JP2014028385A - Temperature estimation method for cast piece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature estimation method for a cast metal in which longer-direction temperature difference of the cast metal and recuperation of the surface of the cast metal are taken into account.SOLUTION: There is provided the temperature estimation method for a cast metal, for deriving a temperature of a cast metal 10 charged into a heating furnace 14 after being cast by a continuous casting, cut into a predetermined dimension, and housed in a thermal insulation cover 13. The temperature estimation method comprises the steps of: obtaining a three-dimensional computational model in which a plurality of calculation grids in a longer direction, a width direction, and a thickness direction on the cast metal 10 are arranged; calculating temperature of each calculation grid based on operation result of the continuous casting; correcting the temperature of each calculation grid based on a correction value obtained by multiplying a temperature difference between a temperature measurement value at a measurement part of the surface of the cast metal 10 when the cast metal 10 is moved to the heating furnace 14 and the temperature of the calculation grid by an adjustment value; obtaining a temperature change of each calculation grid with respect to the cast metal 10 traveling within the heating furnace 14; and estimating a temperature distribution of the whole cast metal 10 when being extracted from the heating furnace 14. The adjustment value becomes large according to the length of time period when the measurement part is housed in the thermal insulation cover 13, and the adjustment value is a value more than 0 and less than 1.

Description

The present invention relates to a method for estimating the temperature of a slab that is cut into a predetermined size through continuous casting and heated in a heating furnace.

The slab that has been removed from the continuous casting machine and cut to a predetermined size is heated in a heating furnace, and then subjected to a plurality of sizing processes to obtain a target thickness and width.
The load applied to the slab for each sizing process is determined mainly according to the temperature of the slab, and when a load larger than the load suitable for the slab temperature is applied to the slab, the load generated in the rolling mill is designed. If the value is exceeded, the rolling mill may be damaged in some cases. On the other hand, if the load applied to the slab is small, the number of necessary sizing processes increases and the production efficiency decreases.

The temperature of the slab is estimated by a computer, and the computer calculates the load applied to the slab in one sizing process based on the estimated temperature of the slab.
As a method for estimating the temperature of the slab, there is a method using a partial differential equation of heat transfer, and a specific example is described in Patent Document 1.
The method of Patent Document 1 includes a skid portion that contacts the skid by a partial differential equation of heat transfer,
The temperature of the slab is calculated for each skid that is not in contact with the skid, and the temperature of the entire slab is estimated.

By the way, whatever the method of calculating the slab temperature, the slab temperature estimated by the computer is different from the actual temperature. Therefore, when the load applied directly to the slab is calculated from the estimated temperature of the slab without considering this difference, the calculated load may exceed the appropriate range to be applied to the slab, and the rolling mill may be damaged. There is a fear.
Therefore, it is necessary to calculate the load applied to the slab in consideration of the difference between the estimated temperature of the slab and the actual temperature, that is, the temperature estimation accuracy of the slab. If the temperature estimation accuracy of the slab is low (the temperature difference is large), a small value is calculated as the load applied to the slab, resulting in a decrease in production efficiency.

JP-A-3-140415

The slab has different casting conditions and heat dissipation conditions at different positions in the longitudinal direction, and the slab charged into the heating furnace has a different temperature in the longitudinal direction. On the other hand, in patent document 1, the temperature of the whole slab is estimated based on the temperature of the two cross sections between a skid part and a skid, and the point from which temperature differs in the longitudinal direction of a slab is not considered. For this reason, there existed a problem that the temperature estimation precision of a slab became low and production efficiency fell.

In addition, it is well known that a heat insulating cover that suppresses heat dissipation of the slab is installed in front of the heating furnace. When the slab is accommodated in the heat insulating cover, the overall temperature decreases, whereas the surface temperature increases due to recuperation.
Therefore, to increase the temperature estimation accuracy of the slab, it is conceivable to measure the surface temperature of the slab and correct the estimated temperature of the slab based on the actual measurement result. When actually measuring the surface temperature of the slab, the temperature of the reheated slab surface is measured.
However, a correction method has not been established as to how to correct the estimated temperature of the slab based on the result of temperature measurement of the surface of the reheated slab.

On the other hand, the temperature adjustment in the heating furnace is determined based on the temperature of the slab charged into the heating furnace. For this reason, measuring the surface temperature of the slab immediately before charging the slab into the heating furnace has great significance in appropriately adjusting the temperature in the heating furnace. If the actual measured value of the surface temperature of the slab can be used for the purpose of correcting the estimated temperature of the slab, one actual value can be used for two purposes (temperature adjustment in the heating furnace and correction of the estimated temperature of the slab). Can be used to achieve the above, and is effective in system design.
This invention is made | formed in view of this situation, and it aims at providing the temperature estimation method of the slab which considered the temperature difference of the longitudinal direction of a slab, and the recuperation of the surface of a slab.

A method for estimating the temperature of a slab according to the present invention that meets the above-described object is a method of deriving a temperature of a slab that is cut into a predetermined dimension through continuous casting and then inserted into a heating furnace after being stored in a heat insulating cover. In the temperature estimation method, a three-dimensional calculation model in which a plurality of calculation grids are arranged in the longitudinal direction, the width direction, and the thickness direction is obtained for the slab, and the temperature of each calculation grid is calculated from the operation results of continuous casting. A first step for obtaining a temperature distribution of the entire piece, and a temperature obtained by measuring the temperature of the measurement part of the surface of the slab when the slab moves from the heat insulation cover to the heating furnace, and the measurement part A second step of calculating a correction value by multiplying a corresponding difference in temperature of the calculation grid by an adjustment value; a third step of correcting the temperature of each calculation grid based on the correction value; and the heating About the slab in progress in the furnace, the heat input to the slab A fourth step of calculating from the temperature in the heating furnace, obtaining a temperature change of each calculation grid, and estimating a temperature distribution of the entire slab when extracted from the heating furnace, and adjusting The value increases according to the length of time that the measuring unit that has measured the temperature is accommodated in the heat insulating cover, and is a value that exceeds 0 and is less than 1.

In the slab temperature estimation method according to the present invention, when the adjustment value is r, r is preferably calculated by the following equation (1).
r = 1−exp (a × t ^ b) Equation 1
Here, t is the time during which the measurement unit is accommodated in the heat insulation cover, and a is (−6.7).
7e-3) × 1.1 or more and (−6.77e-3) × 0.9 or less, b is 0.66 × 0.
The value is 9 or more and 0.66 × 1.1 or less.

In the slab temperature estimation method according to the present invention, there are a plurality of the measurement units at different positions in the longitudinal direction of the slab, and the adjustment value is calculated for each measurement unit to obtain a plurality of correction values, It is preferable to correct the temperature of each calculation grid based on the plurality of correction values.

In the temperature estimation method for a slab according to the present invention, the slab is advanced in a state where the longitudinal direction is along the width direction of the heating furnace in the heating furnace, and the heating furnace is moved along the traveling direction of the slab. Are divided into a plurality of furnace zones, and a plurality of thermometers are disposed in the plurality of furnace zones at different positions in the width direction of the heating furnace, respectively, and the slab is measured based on the measured temperatures of the plurality of thermometers. It is preferable to calculate the amount of heat input.

In the slab temperature estimation method according to the present invention, the temperature of the measurement unit is preferably measured by a radiation thermometer.

The temperature estimation method for a slab according to the present invention obtains a three-dimensional calculation model in which a plurality of calculation grids are arranged in the longitudinal direction, the width direction, and the thickness direction for the slab, and calculates the temperature from the operation results for each calculation grid. Then, correction is performed, the temperature change in the heating furnace is obtained, and the temperature distribution of the entire slab when being extracted from the heating furnace is calculated. Accordingly, the temperature distribution of the entire slab can be obtained in consideration of the occurrence of a temperature difference in the longitudinal direction of the slab.
In addition, the temperature difference between the measured temperature of the slab surface and the estimated temperature of the slab surface increases with the time stored in the heat insulation cover, and is corrected by multiplying an adjustment value greater than 0 and less than 1. Since the value is calculated, a correction value is calculated taking into account the recuperation of the slab surface that progresses according to the time accommodated in the heat insulating cover, and the estimation accuracy of the temperature distribution of the entire slab can be increased, As a result, it is possible to improve production efficiency.

In the slab temperature estimation method according to the present invention, when the adjustment value is calculated by r = 1−exp (a × t ^ b), the adjustment value is determined according to the accommodation time in the heat insulation cover of the measurement unit. It is possible to establish a standard for determining the value, and to establish a guideline for stably improving the estimation accuracy of the temperature distribution of the entire slab.

In the temperature estimation method for a slab according to the present invention, there are a plurality of measurement parts at different positions in the longitudinal direction of the slab, and a plurality of correction values are obtained by calculating adjustment values for each measurement part. When correcting the temperature distribution of the entire slab, the accuracy of the estimated temperature distribution of the entire slab can be reliably increased even if the time stored in the heat insulating cover is different at different positions in the longitudinal direction of the slab. Correction can be performed.

In the temperature estimation method for a slab according to the present invention, the slab is advanced in a heating furnace in a state where the longitudinal direction is along the width direction of the heating furnace, and the heating furnace is a plurality of furnace zones along the traveling direction of the slab. Divided into
When a plurality of thermometers are arranged at different positions in the width direction of the heating furnace in a plurality of furnace zones and the amount of heat input to the slab is calculated based on the measured temperatures of the plurality of thermometers, the temperature in the longitudinal direction is When different slabs move in the heating furnace, the heat input in the longitudinal direction of the slab can be accurately calculated, and changes in the temperature distribution of the entire slab can be obtained stably.

In the slab temperature estimation method according to the present invention, when the temperature of the measurement unit is measured by a radiation thermometer, the temperature of the measurement unit can be efficiently measured remotely.

It is explanatory drawing which shows the mode of the movement of the slab to which the temperature estimation method of the slab which concerns on one embodiment of this invention is applied. It is explanatory drawing which shows the mode of movement of a slab. (A) is explanatory drawing of a heating furnace, (B) is explanatory drawing which shows arrangement | positioning of the thermometer in a heating furnace. It is a block diagram which shows the signal connection of a computer. It is explanatory drawing which shows the temperature calculation method of slab. (A), (B) is explanatory drawing which shows the temperature calculation method of slab. It is a graph which shows distribution of the cross-sectional average temperature of slab. It is a graph which shows the relationship between the surface temperature difference of a slab, and a cross-sectional average temperature difference. It is a graph which shows the relationship between the sensitivity of the cross-sectional average temperature difference with respect to the surface temperature difference of slab, and the accommodation time in a heat insulation cover. (A), (B) is a graph which shows the result of having calculated the load applied to a slab in a sizing press. (A), (B) is a graph which shows the result of having calculated the load applied to a slab in a sizing mill.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIG. 1, a slab 10 to which a slab temperature estimation method according to an embodiment of the present invention is applied is cut into a predetermined dimension by a CC cutter 12 through continuous casting by a continuous casting machine 11. . In this embodiment, the slab 10 cut by the CC cutter 12 has a rectangular cross section, a thickness of 100 to 400 mm, a width of 650 to 3000 mm, and a length of 3 to 30 m, but does not belong to this range. The present invention can also be applied to other slabs.

As shown in FIG. 1 and FIG. 2, the slab 10 cut by the CC cutter 12 is inserted into the heating furnace 14 after being accommodated in the heat insulating cover 13, and a target temperature set in advance in the heating furnace 14. Until heated. The temperature in the heating furnace 14 is adjusted by changing the combustion level of the plurality of combustion burners 15 shown in FIG. 3A provided in the heating furnace 14.
The slab 10 extracted from the heating furnace 14 is processed to a target width and thickness through a plurality of sizing processes. Here, the one-time sizing process indicates one operation of pressing the slab 10 in the width direction in the sizing press, and the slab 1 in the sizing mill.
0 indicates a single pass through the rolling mill. Note that the sizing press applies pre-forming pressure to both ends of the slab 10 in the longitudinal direction, and suppresses cropping generated on the slab 10 by a sizing mill.
Further, FIG. 2 shows one heat insulating cover, but in an actual site, a plurality of heat insulating covers are arranged in parallel on the charging side of the slab of the heating furnace.

As shown in FIG. 2, the slab 10 charged in the heating furnace 14 has the longitudinal direction arranged along the width direction of the heating furnace 14 and the inside of the heating furnace 14 is placed on the extraction side of the heating furnace 14. It moves toward and is extracted from the heating furnace 14.
The heating furnace 14 is divided into a plurality of furnace zones along the traveling direction of the slab 10, as shown in FIGS. 2, 3A, and 3B. In this embodiment, the slab 10 proceeds. Heating zone 1 on the upstream side along the direction
6 and the downstream side is the soaking zone 17. Each furnace zone has a different temperature change state of the slab 10 traveling through the furnace zone, and the heating zone 16 has a higher rate of temperature rise of the slab 10 than the soaking zone 17.

In the heating furnace 14, as shown in FIG. 3B, a plurality of thermometers 18 (thermocouples in the present embodiment) for measuring the temperature in the heating furnace 14 are provided.
In the heating furnace 14, a plurality of thermometers 18 arranged at different positions in the width direction of the heating furnace 14 and a first row 19 in which a plurality of thermometers 18 are arranged along the traveling direction of the slab 10. Second consisting of 18
Column 20 is provided. The first row 19 has two rows, one end of which is disposed in the heating zone 16 and the other end is disposed in the soaking zone 17. The second row 20 is arranged in each of the heating zone 16 and the soaking zone 17.

The slab 10 cast by the continuous casting machine 11 has an overall temperature distribution of the computer 2 shown in FIG.
1 is calculated.
As shown in FIG. 5, the computer 21 generates a three-dimensional calculation model 23 in which a plurality of calculation grids (mesh) 22 are arranged in the longitudinal direction (casting direction), the width direction, and the thickness direction of the slab 10,
The temperature of each calculation grid 22 is calculated to obtain the temperature distribution of the entire slab 10. The temperature of each calculation grid 22 is calculated from the operation results including the casting speed, the amount of cooling water, and the continuous temperature measurement in the tundish when the slab 10 is removed from the continuous casting machine 11.

The slab 10 taken out from the continuous casting machine 11 is conveyed in a state where it is supported by a roll 25 while cooling water is sprayed from the nozzle 24 as shown in FIGS. The In FIG. 1, the description of the nozzle 24 is omitted.
In this Embodiment, about the slab 10 extracted from the continuous casting machine 11, the slab 10 is divided into a some area | region from the contact state of the roll 25, and the blowing state of cooling water, and a temperature change is calculated. .
Specifically, as shown in FIGS. 6A and 6B, the region I is a region in contact with the roll 25, the regions II to IV are non-contact regions with the roll 25, and the regions II to IV The region II is distinguished from the region where the cooling water is not touched, the region III is the region where the cooling water is directly sprayed, and the region IV is the region where the cooling water sprayed onto the region III flows.

As shown in FIG. 6A, for example, when the slab 10 is moving downward at the curved portion, the region
Region II exists above III, and region IV exists below region III. The slab 10 is shown in FIG.
As shown in (), when moving in the horizontal direction, the region IV exists on both sides of the region III.
And the heat deprived from the slab 10 with respect to the regions I to IV is calculated with different calculation formulas,
By reflecting this in the three-dimensional calculation model 23, the temperature of each calculation grid 22 of the three-dimensional calculation model 23 is obtained.
The computer 21 continuously calculates the temperature of each calculation grid 22 and estimates the temperature distribution of the entire slab 10 when the slab 10 is extracted from the heating furnace 14.

Here, the temperature distribution of the entire slab 10 calculated by the computer 21 is calculated based on the operation results, but since it is a theoretical value to the last, the temperature distribution of the entire slab 10 calculated by the computer 21 and Of course, there is a difference between the actual temperature distribution of the entire slab 10.
Therefore, as shown in FIG. 1, a radiation thermometer 26 as an example of a thermometer is provided on the exit side of the heat insulating cover 13.
The computer 21 corrects the temperature distribution of the entire slab 10 calculated as the temperature of the slab 10 coming out of the heat insulating cover 13 based on the temperature of the slab 10 measured by the radiation thermometer 26. Specifically, when the slab 10 in a state where the entirety is accommodated in the heat insulating cover 13 moves to the heating furnace 14,
The temperature of the measurement part on the surface of the slab 10 is measured by the radiation thermometer 26, and the temperature distribution of the entire slab 10 calculated by the computer 21 is calculated based on the temperature difference between the measured value and the temperature of the calculation grid 22 corresponding to the measurement part. to correct.

And the computer 21 is based on the temperature distribution of the slab 10 whole after correction | amendment, and the several combustion burner 15 is set so that the slab 10 at the time of extracting from the heating furnace 14 may become predetermined target temperature. Determine each combustion level.
As shown in FIG. 4, the computer 21 is signal-connected to the plurality of combustion burners 15, the plurality of thermometers 18, and the radiation thermometer 26 via the interface 27.

While the slab 10 is moving in the heating furnace 14, the computer 21 obtains the temperature in the heating furnace 14 measured by each thermometer 18 continuously or at predetermined time intervals, and casts from these temperatures. Piece 10
The amount of heat input to is calculated, and the temperature change of each calculation grid 22 is obtained. Here, conventionally, the heating furnace 14
However, in this embodiment, the temperature of the combustion gas in the combustion burner 15 and the furnace of the heating furnace 14 are calculated. The idea different from the conventional method of calculating the amount of heat input to the slab 10 by using the wall temperature as a heat source is adopted.

The temperature in the heating furnace 14 varies depending on the location even in the same furnace zone. The slab 10 when charged in the heating furnace 14 is different in time from one end to the other end in the longitudinal direction of the slab 10 after continuous casting, and from the short side to the long side after continuous casting. The temperature tends to be lowered. Therefore, in each furnace zone, the temperature is adjusted so that the amount of heat input to the slab 10 is greater on the low temperature side than on the high temperature side with respect to the longitudinal center of the slab 10, and the width of the heating furnace 14 is increased. The temperature in the furnace differs depending on the direction.

In the present embodiment, the temperatures measured by the thermometers 18 arranged at different positions in the width direction of the heating furnace 14 in the heating zone 16 and the soaking zone 17 are adopted as basic data for calculating the heat input amount of the slab 10. doing. Accordingly, in each of the heating zone 16 and the soaking zone 17, it is possible to calculate an accurate amount of heat input for different positions in the longitudinal direction of the slab 10 moving in the heating furnace 14.
The computer 21 continuously calculates the temperature of each calculation grid 22 of the three-dimensional calculation model 23 until the slab 10 is extracted from the heating furnace 14 after the slab 10 is continuously cast. The transition of the entire temperature distribution is obtained, and the temperature of the slab 10 having a temperature difference at different positions in the longitudinal direction of the slab 10 can be accurately calculated.

The computer 21 obtains the temperature distribution of the entire slab 10 when the slab 10 is extracted from the heating furnace 14 based on the temperature change of each calculation grid 22, and a predetermined pitch taken in the longitudinal direction of the slab 10. The cross-sectional average temperature at each position (for example, 100 to 300 mm pitch) is obtained. Next, the computer 21
Calculates the load applied to the slab 10 by a single sizing process based on the cross-sectional average temperature.
The average cross-sectional temperature of the slab 10 when extracted from the heating furnace 14 is as shown in FIG.
It becomes high at the end faces on both sides in the longitudinal direction. This is because both sides in the longitudinal direction have a larger amount of heat absorption than the other parts. In addition, the reason why the average cross-sectional temperature of the slab 10 is lowered at the portion in contact with the skid, which is a conveying means for the slab 10, is because the skid is water-cooled.

Here, in the sizing press, since a force is applied inward from the width direction to the regions on both sides in the longitudinal direction of the slab 10, the load applied to the slab 10 during the sizing press is as follows:
It is determined from the cross-sectional average temperature of the area where the sizing press is performed. Specifically, the load applied to the slab 10 is determined in consideration of the temperature estimation accuracy of the slab 10 by the computer 21 based on the cross-sectional average temperature in the region P1 surrounded by the broken line in FIG. . Based on the determined load, the sizing press is set.

In the sizing mill, force is applied from the thickness direction and the width direction to the entire longitudinal direction of the slab 10, so that the load applied to the slab 10 during the sizing mill is a cross-sectional average over the entire longitudinal direction of the slab 10. The temperature is determined from the lowest value. Specifically, taking into account the temperature estimation accuracy of the slab 10 by the computer 21, based on the cross-sectional average temperature in the region P2 surrounded by the broken line in FIG. The load applied to the slab 10 is determined. And based on this determined load, the setting of a sizing mill machine is performed.

If the average cross-sectional temperature of the slab 10 is not different from the temperature calculated by the computer 21 and the actual temperature, the temperature of the slab 10 by the computer 21 is set when setting the sizing press machine and the sizing mill machine. There is no need to consider the estimation accuracy.
However, there is actually a difference between the temperature estimated by the computer 21 and the actual temperature. Therefore, when setting the sizing press machine and the sizing mill machine without taking into account the temperature estimation accuracy of the slab 10 by the computer 21, the sizing press machine and the sizing mill machine are
There is a risk of applying a load exceeding the design value.

Therefore, taking into account the temperature estimation accuracy of the slab 10 by the computer 21, a load smaller than the load obtained directly from the estimated average temperature of the cross section of the slab 10 is set as a set target value, and the sizing press machine and the sizing mill machine Settings are made.
The difference between the load obtained directly from the estimated temperature of the cross-sectional average of the slab 10 and the load to be the set target value is as follows:
It can be reduced by increasing the temperature estimation accuracy of the slab 10 by the computer 21, and a large value can be adopted as a load to be a set target value.
And since the efficiency of a sizing press and a sizing mill will go up if the value of a setting target value becomes large, the efficiency of the sizing press and a sizing mill can be improved by making the temperature estimation accuracy of the slab 10 by the computer 21 high.

Therefore, in order to improve the temperature estimation accuracy of the slab 10 by the computer 21 and improve the production efficiency, the temperature distribution of the entire slab 10 calculated by the computer 21 is corrected based on the actually measured value by the radiation thermometer 26. Tried to increase accuracy.
First, the difference between the temperature of the measurement part on the surface of the slab 10 measured by the radiation thermometer 26 and the temperature of the calculation grid 22 of the three-dimensional calculation model 23 corresponding to the measurement part is directly adopted as a correction value, and the computer 21 The calculated temperature distribution of the slab 10 was corrected. Hereinafter, the slab 1 measured with the radiation thermometer 26
The temperature of 0 is also referred to as “measured temperature”, and the temperature of the slab 10 calculated by the computer 21 is also referred to as “estimated temperature”.
Specifically, when the measured temperature of the measurement part on the surface of the slab 10 is 1050 ° C. and the estimated temperature of the calculation grid 22 corresponding to the measurement part is 1000 ° C., the temperature difference between 1050 ° C. and 1000 ° C. is 50 ° C.
Is added to the estimated temperature of each calculation grid 22 of the slab 10 as a correction value, and the temperature distribution of the entire slab 10 is corrected.

However, if the difference between the actually measured temperature on the surface of the slab 10 and the estimated temperature of the calculation grid 22 corresponding thereto is used as it is as a correction value, the correction for the entire three-dimensional calculation model 23 becomes excessive, resulting in the slab by the computer 21 The event that the temperature estimation accuracy of 10 became low was confirmed.
Then, experimental investigation and logical examination are performed in order to find out the reason why the correction to the entire three-dimensional calculation model 23 is excessive, and the surface temperature of the slab 10 accommodated in the heat insulating cover 13 is reheated ( It was found that the main cause is that the difference between the surface temperature and the internal temperature decreases with time.

In response to this examination result, the difference between the measured temperature of the slab 10 surface and the estimated temperature of the slab 10 surface (hereinafter,
The relationship between the actually measured cross-sectional average temperature of the slab 10 and the estimated average cross-sectional temperature of the slab 10 (hereinafter also referred to as “cross-section average temperature difference”) It investigated how it changed according to the accommodation time in the heat insulation cover 13. FIG. The actually measured temperature of the cross-sectional average of the slab 10 can be detected by measuring the temperature of the slab 10 after the slab 10 is left in the heat insulating container until the temperature of the surface and inside becomes uniform.
The result of the investigation is as shown in FIG. 8. When the slab 10 is accommodated in the heat insulating cover 13 for 900 seconds, the sensitivity of the cross-sectional average temperature difference to the surface temperature difference (the cross-sectional average temperature difference is expressed as the surface temperature). The value divided by the difference) is about 0.46, and the sensitivity of the cross-sectional average temperature difference to the surface temperature difference is about 0.79 when the slab 10 is accommodated in the heat insulating cover 13 for 3600 seconds. .
This result was the same for the slab different from the slab 10 and the heat insulation cover different from the heat insulation cover 13.

Next, from the results shown in FIG. 8, the horizontal axis represents the time during which the slab 10 was accommodated in the heat insulation cover 13, the vertical axis represents the sensitivity of the cross-sectional average temperature difference with respect to the surface temperature difference, and the slab 10 was retained by the heat insulation cover 13.
FIG. 9 shows the relationship between the sensitivity of the cross-sectional average temperature difference with respect to the time spent in the container and the surface temperature difference.
Five points shown in the graph of FIG. 9 (accommodating time 0 second, 900 seconds, 1800 seconds, 270
0 seconds, 3600 seconds), the time that the slab 10 has been accommodated in the heat insulating cover 13 is 10
In the case of minutes (600 seconds), the sensitivity of the cross-sectional average temperature difference to the surface temperature difference is estimated to be about 0.35. Therefore, when the time during which the slab 10 is accommodated in the heat insulating cover 13 is 10 minutes, the difference between the measured temperature on the surface of the slab 10 and the estimated temperature on the surface of the slab 10 is used as a correction value as it is. It turns out that it becomes an excessive correction | amendment equivalent to about 3 times of correction | amendment.

Moreover, it can be seen from the graph of FIG. 9 that the sensitivity of the cross-sectional average temperature difference with respect to the surface temperature difference increases with the length of time that the slab 10 has been accommodated in the heat insulating cover 13.
Therefore, in order to appropriately correct the temperature distribution of the entire slab 10 from the actually measured temperature on the surface of the slab 10, it is necessary to increase the value of the correction value according to the accommodation time of the slab 10 in the heat insulating cover 13. .

By the way, the slab 10 is cut by the CC cutter 12 and inserted into the heat insulating cover 13 while moving in the longitudinal direction of the slab 10, but the moving speed of the slab 10 is before and after being cut by the CC cutter 12. Is different. Specifically, the slab 10 moves at a casting speed until it is cut by the CC cutter 12, and the moving speed after being cut by the CC cutter 12 is faster than that before being cut by the CC cutter 12.
When the slab 10 is cut by the CC cutter 12, a part of the slab 10 is inserted into the heat insulating cover 13.
Therefore, the time accommodated in the heat insulation cover 13 differs in the position where the longitudinal direction of the slab 10 differs, and the difference of the surface temperature and cross-section average temperature of the slab 10 differs.

In the present embodiment, in consideration of the difference between the surface temperature of the slab 10 and the average cross-sectional temperature in the longitudinal direction of the slab 10, the surface temperature is changed by the radiation thermometer 26 at different positions in the longitudinal direction of the slab 10. It is decided to provide a measurement unit that measures
Then, when the slab 10 moves from the heat insulating cover 13 to the heating furnace 14, the surface temperature is actually measured by the radiation thermometer 26 with respect to a plurality of measurement parts of the slab 10, and each measured value is calculated and obtained. The temperature of each calculation grid is corrected based on a plurality of correction values (that is, the temperature distribution of the entire slab 10 is corrected).
To do. Therefore, it is necessary to obtain an adjustment value for adjusting the correction value for each measurement unit (that is, the sensitivity of the cross-sectional average temperature difference with respect to the surface temperature difference).

From the five points indicated in the graph of FIG. 9, the inventor of the present application shows that the sensitivity of the cross-sectional average temperature difference with respect to the surface temperature difference is the length of time that the slab 10 is accommodated in the heat insulating cover 13. We noticed that it is approaching 1 exponentially depending on.
Then, the condition that the adjustment value becomes larger in accordance with the accommodation time in the heat insulating cover 13 of the measurement unit, is a value greater than 0 and less than 1, and the slab 10 is adopted by adopting the adjustment value that satisfies these two conditions. It was verified whether the temperature estimation accuracy could be improved. The reason why the adjustment value does not include 0 is because it is assumed that the measurement unit is necessarily accommodated in the heat insulating cover 13.
The verification will be described below.

The temperature distribution of the entire slab 10 was corrected through the following steps (1) to (4).
(1) When the slab 10 cut into a predetermined dimension through continuous casting and accommodated in the heat insulating cover 13 moves into the heating furnace 14, the temperature of the surface of the slab 10 is measured for each measurement part of the slab 10 as a radiation temperature. Total 2
(2) At the timing when the slab 10 moves from the heat insulating cover 13 into the heating furnace 14, the computer 21
For the three-dimensional calculation model 23 calculated by (1), the temperature of the calculation grid 22 corresponding (arranged) to each measurement unit is obtained.

(3) For each measurement part, a correction value is calculated by multiplying the difference between the measured temperature of the surface of the slab 10 and the temperature of the calculation grid 22 corresponding to the measured temperature. (4) Based on the calculated plurality of correction values. Then, a value for correcting the temperature of each calculation grid 22 (that is, a value to be added to or subtracted from the calculation grid 22 in the longitudinal direction of the slab 10) is obtained, and the corrected slab 1 is corrected.
Get the temperature distribution of the entire zero

However, the adjustment value of the above (3) increases according to the length of time that the measurement unit has been accommodated in the heat insulating cover 13, and is a value exceeding 0 and less than 1.
The temperature distribution of the entire slab 10 after correction obtained as a result is a case where no adjustment value is introduced (that is,
It was confirmed that the temperature estimation accuracy of the slab 10 is higher than that in the case where the adjustment value is 1.

Further, when the adjustment value is set to a specific value exceeding 0 and less than 1, and within a range where the adjustment value exceeds 0 and less than 1, the measurement unit is changed according to the length of time that the measurement cover is accommodated in the heat insulating cover 13. In some cases, it was also confirmed that the accuracy of estimating the temperature of the slab 10 is higher when the adjustment value is changed according to the housing time in the heat insulating cover 13 of the measurement unit.
Therefore, the temperature estimation accuracy of the slab 10 is reliably ensured by satisfying the point that the adjustment value becomes larger according to the housing time in the heat insulating cover 13 of the measurement unit and the adjustment value is a value exceeding 0 and less than 1. It has been proven to improve.

Next, based on the five points of sensitivity (cross-sectional average temperature difference / surface temperature difference) with respect to each accommodation time shown in the graph of FIG. 9, an equation representing a curve connecting these five points is calculated. Attempted to obtain an adjustment value.
An equation for calculating a temperature change with time in a concentrated heat capacity system in which a temperature change occurs at a constant heat transfer coefficient is an equation representing a curve connecting five points in the graph of FIG. 9, that is, an equation for obtaining a theoretical solution of an adjustment value. Therefore, an equation to obtain the theoretical solution of the adjustment value was derived based on the equation of the concentrated heat capacity system.

Specifically, the fitting parameters a and b in Equation 1 were determined so that the following Equation 1 obtained by modifying the equation of the concentrated heat capacity system becomes a curve connecting five points in the graph of FIG. .
r = 1−exp (a × t ^ b) Equation 1
However, r is an adjustment value, and t is the time during which the measurement unit is accommodated in the heat insulating cover 13.

Then, by setting a = −6.77e−3 and b = 0.66, it has been found that Equation 1 matches a curve connecting five points in the graph of FIG.
In response to this, the temperature difference of the slab 10 by the computer 21 is estimated by multiplying the difference between the actually measured temperature of the surface of the slab 10 and the temperature of the calculation grid 22 corresponding thereto by an adjustment value obtained from the following equation (2). An experiment was conducted as to whether a correction value that increases the accuracy can be calculated. As a result, it was confirmed that the temperature estimation accuracy of the slab 10 was significantly improved as compared with the case where the adjustment value was not adopted.
r = 1−exp ((− 6.77e−3) × t ^ 0.66) Equation 2

In addition, a is (−6.77e−3) × 1.1 or more (−6.77e−3) × 0.
If the value is in the range of 9 or less and b is a value in the range of 0.66 × 0.9 or more and 0.66 × 1.1 or less, the temperature estimation accuracy of the slab 10 may be significantly improved. I found out that I can do it. This variation in a and b is considered to be caused by variation in the heat dissipation rate due to the measurement accuracy by the radiation thermometer 26 and the scale condition of the surface layer of the cast slab 10.
From the above logical examination and experimental examination, a is (−6.77e−3) × 1.1 or more (−6
. 77e-3) x 0.9 or less, b is 0.66 x 0.9 or more and 0.66 x 1.1 or less, and 1-exp (a x t ^ b) is an adjustment value. Thus, it was found that the temperature estimation accuracy of the slab 10 can be reliably increased as compared with the case where the adjustment value is not adopted.

Next, examples carried out for confirming the effects of the present invention will be described.
About the slab 10 when moving from the heat insulating cover 13 to the heating furnace 14 under the conditions described below,
The load applied to the slab 10 in the sizing process was determined.
Condition 1) The difference between the cross-sectional average temperature of the slab 10 calculated by the computer 21 and the actually measured temperature is used as a correction value as it is (that is, no adjustment value is introduced).
Condition 2) The correction value is obtained by introducing the concept of the adjustment value. Note that the adjustment value (r) is a = −6.7 in the calculation formula of r = 1−exp (a × t ^ b).
7e-3, b = 0.66.

Under each condition, a value (hereinafter, referred to as a load) applied to the slab 10 in the sizing process based on the estimated average cross-sectional temperature of the slab 10 calculated by the computer 21 for the slab 10 extracted from the heating furnace 14 The value of the load actually applied to the slab 10 in the sizing process (hereinafter also referred to as “measured load”) was compared.
Here, the sizing press machine and the sizing mill machine are set based on the estimated average temperature of the cross section of the slab 10.
The results are shown in FIGS. 10A, 10B, 11A, and 11B.

In FIGS. 10A, 10B, 11A, and 11B, the horizontal axis indicates the predicted load, and the vertical axis indicates the actually measured load. When the actual load of the slab 10 with the predicted load of 10MN is 9MN, the slab 10 is (10MN) on the graphs of FIGS. 10A, 10B, 11A, and 11B.
, 9MN).
The actual load is obtained by measuring the load applied to the sizing press machine and the sizing mill machine.

10A and 10B show variations in predicted load and actual load in the sizing press, and FIGS. 11A and 11B show variations in predicted load and actual load in the sizing mill.
FIG. 10A and FIG. 11A show the results for Condition 1, and FIG. 10B and FIG.
1 (B) shows the result for Condition 2.

10A and 11A, when the adjustment value was not introduced, the variation between the predicted load and the actually measured load was about ± 30% at the maximum.
On the other hand, when the adjustment value was introduced, as shown in FIGS. 10B and 11B, the variation between the predicted load and the actual load was reduced to about ± 20% at the maximum.
The reduction in the variation between the predicted load and the actually measured load means an improvement in the temperature estimation accuracy of the slab 10 by the computer 21. Therefore, by introducing an adjustment value, a standard for setting the sizing press machine and the sizing mill machine It was found that a large value can be adopted as the set target value and the production efficiency can be increased.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and all changes in conditions and the like that do not depart from the gist are within the scope of the present invention.
For example, if the casting conditions and the heat dissipation conditions are uniform in the longitudinal direction of the slab, one measuring unit may be provided on the slab.

10: slab, 11: continuous casting machine, 12: CC cutter, 13: heat insulation cover, 14: heating furnace, 15: combustion burner, 16: heating zone, 17: soaking zone, 18: thermometer, 19: first Row of 2
0: second row, 21: calculator, 22: calculation grid, 23: three-dimensional calculation model, 24: nozzle, 25: roll, 26: radiation thermometer, 27: interface

Claims (5)

In the slab temperature estimation method for deriving the temperature of the slab inserted into the heating furnace after being cut into a predetermined dimension through continuous casting and housed in a heat insulation cover,
Obtain a three-dimensional calculation model in which a plurality of calculation grids are arranged in the longitudinal direction, the width direction and the thickness direction for the slab, and calculate the temperature of each calculation grid from the operation results of continuous casting to obtain the temperature distribution of the entire slab A first step for obtaining
When the slab moves from the heat insulation cover to the heating furnace, an adjustment value is set for the difference between the temperature obtained by measuring the temperature of the measurement part on the surface of the slab and the temperature of the calculation grid corresponding to the measurement part. A second step of multiplying to calculate a correction value;
A third step of correcting the temperature of each calculation grid based on the correction value;
For the slab in progress in the heating furnace, the amount of heat input to the slab is calculated from the temperature in the heating furnace, the temperature change of each calculation grid is obtained, and when extracted from the heating furnace A fourth step of estimating the temperature distribution of the entire slab,
The slab characterized in that the adjustment value increases according to the length of time during which the measuring unit that has measured the temperature is accommodated in the heat insulating cover, and is a value that is greater than 0 and less than 1. Temperature estimation method. 2. The temperature estimation method for a slab according to claim 1, wherein r is the adjustment value, and r is the following equation (1).
The temperature estimation method of the slab characterized by being calculated by the following.
r = 1−exp (a × t ^ b) Equation 1
here,
t is the time during which the measurement unit is accommodated in the heat insulation cover,
a is a value of (−6.77e−3) × 1.1 or more and (−6.77e−3) × 0.9 or less,
b is a value of 0.66 × 0.9 or more and 0.66 × 1.1 or less. 3. The temperature estimation method for a slab according to claim 1, wherein a plurality of the measurement units are provided at different positions in the longitudinal direction of the slab, and the adjustment value is calculated for each of the measurement units to calculate a plurality of the correction values. And correcting the temperature of each calculation grid based on the plurality of correction values. The temperature estimation method of the slab of any one of Claims 1-3 WHEREIN: The said slab is advanced in the state in which the longitudinal direction followed the width direction of this heating furnace in the said heating furnace, This heating furnace Is divided into a plurality of furnace zones along the direction of travel of the slab, and a plurality of thermometers are respectively disposed at different positions in the width direction of the heating furnace in the plurality of furnace zones. A method for estimating the temperature of a slab, comprising calculating a heat input to the slab based on a measured temperature. The slab temperature estimation method according to any one of claims 1 to 4, wherein the temperature of the measurement unit is measured by a radiation thermometer.

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