plate crown model, a work roll bending force is calculated, and the work roll bending force is calculated based on a plate thickness / shape non-interference control theory. It is another object of the present invention to provide a control method for a cold tandem rolling mill that can be further modified to enable non-interference control of sheet thickness and shape.

  The cold tandem rolling mill control method of the present invention is a cold tandem rolling mill control method for simultaneously controlling the plate thickness and the plate shape in the cold tandem rolling mill, and the influence of the load on the exit side plate thickness in advance. The coefficient of influence of the work roll bending force on the coefficient and the exit side plate thickness is obtained, and the relationship between the plate crown ratio change, the plate width and rolling load and the shape evaluation parameter, and the work roll on the plate crown ratio change are calculated in advance. Obtain the influence coefficient of bending force, detect or estimate the change in the plate crown ratio, the plate width, the rolling load, and determine the exit side plate thickness deviation between the target value of the exit side plate thickness and the estimated value. On the other hand, a temporary reduction position control target value is set on the basis of And calculating the deviation between the calculated value of the shape evaluation parameter and the target value of the shape evaluation parameter, and the work roll bending force that cancels the deviation of the shape evaluation parameter affects the change in the plate crown ratio. The temporary work roll bending force control amount is obtained by using the influence coefficient of the temporary work roll bending force, and the temporary work roll bending force control amount and the temporary reduction position control amount for the plate thickness control are influenced on the exit side plate thickness. Corrected by the plate thickness / shape non-interference control theory using the influence coefficient of the load and the influence coefficient of the work roll bending force on the outlet plate thickness, and based on the corrected work roll bending force control amount and the corrected reduction position control amount, It is characterized by simultaneously controlling the reduction position and the work roll bender.

Moreover, in the control method of the cold tandem rolling mill of the present invention, the following formula (1) is used as a relational expression of the plate crown ratio change β, the plate width W, the rolling load p, and the shape evaluation parameter λ _2. Is preferred.
λ ₂ = f (β, L, p) (1)
Here, λ ₂ : shape evaluation parameter, β = c / h-C / H: change in plate crown ratio, C: entry side plate crown at plate end, c: exit side plate crown obtained from mechanical plate crown , H, h: Incoming / outgoing side plate thickness, L = W / 2 (mm): Half width of plate width W, p = P _N / W (kN / m): Line load ( _PN is a net rolling load, The value obtained by removing the work roll bender force from the rolling load during rolling).

  Further, in the control method of the cold tandem rolling mill of the present invention, the temporary reduction position control amount and the temporary work roll bending force control amount are corrected using the plate thickness / shape non-interference control theory. In addition, the plate thickness control amount realized by the temporary reduction position control amount and the temporary work roll bending force control amount is corrected, the load is corrected based on the corrected plate thickness control amount, and the corrected plate The plate crown ratio change is corrected based on the thickness control amount and the corrected load, the shape evaluation parameter is corrected based on the corrected plate crown ratio change, the corrected plate thickness control amount and the corrected shape evaluation parameter are corrected. It is preferable to obtain the reduction position control amount and the work roll bending force control amount again so as to be the target value.

  In the control method of the cold tandem rolling mill according to the present invention, in addition to the corrected work roll bending force control amount and the reduction position control amount, the rolling tandem rolling mill is inserted at any fixed period before changing the reduction position. For measuring the side tension or the exit side tension, and maintaining the entry side tension or the exit side tension with the tension when the rolling stand exit side plate thickness deviation is in a steady rolling state within a specific range as a target value. It is preferable to control the roll speed of any one or more rolling stands of the rolling stand and the preceding and subsequent rolling stands simultaneously with the rolling position and the work roll bender using a roll speed control amount.

  Moreover, in the control method of the cold tandem rolling mill of the present invention, it is preferable to obtain the relational expression of the plate crown ratio change, the plate width, the rolling load, and the shape evaluation parameter from a linear multiple regression model.

  Further, in the control method of the cold tandem rolling mill of the present invention, the influence coefficient of the load and work roll bending force on the mechanical plate crown at an arbitrary crown definition point is obtained in advance, and the deviation of the shape evaluation parameter is calculated. When the work roll bending force to be offset is determined using the influence coefficient of the change in the plate crown ratio on the work roll bending force and used as the work roll bending force control amount, the linear load is converted into the work roll bending force using the influence coefficient. It is preferable to convert.

According to the present invention, it is possible to grasp the disturbance of the plate thickness and the plate shape due to unsteady disturbance by using a mass flow rule or a mill stretch model, and using the shape evaluation parameter.
Then, the reduction control amount and the work roll bender force control amount are determined based on the difference between the estimated value or the detected value and the target value, but if they are controlled independently, they interfere with each other, and a desired plate thickness and plate shape are obtained. Therefore, both are corrected to a control amount that avoids control interference based on the non-interference control theory.
Furthermore, the tension that fluctuates when the target plate thickness control is performed is calculated in advance, and the roll peripheral speed at which the tension is kept constant even when the reduction position is changed is calculated.
By the way, when finding the relational expression between rolling load, sheet width and sheet crown ratio change and shape evaluation parameter from linear multiple regression model, it is common to exact model used for crown shape control in that multiple regression is used. An evaluation parameter is directly obtained for a phenomenon, and can be controlled with higher accuracy than a so-called mechanical plate crown model. On the other hand, since this relational expression has fewer arguments than the exact model, it is easy to incorporate it into plate thickness / shape non-interference control.
In addition, if the roll speed is changed so as to follow the elongation change and the tension control is performed, the accuracy of the shape control can be further increased.
Since the reduction position and the work roll bending force control amount obtained as described above, or the roll peripheral speed is added to and controlled simultaneously, both the plate thickness and the plate shape can be controlled with high response and high accuracy.

  According to the present invention, the plate shape can be improved while realizing highly accurate plate thickness control, so that the load of the skin pass process can be reduced. Further, it is possible to reduce yielding troubles in the rolling process due to defective shape and the continuous annealing in the subsequent process, and the like.

FIG. 1 is a flowchart for explaining a control method of a cold tandem rolling mill according to an embodiment of the present invention. FIG. 2 is a diagram showing a generally known principle showing the relationship between the plate thickness and the reduction. FIG. 3 is a schematic diagram showing a cold tandem rolling mill to which the control method of the present invention is applied and its control system.

  Hereinafter, with reference to drawings, the control method of the cold tandem rolling mill which is an embodiment of the present invention is explained. FIG. 1 is a flowchart for explaining a control method of a cold tandem rolling mill according to an embodiment of the present invention, and FIG. 2 is a diagram showing a generally known principle showing a relationship between sheet thickness and reduction. First, based on FIG. 1, a method for controlling the plate thickness and the plate shape according to the embodiment of the present invention to the target values at the same time without causing interference between the plate thickness and the plate shape, when the plate thickness and the plate shape are changed from the steady state. explain.

  Mass flow AGC measures the sheet thickness and sheet speed on the rolling mill entrance side and the sheet speed on the exit side to estimate the sheet thickness directly under the roll bite of the rolling mill, and the reduction position based on the difference between the estimated value and the target value. Or it is the control method which changes tension. Since the inlet side plate thickness can be measured in advance and the plate speed can be detected instantaneously, if the tracking accuracy is good in principle, the plate thickness immediately below the roll bite can be estimated without time delay.

  The mass flow AGC calculates the outlet side plate thickness h = H × Vi / Vo according to the constant mass flow rule, assuming that the inlet side plate thickness H, the inlet side plate speed Vi, and the outlet side plate speed Vo are as described above. Since the plate thickness can be estimated by a simple calculation formula, it is widely used because the investment amount is small. When mass flow AGC is applied to the first stand, it is often used as a reduced AGC in a cold tandem rolling mill.

  In the mass flow AGC, the sheet thickness on the delivery side of the rolling mill is estimated according to the mass flow constant rule. However, when the reduction position is changed using the mass flow AGC, the load change becomes large, and the shape change is induced. Moreover, the mechanical plate crown is derived on the assumption that the load distribution between the plate and the work roll is uniform. However, in the case of cold rolling, the load distribution between the plate and the work roll has a strong non-uniformity. Even if the work roll bender force is controlled so that the crown is constant, the plate shape is not constant. Therefore, a method of changing the work roll bending force so as to keep the mechanical plate crown constant by simultaneously controlling the plate thickness and the plate shape must be considered. If this method is possible, it becomes possible to suppress the shape change only by changing the work roll bending force so that the mechanical plate crown change is minimized within the range of the performance of the apparatus, and the effect of shape control appears.

Hereinafter, the control method of the present embodiment will be described with reference to FIG.
First, in step S1, the following numerical values and relational expressions are obtained in advance before entering the calculation.
-Load influence coefficient k _hp on the outlet side plate thickness,
・ Influence coefficient k _hf of work roll bending force on exit side thickness
・ Relationship between plate crown ratio change, plate width and rolling load, and shape evaluation parameters (λ ₂ = f (β, L, p) (1))
・ Influence coefficient γ of work roll bending force on plate crown ratio change,
・ Mill constant M, plastic constant Q (in this case, coincides with 1 / k _hp )

  Next, in step S2, the thickness of the rolling mill exit side is estimated. As a plate thickness estimation means, a mass flow method, a gauge meter method, or the like may be used.

Next, in step S3, a plate thickness control target value Δh ₀ (exit side plate thickness deviation), which is the difference between the estimated delivery side plate thickness and the target plate thickness, is set.

Next, in step S4, a control target value ΔS ₀ of a temporary reduction position for setting the plate thickness to the target plate thickness is set. The control target value ΔS ₀ of the temporary reduction position can be calculated from the generally known principle of FIG. 2 using the estimated delivery side thickness, the target thickness, the mill constant M, and the plastic constant Q. Specifically, ΔS ₀ can be calculated by the following equation (A). At this time, if ΔS ₀ min is tightened, the shape changes due to the load change.
ΔS ₀ = (M + Q) / M × Δh ₀ (A)

Next, in step S5, independently of steps S1 to S4, the deviation of the shape evaluation parameter from the deviation Δβ of the plate crown ratio change and the deviation Δp of the line load change from the steady state by the following equation (1). Δλ ₂ is calculated.
Specifically, during sheet rolling, the entry side plate crown C, the exit side plate crown c obtained from the mechanical plate crown, the entry / exit side plate thicknesses H and h, the rolling load P, and the work roll bender force are detected or calculated. Based on these detected values or calculated values, the shape evaluation parameter λ ₂ is estimated by Equation (1). For the entry side plate crown C (body crown), the value obtained by calculating the material crown during hot rolling by the thickness of the entrance side of the rolling mill according to the similarity rule may be used, or measured with a bar-type light source type profile meter or the like. Also good. Further, the exit plate crown c is obtained by the method described in Patent Document 3. Then, the deviation Δλ ₂ of the shape evaluation parameter is calculated from the deviation Δβ of the sheet crown ratio change and the deviation Δp of the line load change from the reference rolling condition.

λ ₂ = f (β, L, p) (1)
Where λ ₂ : shape evaluation parameter,
β = c / h-C / H: plate crown ratio change,
C: Inboard plate crown at the end of the plate,
c: Outboard plate crown at the plate end determined from the mechanical plate crown,
H, h: Incoming / outgoing side plate thickness,
L = W / 2 (mm): half width of the plate width W,
p = P _N / W (kN / m): Linear load (P _N is a net rolling load, which is a value obtained by removing the work roll bender force from the rolling load during rolling).

For example, the following formula (2) can be used as the above formula (1) for obtaining the shape evaluation parameter λ ₂ . This equation (2) is an example calculated by regression calculation based on exact calculation described in Non-Patent Document 1. Note that this regression equation is obtained for a six-high cold rolling mill, and the coefficient varies depending on conditions such as the rolling mill, the roll diameter, and the crown definition method.

λ ₂ = 3871.9β / √L-0.013790745p + 0.58653766 (2)

From equation (2), the steady-state work roll bender force, the rolling load is P _L , the sheet crown ratio change β is β _L , the work roll bender force is left as it is, and the rolling load P at any rolling speed is When the strip crown ratio change during beta, rolling speed (rolling load) due to the fact that has changed, increments from the shape evaluation parameter lambda ₂ in a steady state (error) △ lambda ₂ is represented by the formula (3).

Δλ ₂ = 3871.9 (β−β _L ) /√L−0.013790475 (P−P _L ) / W (3)

Next, in step S6, the deviation Δλ ₂ of the shape evaluation parameter is set to the shape control target value Δλ ₀ .

Next, in step S7, a work roll bending force ΔF ₀ necessary to cancel the shape control target value Δλ ₀ (to 0) is calculated.
Here, the influence coefficient of the work roll bender force exerted on the plate mechanical ratio change β at each rolling load is set to γ using the mechanical plate crown model.
When the rolling load is equal, the shape evaluation parameter change Δλ ₂ ′ based on the deviation Δβ (= β−β _L ) of the change in the plate crown ratio when the work roll bender _FW is operated is used for the influence coefficient γ described above. This is expressed by equation (4).

Δλ ₂ ′ = 3871.9Δβ / √L
= 3871.9γ (F _W −F _WL ) / √L (4)

Therefore, the work roll bending force ΔF ₀ (= F _W −F _WL ) for keeping the shape constant is expressed by Expression (5) from Expressions (3) and (4).

ΔF ₀ = F _W −F _WL = −Δλ ₂ /3871.9/γ*√L (5)

Although Equation (5) is a rolling load is obtained from the case the same, at the time of actual control, the line load Δp (= P-P L) / W) has occurred. In the case of the expression (3), it can be obtained by substituting the following expression (6) into Δp.
Δp = − (k _cf / k _cp ) × (F _W −F _WL ) / 2L (6)

In the formula (6), k _cf and k _cp are as follows.
k _cf : influence coefficient of work roll bending force on mechanical plate crown at an arbitrary crown definition point k _cp : influence coefficient of load on mechanical plate crown at an arbitrary crown definition point

This is based on the relationship between the work roll bending force ΔF and the load ΔP when Δc = 0. As a result, a deviation Δβ of the plate crown ratio change is generated, and Δλ ₂ is also changed by these deviations. Therefore, Δλ ₂ is obtained from Δp, Δβ, and L, and ΔF ₀ is obtained from Δλ ₂ by development as in equations (3) to (5).

The control amount ΔS ₀ of the temporary reduction position control target value and the temporary work roll bending force control amount ΔF ₀ calculated in the above steps S4 and S7 are changed when the plate thickness control and shape control are considered independently. Therefore, if the control is carried out with the value as it is, it will not be possible to obtain the desired plate thickness and mechanical plate crown because they interfere with each other.

Therefore, in step S8, a plate thickness control target value Δh ₁ is calculated by adding the plate thickness change amount due to the independently calculated work roll bending force ΔF ₀ . That is, if the work roll bending force ΔF ₀ is changed, Δh ₀ will change. Therefore, Δh ₁ when ΔF ₀ is changed is recalculated by the following equation (7).
Δh ₁ = M / (M + Q) × (ΔS ₀ + k _hf × ΔF ₀ ) (7)
(K _hf : influence coefficient of work roll bending force on _delivery side plate thickness)

In step S9, a deviation Δλ ₁ of the shape evaluation parameter is calculated by adding the change in the shape evaluation parameter induced by the load change caused by the plate thickness change (plate thickness control target value Δh ₀ ) calculated independently. That is, if the exit side plate thickness h changes, the plate crown ratio change β also changes, so that the shape evaluation parameter is recalculated based on the above formula (1) or (2). At this time, the value that has not changed can be used as it is. In addition, since a load change becomes a plastic constant x plate thickness change amount, it is obtained by the following formula (8).
ΔP = Q × Δh ₁ = Δh ₁ / k _hp (8)

Next, in step S10, a work roll bending force control amount ΔF ₁ is obtained so that Δh ₁ and Δλ ₁ become the target plate thickness and shape evaluation parameters even if there is an interference term. The work roll bending force control amount ΔF ₁ is obtained in the same manner as the development of the above formulas (3) to (5).
Also, the reduction position control target value ΔS ₁ is obtained in the same manner as the above equation (7).

Further, in step S11, in order to keep the tension constant when the plate thickness changes by Δh ₀ , for example, a control amount Δv ₁ of the roll peripheral speed of the stand immediately before the final stand is obtained.
Specifically, in addition to the work roll bending force control amount ΔF ₁ and the reduction position control amount, before changing the reduction position, the rolling mill entry side tension or the exit side tension is measured at any given period, A roll speed control amount for maintaining the entry side tension or the exit side tension is obtained with the tension when the rolling stand exit side thickness deviation is in a steady rolling state within a specific range as a target value.
For example, when the plate thickness is reduced by 1%, the roll peripheral speed of the stand immediately before the last stand may be reduced by 1%. If the roll peripheral speed of the stand preceding the last stand of the last stand is left as it is, the tension between the subsequent stands will change and the plate thickness will also change from the stand preceding the last stand. In the case of changing the roll peripheral speed of the previous stand, it is preferable to change the roll peripheral speed of the preceding stage from that of the previous stand of the last stand in consideration thereof.

In step S12, the reduction position, the work roll bending force and the roll peripheral speed using ΔS ₁ , Δλ ₁ and Δv ₁ are simultaneously controlled.

FIG. 3 shows a cold tandem rolling mill in which the mass flow AGC considering the plate thickness / shape and tension non-interference control according to the present invention is applied to the final stand. The cold tandem rolling mill shown in FIG. 3 is composed of 6 stages and 4 stands. A plate thickness / crown meter 5 is installed on the entrance side of the final stand, whereby the entry side plate thickness and the entry side crown are measured. The plate speed is measured by the final stand plate speedometer 8. The load detector 6 is installed in the last stand like the No. 1 stand, and the load is measured. These measured values are sent to the plate thickness / shape arithmetic unit 11. The plate thickness / shape calculation device 11 stores a plate thickness target value, a shape target value, and other necessary data. Based on these measured values, target values, etc., the plate thickness / shape calculation device 11 conforms to the logic of the present invention. Each control amount is calculated in the shape / tension non-interference control amount calculation device 12. Among the control amounts obtained by this calculation, the workbending force control amount is sent to the work roll bender 10, the reduction position control target value is sent to the hydraulic pressure reduction device 7, and the roll speed control amount is sent to the motor M. Therefore, the present invention is implemented by sending control amounts calculated in accordance with the logic of the present invention to these control terminals.
FIG. 3 shows a mass flow AGC that does not include a general shape / tension control in the first to third stands, but the present invention may be implemented using a BISRA-AGC or another AGC. .
Since the shape of the rolled material on the final stand exit side becomes the final product as it is, it is necessary to improve the shape as well as the plate thickness. If the shape is distorted, the edges must be trimmed too much, and in the worst case, they may not be sold. In order to avoid this, it is important to apply not only the plate thickness but also the plate thickness, shape, and tension non-interference control technology for improving the shape to the final stand.

  Here, the Example of this invention using the material of the board width 1200mm in the cold dandem rolling mill shown in FIG. 3 on the rolling conditions shown in following Table 1 is shown. As a disturbance, the rolling speed was changed. That is, the rolling speed was increased linearly from about 50 m / min to 440 m / min in about 20 seconds. In the prior art, a tension control method was used for plate thickness control, and a bar-shaped light source was installed as a detector for shape control, and the operator controlled the work roll bender manually by looking at the linearity of the light source projected on the steel plate.

In this embodiment, the plate thickness is controlled by the amount of deviation from the target value at the same time, and at the same time, the roll peripheral speed for keeping the tension constant when the plate thickness is changed by the amount of the plate thickness is adjusted. Control was performed at the previous rolling stand. For shape control, a deviation Δλ ₂ of a shape evaluation parameter is calculated from a deviation Δβ of a change in sheet crown ratio and a deviation Δp of a change in linear load from a reference rolling state at a rolling speed of 50 m / min, and from this shape evaluation parameter deviation Δλ ₂ Based on the formula (2), a work roll bender force control amount that cancels the shape evaluation parameter deviation Δλ ₂ is calculated, and this is corrected based on the plate thickness / shape non-interference control theory. The work roll bender force was controlled so that the desired plate shape could be obtained even if it fluctuated.

These acceleration parts from a rolling speed of 50 m / min to 440 m / min were divided into 10 parts, and the plate shape at each rolling speed was measured by unwinding on a surface plate.
Regarding the plate thickness, in the case of the prior art, the plate thickness variation was 0.9% on average, whereas in the case of using the present invention, the plate thickness variation was within 0.1% on average in the acceleration / deceleration section. there were. Since the thickness tolerance is 0.5% or less with the strictest material, if the present invention is used, the material of the acceleration / deceleration part that has conventionally been out of the tolerance can be relieved and the yield can be improved.

  Regarding the shape, in both the prior art and the present invention, when the rolling speed was 50 m / min, the plate shape had an end extension with a steepness of 0.3%. In the prior art, the edge elongation of the plate shape increases as the speed increases, and when reaching a rolling speed of 450 m / min, the plate shape has an edge elongation with a steepness of 1.5%. In contrast, in the present invention, the edge elongation of the plate shape during acceleration did not change much, and the plate shape had an edge elongation with a steepness of 0.8% even when the rolling speed reached 450 m / min. Since this product needs to have a steepness of less than 1%, it is possible to omit what had to be cut off as a defective part in the prior art or corrected with another line (for example, a tension leveler line). Yield or productivity was greatly saved.

  From the above, it has been found that the use of the present invention makes it possible to improve both the plate thickness and the shape accuracy.

The present invention is not limited to the best mode described above. The plate shape varies depending on the type of rolling mill, rolling conditions, and the like, and therefore λ ₂ indicating the shape evaluation parameter is not limited to the equations (1) and (2). Furthermore, the shape evaluation parameter itself is not limited to λ _2. For example, when the shape of the plate quarter portion is more important than the shape of the plate end portion, the same applies to λ ₄ instead of λ _{2 in} (1). What is necessary is to obtain a regression equation and control the work roll bender power.
Note that λ ₂ and λ ₄ are defined as follows.
λ ₂ = y ₃ −y ₂
λ ₄ = 0.5y ₃ + 4y ₂ −4.5y ₁
Here, y ₃ : plate thickness or tension at the center of the plate width
y ₂ : Plate thickness or tension at a position about 70% (1 / √2) away from the center of the plate width to the plate width
y ₁ : Plate thickness or tension at a position approximately 80% (1 / √ (3/2)) from the plate width center to the plate width

DESCRIPTION OF SYMBOLS 1a ... Upper work roll, 1b ... Lower work roll, 2a ... Upper intermediate roll, 2b ... Lower intermediate roll, 3a ... Upper backup roll, 3b ... Lower backup roll, 4 ... Steel plate, 5 ... Plate thickness and crown meter, 6 ... Load detector, 7 ... Hydraulic reduction device, 8 ... Plate speedometer, 9 ... Adder, 10 ... Work roll bender, 11 ... Plate thickness / shape calculation device, 12 ... Plate thickness / shape / tension non-interference control amount calculation device , 13 ... tension AGC control amount calculation device.

Claims (6)

  A cold tandem rolling mill control method that simultaneously controls the thickness and shape of a cold tandem rolling mill, in advance, the influence coefficient of the load on the exit side thickness and the influence of the work roll bending force on the exit side thickness The coefficient is obtained, and the relationship between the plate crown ratio change, the relation between the plate width and rolling load and the shape evaluation parameter, and the influence coefficient of the work roll bending force on the plate crown ratio change are obtained in advance. While detecting or estimating a change, a sheet width, and a rolling load, obtaining a delivery side thickness deviation between a target value of the delivery side thickness and the estimated value, and setting a temporary reduction position control target value based on the delivery side thickness deviation The shape evaluation parameter is calculated by the relational expression based on the detected value or estimated value of the plate crown ratio change, the plate width, and the rolling load, and the shape evaluation parameter is calculated. The workpiece roll bending force that cancels out the deviation of the shape evaluation parameter is obtained using the influence coefficient of the work roll bending force on the change in the plate crown ratio. Work roll effecting on the influence coefficient of the load on the outlet side plate thickness and the temporary side roll thickness control amount for the temporary work roll bending force control amount and the plate thickness control as the roll bending force control amount It is corrected by the plate thickness / shape non-interference control theory using the influence coefficient of bending force, and based on the corrected work roll bending force control amount and the corrected reduction position control amount, the reduction position and the work roll bender are controlled simultaneously. A control method for a cold tandem rolling mill. _2. The cold tandem rolling mill according to claim 1, wherein the following expression (1) is used as a relational expression of the sheet crown ratio change β, the sheet width W, the rolling load p, and the shape evaluation parameter λ ₂ . Control method.
λ ₂ = f (β, L, p) (1)
Where λ ₂ : shape evaluation parameter,
β = c / h-C / H: plate crown ratio change,
C: Inboard plate crown at the end of the plate,
c: Outboard plate crown at the plate end determined from the mechanical plate crown,
H, h: Incoming / outgoing side plate thickness,
L = W / 2 (mm): half width of the plate width W,
p = P _N / W (kN / m): Linear load (P _N is a net rolling load, which is a value obtained by removing the work roll bender force from the rolling load during rolling).   When correcting the temporary reduction position control amount and the temporary work roll bending force control amount using the plate thickness / shape non-interference control theory, the temporary reduction position control amount and the temporary work roll bending are corrected. The plate thickness control amount realized by the force control amount is corrected, the load is corrected based on the corrected plate thickness control amount, and the plate crown ratio change is changed based on the corrected plate thickness control amount and the corrected load. The shape evaluation parameter is corrected based on the corrected plate crown ratio change, and the corrected plate thickness control amount and the corrected shape evaluation parameter are the same as the original plate thickness control target value and the original shape evaluation parameter. The control method for a cold tandem rolling mill according to claim 1 or 2, wherein the reduction position control amount and the work roll bending force control amount are obtained again so as to become target values.   In addition to the corrected work roll bending force control amount and reduction position control amount, the rolling mill entry side tension or exit side tension is measured at any given period before changing the reduction position, and Using the roll speed control amount for holding the entry side tension or the exit side tension with the tension when the side plate thickness deviation is in a steady rolling state within a specific range as a target value, the rolling stand and the rolling stands before and after the rolling stand The control of the cold tandem rolling mill according to any one of claims 1 to 3, wherein the roll speed of any one or more rolling stands is controlled simultaneously with the reduction position and the work roll bender. Method.   5. The cold tandem rolling mill according to claim 1, wherein the relational expression of a change in plate crown ratio, a plate width, a rolling load, and a shape evaluation parameter is obtained from a linear multiple regression model. Control method.   Calculate the influence coefficient of the load and work roll bending force on the mechanical plate crown at an arbitrary crown definition point in advance, and the plate crown ratio that affects the work roll bending force to offset the deviation of the shape evaluation parameter. The linear load is converted into the work roll bending force by using the influence coefficient when the change coefficient is obtained using the influence coefficient of change and set as the work roll bending force control amount. The control method of the cold tandem rolling mill as described in the item.

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