KR100563260B1 - Cooling control method for compensating set-up temperature by recalculating amount of cooling water - Google Patents

Abstract

The present invention relates to a cooling control method of correcting a set temperature by recalculating the required amount of water cooling to control the winding temperature by compensating the difference between the target temperature and the measured temperature in order to more accurately control the winding temperature of the hot rolled steel sheet.

To this end, the present invention calculates the required amount of water cooling using the thickness, width, speed, measured cooling entrance temperature, target winding temperature and the learning coefficient of the steel sheet, the actual winding temperature and target winding of the steel cold-rolled water-cooled hot-rolled steel sheet If the temperature difference is less than ± 20 ℃, it is wound up and rolled.If the temperature difference is more than + 20 ℃, it is re-cooled by the feedback bank and wound up. It provides a cooling control method for correcting the set temperature by recalculating the required amount of water cooling, characterized in that the step of calculating and cooling the water and winding up.

As described above, the present invention is very effective to improve the CT hit ratio by recalculating the required amount of water cooling and correcting it every control cycle, when the measured CT compared to the target CT is controlled by the control cycle in the same steel sheet, so that the high added value of the desired quality can be achieved. Steel sheet production of the effect is possible.

Hot Rolling Mill, Runout Table, FDT, CT, Winding Machine, Main Bank, Water Cooling

Description

COOLING CONTROL METHOD FOR COMPENSATING SET-UP TEMPERATURE BY RECALCULATING AMOUNT OF COOLING WATER}

1 is a schematic diagram of a cooling system of a typical runout table of a hot rolled steel sheet,

2 is a flowchart showing a conventional cooling control method;

3 is a cooling control method for correcting a set temperature by recalculating the required amount of water cooling according to the present invention;

4 is a comparative graph showing a cooling temperature of a hot-rolled steel sheet cooled by a cooling control method for correcting a set temperature by recalculating the required amount of water cooling according to the present invention and a conventional cooling control method.

♣ Explanation of symbols for main part of drawing ♣

1: Steel sheet 2: Rolling mill 3: Entry thermometer 4: Feed forward bank

5: Intermediate thermometer 6: Feed back bank 7: 측 side thermometer 8: Winder

9: runout table

The present invention relates to a cooling control method for correcting a set temperature by recalculating the required amount of water cooling, and more particularly, to compensate for the difference between the target temperature and the measured temperature in order to more accurately control the final target temperature of the hot rolled steel sheet. A cooling control method of correcting a set temperature by recalculating a required amount of water cooling to control a coiling temperature.

In general, a steel sheet, which is hot rolled hot rolled steel, is rolled, cooled, and wound into a winding machine to produce a general rolled coil. In making such a coil, the coil is wound to a winder after being cooled to a suitable temperature.

The steel sheet in the current hot rolling system is cooled by the cooling system shown in FIG. 1, where the rolled steel sheet 1 is cooled while passing through the runout table 9 and then wound up in the winder 8. have. A cooling system for cooling the steel sheet 1 at a suitable temperature is arranged along the runout table 9. In addition, in the cooling system, an entrance thermometer (3) for measuring the temperature of the steel sheet to be cooled at the system inlet and an intermediate thermometer (5) at the intermediate position of the runout table and an exit thermometer for measuring the temperature of the steel sheet after cooling at the exit of the cooling stand. (7) is installed. The cooling system is arranged up and down with the steel plate 1 drawn in the runout table between, and each part 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 at the upper and lower portions of the cooling system are respectively divided into cooling banks # 1 to # 15, and each cooling bank can control the cooling capacity for cooling the steel sheet.

The cooling bank as described above includes a feed forward bank (# 1 to # 14) for cooling the hot rolled steel sheet to a target temperature, and a feed back for recooling when the cooled steel sheet is higher than the target temperature. Back) It is divided into banks (# 15).

On the other hand, the conventional cooling control method, as shown in Figure 2, depending on the steel type finish finish temperature of the Mokpo (or cold inlet temperature; referred to as FDT) and the target cooling exit temperature (or winding temperature; hereinafter, also referred to as CT ) And hit the FDT and CT accordingly. For this purpose, first, the air cooling amount is calculated using the target FDT, the target CT, and the target mail speed (v), the required water cooling amount is calculated, and the number of main banks is determined. When the FDT and the sheet speed are measured after the steel sheet exits the finish rolling zone, the number of banks of water is reset by recalculating the water cooling rate at regular intervals using the measured FDT and the sheet speed instead of the target FDT and the target sheet speed. The steel plate then exits the runout table to set the CT.

However, in the feed forward control, the number is reduced by calculating the number of banks from FDT, CT, plate speed, and plate thickness, but the setting is incorrect. In the bank), the target temperature is adjusted by adjusting the number of times, but if the control is "-" relative to the target, there is no way to compensate in the feedback bank (# 15 bank), and it is compensated in the next chapter by learning.

General water cooling requirement (T _N ) is calculated by the relational expression of the equation (1).

Where FDT : FDT found value

CT _air : Temperature drop during air cooling

CT : winding temperature target value

The amount of water cooling is obtained 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. The water cooling amount T _w at the runout table is represented by Equation 2 below.

Where l _bank length of the i th bank

H _f : Coil thickness (mm)

v : mail speed

C _p : Specific Heat of Steel Plate

ρ: density of steel sheet

Q _iu : _Heat flux of the i upper bank

Q _id : Heat flux of the i lower bank

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

Where f ₀ : Basic heat flux coefficient

f _2i : Heat flux coefficient of the i th bank

T _iu : Water temperature correction coefficient of upper bank

T _id : Water temperature correction coefficient of lower bank

f _v : Sheet speed correction factor

F ₀ for calculating heat flux As shown in Equation 4 is expressed by the coefficient value and the learning coefficient f ₁ from C ₀ to C ₈ .

Where T _w : Water temperature

W _f : width of steel plate, H _f : Coil thickness (mm)
Actual FDT, Target MT, Target CT, Tw:

Learning coefficient f ₁ in the conventional cooling model The silver is stored at the end of the work on one steel sheet and is used when the next sheet of the same set is being worked on.

However, in the conventional setting model of the feed forward control, as shown in FIG. 2, there is no method to compensate for the material during the "-" control compared to the target temperature range, and thus the winding is wound at a low temperature. Therefore, the quality of the coil is deteriorated, and in order to solve such a problem, conventionally, when one cycle is completed, it relies on the long-term learning that loads the cooling compensation value of the cooling cycle into the next cooling cycle. Therefore, there is a problem in that the hit ratio of the coiling temperature cannot be guaranteed for the material.

In order to solve the above problems, the present invention, unlike the conventional method, compensates the difference between the target temperature and the measured temperature at the "-" control compared to the target temperature to the FDT temperature to recalculate the required amount of water cooling and feed forward ( It is an object of the present invention to provide a cooling control method of correcting a set temperature by recalculating the required amount of water cooling to improve the take-up temperature hit ratio by using for feed forward control.

In order to achieve the above object, the present invention provides a method for controlling the final winding temperature of the hot rolled steel sheet by water cooling in the hot rolling equipment arranged in the order of finishing mill, runout table and winding machine,

Cooling the hot rolled steel sheet by calculating the number of water cooling banks by calculating the required amount of water cooling using the thickness, width, speed, measured cooling entrance temperature, target winding temperature, and learning coefficient of the steel sheet;

Calculating a difference between the measured winding temperature and the target winding temperature of the water-cooled steel sheet and winding the sheet to finish rolling when the temperature difference is less than ± 20 ° C .;

Calculating a difference between the measured winding temperature and the target winding temperature of the water-cooled steel sheet and re-cooling by winding the feedback bank to finish rolling when the temperature difference exceeds + 20 ° C .;

Comprising a step of calculating the difference between the actual winding temperature and the target winding temperature of the water-cooled steel sheet, if the temperature difference is less than -20 ℃ to recalculate the required amount of water cooling, re-determination of the main bank bank rules, and after the water cooling and winding to finish rolling A cooling control method for correcting a set temperature by recalculating a required amount of water cooling is provided.

In addition, the present invention is to calculate the difference between the actual winding temperature and the target winding temperature of the water-cooled steel sheet, if the temperature difference is less than -20 ℃ to recalculate the required amount of water cooling to re-determinate the main bank bank rules, and after cooling, winding to finish rolling In the step, the method for recalculating the required amount of water cooling provides a cooling control method for correcting the set temperature by recalculating the required amount of water cooling, wherein the required amount of water cooling is recalculated by the following equation.

Where T _r : difference between the corrected target CT and the measured CT

) CT _T : Target CT (

)

) CT _A : Actual CT

)

k : correction factor (0 to 1)

k _p : Proportional Gain

k _i Integral Gain

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

First, the present invention is arranged in the order of finishing mill, runout table, and winding machine, and is applied in a hot rolling facility in which a thermometer is installed at the rear end of the hot finishing rolling mill and the front end of the winding machine.

The runout table comprises a plurality of feed forward main banks and one feedback back main bank to cool the rolled steel sheet, and the cooled steel sheet is wound in a coil form in a winding machine.

The main water bank provided in the runout table is a bank provided with a plurality of nozzles, and the cooling of the rolled steel sheet uses a combination of air cooling and water cooling.

In the conventional cooling control cooling water model, the learning coefficientf ₁ Is stored at the end of one steel sheet and is used when the next sheet of the same set is being worked on. However, once the required amount of water cooling in the same steel sheet is calculated by Equation 1, it is calculated as the same value in the water cooling amount calculation, so the feed forward calculation is always performed with an offset, and as much as this offset We will improve the CT hit rate by reducing the offset by reflecting this in the water cooling requirement calculation.

The required amount of water cooling ( T _{N + 1} ) of the i + 1 th control period is obtained in the same manner as in Equation (5).

)Where CT _r : target CT (

)

) CT _A : CT

)

k : correction factor (0 to 1)

k _p : Proportional gain,

k _i : integral gain

The k value of Equation 5 has a space 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, and 4. .

In this way, when the measured CT becomes "-" control relative to the target in each control cycle, the water cooling requirement calculation is newly calculated by Equation 5, and used in the feed forward control to reflect the main water quantity in the front end part. do.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

EXAMPLE

In the hot rolling equipment, which is arranged in the order of finish rolling mill 2, runout table 9, and winder 8 as shown in FIG. 1, and a thermometer is installed between the rear end of the hot finishing rolling mill and the front end of the winder. Is 1.8 mm, the measured FDT is 890 ° C, the target CT is 670 ° C, and the target CT range is set to a range of ± 20 ° C.

4 shows the results of controlling the change of the measured CT by the conventional method and the cooling control model of the present invention shown in FIG. 3 when the product No. DIT3 steel was rolled for the above cooling conditions. As shown in FIG. 4, when the measured CT is lower than the limit ranges 10 and 11 of the target CT 9 by controlling the cooling by the conventional method 12, that is, the difference between the target CT and the measured CT is 20 ° C. In the following case (12), the cooling control is impossible, the initial cooling temperature is maintained as it is wound around the winding machine, while hot rolling by a cooling control method (Fig. 3) to correct the set temperature by recalculating the required amount of water cooling according to the present invention. Cooling the rolled steel sheet was found to be very effective to increase the accuracy of the hit by controlling the measured CT (13) to the target CT or less than ± 20 ℃.

As described above, the present invention, unlike the conventional method, when the actual CT compared to the target CT in the same steel sheet is controlled "-" by the control period, in order to ensure the hit of the CT, to recalculate the required amount of water cooling to correct for each control cycle Therefore, it is very effective in improving the CT hit ratio, so that it is possible to produce high value-added steel sheet of desired quality.

Claims (2)

In the method of controlling the final winding temperature of the hot rolled steel sheet by water cooling in the hot rolling equipment arranged in the order of finishing mill, runout table and winding machine, Cooling the hot rolled steel sheet by calculating the number of water cooling banks by calculating the required amount of water cooling using the thickness, width, speed, measured cooling entrance temperature, target winding temperature, and learning coefficient of the steel sheet; Calculating a difference between the measured winding temperature and the target winding temperature of the water-cooled steel sheet and winding the sheet to finish rolling when the temperature difference is less than ± 20 ° C .; Calculating a difference between the measured winding temperature and the target winding temperature of the water-cooled steel sheet and re-cooling by winding the feedback bank to finish rolling when the temperature difference exceeds + 20 ° C .; Comprising a step of calculating the difference between the actual winding temperature and the target winding temperature of the water-cooled steel sheet, if the temperature difference is less than -20 ℃ to recalculate the required amount of water cooling to re-determine the number of main banks, and after cooling the water and winding to finish rolling A cooling control method for correcting a set temperature by recalculating the required amount of water cooling. The method of claim 1, Calculate the difference between the actual winding temperature and the target winding temperature of the water-cooled steel sheet, and if the temperature difference is less than -20 ° C, recalculate the required amount of water cooling ( T _{N + 1} ) to re-determine the number of main banks, and after winding water-cooled to roll The terminating step is a cooling control method of correcting the set temperature by recalculating the required amount of water cooling, wherein the required amount of water cooling is recalculated by the following equation.

Where T _r : difference between the corrected target CT and the measured CT CT _T Target CT CT _A : Actual CT k : correction factor (0 to 1) k _p : proportional gain k _i : integral gain

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