KR0143325B1 - Cold rolling method for less thickness deviation of rolled plate - Google Patents

Abstract

The present invention relates to a cold rolling method that can reduce the thickness variation of the rolled plate invented to reduce the control amount in the cold rolling and the thickness variation of the rolled plate, and details the rolled plate (6) withdrawn from the uncoiler (1). After the detailed process in the tank (2), the thickness of the rolling plate (6) just before cold rolling is measured by the thickness measuring instrument (5), and the measured value is inputted to the main computer (4) through the A / D converter (3). In this way, the main computer (4) received as described above is to transmit the measured value to the continuous cold rolling mill (8) to reduce the variation in the thickness of the rolled plate of the final product.

Description

Cold rolling method to reduce thickness variation of rolled sheet

The present invention relates to a cold rolling method that can reduce the thickness variation of the rolled plate invented to reduce the control amount in the cold rolling and the thickness variation of the rolled plate, and in particular, conventionally the rolled plate thickness data before the pickling process after hot rolling Considering the thickness, the excessive load was applied to the cold rolling mill by inputting the thickness of the rolling plate into the setup model. It would be.

In general, in an automated cold rolling mill, all processes are controlled by a computer, and in order to actually drive these process control computers, software called a control model is required.

The control model has a function of determining the driving conditions of the rolling mill so that a desired product can be produced, and appropriately changing the operating conditions of the equipment according to the change of the situation during the rolling operation.

One of the cold rolling control models is the setup model, which is an initial value determination software that determines the operating conditions of the mill to obtain a rolled plate with the desired thickness.

The most important of the various equations constituting the setup model is the equation for rolling load.

The rolling load is used to calculate the roll gap and roll speed setpoints, the ultimate goal of the setup model, and to obtain the coefficients needed to drive the Automatic Gauge Controller (hereinafter referred to as AGC).

On the other hand, the roll gap set value and AGC coefficient of the rolling mill are obtained based on the rolling load calculated in the setup model. Defects result in large economic losses.

Therefore, accurate prediction of the rolling load is the most important factor in determining the precision of the rolled plate thickness.

The rolling load equation used in the typical cold rolling set-up model is shown as a relation of variables only as follows.

Where i: rolling stand number

b: material width

k: strain resistance during rolling of the material

K: Tension correction term

R ': Radius of work roll

H, h: Inlet and exit rolled sheet thickness of rolling mill

In order to obtain the target rolling plate thickness h in the rolling load calculation formula (1), an appropriate rolling speed, front and rear tension, etc. are determined according to a predetermined standard, and the deformation resistance k and the friction coefficient are calculated and used according to the theoretical formula.

However, in a conventional method, H, which is a thickness of a material to be rolled, is used by transferring rolling record data obtained in a hot rolling process to a cold rolling mill.

However, the thickness gauge of the hot rolled sheet is less accurate than the thickness gauge of the cold rolled plate, and it is measured in the state of cooling water of high temperature and high pressure of more than 850 ℃. Often fall.

In addition, the hot rolled rolled plate is subjected to a so-called hydrochloric acid bath to remove the oxide layer formed on the skin of the rolled plate before cold rolling, so that the thickness decreases as much as the removed oxide layer.

Therefore, the thickness of the rolled plate measured immediately after hot rolling is expected to have a considerable error with the thickness of the plate just before cold rolling, which has been pickled, and actually has an error of about 20 to 30 μm.

In order to reduce the variation in plate thickness due to the error of the initial value calculation as described above, the present invention actively uses a thickness gauge at the pickling process exit.

At present the instrument simply measures the thickness after the pickling process and is not used at all in the setup calculator. Therefore, by using the thickness measurement measured after pickling in the setup calculation, the initial value can be calculated more accurately.

The initial value accurately calculated in this way not only reduces the control amount of the controllers intensively installed in the first stand, but also reduces the plate thickness variation of the final product.

1 is a schematic view showing a cold rolling method of the present invention.

Figure 2 is a graph comparing the first stand control amount and the conventional stand control amount of the present invention.

Figure 3 is a graph comparing the thickness deviation of the final product of the present invention and the conventional final product thickness.

* Explanation of symbols for main parts of the drawings

1: Uncoiler 2: Pickling tank

3: A / D Converter 4: Main Computer

5: thickness meter 6: rolling plate

7: Looper 8: Continuous cold rolling mill

9: winder

This invention will be described in detail with reference to the accompanying drawings as follows.

1 is a simplified illustration of the system presented in the present invention.

In the conventional cold rolling method, the thickness of the rolled plate 6 measured in hot rolling is transferred to a cold rolling mill to obtain a roll gap and a roll speed, which are initial values of the cold rolling process.

1, the thickness of the rolled plate 6 before the pickling tank 2 is used for calculation of the initial value of cold rolling.

However, this conventional rolling method causes a reduction in the thickness of the rolled plate 6 in the pickling process performed to remove the oxide film formed on the surface of the rolled plate 6 before cold rolling.

Therefore, in the present invention, the rolled plate 6 immediately after cold rolling after the pickled process in the pickling tank 2 with the rolled plate 6 withdrawn from the uncoiler 1 to reduce the thickness control failure. The thickness is measured by the thickness measuring device 5, and the measured value is inputted to the main computer 4 through the A / D converter 3, and the inputted main computer 4 receives the measured value in the continuous cold rolling mill 8 ) To reduce the variation of the thickness of the finished product.

However, there is a time delay by the looper 7 before the rolled plate 6 is cold rolled, so that sufficient time is allowed for the main computer 4 to perform the setup calculation and then transfer the result to the continuous cold rolling machine 8. There is.

EXAMPLE

Next, after obtaining the rolling performance data using the apparatus proposed by the present invention, the effect of the present invention will be analyzed through simulation.

The computer program used for verification has already been recognized as the most effective representation of the rolling mill model in the field.

The present invention proposes a method for reducing the control amount and the variation of the thickness of the rolling plate in cold rolling, there is no change in the friction coefficient during rolling, surface roughness difference of the upper and lower working rolls, and the controller is installed intensively 1 The variation of the thickness of stand No. 5 and the final product thickness of stand No. 5 were compared.

Table 1 is a representative rolling schedule used in the simulation, Table 2 is a representative model of the disturbance on the rolling mill represented as a mathematical model.

Where C _H : High-frequency component amplitude (10㎛) of substrate thickness disturbance

f _H : High frequency component frequency of substrate thickness disturbance (1 Hz)

C _M : Amplitude of common frequency component of substrate thickness disturbance (20㎛)

f _M : General frequency component frequency of substrate thickness disturbance (0.5Hz)

C _L : Low-frequency component amplitude (35㎛) of substrate thickness disturbance

f _L : Low frequency component frequency of substrate thickness disturbance (0.1 Hz)

C _R : amplitude of roll eccentric disturbance (5㎛)

f _R : Frequency of roll eccentric disturbance (V / R)

V: Roll speed of each stand

R: Backup radius of each stand

C _K : Hardness amplitude of disturbance (0.72㎛)

f _K : Hardness frequency of disturbance (1/60 Hz)

The disturbances used in the simulation include thickness deviation disturbance, roll eccentric disturbance, roll eccentric disturbance and hardness deviation disturbance of the hot rolled sheet. Variation in hardness of the raw material during disturbance may be caused by variation in heat history in the rolling length direction during hot rolling.

Most disturbances have the characteristic of appearing repeatedly with a certain size and period. Therefore, in order to use the disturbance term in the simulation, the size and period of the disturbance must be formulated into a certain form, and in general, the shape of the disturbance is approximated by a sine wave.

As shown in Table 2 above, each disturbance term is approximated by a sine wave, and the values used in this simulation are given below Table 2.

The present invention compares the case where the thickness data of the final hot rolled product is used for the cold rolling initial value calculation and the two cases where the thickness after the pickling process is used for the calculation of the cold rolling initial value.

However, the former is used to calculate the initial value to the thickness of about 20-30㎛ to be removed during the pickling process, it is calculated largely in the rolling load, the roll gap set from the rolling load is also set large and the correct thickness due to the roll gap setting error The control becomes difficult, resulting in a large plate thickness variation.

Therefore, in this simulation, about 30 μm to be removed in the pickling process is applied to the step input as the base material thickness disturbance. In the former case, there is a base thickness disturbance, and the latter case there is no base thickness disturbance. Simulations were performed.

The simulation results according to the above simulation conditions and methods are shown in FIGS. 2 and 3.

2 is a simulation result comparing the control amount of the cold rolling No. 1 stand. In the current cold rolling mill, since most of the controllers are concentrated on the first stand, it compares how much the control amount of the first stand depends on the presence of the base material disturbance.

In the figure, the electric wire is inputted when the thickness of the base material is disturbed, that is, the rolling performance data of the hot-rolled product is input to the cold rolling initial value calculation, and the solid wire is the thickness after the pickling process is completed. It shows the case where it is measured and used for a cold rolling initial value calculation.

In the figure, the dashed line is far from 0, so the control input goes in the direction of (-) part, whereas the solid line is mainly applied in a small amount near 0, so that the dotted line requires excessive control input.

As such, excessive control pressure is a factor that exerts an excessive force on the cylinder, and eventually affects the life of the rolling mill itself.

Figure 3 is a simulation result showing the deviation of the thickness of the cold rolling No. 5. Here, the description of the dotted line and the solid line is as shown in FIG. 2. In case of dotted line, the data applied to the main computer is thicker than the thickness that actually enters the cold rolling mill.In this case, the initial value is calculated and the rolling load and the roll gap are set. Error of up to 3㎛ is shown.

The present invention as described above has the effect of preventing equipment accidents by minimizing the load of the rolling mill by minimizing the load of the rolling mill by inputting the rolled sheet thickness after the pickling is completed to the setup calculator, thereby reducing the thickness variation of the rolled plate to the minimum.

Claims (1)

After the rolling plate (6) withdrawn from the uncoiler (1) was subjected to a pickling process in the pickling tank (2), the thickness of the rolled plate (6) immediately before cold rolling was measured by a thickness measuring instrument (5), and the measured value was A /. Input to the main computer (4) through the D converter (3), the main computer (4) received in this way to transmit the measured value to the continuous cold rolling mill (8) to reduce the thickness variation of the rolled plate of the final product Cold rolling method that can reduce the deviation of the plate thickness of the rolled plate, characterized in that.