KR101050792B1 - Cooling Control Method Using Dynamic Reset - Google Patents

Abstract

The present invention reduces the amplitude of the coiling temperature at the point after the tip and the end of the rolled material, and feed-forward by actively correcting the set learning coefficient when the winding temperature of the rolled material is set at a certain amount of deviation from the target coiling temperature. It provides a cooling control method of a hot rolled steel sheet to control to hit the target temperature after the tip of the rolled material by resetting the control.

Hot Rolled Steel Sheet, Cooling Stand, Control Cooling, Dynamic Reset, Feed Forward, Feedback

Description

Cooling Control Technique using Dynamic Preset Updating}

1 is a schematic diagram showing a cooling system for a cooling stage in a manufacturing process of a hot rolled steel sheet.

2 is a configuration correction flowchart for executing a cooling control method using a dynamic reset according to the present invention.

3 is a graph showing an application example by a cooling control method using a dynamic reset according to the present invention.

 The present invention relates to a method for producing a hot rolled steel sheet. More specifically, the present invention relates to a method for cooling a steel sheet, which is carried out after finishing rolling the steel sheet in a hot rolling step of the hot rolled steel sheet and before winding the steel sheet into a coil.

Hot rolled steel sheet is heated in slab produced through continuous casting process or crushing process and made into strip of desired size and shape through rough rolling process and finishing rolling process, and then cooled to secure the required mechanical properties. It is prepared by winding up.

In the production of such coil-shaped hot rolled steel sheet, the finished rolled strip should be cooled and wound at a suitable temperature and cooling rate. As described above, in the production of hot rolled steel sheets, the cooling process after rolling is an important process for determining the physical properties of the final product. Thus, an appropriate cooling system is introduced to cool the steel sheet in a controlled state.

1 illustrates a cooling system for cooling a hot rolled steel sheet in a general hot rolling process.

As shown in FIG. 1, the steel sheet 1 rolled in strip form through a rough rolling process in a hot rolling process is finished rolled in a finishing mill 3 and then cooled while passing through a run out table. The coil 9 is wound in a coil form.

Cooling system is installed in the cooling stand so that the hot rolled steel sheet is cooled at a suitable temperature while passing through the cooling stand.

In this cooling system, an entrance thermometer (11) is installed at the inlet of the cooling system to measure the temperature of the steel sheet passing through the cooling stand, an intermediate thermometer (13) measuring the temperature of the steel sheet in the middle of the cooling stand, and the temperature of the steel sheet at the exit of the cooling stand. An exit thermometer 15 is installed to measure.

The cooling system is divided into a water cooling unit and an air cooling unit disposed above and below the cooling stand, and the water cooling unit is composed of a plurality of cooling banks 5, and each cooling bank 5 is composed of a plurality of nozzles to control cooling. .

The cooling control method of a general cooling system uses a method of controlling cooling by using a cooling inlet temperature, an intermediate cooling temperature, and a cooling exit temperature.

In the conventional cold rolling control method of the hot rolling mill, feedforward control for cooling control by setting to match the target coiling temperature and feedback for compensating the difference between the performance coiling temperature and the target coiling temperature are performed. (feedback) control.

Compensate the target winding temperature when cooling is performed to the cooling set value determined by feedforward control once and the measured temperature is higher than the target temperature (hereinafter referred to as "plus value") by comparing the target temperature with the measured temperature. In order to achieve the target temperature by controlling the cooling water of the feedback bank 19 using feedback control.

However, in the existing cooling control system, when the measured temperature is lower than the target temperature (hereinafter, referred to as a "minus value"), the control is performed in an uncontrollable structure of the rolled material to be cooled. In addition, even when the positive value deviation is larger than the cooling capacity by the feedback bank 19, that is, when the range of the feedback control is exceeded, the target temperature cannot be achieved. In FIG. 1, reference numeral 17 denotes a feedforward bank.

Conventional cooling control uses the results of working on the rolled material to learn and applies the learned results to the subsequent rolled material.

The conventional feedforward control is controlled by dividing the tip of the rolled material and the tip of the rolled material.Two correction factors are applied to the tip of the rolled material, which is the portion where the tension is not applied, and the end of the rolled material, which is the portion where the tension is applied. The control is implemented using the (learning coefficient).

However, if the cooling control is applied by applying this method, the winding temperature oscillates with a large amplitude when the correction coefficient (learning coefficient) between the tip and the tip is remarkably different. That is, there is a problem in that the temperature change is extreme control phenomenon at the front end and the rear end application point.

In addition, when the process conditions of rolling, that is, the temperature of the cooling water, the sheet speed, and the width of the strip sheet are changed a lot, the difference between the resultant winding temperature and the target coiling temperature is greatly generated, which is beyond the control range by the plus and minus values. Cooling control of the rolled material becomes impossible.

In order to control the case where the difference between the target temperature and the measured temperature is a negative value in the existing cooling control system, a method of cooling control by changing the winding target temperature is proposed.

However, in the case of such a control method, there is a problem that can not be properly learned to apply to a subsequent rolling material by using a method useful for the control of the rolling material or the results applied in the work of the rolling material, so that many obstacles are not practical to apply such a method. exist.

Therefore, the present invention is to solve such a problem, it is an object of the present invention to provide a cooling control method for reducing the amplitude of the winding temperature at the point after the tip and the tip of the rolled material.

Another object of the present invention is to hit the target temperature after the end of the rolling material by actively correcting the feed forward control by actively correcting the set learning coefficient when the performance winding temperature by setting the cooling time of the rolled material deviates by a predetermined amount or more from the target winding temperature. It is to provide a cooling control method to control to.

In order to achieve the above object, the cooling control method using the dynamic reset according to the present invention is arranged in the order of hot rolling mill, hot rolling mill, cooling stand, and winding machine, and the rear end of the hot rolling mill, the cooling stand, and the front end of the winding machine. In the method for controlling the cooling temperature of the hot rolled steel sheet by using a hot rolling facility,

A gradual change calculation step of gradually changing a learning coefficient at a control point that distinguishes the front end of the rolled material and the rear end of the rolled material; and

A water cooling amount calculating step of determining a water cooling amount using the calculated incremental change learning coefficient; and

Learning coefficient average calculating step of obtaining an average of the gradual change learning coefficient; and

Calculating a temperature average of a control point to which the gradual change learning coefficient is applied;

Determining whether to reset using a difference between the measured temperature average and a target temperature; And                     

Recalculating a required amount of water cooling amount by using the reset learning coefficient when the reset is determined in the step of determining whether to reset;

It provides a cooling control method of the hot rolled steel sheet comprising a.

The present invention also provides a cooling control method for calculating such a gradual change calculation by the following equation.

Where j: leading point, leading point after leading point

n: Total number of pulses to apply

f ₁ ^le : tip learning coefficient

f ₁ : learning coefficient after tip (steady state)

f ₁ ': Modified learning coefficient

And the present invention provides a cooling control method for resetting the step of determining whether or not such a reset by the following equation.

Hereinafter, the present invention will be described in detail.

Cooling control method according to the dynamic reset according to the present invention is arranged in the order of hot rolling mill, hot rolling mill, cooling stand, and winding machine in the hot rolling equipment equipped with a thermometer at the rear end of the hot rolling mill, the cooling stand and the front end of the winding machine. Apply.                     

In the cooling control method according to the present invention, first, in the progressive change calculation step of gradually changing the learning coefficient at the control point for distinguishing the front end and the rear end of the rolling material passing through the cooling zone, the control point for distinguishing the front end and the rear end The vibration coefficient of the winding temperature control is reduced by gradually changing the learning coefficient based on Equation 1 below.

Where j: leading point, leading point after leading point

n: Total number of pulses to apply

f ₁ ^le : tip learning coefficient

f ₁ : learning coefficient after tip (steady state)

f ₁ ': Modified learning coefficient

In addition, the following equation 2 is used to calculate the learning coefficient mean to calculate the average of the gradual change learning coefficient according to the present invention.

In addition, in the temperature average calculation step of obtaining the measured temperature average of the control point to which the gradual change learning coefficient according to the present invention is calculated, the average winding temperature is calculated using an arithmetic mean, and the following equation is used as Equation 3 below.

In the present invention, the necessity of resetting is determined using the difference between the measured temperature average of the control point to which the gradual change learning coefficient is applied and the target winding temperature. The ratio of the difference between the measured temperature average and the target winding temperature is represented by the following equation (4).

Where CT _t : target winding temperature

In addition, the present invention resets when the ratio for the difference between the measured temperature average and the target winding temperature exceeds the set standard. As such, the learning coefficient used for resetting uses Equation 5 as follows.

Using the reset learning coefficients, the recalculation of the required amount of water cooling is performed and control is performed. The control process of the cooling control method using the dynamic reset according to the present invention as described above is shown in FIG.

Hereinafter will be described in detail through an embodiment of the present invention.                     

As shown in FIG. 1, the hot rolling mill 3, the cooling table, and the winding machine 9 are arranged in order, and the thermometers 11, 13, and 15 are disposed between the rear end of the hot rolling mill 3 and the front of the winding machine 9. Hot rolled carbon steel having a thickness of 2.4 mm and a target coiling temperature (CT) of 600 ° C. was rolled using a hot rolling facility provided with a.

In the case of hot rolling under such hot rolling conditions, the case where the learning coefficient is not gradually changed after the tip and the tip of the rolled material is shown in FIG.

In contrast, when rolling the hot rolled carbon steel having a thickness of 1.6 mm and a target winding temperature (CT) of 620 ° C., the results of controlling the change of the measured CT by the existing method and the present invention are shown in FIGS. 3B and 3. (C) of each is shown.

As shown in (b) of FIG. 3, when the control method according to the present invention is applied, it can be seen that when the negative value control occurs, the control is effectively effective to increase the CT accuracy of the entire coil.

And (c) of Figure 3 shows a case in which the learned after applying the reset applied to the subsequent rolled material. As a result, it can be seen that the resetting according to the present invention is well applied without disturbing learning. In addition to this, it can be seen that the coiling temperature vibration shown in FIG.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and easily changed and equalized by those skilled in the art from the embodiments of the present invention. It includes all changes to the extent deemed acceptable.

The present invention provides a method of controlling the temperature change width by gradually changing the correction coefficient at the front end and the rear end application point of the rolled material, and compensating the difference between the temperature during the plus value control and the negative value control compared to the target temperature and the measured temperature. By re-adjusting the setting and using it for feedforward control, it provides a coiling temperature control method that improves the coiling temperature hit ratio and does not disturb coil to coil learning.

 In addition, unlike the conventional method, the present invention is very effective in hitting the target winding temperature by correcting and resetting the setting of the feedforward control when positive value control and negative value control occur using the target temperature and the measured temperature in the same steel sheet. effective.

And even when the process conditions are severely changed, there is an effect having a control ability to cope flexibly.

Claims (3)

Cooling control method of hot rolled steel sheet using hot rolling equipment arranged in order of hot rolling mill, hot rolling mill, cooling stand, and winding machine, and having a thermometer installed at the rear end of the hot rolling mill, the cooling stand, and the front end of the winding machine. To A gradual change calculation step of gradually changing a learning coefficient at a control point that distinguishes the front end of the rolled material and the rear end of the rolled material; and A water cooling amount calculating step of determining a water cooling amount using the calculated incremental change learning coefficient; and Learning coefficient average calculating step of obtaining an average of the gradual change learning coefficient; and Calculating a temperature average of a control point to which the gradual change learning coefficient is applied; Determining whether to reset using a difference between the measured temperature average and a target temperature; And Recalculating a required amount of water cooling amount by using the reset learning coefficient when the reset is determined in the step of determining whether to reset; Cooling control method of the hot rolled steel sheet comprising a. The method of claim 1, wherein the step of calculating the gradual change is calculated by the following equation.

Where j: leading point, leading point after leading point n: Total number of pulses to apply f ₁ ^le : tip learning coefficient f ₁ : learning coefficient after tip (steady state) f ₁ ': Modified learning coefficient The cooling control method of claim 1, wherein the determining of the reset is determined by the following equation.

Where f _{1avg is the} coefficient of learning coefficient that is the average of the learning coefficients of gradual change.  δ: Ratio of difference between measured temperature average and target winding temperature

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