JP2012161806A - Exit side shape control method in cold rolling machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exit side shape control method in a cold rolling machine capable of rolling without disturbing a shape even when abrupt disturbance occurs.SOLUTION: A differential tension Tat an i-th stand exit side of the cold rolling machine equipped with multiple stands is found. An evaluation value Λ' of an estimated form is calculated by a formula 1 (requirement 1) based on the differential tension T. The value is feed-forwarded to the final stand so as to change the reduction leveling amount. The differential tension means a cross directional tension difference at strip both ends.

Description

  The present invention relates to a strip shape control method of a strip rolled by a cold rolling mill equipped with multiple stands.

  The shape of the strip after passing through the cold rolling process is a critical factor that affects the passability of the continuous annealing process, which is a subsequent process. In the case of poor shape, meandering may occur, and in the worst case, the meandering strip may contact the structure and cause breakage. For this reason, as shown in Patent Document 1, a shape meter is installed on the outlet side of the cold rolling mill to measure the strip shape, and shape control is performed accordingly. The shape meter used is a known device that can detect a change in elongation in the strip width direction.

As shown in Patent Document 1, the shape evaluation value Λ is derived by using a coefficient of a function λ ₁ x + λ ₂ x ² + λ ₃ x ³ + λ ₄ x ^{4 that} approximates the fourth-order elongation distribution in the strip width direction. . Here, x is a value obtained by normalizing the position of the strip in the plate width direction with -1 and +1 at both ends. Of the shape evaluation values, Λ ₁ and Λ ₃ indicate asymmetric shapes, and Λ ₂ and Λ ₄ indicate symmetric shapes. Based on these shape evaluation values, feedback control such as work roll bending and reduction leveling of a cold rolling mill has been performed to control the shape.

  However, there is an inevitable response delay in the method of feedback-controlling the reduction leveling or the like based on the measured value of the shape meter installed on the cold rolling mill exit side as described above. For this reason, there has been a problem that the shape disturbance caused by the disturbance cannot be corrected immediately. Therefore, there has been a demand for a delivery shape control method in a cold rolling mill that can continue rolling without disturbing the shape even in a situation where the shape is disturbed due to material fluctuation or meandering of the original sheet.

JP-A-2-84211

  The object of the present invention is to solve the conventional problems described above, and to control the shape of the outlet side in a cold rolling mill capable of rolling without disturbing the shape even when there is an abrupt disturbance such as material fluctuation of the original plate. Is to provide a method.

  As a result of repeated studies to solve the above problems, the present inventor has found that there is a strong correlation between the differential tension between the stands of the cold rolling mill and the outlet side shape evaluation value. It was confirmed that the disturbance of the shape can be effectively prevented by performing the feedforward control using. Here, the differential tension is the width direction WS end detected by pressure detecting means (for example, a piezoelectric element) arranged at both ends of the tension detecting means (generally a tension meter roll) on the i-th stand exit side, The difference in tension at the DS end, that is, the difference in tension in the width direction at both ends of the strip.

The present invention has been completed on the basis of the above knowledge, and the differential tension T _di on the exit side of the i-th stand of the cold rolling mill having multiple stands is measured, and the estimated shape is based on the differential tension T _di. The evaluation value Λ ′ is calculated, and the value is fed forward to an arbitrary stand after the (i + 1) th to change the reduction leveling amount. The multi-stand means two or more stands.

Incidentally, the calculation of the estimated shape evaluation value Ramuda', i stand out of the side differential tension T _di, the rolled strip width w, i stand out of the side thickness h _i, a i stand transform coefficients as alpha _i, the following equation (1 ).

Moreover, it is preferable to calculate the leveling change amount ΔS ₁ of the feed forward target stand by the following equation (Equation 2).

  Furthermore, it is preferable to perform feedback control of the cold rolling mill based on the measured value of the shape meter installed on the cold rolling mill delivery side.

  According to the delivery side shape control method in the cold rolling mill of the present invention, the calculation is performed based on the differential tension detected on the near side of the final stand of the cold rolling mill, and the feed forward is performed to any subsequent stand. Adjust the reduction leveling amount. By performing the feedforward control in this way, it has become possible to perform rolling without disturbing the shape even under the circumstances in which the shape disturbance due to the original plate occurs. In addition, more stable shape control can be achieved by combining feedback control of a cold rolling mill based on a measurement value of a shape meter installed on the cold rolling mill exit side. For this reason, generation | occurrence | production of the piece elongation shape can be suppressed compared with the past, and the economical effect is also large.

It is a graph which shows shape evaluation value (LAMBDA) ₁ and the differential tension between each stand. It is explanatory drawing of the control outline | summary of this invention. It is a graph which shows the relationship between estimated shape evaluation value (LAMBDA) ₁ 'and outgoing side shape evaluation value (LAMBDA) ₁ . It is a graph which shows the influence which the final stand pressure reduction leveling change amount has on the delivery side shape evaluation value Λ ₁ . It is a block diagram which shows the control content.

Embodiments of the present invention will be described below.
First, the shape evaluation value used in the present invention will be described. A typical shape meter for measuring the shape of the strip is a roll type, in which a large number of piezoelectric elements are arranged in the roll width direction. With these piezoelectric elements, the tension distribution in the width direction of the strip can be measured. The stretched portion of the strip has a low tension, and the non-stretched portion has a high tension. Therefore, the distribution of the elongation in the width direction of the strip, that is, the shape can be measured.

The distribution of elongation in the strip width direction is approximated by a quartic function of λ ₁ x + λ ₂ x ² + λ ₃ x ³ + λ ₄ x ⁴ . Here, x is a value obtained by normalizing the position of the strip in the plate width direction with -1 and +1 at the left and right ends. Shape evaluation values Λ ₁ , Λ ₂ , Λ ₃ , and Λ ₄ are defined using the coefficients of the quartic function as in the following equations.
Λ ₁ = λ ₁ + λ ₃ , Λ ₃ = (1 / √3) λ ₁ + (1 / 3√3) λ ₃
Λ ₂ = λ ₂ + λ ₄ , Λ ₄ = (1/2) λ ₂ + (1/4) λ ₄

Here, Λ ₁ and Λ 3 represent asymmetric shapes, and Λ ₂ and Λ ₄ represent object shapes. In this embodiment, among these shape evaluation values, shape control is performed using Λ ₁ suitable for evaluating the possibility of meandering. However, other shape evaluation values can be used.

FIG. 1 is a graph showing an investigation of a shape evaluation value Λ ₁ measured by a shape measuring device arranged on the exit side of a final stand and a differential tension between each stand for a 6-stand cold rolling mill. Yes, the horizontal axis is the outlet side conversion length calculated using the rolling reduction of each stand. As is apparent from FIG. 1, it is recognized that there is a strong correlation between the shape evaluation value Λ ₁ and the differential tension between the stands. Therefore, in the present invention, shape control is performed using this relationship.

FIG. 2 is an explanatory diagram of an outline of control according to the present invention. In the present invention, the differential tension T _di on the exit side of the i-th stand of the cold rolling mill having multiple stands is obtained. In FIG. 2, tension meters 1 and 2 are installed on the outlet side of each stand of a cold rolling mill having six stands, and the tension is measured. As in the prior art, a shape detector 3 is installed on the final stand exit side to measure the shape.

Using the differential tension T _di measured by the tension meter on the i-th stand exit side, the rolled sheet width w, and the plate thickness h _i on the i-th stand exit side, the estimated shape evaluation value Λ ₁ ′ according to the above-described equation ( ₁ ). Calculate Note that α _{i in} this equation is a conversion coefficient from the i-th stand outlet side differential tension to the shape evaluation value. The estimated shape evaluation value Λ ₁ ′ thus obtained is strong as shown in the graph of FIG. 3 and the shape evaluation value Λ ₁ obtained based on the measurement value of the shape detector 3 on the final stand exit side. It was confirmed that there was a correlation.

In the present invention, the estimated shape evaluation value Λ ₁ ′ is fed forward to the final stand, and the reduction leveling amount is changed. For this purpose, it is necessary to investigate in advance the influence of the reduction leveling change amount on the shape evaluation value Λ ₁ in the cold rolling mill to be controlled. In this embodiment, as shown in the graph of FIG. 4, it was confirmed that the relationship which can be shown by a linear function was materialized between both. Therefore, if the gradient is expressed by ∂Λ ₁ / ∂S _l , the amount of reduction leveling required to make the variation of the shape evaluation value Λ ₁ zero is calculated from the estimated shape evaluation value Λ ₁ ′ according to the equation (2). be able to. If the leveling amount of the final stand is controlled based on the calculation result, it is possible to maintain the rolling without causing shape disturbance. The overall control content is as shown in FIG.

  As described above, in the present invention, the feed level control of the reduction level of the subsequent stage stand is performed based on the differential tension detected on the front side of the final stand of the cold rolling mill. There is no. For this reason, it is possible to perform rolling without disturbing the shape even when there is a sudden disturbance such as material fluctuation of the original plate.

  Needless to say, if the conventional feedback control based on the shape detection result of the shape detector 3 arranged on the final stand exit side is used together, the shape can be further stabilized.

When the present invention was implemented in the actual cold rolling line of the applicant company, the average value of the shape evaluation value Λ ₁ was reduced to 80% before the implementation, and the standard deviation could be suppressed to 70%. It was confirmed that there was a sufficient practical effect.

1 Tension meter 2 Tension meter 3 Shape detector

Claims (4)

The differential tension T _di on the exit side of the i-th stand of the cold rolling mill having multiple stands is obtained, the estimated shape evaluation value Λ ′ is calculated based on the differential tension T _di , and the value is fed forward to the subsequent stage stand. A method for controlling the shape of the outlet side in a cold rolling mill, characterized in that the amount of reduction leveling is changed. Assuming that the estimated shape evaluation value Λ ′ is T i, the i-th stand exit side differential tension is T _di , the rolled plate width is w, the i-th stand exit side plate thickness is h _i , and the i-th stand conversion coefficient is α _i , The exit side shape control method in the cold rolling mill according to claim 1, wherein the method is performed according to the equation (1).
3. The outlet side shape control method in a cold rolling mill according to claim 2, wherein the leveling change amount ΔS ₁ of the final stand is calculated by the following equation (Formula 2).
  2. The delivery side shape control method in a cold rolling mill according to claim 1, wherein feedback control of the cold rolling mill based on a measured value of a shape meter installed on the delivery side of the cold rolling mill is also performed.