JP2014180670A - Cooling control method for hot-rolled material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling control method for a hot-rolled material, capable of controlling a winding temperature with high accuracy over the full length of the hot-rolled material.SOLUTION: When dividing a hot-rolled material into a plurality of control units in the long direction and controlling a temperature by use of a heat transfer coefficient obtained by multiplying a heat transfer coefficient determined by a model expression by a prescribed learning value in each control unit, the control unit is classified into three parts of a tip part, a steady part, and a tail end part along the long direction of the hot-rolled material, a learning coefficient of the heat transfer coefficient of each control unit belonging to each part is calculated in each of the three parts, and an average value thereof is used as the learning value of the heat transfer coefficient of each part. In the temperature control performed in each control unit, the learning value of the heat transfer coefficient corresponding to the part to which the control unit belongs is used. In a boundary part between the parts, the learning value varied stepwise in each control unit is used.

Description

  The present invention relates to a cooling control method for a run-out table of a hot rolled material such as a hot rolled steel sheet rolled in a hot rolling facility. Each hot-rolled material has a target coiling temperature, and cooling control is performed by the coiling temperature control device so that the coiling temperature falls within the target tolerance range.

  Winding temperature control is based on the temperature results on the exit side of the finish rolling mill (finishing mill) for each control unit (called a cutting plate) in which hot-rolled steel sheets such as hot-rolled steel sheets are divided in the lengthwise direction into constant length units. And feedforward (FF) control for determining the cooling pattern, and feedback (FB) control for correcting the cooling amount based on the actual winding temperature.

  The heat transfer coefficient of the steel sheet when performing the temperature calculation used for these controls is obtained by multiplying the heat transfer coefficient determined by the model formula with the learning value for each rolled material group divided by the steel type, sheet thickness, target temperature, etc. Values are adopted.

  Various methods are used to reflect the learned value of this heat transfer coefficient in the temperature calculation. Generally, the heat obtained from the actual winding temperature of the cut plate at regular pitch intervals in the longitudinal direction of the steel plate. A technique for calculating a learning coefficient of a transfer coefficient and updating the learning value of the same rolling group using the average value as a learning value of a heat transfer coefficient of the steel sheet is performed. As described in Patent Documents 1 to 3 and many other documents, the learning coefficient of each cut plate is obtained by a sequential least square method.

  In addition, it is known that the temperature fluctuation characteristics differ in the longitudinal direction of the steel sheet, and in particular, the control accuracy of the coiling temperature is poor at the front end and tail end in the longitudinal direction of the steel sheet as compared with the stationary part.

  In this regard, Patent Document 1 discloses a technique for suppressing temperature fluctuations at the front end of the steel plate. Specifically, the learning value of the heat transfer coefficient of the same rolling group is updated using the average value of the learning coefficient of the tip part as the learning value of the heat transfer coefficient of the tip part. In the temperature calculation for setting water injection, the learning value is reflected only on the heat transfer coefficient of the tip, and the tip and the other parts are handled separately.

  In the technique described in Patent Document 2, paying attention to the difference in temperature fluctuation characteristics in the longitudinal direction of the steel sheet, one steel sheet is divided into several sections in the longitudinal direction, and heat transfer is performed for each divided section. A mechanism that gives coefficient learning values is adopted. However, no learning value according to the type of rolled material is provided.

JP-A-11-33616 Japanese Patent No. 2783124 Japanese Patent Publication No. 6-88060

  Based on the techniques shown in Patent Documents 1 and 2 above, as a method for improving the control accuracy of the coiling temperature at the tip and tail ends of the steel plate, the steel plate in the longitudinal direction, the tip portion, the steady portion, Classify into three parts of the tail end, each to have a learning value of the heat transfer coefficient, update the learning value of each heat transfer coefficient using the average value of the heat transfer coefficient of each part, In the temperature calculation, a method of controlling so as to correct the heat transfer coefficient using the learning value of the part to which the cutting plate to be calculated belongs can be considered.

  However, by this method, when water injection control is performed with the learning value of the heat transfer coefficient being different in the three parts of the steel sheet in the longitudinal direction, the stationary part, and the tail end, the boundary at which the learning value of the heat transfer coefficient is switched. In this case, the water injection pattern changes abruptly, and it is difficult to control the coiling temperature with high accuracy at the boundary portion.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a method for controlling the cooling of a hot rolled material that can control the coiling temperature with high accuracy over the entire length of the hot rolled material. To do.

  As a result of investigations to solve the above problems, the present inventor is calculated for each control unit (cut plate) divided in the longitudinal direction of a hot-rolled material such as a hot-rolled steel plate in the learning calculation of the heat transfer coefficient. The learning coefficient has a different tendency depending on which part (tip, tail, and steady part) in the longitudinal direction of the hot-rolled material the target control unit belongs to. Although there is a possibility that a problem occurs in the control accuracy, it has been found that the coiling temperature can be controlled with high accuracy over the entire length of the hot-rolled material by smoothly changing the learning coefficient in the control unit at the boundary portion of these parts.

  That is, according to the present invention, when the hot rolled material rolled in the hot rolling facility is cooled by the cooling facility and controlled to a predetermined winding temperature, the hot rolled material is divided into a plurality of control units in the longitudinal direction. A cooling control method for a hot-rolled material that performs temperature control using a heat transfer coefficient obtained by multiplying a heat transfer coefficient determined by a model formula by a predetermined learning value for each control unit, the control unit being Categorized into three parts, a tip part, a steady part, and a tail part, along the longitudinal direction of the hot rolled material, and for each of these three parts, a learning coefficient of a heat transfer coefficient for each control unit belonging to each part In the temperature control performed for each control unit, the learning value of the heat transfer coefficient corresponding to the part to which the control unit belongs is used as the learning value of the heat transfer coefficient for each part. At the boundary of these parts Provides a cooling control method for hot-rolled, which comprises using a learned value is varied stepwise for each of the control units.

  Change the learning value of the heat transfer coefficient of the control unit belonging to the boundary part so as to apportion the learning value of the parts on both sides of the boundary part, or increase or decrease in a curve in the longitudinal direction of the hot rolled material It is preferable to make it.

  According to the present invention, the learning value of the heat transfer coefficient is changed stepwise for each control unit at the boundary between the front end, the steady portion, and the tail end in the longitudinal direction of the hot rolled material. The fluctuation can be suppressed, and the coiling temperature of the hot rolled material can be controlled with high accuracy.

It is the schematic which shows an example of the rolling cooling equipment for enforcing the cooling control method of the hot rolling material of this invention. It is a figure which shows the result and setting learning value which calculated | required the learning coefficient of the heat-transfer coefficient for every cut plate back-calculated from the performance which rolled the same rolling group last time with respect to a coil (hot rolling material) longitudinal direction position. The cut plate is classified into three parts, that is, a tip part (LE), a steady part (MID), and a tail part (TE) along the longitudinal direction of the hot-rolled material, and the heat transfer coefficient is determined for each of these three parts. It is a figure which shows the result of having calculated | required the learning value. The learning values of a plurality of cut plates belonging to the boundary part of the tip part (LE), the stationary part (MID), and the tail part (TE) of the present invention are changed so as to apportion the learning values of the parts on both sides of the boundary part. It is a figure which shows the case where it was made to do. It is a figure which shows the case where the learning value of the some cut plate which belongs to the boundary part of the front-end | tip part (LE) of this invention, a stationary part (MID), and a tail end part (TE) is changed in a curve. It is a figure which shows the example of the change (acceleration / deceleration rate) of the plate | board speed of a hot rolling material.

First, the concept that led to the present invention will be described.
The true heat transfer coefficient of hot-rolled material changes for each part of the tip, steady part, and tail end in the longitudinal direction of the hot-rolled material, and generally changes abruptly at each boundary. Instead, it changes smoothly in a single steel plate. In consideration of this point, based on the background art, the hot rolled material is divided into a tip portion, a steady portion, and a tail end portion, each having a learning value of the heat transfer coefficient, and the average of the heat transfer coefficient of each part. When each learning value is updated using the value, it is considered that an error between the temperature prediction and the actual result occurs at the boundary of each part.

  On the other hand, if the true heat transfer coefficient changes abruptly at the boundary of each part, if the calculated water injection setting and the actual cooling performance can be completely synchronized based on the above background technology, a temperature deviation will occur at that boundary. Should not. However, due to changes in the sheeting speed of the hot rolled material, etc., there is actually a tracking error between the calculated water injection position in the longitudinal direction of the hot rolled material and the actual cooling position, and the water injection setting and cooling results do not match. Sometimes, it becomes a factor of temperature deviation.

  For this reason, in the present invention, in order to prevent these inconveniences, each control unit (cut plate) at the boundary portion of the tip portion, the steady portion, and the tail end portion in the longitudinal direction of the hot rolled material. The learning value of the heat transfer coefficient changed stepwise is changed stepwise.

Hereinafter, the present invention will be specifically described with reference to the accompanying drawings.
FIG. 1 is a schematic view showing an example of rolling cooling equipment for carrying out the method for controlling cooling of a hot rolled material according to the present invention. The rolling cooling equipment 1 is provided on a runout table 22 provided on the downstream side of a finishing mill 21 (only the final stand is shown). The hot-rolled material (for example, steel strip) S rolled by the finish rolling mill 21 runs on the run-out table 22 and is wound on a winder (down coiler) 23.

  The rolling cooling facility 1 has a cooling unit 2 that is arranged above and below to inject cooling water into the hot rolled material S. Cooling water is supplied to the cooling unit 2 from a cooling water supply means (not shown). Each of these cooling units 2 is divided into a plurality of cooling banks 3. And the cooling amount with respect to the hot-rolled material S is controlled by adjusting the water injection amount to each bank 3 of such a cooling part 2. FIG.

Moreover, the rolling cooling facility 1 includes an entry-side thermometer 4 that measures the temperature of the hot rolled material S that leaves the finish rolling mill 21 and is fed into the cooling facility 1, and the thickness of the hot rolled material S after finish rolling. A thickness gauge 5 that measures the temperature, an inlet speed detector 6 that measures the unwinding speed of the hot rolled material S of the finishing mill 21 that is the supply speed of the hot rolled material S to the cooling facility, and the winding time A delivery-side thermometer 7 for measuring the temperature of the hot-rolled material S and a delivery-side for measuring the take-up speed of the hot-rolled material of the winder 23 that is the take-out speed of the hot-rolled material S from the cooling facility. And a speed detector 8. In addition, the rolling cooling facility 1 includes a cooling control unit 9 that calculates a water injection pattern to the cooling unit 2 in order to control the hot rolled material S to a desired winding temperature, and calculation of the water injection pattern by the cooling control unit 9. For this purpose, a learning value calculation unit 10 that calculates a learning value of a heat transfer coefficient and outputs it to the cooling control unit 9 and a bank that outputs a water injection command to the cooling unit 2 based on the water injection amount output from the cooling control unit 9 And an open / close input / output unit 11.

Next, the cooling control operation by the rolling cooling facility 1 will be described.
The cooling control unit 9 calculates a water injection pattern to each bank 3 of the cooling unit 2 in order to cool the hot rolled material S to a desired winding temperature over the entire length, and thereby the winding temperature of the hot rolled material S To control. The control at this time determines the cooling pattern based on the temperature results obtained by the inlet side thermometer 4 on the exit side of the finish rolling mill 21 for each cut plate which is a constant length unit in the longitudinal direction of the hot rolled material S. Feedforward (FF) control, and feedback (FB) control that corrects the cooling amount based on the actual winding temperature obtained by the delivery-side thermometer 7. For example, in the FF control, the temperature drop obtained by using the actual temperature obtained by the inlet side thermometer 4 and the heat transfer coefficient of the hot rolled material, and further, the hot rolled material S obtained by the plate thickness meter 5 A water injection pattern is calculated based on the plate thickness and the conveyance speed measured by the entry side speed detector 6 and the exit side speed detector 8.

  At this time, the heat transfer coefficient of the hot-rolled material used when performing temperature calculation in the FF control and FB control of the cooling control unit 9 includes the steel type, sheet thickness, target temperature, etc. A value obtained by multiplying the learning value of each rolled material group divided by the above is adopted. The learning value of the heat transfer coefficient is calculated by the learning value calculation unit 10 and reflected in the water injection pattern calculation of the cooling control unit 9. The learning value calculation unit 10 uses a learning value that is calculated and updated based on the results when the same rolling group was rolled last time.

  In this way, the water injection amount of each bank 3 is calculated, the calculated water injection amount of the bank 3 is output to the bank opening / closing input / output unit 11, and the water injection command is output from the bank opening / closing input / output unit 11 to each bank 3. Cooling control is performed.

  By the way, conventionally, as a learning value of such a heat transfer coefficient, a learning coefficient of a heat transfer coefficient for each cut plate is calculated by, for example, a sequential least square method, and an average value thereof is used.

  However, the temperature fluctuation characteristics in the longitudinal direction of the hot-rolled material are different.In particular, the tip and tail ends in the longitudinal direction of the hot-rolled material have poor control accuracy of the coiling temperature compared to the steady portion, and supercooling and The frequency of defective temperatures due to insufficient cooling is high. When the learning coefficient for each cut plate calculated backward from the actual result of rolling the same rolling group is obtained with respect to the coil (hot rolled material) longitudinal position, as shown in FIG. The learning coefficient error at the front end (LE) and the tail end (TE) is large, and the actual winding temperature is out of tolerance. In addition, since the learning coefficients of the front end (LE) and the tail end (TE) are greatly deviated from the set learning value, the average value of only the learning coefficient of the cut plate of the stationary part (MID) after the coil winding is completed. Is calculated as the learning value this time, and the learning value of the same rolling group is updated. In this case, the error (temperature error) between the learning coefficient and the set learning value at the tip and tail ends is not reflected in the next setting. .

In addition, a front-end | tip part (LE), a stationary part (MID), and a tail end part (TE) are defined as follows.
Tip (LE): From the hot rolled material tip, the cut plate on the run-out table at the moment when the tip winds around the coiler. Tail end (TE): At the moment when the hot rolled material tail passes through the finishing mill. Cut plate on the run-out table before coiler winding Stationary portion (MID): Cut plate other than tip (LE) and tail (TE)

  For this reason, in this invention, based on the said patent documents 1 and 2, a cutting plate which is a control unit is made into a front-end | tip part (LE), a stationary part (MID), and a tail end part along the longitudinal direction of a hot-rolled material. (TE) is classified into three parts, and for each of these three parts, the learning coefficient of the heat transfer coefficient for each cutting plate belonging to each part is calculated, and the average value thereof is the learned value of the heat transfer coefficient for each part. In the temperature control performed for each cut plate, the learning value of the heat transfer coefficient corresponding to the part to which the cut plate belongs is used.

  However, as shown in FIG. 3, the learning values of the heat transfer coefficients of the tip (LE), the steady part (MID), and the tail end (TE) are different from each other as shown in FIG. There is a possibility that a level difference occurs and the water injection pattern changes abruptly at that portion, causing a problem in temperature control accuracy.

  Therefore, in the present invention, a learning value that is changed stepwise for each cutting plate as a control unit is used at the boundary between these parts.

  For example, the learning values of a plurality of cut plates belonging to the boundary part may be changed so as to apportion the learning values of the parts on both sides of the boundary part. Specifically, as shown in FIG. 4, it is assumed that the learning value of the front end portion (LE) is 0.7, the learning value of the stationary portion (MID) is 0.8, and the cutting plates of those boundary portions Assuming that the number is N (arbitrary number), the learning values of the first cut plate, the second cut plate,..., The N cut plate are 0.7 + {(0.8−0.7 ) / (N + 1)} × 1, 0.7 + {(0.8−0.7) / (N + 1)} × 2,..., 0.7 + {(0.8−0.7) / (N + 1) )} × N.

  Instead of apportioning the learning value in this way, for example, the learning value of the cut plate at the boundary portion may be set so as to increase or decrease in a curve in the longitudinal direction of the hot rolled material as shown in FIG. . This can be realized by setting the change in the learning value of the N cut plates at the boundary to be approximated by a curve.

  The boundary length (that is, the number of cut plates) is arbitrary, but can be set according to the plate speed of the hot rolled material. That is, since the sheet passing speed of the hot rolled material is not constant, as shown in FIG. 6, acceleration / deceleration is performed after winding the tip and after finishing the tail end. ) Can be determined. For example, when the acceleration rate is 40 mpm / s, the boundary part is a four-cut plate and the tip part learning value is changed to the steady part learning value. When the deceleration rate is 20 mpm / s, the boundary part is an eight-cut plate and the steady part An example of transition from the learning value to the tail end learning value can be given.

  In this way, at the boundary between the tip (LE), the stationary part (MID), and the tail end (TE), by using the learning value that is changed step by step for each cut plate, the water injection pattern of that part is A sudden change is prevented, temperature fluctuations at the boundary can be suppressed, and the coiling temperature of the hot rolled material can be controlled with high accuracy.

  By actually applying the present invention, even if it is a hot-rolled material with poor winding temperature accuracy at the front end (LE) and the tail end (TE), the CT defect rate is extremely low as 0.62%. I was able to.

DESCRIPTION OF SYMBOLS 1 Rolling cooling equipment 2 Cooling part 3 Cooling bank 4 Incoming side thermometer 5 Thickness gauge 6 Incoming side speed detector 7 Outlet side thermometer 8 Outlet side speed detector 9 Cooling control part 10 Learning value calculating part 11 Bank opening / closing input / output Part 21 Finishing mill 22 Runout table 23 Winding machine

Claims (3)

When the hot rolled material rolled in the hot rolling facility is cooled by the cooling facility and controlled to a predetermined coiling temperature, the hot rolled material is divided into a plurality of control units in the longitudinal direction. In addition, a method for controlling the cooling of a hot-rolled material that performs temperature control using a heat transfer coefficient obtained by multiplying a heat transfer coefficient determined by a model formula by a predetermined learning value,
The control unit is classified into three parts, a tip part, a steady part, and a tail part, along the longitudinal direction of the hot-rolled material, and heat transfer for each control unit belonging to each part is made for each of these three parts. Calculate the learning coefficient of the coefficient, use the average value thereof as the learning value of the heat transfer coefficient for each part,
In the temperature control performed for each control unit, the learning value of the heat transfer coefficient corresponding to the part to which the control unit belongs is used, and learning that is changed stepwise for each control unit at the boundary part of these parts. A method for controlling cooling of a hot-rolled material, characterized by using a value.   2. The hot rolled material according to claim 1, wherein the learning value of the heat transfer coefficient of the control unit belonging to the boundary portion is changed so as to apportion the learning values of the portions on both sides of the boundary portion. Cooling control method.   The method for controlling cooling of a hot-rolled material according to claim 1, wherein the learning value of the heat transfer coefficient of the control unit belonging to the boundary portion is increased or decreased in a curved manner in the longitudinal direction of the hot-rolled material. .

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