JP2003290808A - Method for controlling sheet width in tandem cold rolling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a cold-rolled sheet having highly accurate width at a high yield by correcting the controlled variable of a shape control means in accordance with the measured value of the sheet width on the outlet side of the final stand when performing cold rolling with a tandem cold rolling mill. <P>SOLUTION: A numerical formula model expressing the variation in the sheet width on the outlet side of the final stand is preliminarily prepared by taking the amount of change of the shape control means at each stand as a variable, and the sheet width on the outlet side of the final stand is continuously measured. The controlled variable of the shape control means at each stand is corrected so that the sheet width on the outlet side of the final stand coincides with the target value on the basis of the numerical formula model by taking the measured value as a variable. In addition to the control, a numerical formula model expressing the variation of the sheet width on the outlet side of the final stand is preliminarily prepared by taking the variation of the rolling load at each stand, the variation of each inter-stand tension and the amount of change of the shape control means at each stand as variables, and the rolling load during the rolling is continuously measured. The controlled variable of the shape control means at each stand is corrected so that the sheet width on the outlet side of the final stand coincides with the target value by substituting this measured value and the variation of each inter-stand tension into the numerical formula model. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip width control method for producing a cold-rolled metal sheet having a high yield by suppressing strip width variation and satisfying strip width tolerance in cold tandem rolling.

[0002]

2. Description of the Related Art As a method for adjusting and controlling the strip width of a material to be rolled in cold tandem rolling, for example, JP-A-1-262011 and JP-A-1-262 are available.
As disclosed in Japanese Patent No. 013, there is a method of estimating the plate width change amount from the tension, the shape of the material to be rolled and the crown change amount, and adjusting the tension. However, it is difficult to apply the tension operating method to the continuous portion of the preceding rolled material and the succeeding rolled material during continuous rolling which is easily broken. Further, the increase in the tension between the stands acts on the reduction of the plate thickness, and it is also a drawback that it interferes with the plate thickness control.

On the other hand, as disclosed in Japanese Patent Laid-Open No. 154527/1993, when calculating a target plate width adjustment amount of a rolled plate material and distributing this to the plate width adjustment amount of each stand, The amount of crown change calculated from the relationship between the amount of width adjustment and the amount of change in crown on each stand exit side and the amount of change in plate width
Set the strip width adjustment amount so that it is within the allowable range of the crown change amount calculated from the rolling conditions, and operate the crown control end (shape control means such as roll bender) of the rolling stand according to the calculated crown change amount. There is a way to do it. However, the influence of the shape control means on the plate width variation is individually grasped for each stand, and no consideration has been given to how the degree of influence changes in the latter stand. Therefore, further improvement is required to control the plate width with higher accuracy.

[0004]

The present invention has been devised to solve such a problem, and the change amount of the shape control means in each stand affects the plate width fluctuation amount on the exit side of the final stand. By using the mathematical model that incorporates the influence, the control amount of the shape control means in each stand is corrected during rolling, the strip width is accurately controlled, and a cold strip with a constant strip width is manufactured with high yield. The purpose is to

[0005]

The strip width control method for cold tandem rolling according to the present invention has the following object.
When performing cold rolling with a cold tandem rolling mill, a mathematical model representing the strip width variation on the final stand outlet side is created in advance with the change amount of the shape control means at each stand as a variable, and the strip width on the final stand outlet side is also created. Is continuously measured, and based on the mathematical model with the measured value as a variable, the control amount of the shape control means in each stand is corrected so that the plate width on the delivery side of the final stand matches the target value. To do. In addition, while preliminarily creating a mathematical model representing the strip width variation on the exit side of the final stand with the variation of the rolling load in each stand, the variation in the tension between each stand, and the variation of the shape control means in each stand as variables, After controlling the strip width on the exit side of the final stand by the above method at the beginning of rolling, the rolling load during rolling is continuously measured, and the measured value and the change amount of each stand tension are substituted into the mathematical model. The control amount of the shape control means in each stand is corrected so that the plate width on the delivery side of the final stand matches the target value.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have made it possible to accurately control the strip width by correcting the control amount of the shape control means in each stand when continuously cold rolling a metal strip in a cold tandem rolling mill. A variety of strip width control methods that can be controlled to produce a cold-rolled strip with a constant strip width have been studied. As a result, it was noted that the amount of change in the shape control means in each stand, the amount of change in rolling load in each stand, and the amount of change in tension between each stand were proportional to the strip width variation on the delivery side of the final stand. Then, it was found that the plate width fluctuation can be accurately suppressed by using a mathematical model that incorporates the influence of the change amount of the shape control means in each stand on the plate width fluctuation amount on the delivery side of the final stand.

When the control amount of the shape control means increases, the plate width of the stand decreases, but the degree of influence becomes smaller in the latter stand. For example, as shown in FIG.
o. If the work roll bender strength increases with one stand, No. The strip width on the stand-out side of the 1st stand decreases, but the degree of influence is No. 1. It becomes smaller after 2 stands. Further, as the rolling load increases, the strip width increases at the stand, but the effect of increasing the rolling load becomes smaller in the latter stand. For example, as shown in FIG. If the rolling load increases with one stand, No. 1 The board width on the stand-out side of the 1 stand increases, but the degree of influence is No. 1. It becomes smaller after 2 stands. Further, as shown in FIG. 1-No.
When the tension between the stands of No. 2 increases, No. 2 1, No. Two
The plate width decreases on the stand-out side, but the degree of influence is No.
It becomes smaller after 3 stands.

As shown in FIG. 4, the strip width variation on the delivery side of the final stand has a substantially linear relationship with the variation of the shape control means, the variation of the rolling load, and the variation of the inter-stand tension. Therefore, the plate width variation on the delivery side of the final stand can be predicted by the following equation (1). In the formula, i is the rolling mill at the i-th stand from the upstream stand side, n is the number of stands, ΔW
Is the strip width variation on the exit side of the final stand, ΔFi is the variation of the shape control means at the i stand, ΔPi is the variation of the rolling load at the i stand, and ΔTi is the variation of the tension between the (i-1) stand and the i stand. , Ai, bi, and ci represent influence coefficients.

[0009]

The influence coefficients ai, bi, and ci are constants determined by manufacturing types such as strip width, strip thickness, steel grade, etc., and are analytical models that are coupled with experiments or elastic deformation analysis of rolls and plastic deformation analysis of material. Can be obtained by simulation using. Therefore, a table of influence coefficients ai, bi, ci is set for each section such as plate width, plate thickness, steel type, etc., or the effect coefficients ai, bi, ci are set as a function of plate width, plate thickness, steel type, etc. You can formulate.

In the feedback control based on the measured value of the strip width on the exit side of the final stand, the strip width on the exit side of the final stand has a linear relationship with the control amount of the shape control means of each stand. Use the prediction formula shown in. In the formula, W ¹ represents the actual measured value of the plate width on the delivery side of the final stand, and W represents the corrected plate width after controlling the shape control means. The measured value W ¹ of the board width at the exit side of the final stand is calculated by the formula (2)
And the change amount ΔFi of the shape control means in each stand is calculated so that the corrected plate width W on the delivery side of the final stand becomes the target value W ^0, and the control amount of the shape control means is corrected.

There are innumerable combinations of the change amounts ΔFi of the shape control means in which the plate width W on the delivery side of the final stand becomes the target value W ^{0 in the} equation (2), but the change in shape is small in each stand. It is preferable to equalize the change amounts of the shape control means of each stand according to the following formula (3).

As the feedforward control, the control amount of the shape control means is corrected based on the prediction formula shown in the formula (1). The correction method will be described. In the feed-forward control, the rolling load at each stand is continuously measured, the change amount ΔPi and the tension change amount ΔTi between the stands are substituted into the formula (1), and the strip width variation amount ΔW on the exit side of the final stand is calculated. The change amount ΔFi of the shape control means in each stand is calculated so as to be 0, and the control amount of the shape control means is corrected.

In equation (1), there are innumerable combinations of the change amounts ΔFi of the shape control means for which the plate width variation amount ΔW on the exit side of the final stand becomes 0, but the stands are changed so that the change in the shape of each stand becomes small. The rolling load change amount ΔPi and the tension change amount ΔTi between the stands are substituted into the following formula (4) for each time, and the influence amount ΔWi on the strip width variation on the exit side of the final stand is calculated.
It is preferable to calculate the change amount ΔFi of the shape control unit for which 0 becomes 0 to correct the control amount of the shape control unit. ΔWi = aiΔFi + biΔPi + ciΔTi (4)

When the plate width is controlled by the feedforward control, prior to the feedforward control,
It is indispensable to correct the control amount of the shape control means by feedback control at the beginning of rolling so that the strip width becomes a target value. Comparing the feedforward control and the feedback control, the feedforward control has an advantage that the control time delay is smaller than that of the feedback control, but the control model error is likely to occur. Feedback control is superior in terms of accuracy. A work roll bender, an intermediate roll bender, an intermediate roll shift, or the like can be used as the shape control means for controlling the plate width. When importance is attached to responsiveness, it is preferable to use a work roll bender or an intermediate roll bender.

[0016]

[Embodiment] Application of feedback control: 6-high rolling mill 4
Using a cold tandem rolling mill 1 (FIG. 5) equipped with a stand,
A low carbon steel strip having a plate thickness of 2.3 mm and a plate width of 1020 mm was cold-rolled to a plate thickness of 0.6 mm. Of the shape control means, only the work roll bender was used as the plate width control means.
Continuously measure the board width on the exit side of the final stand with a board width gauge 5,
The measured value W ¹ was input to the host computer 2. Then, the process computer 3 calculates the change amount ΔFi of the shape control means of each stand so as to equalize the change amount of the shape control means of each stand, and sets the work roll bender 4 to a predetermined value. changed. The strip width after rolling was measured with a strip width gauge, and the transition of strip width was obtained in the steady portion excluding the unsteady portion of the coil top end. In this case, the plate width variation was within the range of 0.3 mm with respect to the target value (Fig. 6a).

On the other hand, the influence of the shape control means on the variation of the strip width of the material to be rolled is examined only by the stand concerned, and the conventional strip width control method which does not take into consideration the fact that the degree of influence changes in the latter stand (Japanese Patent Laid-Open No. Hei 10-1999) No. 5-154527), the strip width control effect of the work roll bender is ignored and the strip width control effect of the work roll bender is overestimated. In addition, the plate width was wider than the target value of the plate width by 1.0 mm or more at the maximum (FIG. 6b).

Feedback control + feed forward
Application of control: Plate thickness 2.4 mm, plate width 93 as material to be rolled
Using a low carbon steel strip of 0 mm, it was cold-rolled to a plate thickness of 0.6 mm. Of the shape control means, only the work roll bender was used as the plate width control means. At the beginning of rolling, the strip width on the delivery side of the final stand was continuously measured by the strip width meter 5, and the measured value W ¹ was input to the host computer 2. Then, in order to equalize the change amount of the shape control means of each stand,
The process computer 3 calculated the change amount ΔFi of the shape control means of each stand according to the equation (3), and changed the work roll bender 4 to a predetermined value. After that, the feedforward control was switched to and the plate width was controlled. In the feed-forward control, the rolling load at each stand is continuously measured, and the change amount ΔPi and the tension change amount ΔTi between each stand are substituted into the equation (4) to determine the strip width fluctuation on the delivery side of the final stand. The change amount ΔFi of the shape control means in each stand was calculated so that ΔWi exerted on the work roll bender 4 was changed to a predetermined value. As a result of measuring the strip width of the obtained cold rolled steel sheet, the strip width variation amount was within the range of 0.4 mm with respect to the target value (Fig. 7a). On the other hand, a conventional plate width control method (Japanese Patent Application Laid-Open No. 5-1
54527), due to the effect that the plate width control effect of the work roll bender is reduced in the latter stage stand,
A maximum of 1.0 against the target value of strip width after the start of rolling
The plate width was wider than mm (Fig. 7b).

As is clear from the comparison between the above two embodiments, the plate width accuracy is greatly improved by performing feedback control or feedforward control of the shape control means with a mathematical model that incorporates the degree of influence on the rear stand. It was confirmed that cold-rolled steel strip can be manufactured with high productivity.

[0020]

As described above, the plate width control method of the present invention uses a mathematical model that takes in the influence of the change amount of the shape control means in each stand on the plate width fluctuation on the exit side of the final stand. The control amount of the shape control means in each stand is corrected. Therefore, since it is taken into consideration that the strip width control effect of the shape control means is reduced in the latter stand, a cold rolled metal strip having a good strip width accuracy and a constant strip width can be manufactured with a high yield.

[Brief description of drawings]

FIG. 1 No. Graph showing the effect of increasing work roll bender force in one stand on plate width fluctuation

FIG. 2 No. Graph showing the effect of rolling load increase on strip width in one stand

FIG. 3 No. 1-No. Graph showing the effect of increase in tension between two stands on plate width fluctuation

FIG. 4 is a graph showing the effect of increase in work roll bender force (a), increase in rolling load (b), and increase in inter-stand tension (c) on strip width variation on the exit side of the final stand.

FIG. 5 is a schematic view of a cold tandem rolling mill used in Examples.

FIG. 6 is a graph comparing strip width fluctuation amounts of cold-rolled steel strips produced by the method of the present invention (a) and the conventional method (b).

FIG. 7 is a graph comparing strip width fluctuation amounts of cold rolled steel strips manufactured by the method of the present invention (a) and the conventional method (b).

Claims (2)

[Claims] 1. When cold rolling with a cold tandem rolling mill, a mathematical model representing the strip width variation on the delivery side of the final stand is created in advance with the change amount of the shape control means in each stand as a variable, and the final stand is also prepared. The board width on the delivery side is continuously measured, and the control amount of the shape control means in each stand is corrected so that the board width on the delivery side of the final stand matches the target value based on the mathematical model with the measured value as a variable. A strip width control method in cold tandem rolling characterized by the above. 2. The final stand with the amount of change in rolling load at each stand, the amount of change in tension between each stand, and the amount of change in shape control means at each stand as variables during cold rolling with a cold tandem rolling mill. A mathematical model representing the strip width variation on the delivery side is created in advance, and the strip width on the delivery side of the final stand is controlled by the method according to claim 1 at the beginning of rolling, and then the rolling load during rolling is continuously measured. Then, by substituting the measured value and the change amount of tension between each stand into the mathematical model, the control amount of the shape control means in each stand is corrected so that the plate width on the delivery side of the final stand matches the target value. A method for controlling strip width in cold tandem rolling.