KR20020045429A - Thickness estimation apparatus of rolling strip by using elastic line and plastic line and its estimation method - Google Patents

Abstract

PURPOSE: An apparatus and a method for estimating thickness of a rolled strip using elastic coefficient and plastic coefficient are provided to improve thickness accuracy and product accuracy of a hot rolled strip by accurately estimating thickness of a strip proceeding between stands in hot finish rolling. CONSTITUTION: The method for estimating thickness of a rolled strip using elastic coefficient and plastic coefficient comprises a first step (S1) in which preset information is inputted according to rolling conditions of the strip; a second step (S2,S3) of setting thickness(h) in the information inputted in the first step as an arbitrary thickness(h1) and calculating rolling forces; a third step (S4,S5) of calculating elastic line and plastic line using the arbitrary thickness and rolling forces calculated in the second step; a fourth step (S6,S7) of comparing the two thickness values by calculating the arbitrary thickness(h1) from a point at which the elastic line and the plastic line calculated in the third step are reciprocally contacted and a thickness(h2) at the reciprocally contacted point; and a fifth step (S8,S9) of applying rolling forces so that the strip is rolled to the thickness(h2) when the error is contained in the error limits by comparing an error of the two thickness values in the fourth step with preset error limits.

Description

Thickness estimation apparatus of rolling strip by using elastic line and plastic line and its estimation method

The present invention relates to an apparatus for predicting the thickness of a rolled steel sheet for predicting the thickness of the rolled steel sheet running between rolling stands in hot finishing rolling, and to a method for predicting the thickness of the rolled steel sheet. The present invention relates to a thickness estimating apparatus and a method of predicting the same.

The slab manufactured in the machine is passed through a plurality of rolling stands to produce a rolled hot rolled steel sheet set to a thickness that can be used as a material desired by the consumer or cold rolling process.

The hot rolled steel sheet is gradually rolled to the thickness of the final rolled steel sheet while passing through a plurality of rolling stands, at this time, the thickness of the hot rolled steel sheet running between the plurality of rolling stands to measure the hot rolled steel sheet to the exit side of the next rolling stand Set the thickness of, and thereby set the rolling load and the roll gap.

However, it is possible to measure the thickness of the steel sheet to proceed by installing a thickness meter between the plurality of rolling stands, but it is not possible to install the thickness meter due to the high temperature of the rolled steel sheet, the cooling water, the steam by the cooling water, the installation position, etc. Difficulties follow In addition, even if the thickness gauge is installed on-line, it is difficult to install due to the frequent occurrence of failure due to poor working environment and the expensive price of the thickness gauge.

Therefore, a method of calculating the thickness of the hot rolled steel sheet coming out of the rolling stand is developed through a gauge meter model using the linear behavior of the rolling mill without using such a thickness gauge. However, in conclusion, the gauge meter model using this linear behavior is simply calculated only by the relationship between the thickness and the load of the rolled steel sheet, and the predicted thickness of the rolled sheet is less reliable. Hereinafter, a model of the gauge meter using the linear behavior will be described in detail.

1 is a conceptual diagram showing a thickness prediction apparatus of a rolled steel sheet according to the prior art, Figure 2 is a graph showing a plastic curve and elastic line for predicting the thickness of the rolled steel sheet.

As shown in FIG. 1, the upper part of the rolled steel sheet 3 having the looper 9 installed therebetween between the shear rolling stand (hereinafter referred to as a 'stand') i and the rear end stand i + 1. The pressure in the direction to maintain the tension of the rolled steel sheet (hereinafter referred to as 'steel plate') (3). Each stand (i, i + 1) is provided with a load cell (5) as a load measuring device to measure the rolling load, and the work roll (1) accommodated in the stand (i, i + 1) Cylinders 7i and 7i + 1 are installed to apply rolling loads.

In the structure having such a rolling system, in order to measure the thickness of the steel sheet 3 coming out from the front end of the shear stand i, information about the steel sheet 3 is input from the supervisory control computer (SCC) 10, and a gauge meter The calculating part 12 uses the information of the steel plate 3 input from the SCC 10, the rolling load ΔP measured from the load cell 5i, and the gap between the two work rolls 1 of the shear stand i. By using the same formula as in Equation 1, the exit thickness deviation Δh (starting thickness (H)-exit thickness (h)) is calculated.

Where h is the exit thickness, S is the roll gap, P is the rolling load, and K is the stiffness coefficient of the roll.

By using the thickness deviation of the steel sheet 3 calculated from the gauge meter calculation unit 12, the deviation from the target thickness is transmitted to the hydraulic cylinder 7i + 1 through the FF AGC (Feedforward Automatic Gauge Control) 14. It sets and outputs to the hydraulic cylinder 7i + 1 of the rear | right stand (i + 1).

However, this metric calculation method is far from the actual rolling behavior because it is formulated only for the linear behavior between thickness and load. As a reason, the actual rolling phenomenon has considerable nonlinearity due to various variables such as temperature, oil film thickness and friction. Therefore, the controller designed for the rolling mill cannot exhibit satisfactory performance without considering such nonlinearity, so that the stand exit thickness can be accurately calculated only by considering the nonlinearity.

On the other hand, as shown in Figure 2, the exit thickness h of the rolling mill is determined at the intersection of the elastic line (EL; Elastic Line) and the plastic curve (PL; Plastic Line). The elastic line is a relationship representing the linear behavior between the thickness and the rolling load as in Equation 1, but the plastic curve is a nonlinear behavior. Therefore, predicting and determining the exit thickness only by the linear behavior of the elastic line has the disadvantage of lowering the reliability of the prediction.

On the other hand, the patents already published as a technique for calculating the thickness of the steel sheet, "Japanese Patent Laid-Open No. 7-214125 (name of the invention: a method for controlling plate thickness in a tandem rolling mill)" and "Japanese Patent Laid-Open No. 10- 34219 (Invention: Thickness Control Method in Hot Rolling Mill) and "Japanese Patent Application Laid-open No. Hei 9-66309 (Invention: Thickness Control Method and Apparatus)", and the technical spirit of these patents. The problem is as follows.

Firstly, the thickness gauge for plate thickness control is installed only at the end of the stand and used for feedback control. However, the thickness of the final rolled steel sheet is the target thickness and error range because it does not provide information on the thickness between the stands. Has a disadvantage of being large.

Secondly, the model used for calculating the thickness of the steel plate between the stands is a simplified model using the linear gauge metric as described above using the rolling load and the roll gap measurement, and the degree of thickness control is inferior. There are disadvantages.

The present invention is provided to solve the problems of the prior art as described above, in consideration of the elastic modulus and plasticity coefficient of the rolled steel sheet using the elastic modulus and plasticity coefficient that can accurately predict the thickness of the steel sheet coming out of the rolling stand An object of the present invention is to provide a thickness prediction device for a rolled steel sheet and a prediction method thereof.

1 is a conceptual diagram showing a thickness prediction apparatus of a rolled steel sheet according to the prior art,

2 is a graph showing a plastic curve and an elastic line for predicting the thickness of the rolled steel sheet,

3 is a conceptual diagram illustrating a thickness predicting device of a rolled steel sheet using an elastic modulus and a plastic modulus according to an embodiment of the present invention;

4 is a flowchart illustrating an algorithm of the apparatus for predicting the thickness of the rolled steel sheet illustrated in FIG. 3.

♠ Explanation of symbols on the main parts of the drawing ♠

1: work roll 3: rolled steel sheet

5, 5i + 1: Load cell 7, 7i + 1: Hydraulic cylinder

9: Looper 10: SCC (Supervisory Control Computer)

12: Gauge meter calculation unit 14: FF AGC

20: input unit 30: thickness and load calculation unit

40: elastic / plastic curve calculation unit 50: thickness error comparison unit

60: output unit

According to the present invention for achieving the object as described above, in the thickness prediction apparatus of the rolled steel sheet for predicting the thickness of the steel sheet to be rolled while passing through a plurality of rolling stands, from the information input from the SCC (Supervisory Control Computer) The thickness and load calculation unit for arbitrarily setting the exit side steel plate thickness of the rolling stand and calculating the rolling load, and the elastic line and the plastic curve are calculated using the thickness and the load calculated in the thickness and load calculation unit, and the thickness of the site where the two curves are in contact with each other. And an error comparison unit for comparing an error between the thickness calculated by the thickness and the load calculation unit and the thickness calculated by the curve operation unit with a set error limit value, wherein the error is included in the error limit value. Predictive control of the rolling load of the rolling stand to have the thickness calculated by the curve calculation unit It is provided with a thickness prediction apparatus of rolled steel.

Further, according to the present invention, in the thickness prediction method of the rolled steel sheet for predicting the thickness of the steel sheet to be rolled while passing through a plurality of rolling stands, the first step of receiving information already set according to the rolling conditions of the steel sheet, and the first A second step of calculating the rolling load by setting the thickness h to an arbitrary thickness h1 among the input information of the first step, and an elastic line and a plastic curve using the arbitrary thickness and the rolling load calculated in the second step. Calculating a thickness (h1) and a thickness (h2) at the point of contact with each other and comparing the two thickness values from the point where the elastic line and the plastic curve calculated at the step (3) contact each other. Comparing the error of the two thickness values with the error range limit value that is already set in the fourth step, and the steel sheet having the thickness h2 when the error is included in the error range limit value. The thickness of the rolled steel plate prediction method for applying a rolling load is provided to be rolled.

In the following, with reference to the accompanying drawings, a preferred embodiment of the thickness prediction device and the prediction method of the rolled steel sheet using the elastic modulus and plasticity coefficient according to the present invention will be described in detail.

3 is a conceptual diagram illustrating a thickness prediction apparatus of a rolled steel sheet using an elastic modulus and a plasticity coefficient according to an embodiment of the present invention, and FIG. 4 illustrates an algorithm of the thickness prediction apparatus of a rolled steel sheet illustrated in FIG. 3. It is a flow chart.

As shown in FIGS. 3 and 4, the input unit 20 has the exit thickness h, the exit thickness H, and the tension t _b , t _f according to the steel sheet rolling conditions from the SCC (Supervisory Control Computer) 10. And a setup value, and the setup value is set as a mathematical model in consideration of the desired product thickness, final stand speed, and the like in the SCC 10.

The set value thus set is input from the input unit 20 to the thickness and load calculation unit 30. The thickness and load calculating part 30 sets an arbitrary exit thickness h1, and calculates the rolling load P1 in the exit thickness h1 using the rolling load calculation formula of the said Formula (1).

Then, the exit thickness h1 and the rolling load P1 are input to the elastic / plastic curve calculating unit 40. The elastic / plastic curve calculating unit 40 calculates the plasticity coefficient and elastic modulus, and uses the plasticity coefficient. Find the intersection of the plastic curve and the elastic line using the elastic modulus and set it as the exit thickness (h2).

Then, the thickness error comparison unit 50 compares the random exit thickness h1 and the calculated exit thickness h2, and if the error between the two values is small, the exit thickness h2 calculated by the output unit 60 is the exit thickness. It is determined by (h) and output to FF AGC (Feedforward Automatic Gauge Control) 14, and FF AGC 14 calculates the rolling load for the input exit thickness h and calculates the hydraulic pressure of the rear stand (i + 1). Activate the cylinder 7i + 1.

The signal flow relationship according to the thickness prediction method of the rolled steel sheet using the elastic modulus and plasticity coefficient configured as described above will be described in detail.

First, the SCC 10 receives setup values such as the exit thickness h, the exit thickness H, and the tensions t _b and t _f (S1). These setup values can be determined as a mathematical model in consideration of the desired product thickness and final stand speed in the SCC (10), the setup value can be determined.

Then, the exit thickness h received from the SCC 10 is set to an arbitrary exit thickness h1 (S2). Here, the exit thickness (h) of each stand will have the value set in the setup if there is no disturbance or malfunction. However, since non-linear phenomena such as unknown disturbance and vibration exist in each stand, first, the input exit thickness h is set to an arbitrary exit thickness h1 to obtain the actual exit thickness.

And the rolling load P1 in the exit thickness h1 is calculated | required using the rolling load calculation formula in following formula (2) (S3).

Here, Z _P is the reduction force coefficient, b is the plate width, l _d is the length of the projection contact arc, and Km represents the deformation resistance.

On the other hand, the nonlinear PL is determined by an equation model such as Equation 3.

In the elastic / plastic curve calculation unit 40, as shown in FIG. 2, the plasticity coefficient ∂P1 / at the point (h1, P1) set using the exit thickness h1 and the rolling load P1 set previously. ∂h1) is calculated (S4). Here, the calculated plasticity coefficient becomes the slope of the tangent of the point (h1, P1) in the PL curve in FIG. Then, the elastic line of the EL represented by the equation (1) is drawn (S5) to find the intersection point of PL and EL, and then the thickness h2 at this intersection point is obtained (S6). It is determined whether the error between the thickness h2 thus obtained and the thickness h1 obtained above is smaller than ε (ε ≒ 0) arbitrarily set (S7). Here, if the error between the two thickness values is sufficiently smaller than the randomly set ε, the thickness converges to an arbitrary value and is an accurate calculation. The thickness (h2) is set as the thickness (h) (S8), and the thickness (h) is final. Set the exit thickness (h). And the rolling load P2 is calculated by this formula (2) using this thickness h2 (S9). Then, the hydraulic cylinder 7i + 1 is operated so that the calculated rolling load can be applied to the rear end stand i + 1.

If the errors h2-h1 of the two thickness values are not sufficiently smaller than the arbitrarily set error ε, the rolling load P1 is calculated from the calculated calculated thicknesses h1.

As described in detail above, the thickness prediction apparatus of the rolled steel sheet using the elastic modulus and the plasticity coefficient of the present invention and the prediction method thereof are conventionally estimated by using the elastic modulus and the plastic modulus to predict the thickness of the rolled steel sheet coming out from the rolling stand. Rather than predicting the thickness using only the linear elastic line of, it is advantageous to predict the stand exit thickness by using the nonlinear plastic curve together to estimate the thickness.

Although the technical concept of the thickness prediction device and the prediction method of the rolled steel sheet using the elastic modulus and plasticity coefficient of the present invention has been described with the accompanying drawings, this is illustrative of the best embodiment of the present invention by way of example It is not intended to limit. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (2)

In the thickness prediction device of the rolled steel sheet for predicting the thickness of the steel sheet rolled while passing through a plurality of rolling stands (i, i + 1), A thickness and load calculation unit for arbitrarily setting the outgoing steel sheet thickness of the rolling stand i from information input from a supervisory control computer (SCC) and calculating a rolling load; A curve calculation unit for calculating an elastic line and a plastic curve by using the thickness and the load calculated by the thickness and load calculation unit, and calculating the thickness of a portion where the two curves are in contact with each other; An error comparison unit for comparing an error between the thickness calculated by the thickness and load calculation unit and the thickness calculated by the curve operation unit with a set error limit value, When the error is included in the error limit value, the thickness prediction apparatus of the rolled steel sheet, characterized in that for predicting and controlling the rolling load of the rolling stand (i + 1) so that the rolled steel sheet has a thickness calculated by the curve calculation unit. In the thickness prediction method of the rolled steel sheet for predicting the thickness of the steel sheet rolled while passing through a plurality of rolling stands (i, i + 1), A first step of receiving information already set according to the rolling conditions of the steel sheet; A second step of calculating a rolling load by setting a thickness h to an arbitrary thickness h1 among the inputted information of the first step; A third step of calculating elastic lines and plastic curves using any thickness and rolling load calculated in the second step; A fourth step of comparing the two thickness values by calculating the arbitrary thickness h1 and the thickness h2 at the point of contact with each other from the point where the elastic line and the plastic curve calculated in the third step are in contact with each other; In the fourth step, when the error is included in the error range limit value by comparing the error of the two thickness values with the previously set error range limit value, a rolling load is applied to roll the steel sheet to the thickness h2. Thickness prediction method of the rolled steel sheet.