KR100568358B1 - Hot strip cooling control mothode for chage target temperature - Google Patents

Abstract

The present invention is to change the winding target temperature through the PI controller to control the difference between the target temperature and the measured temperature in the "-" control compared to the target temperature to re-calculate the required amount of water cooling to improve the coiling temperature hit ratio and to enable the production of high value-added steel It relates to a cooling control method of a hot rolled steel sheet by changing a target temperature, which is arranged in the order of finishing mill, runout table, and winding machine, and the rear end of the hot finishing rolling mill, between banks 8 and 9 on the runout table. And the first, second and third thermometers installed at the front end of the winder, wherein the thickness, width, speed, measured finish rolling temperature (FDT), measured intermediate target cooling temperature (MCT) and target winding temperature ( CT), measured winding temperature and learning coefficient are used to calculate the required amount of water cooling for feedforward control, and the difference between the measured winding temperature of steel sheet and target winding temperature for each control cycle. Calculate the CT target temperature according to the temperature difference, recalculate the water cooling requirements accordingly, determine the shear water bank using the corrected water cooling requirements for shear feedforward control, and recalculate the learning coefficient for each learning point and apply it. It is.

Hot Rolling, Cooling, Finish Rolling Temperature (FDT), Intermediate Cooling Temperature (MCT), Winding Temperature (CT)

Description

HOT STRIP COOLING CONTROL MOTHODE FOR CHAGE TARGET TEMPERATURE}

1 is a process diagram schematically showing a runout table cooling system in a hot rolling process.

2 is a flowchart illustrating a cooling control method according to the present invention.

3 is a graph comparing a target temperature hit in conventional cooling control with a target value hit in winding temperature in cooling control according to the present invention.

* Description of the symbols for the main parts of the drawings *

1: steel sheet 2: finishing mill (F1)

3: filament rolling mill (Fn) 4: first thermometer

5: feed forward bank (# 1 ~ # 14) 6: the second thermometer

7: feedback bank (# 15) 8: third thermometer

9: winder

The present invention relates to a cooling control method of a hot rolled steel sheet, and more particularly, in order to hit the final target temperature of the hot rolled steel sheet, the winding target temperature is compared with the performance temperature, and the winding target temperature is changed by the difference to change the required amount of water cooling. The present invention relates to a cooling control method of a hot rolled steel sheet by changing a winding target temperature which raises a target winding temperature hit point by recalculating.

During hot rolling, the steel sheet, which is a hot rolled steel, is manufactured as a general coil by cooling to a target temperature after rolling and winding it on a winder. In making such a hot rolled steel sheet into a coil, the wound coil must be cooled to a suitable temperature.

In the current hot rolling system, as illustrated in FIG. 1, a cooling system is configured to cool the hot rolled steel sheet 1 such that the coil wound up reaches a target temperature.

As shown in Fig. 1, in the hot rolling system, the steel sheet is rolled in the finishing mill 3, and then wound by the winder 9 through a run out table.

At this time, the cooling system is composed of a plurality of feed forward banks (# 1 ~ # 14) (5) arranged along the runout table.

In addition, for the cooling control, a first thermometer 4 for measuring the temperature of the hot-rolled steel sheet is installed at the inlet of the # 1 feedforward bank, and is installed in the middle of the plurality of feedforward banks 5 to provide an intermediate temperature. The second thermometer 6 for measuring the temperature and the third thermometer 8 for measuring the temperature of the steel sheet after cooling at the exit side of the feedback bank (# 15) 17 located at the end are provided.

The cooling system is arranged up and down with a runout table in between.

Each feed forward bank (# 1 ~ # 14) is composed of a water cooling unit for cooling by spraying water on the steel plate, and an air cooling unit for cooling the steel plate with air.

The water cooling unit and the air cooling unit, which are arranged at the top and bottom of the cooling system, are divided into cooling banks. The cooling bank can control the cooling capacity for cooling the steel sheet, respectively.

On the other hand, the existing cooling control method according to the steel grade, the target finishing rolling temperature (or cooling inlet temperature) (hereinafter referred to as 'FDT'), the intermediate target cooling temperature (hereinafter referred to as 'MCT'), and the target cooling exit temperature (Or winding temperature) (hereinafter referred to as 'CT'), and the water cooling amount of each of the banks # 1 to # 15 to adjust the FDT and CT accordingly.

And, for some steel grades (hot rolled high grade steel), the primary feedforward control for hitting the intermediate target cooling temperature (MCT) on the basis of the second thermometer (6), and the secondary feed for adjusting the winding temperature (CT) Forward control is performed. Finally, the difference between the target CT and the performance CT is compensated by the feedback control method.

To this end, first, by using the set target FDT, target MCT, target CT and target gutter speed v, the air cooling amount is calculated, the required water cooling amount is calculated, and the number of main banks is determined.

At this time, if the FDT and the plate speed are measured after the steel sheet exits the finish rolling zone (3), the water cooling amount is recalculated at regular intervals using the performance FDT and the rate plate speed instead of the target FDT and the target plate speed to determine the number of main banks. Reset.

In the feedforward control as described above, the setting is calculated by calculating the doubling bank with FDT, MCT, CT, plate speed, and plate thickness. To set the target temperature.

However, if the "-" control is compared to the target, the difference between the target temperature and the measured temperature is reflected in the calculation of the water cooling requirement for each control cycle, and the method of recalculating the water cooling requirement is applied to the "-" control of the target. The degree of control could be secured to some extent, but still limited in learning.

The general required amount of water cooling (T _N ) is shown in Equation 1 below.

Here, FDT represents the FDT performance value, CT _air represents the temperature drop amount at the time of _air cooling, and CT represents the coiling temperature target value.

The amount of water cooling is calculated by calculating the amount of temperature drop by water cooling per bank depending on whether each bank is used or not, and then sums the sums of all banks. At this time, the water cooling amount (Tw) in the run-out table is as shown in equation (2).

는 강판의 밀도이며, Qiu는 i번째 상부뱅크의 열유속이고, Qid는 i번째 하부뱅크의 열유속을 나타낸다.In Equation 2, lbank is the length of the i-th bank, Hf is the coil thickness, v is the plate speed, Cp is the specific heat of the steel sheet,

Is the density of the steel sheet, Qiu is the heat flux of the i-th upper bank, and Qid is the heat flux of the i-th lower bank.

The upper and lower heat flux values for each bank used in Equation 2 are expressed as Equation 3 below.

In the above formula, fo is a basic heat flux coefficient, f2i is a heat flux coefficient of the i-th bank, Tiu is a water temperature correction coefficient of the upper bank, Tid is a water temperature correction coefficient of the lower bank, and fv is a plate speed correction coefficient.

The factor fo for calculating the heat flux is expressed by the coefficient values of C0 to C8 and the learning coefficient f1, as shown in Equation 4 below.

Where Wt is the water temperature and Wf is the width of the steel sheet.
In addition, l is a board | plate length and v is a board | substrate speed | rate.

The learning coefficient f1 in the existing cooling model is stored after the work on one steel sheet and used as it is when the next chapter of the same set is worked.

However, in the conventional setting model of feedforward control, the i + 1th water cooling requirement (T _{N + 1} ) is calculated by compensating the difference between the target temperature and the measured temperature to the finish rolling temperature for the "-" control to the target temperature. By recalculating and applying as shown in Equation 5, it was possible to prevent the degree of control decrease due to the "-" control to the target. The learning logic applied in the next chapter is applied as in Equation 6, but it does not reflect the overall error of the subject and often causes a deviation.

Where Tr is the correction temperature difference (target CT and actual CT difference), Tr (j) is the sum of the Tr values, CT _T is the target CT, CT _A is the actual CT, and k is the correction coefficient (0 to 1). ), K _p and k _i are proportional gain and integral gain.

As described above, the correction coefficient k has a value between 0 and 1. If the measured CT in the i-th control period has a smaller value than the target CT, T _{N + 1} is calculated to be larger than T _N , and is calculated to reduce the main quantity by Equations 1,2,3,4. .

,(목표온도< 실측온도 일때)

(When target temperature <actual temperature)

,(목표온도≥실측온도 일때)

(When target temperature ≥ measured temperature)

₁목표온도=실측온도 일때이고,

₂는 목표온도≥실측온도 일때이고, FDT_L 은 학습점의 FDT이고, CT_L은 학습점의 CT이며, avgu은 u의 평균값이고,

는 피드백 뱅크(#15)(7)의 수냉강하량이고,

은 피드포워드 뱅크(#1~#15)(5)의 수냉강하량이고,

는 기본열유속계수 학습계수(학습전,학습후)이고, k는 학습보정 게인(0~1)이다.here,

₁ When target temperature = actual temperature

₂ is the target temperature ≥ measured temperature, FDT _L is the FDT of the learning point, CT _L is the CT of the learning point, avgu is the mean value of u,

Is the amount of water cooling of the feedback bank (# 15) (7),

Is the amount of water cooling of the feedforward banks (# 1 to # 15) 5,

Is the basic heat flux coefficient learning coefficient (before and after learning), and k is the learning compensation gain (0 ~ 1).

In addition, some steel grades (hot rolled high grade steels) are subjected to the first feedforward control for hitting the intermediate target cooling temperature and the second feedforward control for adjusting the winding temperature based on the intermediate thermometer. The difference in earnings CT is compensated for by feedback control, but still depends on learning to control "-" against target.

The present invention has been proposed to solve the above-mentioned problems, and its object is to recalculate the required amount of water cooling by changing the winding target temperature through the PI controller and the difference between the target temperature and the measured temperature when controlling the target temperature with "-". The present invention provides a cooling control method for hot rolled steel sheet by changing the winding target temperature to improve the coiling temperature hit ratio and enable high value-added steel production.

As a construction means for achieving the above object, the present invention is arranged in the order of finishing mill, runout table and the winding machine, the rear end of the hot finishing rolling mill, between the eighth bank and the nineth bank on the runout table and the front end of the winding machine In the method of controlling the temperature of the hot rolled steel sheet in a hot rolling facility, the first, second and third thermometers

A) Water cooling required for feedforward control using the thickness, width, speed, measured finish rolling temperature (FDT), measured intermediate target cooling temperature (MCT), target winding temperature (CT), measured winding temperature and learning coefficient Calculating;

B) calculating the difference between the measured winding temperature and the target winding temperature of the steel sheet for each control period, correcting the CT target temperature according to the temperature difference, and recalculating the required amount of water cooling accordingly;

C) determining a shear injection bank using the corrected water cooling requirement for shear feedforward control; And

D) applying the finally applied learning coefficient to each learning point.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in detail.

2 is a flow chart illustrating a cold rolling method according to the present invention. When rolling is performed, a learning coefficient is input to calculate a required amount of water cooling (101), and the measured winding temperature and the target temperature calculated by the learning coefficient are shown. Comparing with the temperature deviation is calculated (102).

At this time, if the temperature deviation is more than 20 degrees apart, the winding target temperature is corrected (103). Then, the required amount of water cooling is recalculated according to the corrected winding target temperature (104).

In the above, if the temperature deviation is within 20 degrees, the winding target temperature is not corrected.

Then, the number of the number of banks of the bank according to the set winding target temperature and the required amount of water cooling is calculated (105), and the number of bottles of water is carried out by the calculated amount (106). At this time, the used learning coefficient is stored (107) and used for the next control cycle.

Steps 100 to 107 are repeatedly executed for each cooling control cycle.

The present invention is arranged in the order of finishing mill (3), the run out table 10 and the winding machine (9), the rear end of the finishing mill (3), the eighth bank (# 8) and 9 on the runout table (10) It is applied in hot rolling equipment in which first to third thermometers 4, 6, and 8 are installed between the bunbanks # 9 and the front end of the winder 9.

In the conventional cooling control cooling water model, the learning coefficient f1 is stored after the work on one steel plate and used as it is when the next chapter of the same set is worked.

However, in the present invention, once the required amount of water cooling in the same steel sheet is calculated by Equation 1, the CT target temperature is changed by Equation 7 below when controlling "-" against the target, and then the learning coefficient is expressed by Equation 8. Change the value and apply it after recalculating the required amount of water cooling. Thus, the degree of winding temperature control is improved, and the quality can be improved by reducing the bowel deviation by appropriate learning of the next work.

The correction target temperature of the i + 1th control period is obtained as shown in Equation 7 below.

Where CT _{aim (i)} is the modified CT target temperature in the i th control period, CT _{aim (i-1)} is the modified CT target temperature in the i-1 th period, and CT _{a (i)} is CT It is a target temperature, CT _{m (i)} is CT measurement temperature, and (alpha) is a gain (0-1).

Then, the learning of the next chapter is obtained as in Equation 8 below.

Here, f2 _{i + 1} is a post-learning learning coefficient, f2 _i is a pre-learning learning coefficient, MCT _{m (i)} is an intermediate thermometer measured value, and k is a correction coefficient.

If the CT measured in the i-th control period has a smaller value than the target CT, the CT _{aim (i)} is calculated as a large value, and thus the main quantity is calculated by the above equations 1,2,3,4. On the contrary, when the measured CT becomes "-" relative to the target, the water cooling requirement calculation is newly calculated by Equation 7 , and used to feed forward control, and is reflected in calculating the front end water quantity, and also by Equation 8 automatically. You will have the appropriate learning coefficient for the next material. Hereinafter, the present invention will be described in detail through examples.

Example

As shown in FIG. 1, the finishing mill 3, the run-out table 10, and the winding machine 9 are arranged in order, and the thermometers 4 and 8 are arranged between the rear end of the finishing rolling machine 3 and the front end of the winding machine 9. ), In the hot-rolled hot rolled equipment, when the TRIP steel with a thickness of 2.6 mm and the target FDT of 870 ^o C and the target CT of 380 ^o C was rolled, the change of the measured CT was measured by the conventional method and the cooling control model of the present invention, respectively. Controlled. 3 shows the cooling control results as described above. As shown in FIG. 3, the cooling control method using the control method of the present invention was found to be very effective in increasing the CT accuracy.

 As described above, the present invention, unlike the conventional method, in order to ensure the hit ratio of the CT when the actual CT compared to the target CT in the same steel sheet by the control period in the same steel sheet, to change the CT target temperature, accordingly By recalculating the required amount of water cooling and correcting it for each control cycle, the CT hit ratio is improved and each learning coefficient is corrected, thereby solving various problems caused by learning, thereby enabling high value-added steel production.

Claims (3)

In the hot rolling equipment in which the first, second and third thermometers are arranged in the order of finishing mill, runout table and winding machine, and are arranged at the rear end of the hot finishing rolling mill, between banks 8 and 9 on the runout table, and in front of the winding machine. In the method of controlling the temperature of the hot rolled steel sheet, A) Water cooling required for feedforward control using the thickness, width, speed, measured finish rolling temperature (FDT), measured intermediate target cooling temperature (MCT), target winding temperature (CT), measured winding temperature and learning coefficient Calculating; B) calculating the difference between the measured winding temperature and the target winding temperature of the steel sheet for each control period, correcting the CT target temperature according to the temperature difference, and recalculating the required amount of water cooling accordingly; C) determining a shear injection bank using the corrected water cooling requirement for shear feedforward control; And D) Cooling control method of the hot rolled steel sheet by changing the winding target temperature, characterized in that consisting of the step of applying the finally applied learning coefficient for each learning point. The method of claim 1, wherein the method comprises Adjust the target temperature of i + 1st control cycle

Where CT _{aim (i)} is the modified CT target temperature in the i th control period, CT _{aim (i-1)} is the modified CT target temperature in the i-1 th period, and CT _{a (i)} is CT is the target temperature, CT _{m (i)} is the CT measured temperature, and α is the gain (0 ~ 1).) Cooling control method of the hot rolled steel sheet by changing the winding target temperature, characterized in that calculated by. The method of claim 1, wherein the method comprises: d) learning coefficients for the next chapter.

Winding, characterized in that f2 _{i + 1} is a post-learning coefficient, f2 _i is a pre-learning coefficient, MCT _{m (i)} is an intermediate thermometer, and k is a correction coefficient. Cooling control method of hot rolled steel sheet by changing target temperature.

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