KR100949683B1 - Method of compensationg change of mold level caused by fluctuation of mass-flow - Google Patents

Abstract

The present invention is to control the surface level fluctuation so that the mass-flow imbalance during rolling the slab provided in the thin slab and the mini mill process in the intermediate rolling process does not affect the fluctuation of the surface level of the upstream. It is about a method. The present invention obtains the amount of change in the thickness and speed of the raw material on the exit side of the mill, calculates the correction amount of the cross section of the mold exit therefrom, and controls the cross-sectional area of the mold exit accordingly to keep the level of water level constant.

      Thin Slab, Mini Mill, Surface Control, Mass Flow

Description

Method of controlling the water level according to the mass flow variation {METHOD OF COMPENSATIONG CHANGE OF MOLD LEVEL CAUSED BY FLUCTUATION OF MASS-FLOW}

1 is a schematic diagram of a thin slab and mini mill player and rolling mill.

Figure 2 is a schematic diagram of the water level compensation device according to the present invention.

      <Explanation of symbols for the main parts of the drawings>

1: Ladle 2: Tundish

3: Mold 4: Segment

5: rolling mill 6: slab

7: Speed measuring instrument 8: Rolling load measuring instrument

9: compensation circuit 10: water level controller

11: stopper-rod

In the present invention, when the slab provided in the playing process in the thin slab and mini mill mill rolling and rolling process is rolled in the rolling process, the upstream surface of the slab when the rolling speed of the slab changes according to the thickness variation of the slab to keep the mass flow constant. The present invention relates to a method of suppressing fluctuations in the surface level generated by affecting the level.

Patent application No. 2000-81899 calculates the inclination of the level of the level control driver to cope with the sudden level change of the level, and also detects the sudden change of the level of the level and maintains the level of the level using fuzzy logic In Patent Application No. 2000-67323, the level of hot water in the continuous casting line such as the mini mill factory is changed to the main speed change, the tundish weight change, and the periodic disturbance such as the clogging of the SEN and the unclogging. Nevertheless, a technique has been proposed to control the level of water in a stable and reliable manner. In addition, Patent Application No. 1997-26864 calculates the sliding hyperplane to control high accuracy so that even if disturbances such as stick-slip occurring between the inner wall of the mold and molten steel occur in a general player, the sliding hyperplane is not affected. Technology has been proposed.

In general, the playing and rolling processes of thin slab and mini mills are as follows. As shown in FIG. 1, molten steel dissolved in the steelmaking process is transported in the ladle 1. Since it is difficult to directly inject the molten steel transported in the ladle 1 into the mold 3, the molten steel is injected into the mold 3 after the molten steel is once contained in the tundish 2. The molten steel enters the rolling roll past the segment 4 while cooling in the mold 3. In the rolling roll, the slab is rolled by using the automatic thickness control in the rolling mill 5 of two stages in order to make the incoming slab 6 into a material having a desired thickness.

As such, when the slab 6 passing the mold 3 and the segment 4 is rolled in the two-stage rolling mill 5, a variation in thickness may occur in the material. That is, since the cooling pattern is changed according to the speed of the continuous casting, the thickness variation of the material may occur, and the thickness variation of the material may occur due to the uneven distribution of the roll load of the segment 4 such as bulging. When a material having a thickness variation enters the rolling mill 5, the rolling mill 5 measures the thickness variation of the inlet side and offsets the thickness variation of the outlet side by adjusting the roll gap using an automatic thickness control method.

Unlike the general playing and rolling processes, the playing and rolling processes of the thin slab and mini mills are characterized by continuous play and rolling and have a short length. Variation in the overall mass flow caused by the change in the thickness of the material on the inlet side of the rolling mill 5 or the change in the rolling load of the rolling mill 5 also changes the speed of the inlet side material, and this change changes the velocity component of the slab. When the velocity of the slab moving along the segment 4 changes, the length of the upstream and the flow velocity are affected, which acts as a disturbance factor of fluctuations in the level of the playing surface, thereby changing the level of the slab. In the hot water level control up to now, the amount of fluctuation of the mass flow generated by adjusting the roll spacing of the rolling mill 5 changes the speed component of the raw material on the inlet side of the rolling mill 5, and the mold 3 to the rolling mill 5. Since the length component of was changed, it was recognized as a disturbance component that eventually caused fluctuations in the water level, and control was performed.

The present invention has been made to solve the problems of the prior art described above, when the overall mass flow fluctuation due to the change in the thickness of the material or the change of the rolling load in the rolling mill 5 is expected, the mold (3) By compensating for the change in the cross-sectional area per unit time passing through), it enables strict control of fast and disturbing processes such as thin slabs and mini mills, and breakouts. The purpose of this is to prevent accidents in which casting is interrupted due to part rupture and to more precisely perform the water level control.

In order to achieve the above object, according to the present invention, in the method of controlling the fluctuation of the trough level of the tundish according to the fluctuation of the mass flow of the rolling mill in the playing and rolling process of the thin slab and mini mill, the exit material speed of the rolling mill Measuring a rolling load; Obtaining an exit speed change amount and an exit thickness change amount of the work material from the work speed and the rolling load; Obtaining an entry speed compensation amount using the exit speed change amount and the thickness change amount; And controlling an entrance side material speed change amount according to the correction amount.
The present invention can be controlled by adjusting the cross-sectional area of the mold discharged slab in accordance with the correction amount of the inlet side material speed. In addition, the present invention can measure the exit speed and the rolling load of the raw material using a speed gauge and a rolling load measuring instrument provided on the exit side of the rolling mill.
When the fluctuation of the mass flow occurs in the rolling mill 5, a backward slip occurs, and thus the fluctuation of the free loop of the inlet-side material of the rolling mill 5 occurs. In order to make this clearance loop constant, control can be performed in the form which changes the speed | rate of the raw material of the rolling mill 5 entrance side. In general, the equation of mass flow that normally occurs in the rolling mill 5 is determined as follows.

(Eq. 1)

Where M is the inlet side material massflow of the rolling mill 5, m is the outlet side material massflow of the rolling mill 5, σ is the density, W is the inlet side material width, w is the outlet side material width, and H is The inlet side material thickness, h is the outlet side material thickness, V is the velocity of the inlet material, v is the velocity of the outlet material. That is, the inlet side massflow and the outlet side massflow of the rolling mill 5 are the same.

To keep the mass flow constant from Eq. 1, the velocity of the inlet material that must be changed when the material thickness changes is given by Eq.

(Eq. 2)

Here, the speed change amount of the inlet side material which is changed by the mass flow variation of the rolling mill 5 is represented by the logarithm of the speed change amount of the outlet side material, the thickness change amount of the outlet side material, and the thickness change amount of the inlet side material. Here, the speed change amount of the exit material and the thickness change amount of the exit material can be obtained by measuring the speed and the rolling load of the material on the exit side of the rolling mill, respectively. Assuming that there is no change in the inlet material thickness, the sum of these two amounts eventually results in a change in velocity of the inlet material. Since the speed change amount of the inlet material corresponds to the change of the cross-sectional area per unit time of the slab exiting the mold 3 directly under the mold 3, the speed change amount of the material of the inlet material causes fluctuations in the water level. As a result, the fluctuation of the mass flow causes fluctuations in the water surface, and a correction equation such as Equation 3 is used to control this.

(Eq. 3)

Where α is the compensation coefficient of the speed variation of the exit material, β is the compensation coefficient of the thickness variation of the exit material.

2 is a block diagram of a system for controlling the water level using the principles of the present invention. Rolling using a rolling load measuring instrument 8 which measures the material velocity on the exit side and the load of the rolling mill 5 using a speed measuring instrument 7 capable of measuring the speed at the exit side of the rolling mill 5. The load is measured and input to the compensation circuit (9). In the compensating circuit 9, the thickness change amount of the exit material from the rolling load is calculated, the speed change amount of the exit material is calculated, multiplied by the correction constant according to Equation 3, and the correction amount is obtained and inputted to the floor level controller 10. The water level controller 10 drives the stopper rod 11 which controls the cross-sectional area of the slab according to the correction amount calculated by the compensation circuit 9 when calculating the cross-sectional area per unit time of the slab currently exiting the mold 3. Level control is performed.

The present invention is to measure the variation factors of mass flow caused by the thickness variation of the rolling mill (5) in the play and rolling process in thin slabs and mini mills, and the thickness variation terms of the material exit side and the material exit side speed variation By inputting this into the compensation term of the water level control, it is possible to perform more precise water level control, thereby improving yield and reducing breakout occurrence. The embodiment of the method for controlling the water level according to the mass flow fluctuation according to the present invention has been described with reference to the accompanying drawings, which describes the best embodiment of the present invention by way of example and does not limit the present invention. In addition, any person having ordinary skill in the art may make various changes and modifications without departing from the scope of the technical idea of the present invention.

Claims (4)

In the method of controlling the fluctuation of the tumble level according to the fluctuation of the mass flow of the rolling mill in the performance and rolling process of thin slabs and mini mills, Measuring the material velocity and the rolling load on the outlet side of the rolling mill; Obtaining an exit speed change amount and an exit thickness change amount of the work material from the work speed and the rolling load; Obtaining an entry speed compensation amount using the exit speed change amount and the thickness change amount; And And a step of controlling the water level according to the mass flow fluctuation, including controlling an amount of change in the inlet side material speed according to the correction amount. The method of claim 1, wherein the inlet-side material speed change is controlled by adjusting a cross-sectional area of a mold from which the slab is discharged according to the correction amount. The method of claim 1, wherein the compensation amount is calculated by the following equation. (Eq. 3)

(Where v is the exit velocity, h is the exit thickness, α is the compensation coefficient of the exit velocity, and β is the compensation coefficient of the exit thickness) The method of claim 1, wherein the exit speed and the rolling load of the material are measured by using a speed gauge and a rolling load meter provided at the exit of the rolling mill.

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