KR20020036140A - Cooling control method of hot strip using intermediate pyrometer on run-out table - Google Patents

Abstract

PURPOSE: A method for controlling cooling of a hot rolled strip using pyrometers is provided which performs accurate cooling of the hot rolled strip by installing an intermediate pyrometer between a finishing rolling mill and a tension reel in a method for controlling cooling of the hot rolled strip coiled on the tension reel. CONSTITUTION: In a method for measuring temperatures of a proceeding hot rolled strip by installing a first pyrometer at the exit side of a finishing rolling mill, a third pyrometer at an entrance side of a tension reel and a second pyrometer at the intermediate part of the finishing rolling mill and the tension reel, and controlling cooling of the hot rolled strip proceeded from a cooling mean positioned between each of the pyrometers, the method for controlling cooling of the hot rolled strip comprises the steps of storing learning coefficients between the first pyrometer and the second pyrometer and between the second pyrometer and the third pyrometer (S2); correcting the learning coefficient from the first pyrometer to the second pyrometer using a real measured temperature measured from the second pyrometer (S3); determining a cooling amount by the cooling means positioned between the first pyrometer and the second pyrometer using the corrected learning coefficient (S4); and determining a cooling amount by the cooling means positioned between the second pyrometer and the third pyrometer by utilizing the real measured temperature in feed forward controlling (S6).

Description

Cooling control method of hot strip using intermediate pyrometer on run-out table}

The present invention relates to a method of controlling the cooling of a hot rolled steel sheet in the production of a hot rolled coil by winding the rolled hot rolled steel sheet to a winding machine, and in particular, an intermediate temperature measured from an intermediate thermometer by installing an intermediate thermometer between the finishing mill and the winding machine. The present invention relates to a cooling control method of a hot rolled steel sheet to enable a target cooling control.

Slabs and billets manufactured in the machine are transformed into steel in the form desired by the consumer through a number of rolling mills. In general, hot rolled steel sheets (hereinafter referred to as 'steel plates') are rolled into steel sheets through a plurality of rolling mills, and the steel sheets passed through the finish rolling mill are cooled while passing through a cooling system, and the tension reel ) Into a hot rolled coil (hereinafter referred to as a 'coil'). In making this coil, the coil must be cooled to a suitable temperature.

1 is a schematic diagram of a cooling system having a general intermediate thermometer.

As shown in FIG. 1, the rolled steel sheet 10 in a number of rolling mills is cooled to a temperature suitable for winding up as it passes through the cooling system 1. The steel sheet 10 is rolled by the finishing mill 13 and then wound by the winder 17 after advancing along a top surface of a run out table (not shown). The cooling system 1 for cooling the steel sheet 10 is arranged along the run out table. In addition, an entrance thermometer 21 and an exit thermometer 23 are provided at the inlet and the outlet of the cooling system 1, respectively. In the entrance thermometer 21, the temperature of the steel sheet 10 entering the cooling system 1 is measured. The measurement and the exit thermometer 23 measure the temperature of the steel sheet 10 advancing from the cooling system 1 to the winder 17 and measure the winding temperature before winding.

On the other hand, the cooling system 1 is arranged up and down between the run out tables. Each cooling system 1 consists of a water cooling part which cools a steel plate by pouring water into a steel plate, and an air cooling part which cools a steel plate with air. The water cooling unit and the air cooling unit disposed on the upper and lower portions of the cooling system 1 are divided into air cooling banks and water cooling banks, respectively. Each of these cooling banks 30F and 30R controls a cooling capacity for cooling the steel sheet. .

Conventional cooling control sets the target cooling inlet temperature (hereinafter referred to as 'FDT') and cooling outlet temperature (hereinafter referred to as 'CT') according to the steel grade, and cools the steel sheet to hit the FDT and CT accordingly. do. For this operation, first, the air cooling amount is calculated by using the target FDT, the target CT, and the target moving speed v of the steel sheet, and after calculating the required water cooling amount, the number of water cooling banks is determined. After the steel sheet 10 exits the finishing mill 13, if the performance FDT and the performance steel plate moving speed v of the steel plate are measured, the performance FDT and the performance steel plate moving speed v instead of the target FDT and the target steel plate moving speed v Recalculate the water cooling amount at regular intervals using) and reset the number of water cooling banks. Then, the steel sheet 10 exits the runout table to adjust the CT.

The learning factor is involved in the calculation method of water cooling by water cooling, which will be described in detail below.

The water cooling drop amount is calculated by calculating the temperature drop amount by water cooling per banks 30F and 30R according to whether each bank 30F or 30R is used, and calculating the sum of the total water cooling banks 30F and 30R. The total water cooling amount Tw at the run out table is expressed by Equation 1 below.

Where lbank is the length of the i-th bank, Hf is the thickness of the steel sheet, v is the traveling speed of the steel sheet, Cp is the specific heat of the steel sheet, ρ is the density of the steel sheet, and Qiu is the heat flux of the i-th upper bank. , Qid represents the heat flux of the i th lower bank.

The upper and lower heat flux values Qiu and Qid of banks 30F and 30R, which are one factor in Equation 1, are calculated through Equation 2.

Here, fo is the basic heat flux coefficient, f2i is the heat flux coefficient of the i-th bank, Tiu is the water temperature correction coefficient of the upper bank, Tid is the water temperature correction coefficient of the lower bank, and fv is the running speed correction coefficient.

On the other hand, as shown in Figure 1, as a cooling control method of the recently developed hot rolled steel sheet has been proposed to install the intermediate thermometer 22 in the intermediate position of the run-out table, and to effectively use it for the winding temperature hit . In this method, however, the intermediate thermometer 22 is used only as an auxiliary means of the winding temperature hit, rather than the cooling control according to the intermediate temperature (hereinafter referred to as 'MT'). Instead of the target MT, only the method of correcting and replacing the intermediate temperature deviation (actual MT-target MT) multiplied by the gain value is used.

In consideration of the intermediate thermometer 22, the method of calculating the amount of water cooling drop involves learning coefficients at the front and rear ends of the cooling system 1, respectively. Here, the front end of the cooling system 1 represents the zone from the entry thermometer 21 to the intermediate thermometer 22, and the rear end represents the zone from the intermediate thermometer 22 to the exit thermometer 23.

On the other hand, fo for calculating the heat flux in the method of calculating the water cooling drop in consideration of the intermediate thermometer 22, as shown in Equation 3, the heat treatment parameter coefficient value of C0 to C8 and the cooling system divided on the basis of MT It can be represented by the front and rear learning coefficients f1 and f2.

Here, Tw is water temperature and Wf is the width of a steel plate.

In the cooling control method of the hot-rolled steel sheet 10, the learning coefficients f1 and f2 in the cooling model have stored the learning coefficients corresponding to the steel sheet 10 in the memory unit after the work for one steel sheet 10 is completed. If the cooling conditions of the same steel sheet are given, the cooling control is performed using the stored learning coefficients as they are. However, the cooling control of the hot rolled steel sheet in this manner cannot be formalized according to the numerous steel grades or the temperature change while the steel sheet is cooled, so that it is difficult to hit the intermediate temperature and the winding temperature to the target temperature. And there is a disadvantage that the reliability is also low.

The present invention is provided to solve the problems of the prior art as described above, by reflecting the measured MT in the shear learning coefficient f1 to correct the amount of water cooling calculated in the next control period and at the same time the actual MT value at the end of the water cooling It is an object of the present invention to provide a cooling control method for a hot rolled steel sheet that is applied by a feedforward control method and controls to hit a winding target temperature.

1 is a schematic diagram of a cooling system having a general intermediate thermometer,

2 is a flowchart of a cooling control method according to an embodiment of the present invention;

FIG. 3 is a comparison graph illustrating measured temperatures when the hot rolled steel sheet is cooled by the cooling control method shown in FIG. 2 and the cooling method according to the related art.

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

1: cooling system 10: hot rolled steel sheet

13: finish rolling mill 17: tension reel

21: entrance thermometer 22: intermediate thermometer

23: exit thermometer 30F, 30R: bank

According to the present invention for achieving the object as described above, the first thermometer is on the exit side of the finishing mill, the third thermometer is on the inlet side of the tensioner (Reel), the second thermometer of the finishing mill and the winding machine A method of measuring the temperature of a hot rolled steel sheet provided in an intermediate portion and controlling the cooling of a hot rolled steel sheet running from cooling means located between the respective thermometers, wherein the first and second thermometers are provided with each other. Storing the learning coefficient between the second thermometer and the third thermometer, correcting the learning coefficient from the first thermometer to the second thermometer using the measured temperature measured from the second thermometer, and correcting the learning. Determining a cooling amount by cooling means located between the first and second thermometers by using a coefficient, and feeding the measured temperature. Utilizing the word (feedforward) controlled by said second thermometer and a cooling control method of the hot rolled steel sheet comprising the step of determining the amount of cooling by the cooling means is located between the third thermometer is provided.

In addition, the learning coefficient correction step of the present invention is calculated by the equation (4).

In the following, with reference to the accompanying drawings a preferred embodiment of the cooling control method of a hot rolled steel sheet using a thermometer according to the present invention will be described in detail.

As shown in FIG. 1, in the cooling system 1, an intermediate thermometer 22 is positioned between the entrance thermometer 21 and the exit thermometer 23, and between the entrance thermometer 21 and the intermediate thermometer 22. It is provided with a shear cooling apparatus having a plurality of banks 30F, and a rear stage cooling apparatus having a plurality of banks 30R between the intermediate thermometer 22 and the exit thermometer 23, along the runout table. Cool the conveyed steel sheet 10.

And the steel plate 10 conveyed along a runout table is wound up by the winding machine 17, and becomes a coil. The cooling control method in the cooling system 1 installed as described above is executed through the steps described below.

2 is a flowchart of a cooling control method according to an embodiment of the present invention, Figure 3 is a measured temperature when the hot-rolled steel sheet is cooled by the cooling control method shown in Figure 2 and the cooling method according to the prior art Is a comparison graph.

As shown in Figure 2, the slab is rolled into a hot rolled steel sheet through a rolling mill (S1).

And the temperature of the hot-rolled steel plate 10 which moves along a runout table is measured using the entry / exit thermometers 21 and 23 provided in the cooling system 1. Using the measured temperature, the shear learning coefficient f1 i is set using Equation 3 (S2), and using the temperature measured by the intermediate thermometer 22 from the stored learning coefficient, Similarly, the shear learning coefficient (shear f1 i + 1) is corrected (S3). At this time, the shear learning coefficient f1 i + 1 of the i + 1 th control period is calculated as shown in Equation 4, and the stored learning coefficient will be described below.

Here, f1i is the shear learning coefficient of the i-th control period, the measured FDTi is the FDT measured in the i-th control period, the measured MTi is the MT measured in the i-th control period, and k is a learning correction coefficient.

K in Equation 4 has a value between 0 and 1, and if the measured MT in the i-th control period has a larger value than the target MT, f1 i + 1 is calculated to be smaller than f1 i. Equations 1 and 2 are calculated to increase the amount of shear water ejected from the shear bank 30F (S4).

In addition, by using the measured MT, a post-learning coefficient (post-f2 i + 1) is calculated by Equation 3 to control feedforward (S5), and the calculated post-learning coefficient (post-f2 i + 1) is calculated. The amount of trailing edges of the trailing bank 30R is calculated by applying to Equations 1 and 2 (S6).

The above-described front and rear learning coefficients fl i + 1 and f2 i + 1 are stored, and the learning coefficients previously set as the learning coefficients are corrected (S7).

In this way, as the measured MT changes in each control period, the shear learning coefficient is newly obtained using Equation 4. This value is substituted into Equation 3 and used for feedforward control. Reflected in the calculation. The next measured MT value is used to determine the back end quantity again by Equation 3.

EXAMPLE

In the cooling system installed as shown in FIG. 1, the rolled hot rolled steel sheet had a thickness of 3.0 mm and a target FDT of 870 ^o C, a target MT of 700 ^o C, and a target CT of 540 ^o C. And the results of cooling control of the changes in the measured CTs by the conventional cooling control method and the cooling control method of the present invention, respectively.

As shown in FIG. 3, the temperature graph formed at the upper end portion of the graph is a graph comparing the measured MT according to the conventional cooling control method and the measured MT according to the cooling control method according to the present invention, when the target MT is 700 ° C. It can be seen that the temperature distribution according to the prior art shows a larger deviation than the temperature distribution according to the cooling control method of the present invention.

In addition, the temperature graph formed on the lower end of the graph is a graph comparing the actual CT according to the conventional cooling control method and the actual CT according to the cooling control method according to the present invention, when the target CT is 540 ℃ temperature distribution according to the prior art It can be seen that the deviation is greater than the temperature distribution according to the cooling control method of the present invention. Therefore, it can be seen that the cooling control method of the present invention is very effective in increasing the hitting degree of MT and CT.

As described in detail above, the cooling control method of the hot rolled steel sheet using the thermometer of the present invention has the advantage that the quality of the hot rolled steel sheet can be improved by cooling to close to the target cooling rate and the target coiling temperature carried out according to the steel grade.

Although the technical idea of the method for controlling the cooling of a hot rolled steel sheet using the thermometer of the present invention has been described with the accompanying drawings, this is by way of example and not by way of limitation. 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)

The first thermometer is installed at the exit of the finishing mill, the third thermometer is at the entrance of the tension reel, and the second thermometer is installed at the middle of the finishing mill and the winding machine to measure the temperature of the hot rolled steel sheet. In the method for the cooling control of the hot rolled steel sheet running from the cooling means located between each of the thermometers, Storing a learning coefficient between the first and second thermometers and between the second and third thermometers; Correcting a learning coefficient from the first thermometer to the second thermometer by using the measured temperature measured from the second thermometer; Determining the amount of cooling by the cooling means located between the first and second thermometers using the corrected learning coefficients; And determining the amount of cooling by the cooling means located between the second thermometer and the third thermometer by utilizing the measured temperature for feed forward control. The method of claim 1, The learning coefficient correction step of the cooling control method of the hot rolled steel sheet, characterized in that calculated by the following equation 1. [Equation 1] Here, f1i + 1 is a corrected learning coefficient, f1i is a stored learning coefficient, measured FDTi is a temperature measured at a first thermometer measured at an i th control period, and measured MTi is a first measured at an i th control period. 2 Temperature measured by thermometer, k being learning correction factor.