JP7196875B2 - Controlled cooling method and controlled cooling device for steel plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a controlled cooling method and a controlled cooling apparatus for a steel plate.

In the cooling temperature control of steel plates, which are typified by hot-rolled steel plates and thick steel plates, temperature changes in the steel plates caused by water cooling are predicted using a temperature prediction model before the start of cooling. Cooling is performed after calculating the usage pattern of the cooling water valve, the amount of cooling water, and the steel plate conveying speed so as to achieve the temperature. Therefore, the accuracy of predicting the temperature change of the steel sheet due to water cooling affects the accuracy of temperature control of the steel sheet. If the temperature of the steel sheet at the completion of cooling deviates from the target temperature, the material characteristics necessary for the product cannot be obtained, so it is required to control the temperature of the steel sheet at the completion of cooling with high accuracy. In recent years, the length of steel sheets tends to increase in order to improve production efficiency, and it is required to control the temperature at the completion of cooling over the longitudinal direction of steel sheets with high accuracy. Against this background, in general steel plate cooling temperature control, feedback control is applied to operate the cooling device so as to suppress the control deviation, which is the deviation between the actual temperature and the predicted temperature of the steel plate during cooling. . However, in reality, there is a delay in measuring the temperature of the steel plate after cooling water is applied, a time delay due to feedback control calculation time, and a response delay in the cooling water valve. It cannot be implemented. In addition, feedback control is generally set with a delay time so that the control amount does not fluctuate steeply. Therefore, if the control deviation is large, it takes a long time to sufficiently suppress the control deviation.

Therefore, by correcting the parameters of the temperature prediction model based on the deviation between the actual temperature and the predicted temperature of the steel plate and reflecting it in the subsequent temperature prediction calculation, it is possible to suppress the temperature prediction deviation in the section where feedback control is not applied. It is done. In particular, using actual data such as the steel plate temperature measured before the start of cooling, the actual amount of cooling water, and the actual steel plate conveying speed, the temperature change of the steel plate due to water cooling is predicted, and the deviation from the actual steel plate temperature measured after cooling is completed is calculated. Several techniques have been proposed to modify the parameters of the temperature prediction model so as to suppress it. Specifically, in Patent Document 1, the correction parameter of the heat transfer coefficient in the temperature prediction model is expressed by a nonlinear equation according to the rolling state, and the parameters of the nonlinear equation are A technique for correcting is described. In addition, in Patent Document 2, a correction coefficient for the total heat flux is calculated so as to suppress the temperature prediction deviation from the actual temperature of the steel plate, and the operating conditions and the correction coefficient are linked and stored in a database, and are close to each other during subsequent operations. A technique is described in which a database is searched for operating conditions, and a correction factor retrieved from the database is reflected when calculating the temperature prediction. Further, in Patent Document 3, the transformation heat generation amount of the steel sheet is calculated so as to suppress the temperature prediction deviation, and the transformation rate of the steel sheet is calculated by comparing with the transformation heat generation amount when the steel sheet is 100% transformed. Techniques are described for modifying the parameters of the transformation rate equation using the estimated transformation rate.

JP 2007-44715 A JP 2011-200914 A JP 2013-766 A

However, the technology described in Patent Documents 1 to 3 corrects the parameters of the temperature prediction model so as to suppress the temperature prediction deviation, but the set flow rate and the actual flow rate of the cooling water used in the temperature prediction model match. It does not disclose or suggest countermeasures in case of non-compliance. The set flow rate and the actual flow rate of the cooling water used in the temperature prediction model are reduced due to the impurities contained in the cooling water sticking to the inner wall of the pipe and the cooling water valve, the flow reduction due to aging of the water pump, and the cooling water valve. They do not always match due to factors such as changes in flow rate due to deformation. If the cooling water flow rate of each cooling water valve changes uniformly, the technique described in Patent Documents 1 to 3 can suppress the deviation of the cooling water flow rate. Not uniform from valve to valve. Also, although the discrepancy between the set flow rate and the actual flow rate of the cooling water can be suppressed by the feedback control described above, the feedback control cannot be executed over the entire length of the steel plate for the reasons described above. Therefore, it is common to adjust the set flow rate and actual flow rate of cooling water in the temperature prediction model so that the set flow rate and actual flow rate of cooling water match using a flow meter before starting cooling. Frequent adjustment work cannot be performed in terms of human cost and time cost. Therefore, even if the set flow rate of the cooling water used in the temperature prediction model and the actual flow rate do not match, there is a technology that can accurately cool the steel plate to the target temperature without much effort. was expected to provide.

The present invention has been made in view of the above problems, and its object is to save a lot of labor even when the set flow rate of the cooling water used in the temperature prediction model and the actual flow rate do not match. To provide a controlled cooling method and a controlled cooling device for a steel plate that can accurately cool the temperature of the steel plate to a target temperature without the need for cooling.

A steel plate controlled cooling method according to the present invention uses a temperature prediction model to predict the temperature of a steel plate on the delivery side of a cooling device, and based on the predicted temperature of the steel plate, the target temperature of the steel plate on the delivery side of the cooling device. A steel plate controlled cooling method for controlling the flow rate of cooling water injected from a cooling device to achieve a temperature, wherein the temperature of the steel plate at the inlet and outlet sides of the cooling device is continuously generated in the longitudinal direction of the steel plate A measurement step of measuring each cut plate, which is a control unit of a virtual steel plate, the temperature of the cut plate on the inlet side of the cooling device measured in the measurement step, and the cooling when the cut plate passes through the cooling device A prediction step of predicting the temperature of the steel plate on the outlet side of the cooling device for each cut plate using the temperature prediction model using the water flow rate setting value, and the steel plate on the outlet side of the cooling device measured in the measuring step A correction step of correcting the cooling water flow rate setting value in the temperature prediction model so that the temperature of the steel plate on the outlet side of the cooling device predicted in the prediction step matches over all the cut plates; characterized by comprising

In the steel plate controlled cooling method according to the present invention, in the above invention, the correcting step includes the temperature of the steel plate on the outlet side of the cooling device measured in the measuring step and the output of the cooling device predicted in the predicting step. calculating the deviation from the temperature of the steel sheet on the side of each cutting plate, and correcting the flow rate setting value of the cooling water in the temperature prediction model based on the correlation between the deviation and the flow rate setting value.

In the steel plate controlled cooling method according to the present invention, in the above invention, the correcting step includes the temperature of the steel plate on the outlet side of the cooling device measured in the measuring step and the output of the cooling device predicted in the predicting step. Calculate the deviation from the temperature of the steel plate on the side for each cut plate, calculate the total value of the deviation of all cut plates as the total deviation, and based on the calculated total deviation, adjust the cooling water flow rate setting value in the temperature prediction model It is characterized by including a step of correcting.

In the steel plate controlled cooling method according to the present invention, in the above invention, the correcting step includes the temperature of the steel plate on the outlet side of the cooling device measured in the measuring step and the output of the cooling device predicted in the predicting step. The deviation from the temperature of the steel sheet on the side is calculated for each cut sheet, the total value of the deviations of all cut sheets is calculated as the total deviation, and the calculated total deviation and the total deviation calculated for the most recently cooled steel sheet and correcting the flow rate setting value of the cooling water in the temperature prediction model based on the calculated sum.

A controlled cooling device for a steel plate according to the present invention uses a temperature prediction model to predict the temperature of a steel plate on the outlet side of the cooling device, and based on the predicted temperature of the steel plate, the temperature of the steel plate on the outlet side of the cooling device is set as a target. A controlled cooling device for a steel plate that controls the flow rate of cooling water injected from the cooling device so as to reach a temperature, the temperature of the steel plate at the inlet and outlet sides of the cooling device is continuously generated in the longitudinal direction of the steel plate A measuring means for measuring each cut plate, which is a control unit of a virtual steel plate, the temperature of the cut plate on the inlet side of the cooling device measured by the measuring means, and the cooling when the cut plate passes through the cooling device Using the water flow rate setting value, the temperature prediction model predicts the temperature of the steel sheet on the exit side of the cooling device for each cut sheet, and the temperature of the steel sheet on the exit side of the cooling device measured by the measuring means and a control means for correcting the cooling water flow rate set value in the temperature prediction model so that the predicted temperature of the steel plate on the delivery side of the cooling device matches all the cut plates. .

According to the controlled cooling method and the controlled cooling device for steel sheets according to the present invention, even if the set flow rate of the cooling water used in the temperature prediction model and the actual flow rate do not match, much effort is not required. The temperature of the steel plate can be accurately cooled to the target temperature.

FIG. 1 is a schematic diagram showing the configuration of a cooling line for hot-rolled steel sheets to which a controlled cooling method for steel sheets according to an embodiment of the present invention is applied. FIG. 2 is a flow chart showing the flow of controlled cooling processing, which is an embodiment of the present invention. FIG. 3 is a diagram illustrating the actual temperature, the conventional example, and the invention examples 1 to 4 from the start of calculation to cutting plate number 500. In FIG. FIG. 4 is a diagram showing actual temperatures, conventional examples, and invention examples 1 to 4 in sections from cutting plate number 3000 to cutting plate number 3500. FIG. FIG. 5 is a diagram showing actual temperatures, conventional examples, and invention examples 1 to 4 in sections from cutting plate number 4500 to cutting plate number 5000. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION A controlled cooling method for a steel sheet, which is an embodiment of the present invention, will be described below with reference to the drawings.

[Configuration of cooling line for hot-rolled steel]
First, with reference to FIG. 1, the configuration of a cooling line for hot-rolled steel sheets to which a controlled cooling method for steel sheets according to an embodiment of the present invention is applied will be described.

FIG. 1 is a schematic diagram showing the configuration of a cooling line for hot-rolled steel sheets to which a controlled cooling method for steel sheets according to an embodiment of the present invention is applied. As shown in FIG. 1, a hot-rolled steel sheet cooling line 1 (hereinafter abbreviated as cooling line 1) to which a steel sheet controlled cooling method according to an embodiment of the present invention is applied is conveyed in a conveying direction indicated by an arrow. This line cools the steel plate to a target temperature by injecting cooling water onto the steel plate, and includes cooling water valves 2a to 2o, thermometers 3a and 3b, a calculator 4, and a control panel 5.

The cooling water valves 2a to 2o are arranged opposite to the front and back surfaces of the steel plate, and cool the steel plate by injecting cooling water toward the front and back surfaces of the steel plate in accordance with control signals from the control panel 5.

The thermometers 3a and 3b are arranged on the inlet side and the outlet side of the cooling line 1, respectively, and measure the temperature of the steel plate on the inlet side and the outlet side of the cooling line 1 with a period equal to or shorter than the control period of the cooling water valves 2a to 2o. . The thermometers 3a and 3b each output to the computer 4 an electric signal indicating the measured temperature of the steel plate.

The computer 4 is configured by an information processing device such as a computer. The calculator 4 cools the temperature of the steel sheet to the target temperature by executing a controlled cooling process, which will be described later. Specifically, the calculator 4 controls the temperature of the steel sheet on the inlet side and the outlet side of the cooling line 1 measured by the thermometers 3a and 3b. The temperature of the steel plate is cooled to the target temperature by controlling the flow rate of the cooling water.

In the hot-rolled steel cooling line 1 having such a configuration, the computer 4 executes the controlled cooling process described below, so that the set flow rate of the cooling water used in the temperature prediction model does not match the actual flow rate. To accurately cool a steel plate to a target temperature without requiring much labor even in such a case. The operation of the computer 4 when executing the controlled cooling process, which is one embodiment of the present invention, will be described below with reference to FIG.

In this specification, the temperature prediction model means a mathematical model describing heat exchange between cooling water, air, rolls, etc. and the steel sheet. The input variables of the temperature prediction model include the initial temperature of the steel plate and the flow rate (flow rate set value) of the cooling water injected from the cooling water valves 2a to 2o, and the output variable of the temperature prediction model is the output of the cooling line 1. is the temperature of the steel plate on the side.

[Controlled cooling process]
FIG. 2 is a flow chart showing the flow of controlled cooling processing, which is an embodiment of the present invention. The flowchart shown in FIG. 2 starts at the timing when a cut plate of steel plate (virtual steel plate control unit continuously generated in the longitudinal direction of the steel plate) passes the thermometer 3a, and the controlled cooling process is the process of step S1. proceed to

In the process of step S1, the computer 4 measures the temperature of each cut plate i on the inlet and outlet sides of the cooling line 1 using thermometers 3a and 3b and well-known tracking technology. Note that i indicates unique identification information assigned to each cut plate. Thereby, the process of step S1 is completed, and the control cooling process proceeds to the process of step S2.

In the process of step S2, the calculator 4 acquires the flow rate set value Q _i ^k of each cooling water valve k at the time when each cutting plate i passes through the cooling water valves 2a to 2o. Note that k indicates unique identification information assigned to each cooling water valve. Thereby, the processing of step S2 is completed, and the controlled cooling processing proceeds to the processing of step S3.

In the process of step S3, the computer 4 uses the temperature prediction model to determine the temperature of each cut plate i on the inlet side of the cooling line 1 obtained in the process of step S1 and the temperature of each cut plate i obtained in the process of step S2. The temperature of each cut plate i on the outlet side of the cooling line 1 is predicted from the flow rate setting value Q _i ^k of the cooling water valve k at the time when . In this process, assuming that the heat flux due to the cooling water is expressed as a function of the set flow rate f(V) of the cooling water, the flow rate correction coefficient Wk for correcting the flow rate of the cooling water injected from the cooling water valve _k is is used to predict the temperature of each cutting plate i with the heat flux by the cooling water as f(V, W _k ). In the first control cooling process, the flow rate correction _{coefficient Wk} is set to the initial value. Thereby, the processing of step S3 is completed, and the controlled cooling processing proceeds to the processing of step S4.

In the processing of step S4, the computer 4 causes the steel plate to flow through the cooling line so that the flow rate fluctuation of the cooling water injected from each cooling water valve k is reflected in the temperature prediction calculation of each cut plate i on the outlet side of the cooling line 1. 1, the flow rate correction coefficient Wk of each cooling water valve _k is corrected. Specifically, first, the computer 4 calculates the temperature of each cut plate i on the output side of the cooling line 1 measured in the process of step S1 and the temperature of each cut plate i on the output side of the cooling line 1 calculated in the process of step S3. A deviation ΔT _i from the temperature of the plate i is calculated for each cutting plate i. Next, the calculator 4 calculates the correlation between the calculated deviation ΔT _i and the flow rate set value Q _i ^k of the cooling water valve k. Specifically, the computer 4 performs linear regression of the deviation ΔT _i with the flow rate set value Q _i ^k for the cooling water valve k using the least-squares method to construct Equation (1) shown below. Then, when the slope A _k of equation (1) is equal to or greater than the predetermined value x, the calculator 4 corrects the flow rate correction coefficient W _k to the flow rate correction coefficient W _k ' (=W _k −α), and formula (1) is less than the predetermined value x, the flow rate correction coefficient W _k is corrected to the flow rate correction coefficient W _k ′ (=W _{k +} α). However, α indicates a predetermined constant. Note that the process of step S4 is not executed for the cooling water valve k for which the flow rate set value Q _i ^k does not change. Thereby, the processing of step S4 is completed, and the controlled cooling processing proceeds to the processing of step S5.

In the process of step S5, the computer 4 controls the temperature prediction calculation of each cut plate i on the outlet side of the cooling line 1 to reflect short-term fluctuations in the total flow rate of the cooling water injected to the hot rolled steel plate. The flow rate correction _{coefficient Wk} is uniformly corrected for all cooling water valves injecting water. Specifically, first, the calculator 4 calculates the total value of the deviations ΔT _i of all the cut plates as the total deviation ΣΔT _i using the deviations ΔT _i calculated in the process of step S4. Next, when the total deviation ΣΔT _i of the cooling water valve that injected cooling water during cooling of the hot-rolled steel sheet is equal to or greater than a predetermined value y, the calculator 4 replaces the flow rate correction coefficient W _k with the flow rate correction coefficient W _k ′ ( = W _k × (1 + β)), and when the total deviation ΣΔT _i is less than the predetermined value y, the flow rate correction coefficient W _k is corrected to the flow rate correction coefficient W _k ' (= W _k × (1-β)) corrected to However, β indicates a predetermined constant. Thereby, the processing of step S5 is completed, and the controlled cooling processing proceeds to the processing of step S6.

In the processing of step S6, the computer 4 determines whether or not the correction processing of the flow correction _coefficient Wk in the processing of steps S4 and S5 has the same tendency as the correction processing of the flow correction _coefficient Wk for other hot-rolled steel sheets. Based on the determination result, the flow rate correction _{coefficient Wk} is corrected so as to suppress or promote the correction processing in steps S4 and S5. Specifically, first, the calculator 4 calculates the total deviation ΣΣΔT _i by combining the total deviation ΣΔT _i calculated in the process of step S5 with ΣΔT _i for the plurality of hot-rolled steel sheets that have been cooled most recently. Next, if the total deviation ΣΣΔT _i of the cooling water valve that jets the cooling water to a plurality of hot-rolled steel sheets is equal to or greater than a predetermined value z, the calculator 4 replaces the flow rate correction coefficient W _k with the flow rate correction coefficient W _k ′. (= W _k × (1 + γ)), and if the total deviation ΣΣΔT _i is equal to or greater than the predetermined value z, the flow correction coefficient W _k is changed to the flow correction coefficient W _k ' (= W _k × (1-γ)) to correct. However, γ indicates a predetermined constant. Thereby, the processing of step S6 is completed, and the controlled cooling processing proceeds to the processing of step S7.

〔Example〕
In this example, a temperature prediction simulation of a hot-rolled steel sheet was performed. Specifically, in this simulation, 5000 cut plates of a predetermined length (cut plate numbers 1 to 5000 in order from the tip) continuously generated from the tip of 92 connected coils were cooled. , conventional temperature prediction calculation (conventional example), temperature prediction calculation (invention examples 1 to 3) in which the processes of steps S4, S5, and S6 shown in FIG. 2 are performed independently, and the processes of steps S4 to S6 shown in FIG. A temperature prediction calculation (Invention Example 4) was performed in which all were performed. The constants in each calculation in steps S4 to S6 were x=10° C., α=0.050, y=10° C., β=0.02, z=10° C., and γ=0.0. The initial values of the flow rate correction coefficients are all set to 1.

FIG. 3 shows actual temperature (line L1), conventional example (line L2), invention example 1 (line L3), invention example 2 (line L4), invention example 3 (line L5), and invention example 4 (line L6). is illustrated in the section from the start of calculation to cutting plate number 500. As shown in FIG. 3, since the initial value of the flow rate correction coefficient is set to 1, the conventional example and the invention examples 1 to 4 are the same at first. In addition, in the section up to cutting plate number 200, the actual temperature and invention examples 1 to 4 appear alternately, so the correction direction of the flow rate correction coefficient also alternates, and there is not much difference between the conventional example and invention examples 1 to 4. No.

However, in the section of cut plate numbers 200 to 480, hot-rolled steel sheets whose actual temperatures are about 20 ° C higher than those of Invention Examples 1 to 4 continue, so in the process of step S5, the predicted temperature is increased. It can be seen from invention example 2 (line L4) in this section that the flow rate correction coefficient is continuously corrected in the negative direction. On the other hand, since there is little tendency for temperature prediction errors due to differences in the set flow rates of the cooling water valves, the correction by the processing in step S4 is not often performed (Invention Example 1 (line L3)). Further, in the vicinity of the cut plate number 430, since the deviation of the same sign continues over the most recent hot-rolled steel sheets, correction is performed by the processing of step S6 (Invention Example 3 (L5)).

FIG. 4 shows actual temperature (line L1), conventional example (line L2), invention example 1 (line L3), invention example 2 (line L4), invention example 3 (line L5), and invention example 4 (line L6). is illustrated in the section from cutting plate number 3000 to cutting plate number 3500. As shown in FIG. 4, the correction by each process of steps S4 to S6 has progressed, and it can be seen that invention examples 1 to 3 are more accurate than the conventional example. In addition, FIG. 5 shows actual temperature (line L1), conventional example (line L2), invention example 1 (line L3), invention example 2 (line L4), invention example 3 (line L5), and invention example 4 (line L6) is illustrated in the section from cut plate number 4500 to cut plate number 5000. The correction by the processing of steps S5 and S6 works effectively, and invention examples 2 and 3 follow the actual temperature. Example 1 cannot follow changes in the actual temperature. The above results are summarized in Table 1 below, and it can be seen that invention examples 1 to 3 are also more accurate than the conventional example, but invention example 4 is the most accurate. From the above results, it was confirmed that the temperature prediction accuracy is improved by implementing the present invention.

Although the embodiments to which the inventions made by the present inventors are applied have been described above, the present invention is not limited by the descriptions and drawings forming part of the disclosure of the present invention according to the embodiments. That is, other embodiments, examples, operation techniques, etc. made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

1 Cooling line for hot-rolled steel sheet 2a to 2o Cooling water valves 3a, 3b Thermometer 4 Computer 5 Control panel

Claims (4)

A temperature prediction model is used to predict the temperature of the steel plate on the outlet side of the cooling device, and based on the predicted temperature of the steel plate, the cooling device sprays so that the temperature of the steel plate on the outlet side of the cooling device reaches the target temperature. A controlled cooling method for a steel plate that controls the flow rate of cooling water,
a measuring step of measuring the temperature of the steel plate at the entrance side and the exit side of the cooling device for each cutting plate, which is a control unit of a virtual steel plate continuously generated in the longitudinal direction of the steel plate;
Using the cut plate temperature on the inlet side of the cooling device measured in the measurement step and the cooling water flow rate setting value when the cut plate passes through the cooling device, the temperature prediction model is used to determine the outlet side of the cooling device. A prediction step for predicting the temperature of the steel plate in each cut plate,
The temperature prediction is performed so that the temperature of the steel sheet on the delivery side of the cooling device measured in the measuring step and the temperature of the steel plate on the delivery side of the cooling device predicted in the prediction step match over all the cut plates. a correction step for correcting the cooling water flow setpoint in the model;
including
The correction step calculates, for each cut plate, the deviation between the temperature of the steel sheet on the exit side of the cooling device measured in the measuring step and the temperature of the steel sheet on the exit side of the cooling device predicted in the prediction step. , calculating the total value of the deviations of all the cut plates as the total deviation, and correcting the flow rate setting value of the cooling water in the temperature prediction model based on the calculated total deviation. . The correction step calculates, for each cut plate, the deviation between the temperature of the steel sheet on the exit side of the cooling device measured in the measuring step and the temperature of the steel sheet on the exit side of the cooling device predicted in the prediction step. 2. The controlled cooling method for a steel plate according to claim 1, further comprising the steps of correcting the flow rate setting value of the cooling water in the temperature prediction model based on the correlation between the deviation and the flow rate setting value. The correction step calculates, for each cut plate, the deviation between the temperature of the steel sheet on the exit side of the cooling device measured in the measuring step and the temperature of the steel sheet on the exit side of the cooling device predicted in the prediction step. , Calculate the sum of the deviations of all cut plates as the total deviation, calculate the sum of the calculated total deviation and the total deviation calculated for the most recently cooled steel plate, and predict the temperature based on the calculated sum 3. The controlled cooling method for a steel plate according to claim 1, further comprising a step of correcting the set value of the cooling water flow rate in the model. A temperature prediction model is used to predict the temperature of the steel plate on the outlet side of the cooling device, and based on the predicted temperature of the steel plate, the cooling device sprays so that the temperature of the steel plate on the outlet side of the cooling device reaches the target temperature. A controlled cooling device for a steel plate that controls the flow rate of cooling water,
measuring means for measuring the temperature of the steel plate on the inlet side and the outlet side of the cooling device for each cut plate;
Using the temperature of the cut plate on the inlet side of the cooling device measured by the measuring means and the flow rate setting value of the cooling water when the cut plate passes through the cooling device, the temperature prediction model is used to determine the outlet side of the cooling device. Predict the temperature of the steel sheet at the outlet side of the cooling device measured by the measuring means and predict the temperature of the steel sheet at the exit side of the cooling device measured by the measuring means. a control means for correcting the cooling water flow rate set value in the temperature prediction model so that the temperature of the steel plate on the outlet side of the cooling device that has been set is consistent over all the cut plates;
with
The control means calculates, for each cut plate, a deviation between the temperature of the steel plate on the delivery side of the cooling device measured by the measuring device and the predicted temperature of the steel plate on the delivery side of the cooling device. is calculated as the total deviation, and the set value of the cooling water flow rate in the temperature prediction model is corrected based on the calculated total deviation .

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