JP2015167956A - Breakout prediction method in continuous casting facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably perform an early and high-accuracy breakout prediction even when an upper/lower temperature difference is reduced rapidly by a difference between casting states.SOLUTION: The breakout prediction method performs the steps of: determining whether or not a temperature difference at a current time point obtained by subtracting a lower stage temperature from an upper stage temperature at a current sampling time point is equal to a predetermined value α or more; then subtracting a temperature difference at a previous time point, obtained by subtracting a lower stage temperature from an upper stage temperature at a previous sampling time point before a predetermined sampling cycle from the current sampling time point, from the temperature difference at the current time point; dividing the difference obtained by the subtraction by the predetermined sampling cycle; dividing the difference obtained by the division by the temperature difference at the current time point when the temperature difference at the current time point is equal to the predetermined value α or more; calculating an estimated value DTr obtained by dividing the value obtained by the division by the predetermined value α when the temperature difference at the current time point is less than the predetermined value α; and then outputting prediction of subsequent occurrence of breakout BO when the estimated value DTr is equal to a breakout threshold BOth or less.

Description

  The present invention measures the internal temperature below the molten metal surface of the casting mold for continuous casting, and the upstream upper temperature and the downstream lower temperature in the slab drawing direction in time series at predetermined sampling periods. The present invention relates to a breakout prediction method in a continuous casting facility that detects occurrence of slab breakage inside a mold based on the upper stage temperature and the lower stage temperature.

  Conventionally, a constraining breakout has occurred in continuous casting operations of steel. This constraining breakout occurs when the molten steel adheres to the inner surface of the mold due to a change in the inflow state of the mold powder or a rapid change in the molten metal surface level, and when the slab is pulled out as it is, the solidified shell moves from the inner surface to the outer surface. A continuous fracture portion is generated, and a fracture portion grows as the slab is pulled out. The molten steel leaks when the grown fracture portion comes out from the lower end of the mold.

  As a technique for predicting such a constraining breakout, for example, there is a breakout prediction method in continuous casting described in Patent Document 1. In this Patent Document 1, the temperature inside the mold is measured in time series by two upper and lower thermocouples under the meniscus, and the upper and lower temperature differences detected by the upper and lower two thermocouples at an arbitrary time, A ratio with the temperature difference between the upper and lower temperatures after the calculation cycle is calculated, and the occurrence of a restrictive breakout is predicted using the value of this ratio.

JP 2009-2441099 A

  However, since the breakout is predicted using the ratio of the upper and lower temperature difference in the one described in Patent Document 1, the upper and lower temperature difference corresponding to the denominator of the ratio corresponds to the numerator of the ratio due to the difference in the casting state or the like. When there is a change that is very small compared to the upper and lower temperature difference, there is a problem that the ratio of the upper and lower temperature difference becomes extremely large and erroneous detection of breakout prediction occurs.

  The present invention has been made in view of the above, and it is possible to stably and quickly perform a breakout prediction with high accuracy even when the temperature difference between the top and bottom is rapidly reduced due to a difference in the casting state or the like. It is an object of the present invention to provide a breakout prediction method in a continuous casting facility.

  In order to solve the above problems and achieve the object, a breakout prediction method in a continuous casting facility according to the present invention is an internal temperature below a molten metal surface of a casting mold for continuous casting, and is upstream of a slab drawing direction. A breakout prediction method that detects the occurrence of slab breakage inside the mold based on the upper stage temperature and the lower stage temperature by measuring the upper stage temperature on the side and the lower stage temperature on the downstream side in a time-series manner at a predetermined sampling period. A determination step of determining whether or not a current temperature difference obtained by subtracting a lower temperature from an upper temperature at a current sampling time is equal to or greater than a predetermined value; and a pre-sampling before the predetermined sampling period from the current sampling time based on the current temperature difference Subtract the temperature difference before the point where the lower stage temperature was subtracted from the upper stage temperature at the time point, divide the subtracted difference by the predetermined sampling period, If the temperature difference is greater than or equal to the predetermined value, the divided value is divided by the current temperature difference. If the current temperature difference is less than the predetermined value, an evaluation value is calculated by dividing the divided value by the predetermined value. An evaluation value calculating step, and an output step of outputting that the slab rupture will occur thereafter when the evaluation value falls below a predetermined breakout threshold.

  In the breakout prediction method in the continuous casting equipment according to the present invention, in the above invention, the predetermined value is based on a temperature difference between the upper stage temperature and the lower stage temperature when the continuous casting operation is in a steady state. It is a determined value.

  Further, the breakout prediction method in the continuous casting equipment according to the present invention, in the above invention, integrates an evaluation value that satisfies the predetermined integration start threshold value or less when the evaluation value is equal to or lower than the predetermined integration start threshold value. An integration step of calculating the integrated value, wherein the output step outputs that the slab rupture will subsequently occur when the integrated value within a predetermined period falls below a predetermined integration threshold. To do.

  The breakout prediction method for a continuous casting facility according to the present invention is characterized in that, in the above invention, the predetermined integration start threshold is the breakout threshold.

  The breakout prediction method for a continuous casting facility according to the present invention is characterized in that, in the above invention, the predetermined value is a value exceeding 10 ° C.

  The breakout prediction method for a continuous casting facility according to the present invention is characterized in that, in the above invention, the predetermined integration start threshold is a value less than zero.

  The breakout prediction method for a continuous casting facility according to the present invention is characterized in that, in the above invention, the predetermined integration threshold is a value less than zero.

  In the breakout prediction method in the continuous casting equipment according to the present invention, in the above invention, the predetermined value is individually determined for each pair of the upper thermocouple for detecting the upper temperature and the lower thermocouple for detecting the lower temperature. It is characterized by setting.

  According to the present invention, from the current temperature difference, the previous time point temperature difference at the previous sampling time point before the predetermined sampling period from the current sampling time point is subtracted, and the subtracted difference is divided by the predetermined sampling period. If the value is equal to or greater than the value, the divided value is divided by the current temperature difference. If the current temperature difference is less than the predetermined value, an evaluation value is calculated by dividing the divided value by the predetermined value. Is output when the slab breakage occurs after the threshold value falls below the predetermined breakout threshold, so even if the temperature difference between the top and bottom is drastically reduced due to differences in casting conditions, etc. Thus, breakout prediction can be performed early and with high accuracy.

FIG. 1 is a schematic diagram showing a schematic configuration of a continuous casting facility according to Embodiment 1 of the present invention. FIG. 2 is a perspective view showing a schematic configuration of a mold of a continuous casting facility. FIG. 3 is a cross-sectional view of the mold. FIG. 4 is a flowchart showing a breakout prediction processing procedure of the first embodiment by the controller. FIG. 5 is an explanatory diagram illustrating a temperature difference calculation process associated with a temperature change between the upper temperature detected by the upper thermocouple and the lower temperature detected by the lower thermocouple. FIG. 6 is a diagram showing the relationship between the temperature change between the upper stage temperature and the lower stage temperature and the evaluation value calculated based on this temperature change. FIG. 7 is a diagram showing a change with time of an evaluation value in which the first embodiment is applied to a change in temperature of molds having different steady states. FIG. 8 is a diagram for comparing the time variation of the evaluation values according to the prior art and the first embodiment. FIG. 9 is a flowchart showing a breakout prediction processing procedure of the second embodiment by the controller. FIG. 10 is an explanatory diagram for explaining an integral value calculation process accompanying a temperature change between the upper stage temperature detected by the upper stage thermocouple and the lower stage temperature detected by the lower stage thermocouple.

  Hereinafter, a breakout prediction method in a continuous casting facility according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
First, with reference to FIGS. 1-3, the continuous casting installation to which the breakout prediction method in the continuous casting installation which is Embodiment 1 of this invention is applied is demonstrated.

[Continuous casting equipment]
FIG. 1 is a schematic diagram showing a schematic configuration of a continuous casting facility according to Embodiment 1 of the present invention. FIG. 2 is a perspective view showing a schematic configuration of a mold of a continuous casting facility. FIG. 3 is a cross-sectional view of the mold. As shown in FIG. 1, the continuous casting equipment 1 mainly includes a tundish 11, a sliding nozzle mechanism 12, an immersion nozzle 13, a mold 14, a roll group 17, a controller 2, and an input / output unit 3. The mold 14 is provided with an upper thermocouple 31 and a lower thermocouple 32 as temperature sensors.

  In continuous casting, molten steel M is supplied to the tundish 11 from a ladle (not shown). The molten steel M is supplied into the mold 14 through the sliding nozzle mechanism 12 and the immersion nozzle 13. The molten steel M in the mold 14 is cooled by the mold 14 to form the solidified shell 20, and the slab 42 is formed. The roller group 17 provided at the lower part of the mold 14 guides the cast piece 42 in the drawing direction and pulls out the cast piece 42 to perform continuous casting of the cast piece 42.

  The tundish 11 is a bottomed container in which a lining made of a refractory is formed, and a pouring hole is provided in the bottomed portion. The sliding nozzle mechanism 12 has a nozzle that communicates with the pouring hole, and adjusts the discharge amount of the molten steel M from the pouring hole by adjusting the nozzle opening degree under the control of the controller 2. The immersion nozzle 13 has a substantially cylindrical shape, the upper end is connected to the nozzle of the sliding nozzle mechanism 12, the lower end is inserted into the mold 14, and is immersed under the molten metal surface in the mold 14.

  An eddy current sensor 25 is provided inside the mold 14 and on the upper surface of the molten steel M. The eddy current sensor 25 outputs the hot water level to the controller 2. The powder supply pipe 26 supplies mold powder supplied from a powder supply device (not shown) onto the molten steel M surface. The mold powder covers the molten metal surface, prevents oxidation of the molten steel M and temperature decrease, and becomes a molten state and functions as a lubricant between the slab 42 and the inner wall surface of the mold 14. The drawing resistance of the slab 42 is reduced.

  The controller 2 adjusts the nozzle opening degree of the sliding nozzle mechanism 12 in accordance with changes in the molten metal level of the mold 14 and the drawing speed of the slab 42, thereby supplying the molten steel M from the tundish 11 into the mold 14. To adjust the hot water level within a predetermined range.

  On the downstream side of the mold 14, the roll group 17 is arranged along the drawing direction A of the slab 42. The roll group 17 includes a support roll, a guide roll, and a pinch roll. The support roll guides in the drawing direction A while pressing the short side portion and the long side portion of the slab 42. The bulging of the slab 42 is prevented by the pressure contact of the support roll. The guide roll guides the slab 42 in the drawing direction A while maintaining a predetermined radius of curvature. The pinch roll moves the cast piece 42 in the drawing direction A at a predetermined drawing speed by rotating while pressing the cast piece 42 under the control of the controller 2. A spray nozzle group for cooling the slab 42 is arranged in accordance with the position of the roll group 17, and cooling control is performed.

  Here, as shown in FIG. 2, the mold 14 includes a pair of long side cooling plates 15 and a pair of short side cooling plates 16, and is formed in a substantially rectangular tube shape penetrating in the vertical direction. Inside the long side cooling plate 15 and the short side cooling plate 16, a cooling water channel (not shown) is formed along the inner wall surface, and the molten steel M is cooled by circulating the cooling water through the cooling water channel. The molten steel M supplied to the inside of the mold 14 is cooled by the long side cooling plate 15 and the short side cooling plate 16. At this time, the molten steel M is solidified along the inner wall surface of the mold 14 and the solidified shell 20 is formed. In general, the thickness of the solidified shell 20 increases in the drawing direction A.

  A plurality of upper thermocouples 31 and lower thermocouples 32 are embedded in the long side cooling plate 15 and the short side cooling plate 16, respectively. As shown in FIG. 3, the upper thermocouple 31 is arranged on the upstream side in the drawing direction A, and the lower thermocouple 32 is arranged on the downstream side in the drawing direction A. A plurality of upper thermocouples 31 and lower thermocouples 32 are arranged in the horizontal direction. Moreover, the upper stage thermocouple 31 and the lower stage thermocouple 32 are arranged in the vicinity of the position where the solidified shell 20 starts to form, that is, the position close to the molten metal surface, as shown in FIG.

  Here, in the mold 14, the solidified shell 20 is prevented from being baked on the inner wall surface of the mold 14 by the lubricating action of the mold powder in a molten state, and the pulling resistance of the solidified shell 20 is reduced. When an abnormality occurs in the lubrication action due to the insufficient inflow of the mold powder or the like, the molten steel M is seized on the inner wall surface of the mold 14, and the molten steel M is solidified by cooling in this state and is restrained in the mold 14. . On the other hand, since the slab 42 moves in the drawing direction A at a predetermined drawing speed except for this seized part, the seized part moves at a slower speed than the other parts due to seizure restraint. As a result, as shown in FIG. 1, a reverse solidified shell 20a having a thickness opposite to that of the normal solidified shell 20 in the drawing direction A is formed at the top of the seizure portion. The break portion 21 is formed at the boundary portion with the No. 20, and a breakout BO in which the molten steel M flows out of the slab 42 is generated.

  Based on the upper temperature detected by the upper thermocouple 31 and the lower temperature detected by the lower thermocouple 32, the controller 2 performs the breakout prediction processing for predicting the occurrence of the breakout, and the breakout occurs. The alarm is output through the input / output unit 3 at an early stage before the breakout occurs, and further, the breakout response processing is controlled. In the breakout handling process, the drawing speed of the slab 42 is reduced or stopped, and the molten steel M at the fracture portion is resolidified in the mold 14 to form a solidified shell having a sufficient thickness. It is to resume the extraction of the piece 42. If a breakout occurs, in order to stop the operation of the continuous casting facility 1 and then recover it, the removal of a large amount of metal solidified by the molten steel M and the replacement work of rolls to which the metal has adhered Therefore, the productivity and yield of the continuous casting facility 1 are greatly reduced.

[Breakout prediction process]
Next, breakout prediction processing by the controller 2 will be described with reference to FIGS. FIG. 4 is a flowchart showing the breakout prediction processing procedure of the first embodiment by the controller 2. FIG. 5 is an explanatory diagram for explaining a temperature difference calculation process associated with a temperature change between the upper temperature detected by the upper thermocouple 31 and the lower temperature detected by the lower thermocouple 32. FIG. 6 is a diagram showing the relationship between the temperature change between the upper stage temperature and the lower stage temperature and the evaluation value calculated based on this temperature change.

  First, as shown in FIG. 5, the controller 2 acquires the upper stage temperature TU0 and the lower stage temperature TD0, and calculates a temperature difference ΔT0 obtained by subtracting the lower stage temperature TD0 from the upper stage temperature TU0 (step S101). Thereafter, the controller 2 determines whether or not a sampling period (predetermined time) Δt has elapsed (step S102). When the sampling period Δt has not elapsed (step S102, No), this determination process is repeated. When the sampling period Δt has elapsed (step S102, Yes), as shown in FIG. The upper stage temperature TU1 and the lower stage temperature TD1 at (current sampling time t1) are acquired, and a temperature difference ΔT1 obtained by subtracting the lower stage temperature TD1 from the upper stage TU1 is calculated (step S103).

  Thereafter, the controller 2 determines whether or not the temperature difference ΔT1 is greater than or equal to a predetermined value α (step S104). If the temperature difference ΔT1 is equal to or greater than the predetermined value α (step S104, Yes), the evaluation temperature DTs = temperature difference ΔT1 is set (step S105), and if the temperature difference ΔT1 is not equal to or greater than the predetermined value α (step) In S104, No), the evaluation temperature DTs is set to a predetermined value α (step S106). Thereafter, the evaluation value DTr = (ΔT1−ΔT0) / Δt / DTs is calculated using the set evaluation temperature DTs (step S107). As shown in FIG. 6, the predetermined value α is a value determined based on the temperature difference ΔT between the upper stage temperature and the lower stage temperature when the continuous casting operation is in the steady state E. Here, the temperature difference ΔT = 50 ° C. is determined as the predetermined value α.

  Thereafter, the controller 2 determines whether or not the evaluation value DTr is equal to or less than the breakout threshold BOth (see FIG. 6) (step S108). When the evaluation value DTr is equal to or less than the breakout threshold BOth (step S108, Yes), a breakout is expected to occur. Therefore, an alarm is output and the pulling speed is obtained by manual intervention by the operator or automatic control by the controller 2 itself. A breakout occurrence corresponding process such as lowering or stopping is performed (step S109), the temperature difference ΔT1 is further replaced with a temperature difference ΔT0 (step S110), the process proceeds to step S102, and a process at the next sampling time is performed. On the other hand, if the evaluation value DTr is not less than or equal to the breakout threshold BOth (No in step S108), the temperature difference ΔT1 is replaced with the temperature difference ΔT0 (step S110), and the process proceeds to step S102, and at the next sampling time point. Perform the process.

  For example, as shown in the upper part of FIG. 6, the upper temperature time change curve LU and the lower temperature time change curve LD generally intersect before the time point tb when the breakout BO occurs, and the above-described fracture portion 21 is generated. A breakout BO occurs at time tb when the part 21 comes out of the mold 14. The lower part of FIG. 6 shows the time change of the evaluation value DTr when the sampling period Δt = 1 second. The evaluation value DTr becomes equal to or less than the breakout threshold BOth (= −0.15) at time ts, and the controller 2 performs breakout occurrence response processing such as outputting an alarm from the input / output unit 3 at this time ts.

  In the first embodiment, as shown in FIG. 6, the temperature difference ΔT in the steady state E where the temperature difference between the upper and lower sides is almost constant is set as the predetermined value α, and the current temperature difference ΔT1 is less than the predetermined value α. Since the evaluation value DTr is corrected so as to calculate the evaluation value DTr obtained by dividing the value of (ΔT1−ΔT0) / Δt by a constant value α when the value becomes smaller, the evaluation value DTr does not become extremely large. In addition, the vicinity of the peak value of the evaluation value DTr can be suppressed, and a stable and highly accurate breakout prediction process can be performed. The predetermined value α is not limited to the temperature difference ΔT in the steady state E.

  If the current temperature difference ΔT1 is equal to or greater than the predetermined value α, the predetermined value α is set to the current temperature difference ΔT1, and therefore the evaluation value DTr can be normalized regardless of the magnitude of the temperature difference ΔT. Even if the temperature difference ΔT in the steady state varies depending on the setting state of the continuous casting equipment including the upper stage thermocouple 31 and the lower stage thermocouple 32 and the continuous casting object, the breakout threshold value BOth can be shared.

  For example, in each upper stage of FIGS. 7A to 7C, the temperature differences ΔTa, ΔTb, ΔTc in the steady state have a magnitude relationship of ΔTa> ΔTb> ΔTc. Conventionally, as shown in the lower part of FIGS. 7A to 7C, the time change of the temperature difference ΔT, that is, DT / dt = (ΔT1−ΔT0) / dt is used as the evaluation value for the breakout prediction. The values of the characteristic curves La, Lb, and Lc of the respective evaluation values, particularly, the characteristics in the vicinity of the downward convex peak before the occurrence of the breakout BO were different. For this reason, the breakout threshold value BOth cannot be determined uniformly, and it is unavoidable that the breakout prediction process has a large variation. Further, when the time change of the temperature difference ΔT suddenly decreases, the evaluation value has a large peak value that is convex downward.

  In the first embodiment, for example, when the current temperature difference ΔT1 is equal to or lower than the steady-state temperature difference ΔT (ΔTa, ΔTb, ΔTc), (DT / dt) is changed to the temperature difference ΔT (ΔTa, ΔTb, ΔTc). Therefore, the normalized evaluation value DTr can be obtained even if the temperature differences ΔT (ΔTa, ΔTb, ΔTc) in the steady state are different. That is, normalization is performed by dividing by a large value (current temperature difference ΔT) when the temperature difference ΔT is large and by dividing by a small value (current temperature difference ΔT) when the temperature difference ΔT is small.

  Further, when the temperature difference ΔT1 is less than the predetermined value α, the evaluation temperature DTs is corrected to be set to the predetermined value α, which is a constant value. Even if the temperature difference ΔT1 is less than the predetermined value α, the characteristics of the evaluation value DTr can be normalized. Therefore, a common breakout threshold BOth can be set, and stable and highly accurate breakout prediction can be performed at an early stage. Further, since such normalization can be performed, the time from the breakout prediction time to the breakout time can be accurately estimated.

  FIG. 8A shows an example of evaluation value time variation when the conventional (DT / dt) is used as an evaluation value, and FIG. 8B shows the same upper stage temperature time change as FIG. 8A. 6 shows an example of evaluation value time fluctuation when the evaluation value DTr of Embodiment 1 is applied to the curve LU and the lower temperature change curve LD. The curve LM shows the change over time of the molten metal surface level fluctuation. In the evaluation value time variation characteristic L1 shown in FIG. 8A, a large peak value is exhibited in the region N corresponding to the time variation of the molten metal surface fluctuation level, but the embodiment shown in FIG. In the evaluation value time variation characteristic L2 by 1, a large peak value does not appear even when the temperature time change characteristic is the same as that in FIG. 8A, and stable breakout prediction can be performed.

  Further, the predetermined value α is preferably 10 ° C. or more based on empirical values for various continuous casting equipment or various continuous casting objects. The predetermined value α is more preferably 30 ° C. or higher. The predetermined value α is not limited to the temperature difference ΔT between the upper stage temperature and the lower stage temperature in the steady state E of the continuous casting equipment, and can be a value unique to the continuous casting equipment or the object of continuous casting.

  The upper stage temperature TU0 and the lower stage temperature TD0 acquired by the controller 2 are the temperatures of the pair of the upper stage thermocouple 31 and the lower stage thermocouple 32 along the drawing direction A. A plurality of upper thermocouples 31 and lower thermocouples 32 are arranged in the horizontal direction, but it is preferable to perform breakout prediction processing for each pair.

  Further, the controller 2 acquires the upper stage temperature and the lower stage temperature every predetermined fixed sampling period Δt, but may be a variable sampling period. The variable sampling period is preferably shortened as the difference between the temperature difference ΔT0 and the temperature difference ΔT1 increases.

(Embodiment 2)
In the second embodiment, even when an uncertain state occurs in which the evaluation value increases momentarily and falls below the breakout threshold BOth, such as noise, the breakout can be reliably predicted. The evaluation value DTr that is equal to or less than the breakout start threshold value β corresponding to the breakout threshold value BOth is integrated so that the breakout is predicted when the integrated value IDT becomes the integration threshold value γ.

  Here, a breakout prediction process by the controller 2 according to the second embodiment will be described with reference to FIGS. FIG. 9 is a flowchart showing a breakout prediction processing procedure of the second embodiment by the controller 2.

  First, similarly to the first embodiment, the controller 2 acquires the upper stage temperature TU0 and the lower stage temperature TD0, and calculates a temperature difference ΔT0 obtained by subtracting the lower stage temperature TD0 from the upper stage temperature TU0 (step S201). Thereafter, the integral value IDT = 0 is set (step S202). Thereafter, it is determined whether or not a sampling period (predetermined time) Δt has elapsed (step S203). If the sampling period Δt has not elapsed (step S203, No), this determination process is repeated. If the sampling period Δt has elapsed (step S203, Yes), the sampling time (current sampling time) is reached. The upper stage temperature TU1 and the lower stage temperature TD1 are acquired, and a temperature difference ΔT1 obtained by subtracting the lower stage temperature TD1 from the upper stage TU1 is calculated (step S204).

  Thereafter, it is determined whether or not the temperature difference ΔT1 is greater than or equal to a predetermined value α (step S205). If the temperature difference ΔT1 is equal to or larger than the predetermined value α (step S205, Yes), the evaluation temperature DTs = temperature difference ΔT1 is set (step S206), and if the temperature difference ΔT1 is not equal to or larger than the predetermined value α (step) In S206, No), the evaluation temperature DTs is set to the predetermined value α (step S207). Thereafter, the evaluation value DTr = (ΔT1−ΔT0) / Δt / DTs is calculated using the set evaluation temperature DTs (step S208). As shown in FIG. 6, the predetermined value α is a value determined based on the temperature difference ΔT between the upper stage temperature and the lower stage temperature when the continuous casting operation is in the steady state E. Here, the temperature difference ΔT = 50 ° C. is determined as the predetermined value α.

  Thereafter, the controller 2 determines whether or not the evaluation value DTr is equal to or less than the integration start threshold value β (step S209). If the evaluation value DTr is equal to or less than the integration start threshold β (step S209, Yes), an integration process for adding the evaluation value DTr to the integration value IDT is performed (step S210), and the process proceeds to step S211. On the other hand, if the evaluation value DTr is not less than or equal to the integration start threshold value β (step S209, No), the process proceeds to step S211 as it is.

  In step S211, it is determined whether or not the integral value IDT has become equal to or less than the integral threshold value β (step S211). When the integration value IDT is less than or equal to the integration threshold β (step S211, Yes), the occurrence of a breakout is expected, so an alarm is output and the pulling speed is controlled by manual intervention by the operator or automatic control by the controller 2 itself. Breakout occurrence handling processing such as reduction or stop is performed (step S212), and the temperature difference ΔT1 is replaced with the temperature difference ΔT0 (step S213). On the other hand, if the integral value IDT is not less than or equal to the integral threshold β (step S211, No), the temperature difference ΔT1 is replaced with the temperature difference ΔT0 as it is (step S213). Thereafter, it is determined whether or not a predetermined time TP has elapsed since the first integration start threshold value β was exceeded (step S214). If the predetermined time TP has not elapsed (step S214, No), the process proceeds to step S203, and the integration process of the integration value IDT described above is continued. On the other hand, if the predetermined time TP has elapsed (step S214, Yes), the process proceeds to step S202, the integral value IDT is cleared to 0, and an integration process of a new integral value IDT is performed.

  For example, the lower part of FIG. 10 corresponding to FIG. 6 shows the time change of the evaluation value DTr when the sampling period Δt = 1 second. Then, the evaluation value DTr is integrated from the time point ts that is first less than or equal to the integration start threshold value β, and the integration value IDT (shaded portion) obtained by integrating the evaluation value DTr that is equal to or less than the integration start threshold value β is equal to or less than the integration threshold value γ. At time td, the controller 2 performs a breakout occurrence handling process such as outputting an alarm from the input / output unit 3.

  The integration start threshold value β may be the same as the breakout threshold value BOth. Further, the integration start threshold value β is preferably smaller than the breakout threshold value BOth (positioned on the upper side in FIG. 10). Further, the integration threshold β is preferably a value less than 0. Further, the integration threshold β is more preferably a value less than −0.06.

  Further, the integral value γ is preferably a value less than 0, and more preferably a value less than −1.12.

  In the first embodiment, an evaluation value DTr that is equal to or less than the integration start threshold value β of the evaluation value DTr is integrated, and when the integration value IDT is equal to or less than the integration threshold value γ, occurrence of a breakout is predicted. Therefore, stable and highly accurate breakout prediction can be performed.

  In the first and second embodiments described above, the signs of the evaluation value DTr and the integration value IDT may be appropriately changed. In this case, the determination based on the threshold value is reversed.

  In the first and second embodiments described above, the breakout prediction time point is set to one time point. However, the present invention is not limited to this, and a plurality of time points may be provided in stages. For example, a plurality of breakout threshold values BOth may be provided in stages, or a plurality of integration threshold values β may be provided in stages. In these cases, it is preferable that the breakout occurrence handling process is a stepwise output. For example, in the first stage, an alarm is issued to prompt manual treatment, and in a stage close to the final stage, the controller 2 itself may perform control to reduce or stop the drawing speed or the like.

  Note that the predetermined value α described above is preferably set for each of the pair of upper thermocouples 31 and lower thermocouples 32, so that finer breakout prediction can be performed.

  Moreover, each component of Embodiment 1 and 2 mentioned above can be combined suitably.

  Although the embodiment to which the invention made by the present inventor is applied has been described above, the present invention is not limited by the description and the drawings that form a part of the disclosure of the present invention according to this embodiment. That is, other embodiments, examples, operational techniques, and the like made by those skilled in the art based on the present embodiment are all included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Continuous casting equipment 2 Controller 3 Input / output part 11 Tundish 12 Sliding nozzle mechanism 13 Immersion nozzle 14 Mold 15 Long side cooling plate 16 Short side cooling plate 17 Roll group 20 Solidified shell 20a Reverse solidified shell 21 Breaking part 25 Eddy current sensor 26 Powder supply Tube 31 Upper thermocouple 32 Lower thermocouple 42 Cast slab M Molten steel BO Breakout BOth Breakout threshold TU0, TU1 Upper temperature TD0, TD1 Lower temperature Δt Sampling cycle α Predetermined value β Integration start threshold γ Integration threshold DTr Evaluation value IDT Integration value

Claims (8)

An internal temperature below the molten metal surface of a casting mold for continuous casting, and an upstream upper stage temperature and a downstream lower stage temperature with respect to the slab drawing direction are measured in time series at predetermined sampling periods, and the upper stage temperature and A breakout prediction method for detecting occurrence of slab breakage inside a mold based on the lower stage temperature,
A determination step of determining whether or not a current temperature difference obtained by subtracting the lower temperature from the upper temperature at the current sampling time is equal to or greater than a predetermined value;
Subtracting the previous temperature difference obtained by subtracting the lower temperature from the upper temperature at the previous sampling time before the predetermined sampling period from the current sampling time from the current temperature difference, and dividing the subtracted difference by the predetermined sampling period. If the temperature difference is greater than or equal to the predetermined value, the divided value is divided by the current temperature difference. If the current temperature difference is less than the predetermined value, an evaluation value is calculated by dividing the divided value by the predetermined value. An evaluation value calculating step,
An output step for outputting that the slab breakage occurs thereafter when the evaluation value is equal to or lower than a predetermined breakout threshold;
A breakout prediction method comprising:   2. The breakout prediction method according to claim 1, wherein the predetermined value is a value determined based on a temperature difference between the upper stage temperature and the lower stage temperature when a continuous casting operation is in a steady state. An integration step of calculating an integration value obtained by integrating an evaluation value that satisfies the predetermined integration start threshold value or less when the evaluation value becomes a predetermined integration start threshold value or less,
3. The breakout according to claim 1, wherein the outputting step outputs that the slab rupture is generated after that when the integral value within a predetermined period becomes a predetermined integral threshold value or less. Prediction method.   The breakout prediction method according to claim 3, wherein the predetermined integration start threshold is the breakout threshold.   The breakout prediction method according to any one of claims 1 to 4, wherein the predetermined value is a value exceeding 10 ° C.   6. The breakout prediction method according to claim 3, wherein the predetermined integration start threshold is a value less than zero.   The breakout prediction method according to claim 3, wherein the predetermined integration threshold is a value less than zero.   The break according to any one of claims 1 to 7, wherein the predetermined value is individually set for each of a pair of an upper thermocouple for detecting an upper temperature and a lower thermocouple for detecting a lower temperature. Out prediction method.

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