JP5768700B2 - Slab temperature estimation method and slab temperature estimation device - Google Patents

Description

  The present invention relates to a slab temperature estimation method and a slab temperature estimation device for estimating a slab temperature in a continuous casting machine.

  In the operation of a continuous casting machine, it is extremely important to grasp the solidification state of the slab during continuous casting. For example, if the slab comes out of the continuous casting machine with the inside not completely solidified due to insufficient cooling (secondary cooling) after cooling through the mold, When cut, the internal molten steel flows out, causing a major problem. For this reason, it is important to accurately grasp the solidification state of the slab in order to prevent the slab from slipping out of the continuous casting machine when the inside is not completely solidified.

  On the other hand, in order to suppress the occurrence of quality troubles such as cracks on the surface of the slab, the temperature of the slab becomes brittle in the straightening part that bends the slab drawn vertically from directly below the mold vertically downward. It is necessary to set the secondary cooling condition so as not to be applied. Further, the water density distribution in the width direction of the slab is not uniform due to the arrangement and characteristics of the cooling spray. For this reason, in general, the distribution shape in the width direction of the solidification completion position of the slab is not flat, and some unevenness occurs, and if this unevenness becomes severe, impurities are concentrated in the recessed portion and cracks are likely to occur. Decreases.

  Against this background, many techniques for measuring the internal temperature of a slab during continuous casting have been proposed. However, since the ambient temperature of the continuous casting machine is high and very severe, there is no technology that can measure the internal temperature of the slab online. For this reason, until now, estimating the internal temperature of a slab by the numerical calculation using a heat-transfer model is performed (refer patent document 1).

  Specifically, the technique described in Patent Document 1 first virtually generates a calculation surface perpendicular to the casting direction in a slab during continuous casting every time casting of a predetermined length proceeds. Next, this technology is based on the average cooling condition of the zone that passed immediately before when the calculation surface passes through a plurality of zones set continuously in the casting direction and reaches the next zone entry boundary. To calculate the temperature distribution in the calculation plane. And this technology gives the temperature distribution in the obtained calculation plane as the initial value of the calculation to be performed after the next zone, and calculates the temperature distribution in the calculation plane sequentially, thereby calculating at the final zone entry boundary Obtain the in-plane temperature distribution.

JP 2002-178117 A Japanese Patent Laid-Open No. 9-24449 JP 10-2901060 A

  By the way, when estimating the solidification state of the slab by numerical calculation, the actual solidification state is confirmed by hammering the slab and adjusting the parameters of the heat transfer model based on the confirmation result. Compensation for consistency with the state is performed. And once adjustment of the parameter of a heat transfer model is performed, the operation which trusted the calculation result in that state is performed. However, if the operating conditions differ from the time when the parameters were adjusted, such as when the casting conditions and steel types are different, or when the cooling equipment has been changed, aging deterioration or temporary failure, etc., the solidification state is estimated by calculation. The result is different from the actual one, and the solidification state of the slab cannot be estimated with high accuracy.

  In order to solve such problems, techniques described in Patent Document 2 and Patent Document 3 have been proposed. Specifically, the technique described in Patent Document 2 is based on the temperature and control of the slab obtained as a result of casting based on the flow rate command of the cooling spray set using a control model that formulates the physical phenomenon of the continuous casting machine. The parameter of the control model is corrected from the difference between the slab temperature calculated using the model. The technique described in Patent Document 3 corrects the heat flux distribution from the surface of the slab so that the calculated value of the surface temperature at the measurement point of the slab matches the measured value.

  According to the techniques described in Patent Documents 2 and 3, the measured value of the slab temperature and the calculated value can be matched at the measurement point by correcting the parameters of the model. However, since the calculated value of the internal temperature of the slab does not coincide with the actual internal temperature, there is no guarantee that the solidification state can be estimated with high accuracy even if the corrected model is used. For this reason, there exists a possibility that the solidification completion position of a slab may remove | deviate from a continuous casting machine, and will become a big trouble. Moreover, the temperature of the slab in the straightening part is applied to the embrittlement region, which may cause a quality trouble that causes cracks on the surface of the slab. Moreover, since there is no description regarding estimation of the width direction shape of a coagulation completion position, it cannot suppress that an unevenness | corrugation arises in the width direction shape of a coagulation completion position.

  This invention is made | formed in view of the said subject, The objective is to provide the slab temperature estimation method and slab temperature estimation apparatus which can estimate the temperature of a slab with high precision.

  In order to solve the above problems and achieve the object, the slab temperature estimation method according to the present invention is based on the heat transfer calculation using the heat transfer model, and the thickness of the slab at the first position in the casting direction of the continuous casting machine. A first position in the casting direction from the temperature distribution using a relational expression between a temperature distribution estimating step for estimating a temperature distribution in a direction and a velocity of an ultrasonic wave propagating in a thickness direction of the slab. Is used to calculate the ultrasonic velocity distribution in the thickness direction of the slab and to estimate the ultrasonic wave propagation time in the thickness direction of the slab at the first position in the casting direction by using the calculated velocity distribution. An estimation step, a propagation time measurement step for measuring the propagation time of the ultrasonic wave in the thickness direction of the slab at the first position in the casting direction, and a heat transfer calculation using a heat transfer model The surface of the slab in two positions A surface temperature estimation step for estimating the degree, a surface temperature measurement step for measuring the surface temperature of the slab at the second position in the casting direction, the estimated value of the propagation time of the ultrasonic wave coincides with the measured value, and The thermal conductivity included in the heat transfer model, the heat transfer coefficient between the heat removal mold and the solidified shell in the mold, and the heat of the secondary cooling zone so that the estimated value of the surface temperature matches the measured value. A correction step for correcting the value of at least one parameter of the transfer coefficient, and a temperature estimation step for estimating the temperature of the slab by heat transfer calculation using a heat transfer model in which the parameter is corrected. It is characterized by.

  The slab temperature estimation method according to the present invention is characterized in that, in the above invention, the method includes a step of estimating a solidification completion position of a slab in a continuous casting machine based on the temperature of the slab estimated in the temperature estimation step. To do.

  In the slab temperature estimation method according to the present invention, in the above invention, the correction step includes a step of correcting the parameter so that the estimated values of the surface temperature at a plurality of positions in the width direction of the slab coincide with the measured values. It is characterized by.

  The slab temperature estimation method according to the present invention includes the step of estimating the distribution state of solidification completion positions in the width direction of the slab based on the estimated values of the surface temperatures at a plurality of positions in the width direction of the slab in the above invention. It is characterized by including.

  In order to solve the above-mentioned problems and achieve the object, the slab temperature estimation device according to the present invention is a slab thickness at the first position in the casting direction of a continuous casting machine by heat transfer calculation using a heat transfer model. A first position in the casting direction from the temperature distribution by using a temperature distribution estimating means for estimating a temperature distribution in the direction and a relational expression between the temperature of the slab and the velocity of the ultrasonic wave propagating in the thickness direction of the slab. Is used to calculate the ultrasonic velocity distribution in the thickness direction of the slab and to estimate the ultrasonic wave propagation time in the thickness direction of the slab at the first position in the casting direction by using the calculated velocity distribution. An estimation means, a propagation time measurement means for measuring the propagation time of the ultrasonic wave in the thickness direction of the slab at the first position in the casting direction, and a heat transfer calculation using a heat transfer model, Estimate the surface temperature of the slab at 2 positions A surface temperature estimating means, a surface temperature measuring means for measuring a surface temperature of the slab at the second position in the casting direction, an estimated value of the propagation time of the ultrasonic wave coincides with a measured value, and the estimated surface temperature Of the thermal conductivity included in the heat transfer model, the heat transfer coefficient between the heat removal mold and the solidified shell in the mold, and the heat transfer coefficient of the secondary cooling zone so that the value matches the measured value Correction means for correcting the value of at least one parameter, and temperature estimation means for estimating the temperature of the slab by heat transfer calculation using a heat transfer model in which the parameter is corrected. .

  According to the slab temperature estimation method and the slab temperature estimation device according to the present invention, the temperature of the slab can be estimated with high accuracy.

FIG. 1 is a schematic diagram showing a configuration of a continuous casting machine to which a solidification completion position estimation device according to an embodiment of the present invention is applied. FIG. 2 is a block diagram showing the configuration of the coagulation completion position estimation apparatus that is an embodiment of the present invention. FIG. 3 is a flowchart showing a flow of solidification completion position estimation processing according to an embodiment of the present invention. FIG. 4 is a diagram showing the measured value of the surface temperature at the position where the surface thermometer is disposed and the estimated value and measured value of the solidification completion position before and after the parameter correction. FIG. 5 is a diagram showing estimated values and measured values of the solidification completion position in the width direction of the slab before and after the parameter correction.

  Hereinafter, with reference to the drawings, the configuration and operation of a coagulation completion position estimation apparatus according to an embodiment of the present invention will be described.

[Construction of continuous casting machine]
First, a configuration of a continuous casting machine to which a solidification completion position estimation device according to an embodiment of the present invention is applied will be described with reference to FIG.

  FIG. 1 is a schematic diagram showing a configuration of a continuous casting machine to which a solidification completion position estimation apparatus according to an embodiment of the present invention is applied. As shown in FIG. 1, in a continuous casting machine 1 to which a solidification completion position estimation device according to an embodiment of the present invention is applied, a mold 4 is provided below a tundish 3 filled with molten steel 2, An immersion nozzle 5 serving as a molten steel supply port to the mold 4 is provided at the bottom of the tundish 3. A support roll 6 is installed below the mold 4 in the vertical direction.

  In the casting direction of the slab S, a plurality of cooling zones 7a to 13a and 7b to 13b are arranged as secondary cooling zones. A plurality of spray or air mist spray nozzles are arranged in each cooling zone, and secondary cooling water is sprayed onto the surface of the slab S from each nozzle. In FIG. 1, a reference symbol “a” is illustrated in the cooling zone on the counter-reference surface side (upper surface side), and a reference symbol b is illustrated in the cooling zone on the reference surface side (lower surface side). In this configuration example, there are a total of seven cooling zones, but the number of cooling zones in an actual continuous casting machine varies depending on the length of the machine.

  In the vicinity of the exit side of the final cooling zones 13a and 13b, an ultrasonic transmission sensor 14a and an ultrasonic reception sensor 14b are arranged so as to be opposed to the upper and lower positions of the slab S. The ultrasonic transmission sensor 14a transmits ultrasonic waves to the ultrasonic reception sensor 14b through the slab S. The ultrasonic wave reception sensor 14b receives the ultrasonic wave transmitted by the ultrasonic wave transmission sensor 14a, and the time from the ultrasonic wave transmission sensor 14a transmitting the ultrasonic wave to receiving the ultrasonic wave is the thickness direction of the slab S. Measured as the propagation time of ultrasonic waves at. The position in the casting direction where the ultrasonic transmission sensor 14a and the ultrasonic reception sensor 14b are disposed is defined as a first position in the casting direction.

  Note that the ultrasonic wave includes a transverse wave and a longitudinal wave. Since the transverse wave does not pass through the slab S when a liquid phase is present inside the slab S, it cannot be used for measuring the propagation time. Therefore, when the ultrasonic transmission sensor 14a and the ultrasonic reception sensor 14b use ultrasonic waves of transverse waves, the first position in the casting direction must be always downstream of the assumed solidification completion position. is there. On the other hand, since the longitudinal wave passes through the liquid phase, the propagation time can be measured even when the liquid phase exists. However, in the present invention, the temperature distribution in the thickness direction of the slab S at the first position in the casting direction of the continuous casting machine is estimated by heat transfer calculation using a heat transfer model, and the thickness of the slab S is based on the temperature distribution. The ultrasonic velocity distribution in the direction is estimated, and the estimated propagation time in the thickness direction of the slab S of the ultrasonic wave estimated based on the velocity distribution, and the propagation time measured by the ultrasonic transmission sensor 14a and the ultrasonic reception sensor 14b. Comparison with the measured value is performed. At that time, the temperature distribution in the thickness direction of the slab S and the velocity distribution of ultrasonic waves greatly vary depending on whether or not the liquid phase portion exists in the slab S. Therefore, there arises a problem that the comparison between the estimated propagation time value and the measured propagation time value cannot be performed simply. For this reason, even when the ultrasonic transmission sensor 14a and the ultrasonic reception sensor 14b are those that use longitudinal ultrasonic waves, the first position in the casting direction is set downstream of the assumed solidification completion position. Therefore, it is desirable that the propagation time is not affected by the liquid phase part. However, since the temperature distribution in the thickness direction of the slab S becomes more uniform due to heat diffusion toward the downstream side, it is not preferable that the first position in the casting direction is too far from the solidification completion position.

  A surface thermometer 15 for measuring the surface temperature of the slab S is disposed in the vicinity of the ultrasonic transmission sensor 14a. The position in the casting direction where the surface thermometer 15 is disposed is defined as a second position in the casting direction. Since the second position in the casting direction is related to the measurement of the surface temperature of the slab S, it may be either upstream or downstream of the solidification completion position, unlike the first position in the casting direction. In the present embodiment, the surface thermometer 15 is disposed in the vicinity of the ultrasonic transmission sensor 14a. However, the surface thermometer 15 may be disposed between the more upstream cooling zones. That is, the second position in the casting direction may be the upstream side away from the first position in the casting direction. However, in that case, it is necessary to consider that the slab is in the recuperation process and that measurement errors due to cooling water and steam occur. Further, the surface thermometer 15 may be disposed between the cooling zones on the downstream side. That is, the second position in the casting direction may be the downstream side away from the first position in the casting direction. However, in that case, the surface temperature of the slab S decreases toward the downstream side, and the distribution in the width direction of the surface temperature of the slab S is also made uniform by heat diffusion. In order to obtain the distribution, it is not preferable to move the second position in the casting direction too far from the solidification completion position.

[Configuration of solidification completion position estimation device]
Next, with reference to FIG. 2, the structure of the coagulation completion position estimation apparatus which is one Embodiment of this invention is demonstrated.

  FIG. 2 is a block diagram showing the configuration of the coagulation completion position estimation apparatus that is an embodiment of the present invention. As shown in FIG. 2, the coagulation completion position estimation apparatus 100 according to an embodiment of the present invention is configured by an information processing apparatus such as a workstation or a personal computer. The coagulation completion position estimation apparatus 100 includes a temperature calculation unit 101, an ultrasonic propagation time calculation unit 102, a parameter correction unit 103, and a coagulation completion position when an arithmetic processing unit such as a CPU in the information processing apparatus executes a control program. It functions as the estimation unit 104. The functions of these units will be described later. The coagulation completion position estimation device 100 is connected to an ultrasonic transmission sensor 14a, an ultrasonic reception sensor 14b, a surface thermometer 15, and an output device 110 such as a display device or a printing device.

[Coagulation completion position estimation process]
The solidification completion position estimation device 100 having such a configuration estimates the solidification completion position of the slab S by executing the following solidification completion position estimation processing. The operation of the solidification completion position estimation device 100 when executing this solidification completion position estimation processing will be described below with reference to the flowchart shown in FIG.

  FIG. 3 is a flowchart showing a flow of solidification completion position estimation processing according to an embodiment of the present invention. The flowchart shown in FIG. 3 starts when the continuous casting machine is operated and the slab S passes between the ultrasonic transmission sensor 14a and the ultrasonic reception sensor 14b, and the solidification completion position estimation processing is processing in step S1. Proceed to

  In the process of step S1, the temperature calculation unit 101 arranges the ultrasonic transmission sensor 14a and the ultrasonic reception sensor 14b by secondary cooling calculation (heat transfer calculation related to secondary cooling of the slab using a heat transfer model). A temperature distribution T (x) in the thickness direction of the slab S at the position (first position) (x: a coordinate value representing a position of the slab S in the thickness direction) is calculated. Specifically, in the secondary cooling calculation in the continuous casting machine, a two-dimensional heat transfer equation expressed by the following formula (1) is considered, considering a slab section sliced into unit lengths in the casting direction. Depending on the location in the piece S, it is executed by giving and solving the heat flow rate (see Equation (2)) of the boundary condition of the slab surface in various situations such as water cooling, air cooling, mist cooling, and heat removal from the roll. Since the secondary cooling calculation itself is known at the time of filing of the present invention, a detailed description is omitted.

In the heat transfer calculation in the mold 4, the heat transfer coefficient between the solidified shell and the mold inner wall is h _s , T is the surface temperature of the solidified shell in the mold, and T _m is the mold inner wall temperature. The condition is changed as shown in Equation (3) below. In Equation (1), c is the specific heat of the slab S, ρ is the density of the slab S, k is the thermal conductivity of the slab S, T is the surface temperature of the slab S, and x and y are the slab S, respectively. It is a coordinate value showing the position of the thickness direction and width direction. Also, Q in formula (2) heat flux, h is the heat transfer coefficient, T is the surface temperature, T _a of the slab S denotes the ambient temperature. Thereby, the process of step S1 is completed and the coagulation completion position estimation process proceeds to the process of step S2.

  In the process of step S2, the ultrasonic wave propagation time calculation unit 102 is calculated by the process of step S1 using a relational expression between the temperature of the slab S and the velocity of the ultrasonic wave propagating in the thickness direction of the slab S. The ultrasonic velocity distribution V (T (x)) in the thickness direction of the slab is calculated from the temperature distribution T (x). Then, the ultrasonic wave propagation time calculation unit 102 substitutes the calculated ultrasonic velocity distribution V (T (x)) into the following mathematical formula (4), whereby the ultrasonic wave transmission sensor 14a and the ultrasonic wave reception sensor. An estimated value Δt of the ultrasonic wave propagation time at the position 14b is calculated. Here, D in Formula (4) indicates the thickness of the slab S. Further, the ultrasonic propagation time calculation unit 102 uses the ultrasonic transmission sensor 14a and the ultrasonic reception sensor 14b to propagate ultrasonic waves at the same position as the casting direction position of the slab S for which the temperature distribution T (x) is calculated. Measure time. Thereby, the process of step S2 is completed and the coagulation completion position estimation process proceeds to the process of step S3.

  In the process of step S3, the temperature calculation unit 101 calculates an estimated value of the surface temperature of the slab S at the position where the surface thermometer 15 is disposed by secondary cooling calculation. Further, the temperature calculation unit 101 uses the surface thermometer 15 to measure the surface temperature at the same position as the casting direction position of the slab S where the estimated value of the surface temperature is calculated. Thereby, the process of step S3 is completed, and the solidification completion position estimation process proceeds to the process of step S4.

In the process of step S4, the parameter correction unit 103 causes the estimated value of the ultrasonic wave propagation time obtained by the process of step S2 to coincide with the measured value, and the estimated value of the surface temperature obtained by the process of step S3. Is equal to the measured value, the thermal conductivity c included in Formula (1), the heat transfer coefficient h _s between the heat removal mold and the solidified shell in the mold included in Formula (3), and Formula ( The value of at least one parameter of the heat transfer coefficient h of the secondary cooling zone included in 2) is corrected. Note that when adjusting the value of at least one of the thermal conductivity c, the heat transfer coefficient h _s between the solidified shell and the mold inner wall, and the heat transfer coefficient h in the secondary cooling zone, The heat transfer coefficient h _s may be constant in the width direction of the slab S.

However, since the cooling water amount distribution in the width direction is not uniform in the secondary cooling zone, the heat transfer coefficient h in the secondary cooling zone varies depending on the position in the width direction, thereby changing the solidification completion position in the width direction of the slab S. To do. Therefore, when the width direction distribution of the surface temperature of the slab S can be measured by scanning the surface thermometer 15 in the width direction of the slab S, the slab S is based on the width direction distribution of the surface temperature of the slab S. after correcting the heat transfer coefficient h in the width direction, it is desirable to heat conductivity c and heat transfer coefficient h _s correction to the estimated value of the ultrasound propagation time measurement value matches. Thereby, the process of step S4 is completed and the coagulation completion position estimation process proceeds to the process of step S5.

  In the process of step S5, the solidification completion position estimation unit 104 estimates the temperature of the central portion in the thickness direction of the slab S using the heat transfer model whose parameters are corrected by the process of step S4. The solidification completion position of the slab S is calculated by comparing the phase line temperature. Thereafter, by operating the cooling condition of the slab S so that the solidification completion position is at the end of the continuous casting machine based on the calculation result of the solidification completion position, the equipment capacity of the continuous casting machine is maximized. The slab S can be manufactured with high productivity. Thereby, the process of step S5 is completed and a series of solidification completion position estimation processes are complete | finished.

  As is clear from the above description, in the coagulation completion position estimation process according to an embodiment of the present invention, the ultrasonic propagation time calculation unit 102 performs the ultrasonic transmission sensor 14a and the super transmission by heat transfer calculation using a heat transfer model. The propagation time of the ultrasonic wave in the thickness direction of the slab S at the position where the acoustic wave receiving sensor 14b is disposed is estimated, and the propagation time of the ultrasonic wave in the thickness direction of the slab S is measured at the same position. Further, the temperature calculation unit 101 estimates the surface temperature of the slab S at the position where the surface thermometer 15 is disposed by heat transfer calculation using a heat transfer model, and measures the surface temperature of the slab S at the same position. .

  The parameter correction unit 103 includes the thermal conductivity included in the heat transfer model so that the estimated value of the propagation time of the ultrasonic wave matches the measured value, and the estimated value of the surface temperature matches the measured value. The value of at least one parameter of the heat transfer coefficient between the heat removal mold and the solidified shell in the mold and the heat transfer coefficient of the secondary cooling zone is corrected, and the solidification completion position estimation unit 104 corrects the parameter. The temperature of the slab surface and inside is estimated by heat transfer calculation using the heat transfer model. According to such solidification completion position estimation processing, the parameters of the heat transfer model are corrected using the ultrasonic propagation time and the surface temperature of the slab S that have a relationship with the internal temperature of the slab S. Therefore, the surface and internal temperature of the slab can be estimated with high accuracy.

  In the solidification completion position estimation process according to an embodiment of the present invention, the solidification completion position estimation unit 104 estimates the solidification completion position of the slab in the continuous casting machine based on the estimated internal temperature of the slab. The solidification completion position of the slab can be estimated with high accuracy. In addition, the estimated value and the measured value of the surface temperature at a plurality of positions in the width direction of the slab S are acquired, and the distribution state of the solidification completion position in the width direction of the slab is estimated based on the acquired estimated value and the measured value. Also good. By operating the cooling conditions so that the distribution of the solidification completion position in the width direction of the slab becomes flat, it becomes possible to operate the continuous casting machine without causing internal quality problems such as center segregation. , Can provide excellent quality slabs.

〔Example〕
FIGS. 4A and 4B are diagrams showing the measured value of the surface temperature at the position where the surface thermometer 15 is disposed, and the estimated value and measured value of the solidification completion position before and after the correction of the parameters, respectively. In this example, the present invention was executed after time 20 [min], and the heat conductivity c of the slab and the heat transfer coefficient h in the secondary cooling zone were corrected. In FIG. 4B, the thin line L1 indicates the solidification completion position estimated with the parameters before correction, and the thick line L2 starting from time 20 [min] indicates the solidification completion position estimated with the parameters after correction. Plots P1 to P8 shown in FIG. 4B show the solidification completion positions measured by a known solidification completion position detection device using ultrasonic waves.

  As shown in FIG. 4B, there is a large error between the solidification completion position estimated with the parameter before correction and the measurement value of the solidification completion position, but the solidification completion position estimated with the parameter after correction. And the measured value of the solidification completion position are in good agreement. From this, it was confirmed that by correcting the parameters according to the present invention, the deviation between the estimated value and the measured value of the coagulation completion position is eliminated, and the coagulation completion position can be estimated with high accuracy.

  FIG. 5 is a diagram showing estimated values and measured values of the solidification completion position in the width direction of the slab S before and after the parameter correction. In the figure, the dotted line L3 indicates the solidification completion position estimated with the parameters before correction, the thin line L4 indicates the solidification completion position estimated after correcting the heat transfer coefficient h in the secondary cooling zone, and the thick line L5 indicates the slab. The solidification completion position estimated after correcting the heat conductivity c of the heat and the heat transfer coefficient h in the secondary cooling zone is shown. Plots P11 to P16 show the coagulation completion positions measured by a known coagulation completion position detector using ultrasonic waves.

  In addition, since the temperature variation of the slab due to unevenness in the water amount distribution in the width direction cannot be known unless measurement is performed, in this embodiment, the heat transfer coefficient in the width direction is constant in the initial state, and the surface thermometer 15 By adjusting the heat transfer coefficient in the width direction based on the measured temperature distribution in the width direction of the slab S, the calculated value of the distribution state in the width direction of the surface temperature at the position of the surface thermometer 15 matches the measured value. I let you.

  As shown in FIG. 5, the shape in the width direction of the solidification completion position estimated with the parameters before correction as shown by the dotted line L3 was flat, whereas after the correction as shown by the thin line L4 and the thick line L5. The shape in the width direction of the solidification completion position estimated by the parameter reflects the width direction distribution of the surface temperature. That is, after parameter correction, the solidification completion position in the vicinity of the end portion in the width direction of the slab is positioned more upstream than the solidification completion position in the vicinity of the center portion of the slab. In addition, there is a large error between the solidification completion position estimated with the parameters before correction and the measurement value of the solidification completion position, but the solidification completion position estimated with the parameters after correction and the measurement value of the solidification completion position Are in good agreement. From this, it was confirmed that by correcting the parameters according to the present invention, the deviation between the estimated value and the measured value of the solidification completion position is eliminated, and the solidification completion position in the width direction of the slab can be estimated with high accuracy. .

  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 this embodiment are all included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Continuous casting machine 2 Molten steel 3 Tundish 4 Mold 5 Immersion nozzle 6 Support roll 7a-13a, 7b-13b Cooling zone 14a Ultrasonic transmission sensor 14b Ultrasonic reception sensor 15 Surface thermometer 100 Solidification completion position estimation apparatus 101 Temperature calculation part DESCRIPTION OF SYMBOLS 102 Ultrasonic propagation time calculation part 103 Parameter correction | amendment part 104 Solidification completion position estimation part 110 Output device S Slab

Claims (5)

A temperature distribution estimation step for estimating a temperature distribution in the thickness direction of the slab at the first position in the casting direction of the continuous casting machine by heat transfer calculation using a heat transfer model;
Using the relational expression between the temperature of the slab and the velocity of the ultrasonic wave propagating in the thickness direction of the slab, the velocity distribution of the ultrasonic wave in the thickness direction of the slab at the first position in the casting direction from the temperature distribution. And using the calculated velocity distribution, a propagation time estimation step for estimating the propagation time of the ultrasonic wave in the thickness direction of the slab at the first position in the casting direction;
A propagation time measuring step of measuring a propagation time of ultrasonic waves in the thickness direction of the slab at the first position in the casting direction;
A surface temperature estimation step for estimating the surface temperature of the slab at the second position in the casting direction of the continuous casting machine by heat transfer calculation using a heat transfer model;
A surface temperature measuring step for measuring a surface temperature of the slab at the second position in the casting direction;
The thermal conductivity included in the heat transfer model and heat removal in the mold so that the estimated value of the propagation time of the ultrasonic wave matches the measured value, and the estimated value of the surface temperature matches the measured value. A correction step of correcting a value of at least one parameter of a heat transfer coefficient between the mold and the solidified shell and a heat transfer coefficient of the secondary cooling zone;
A temperature estimation step of estimating a temperature of a slab by heat transfer calculation using a heat transfer model in which the parameters are corrected;
The slab temperature estimation method characterized by including.   The slab temperature estimation method according to claim 1, further comprising a step of estimating a solidification completion position of the slab in a continuous casting machine based on the internal temperature of the slab estimated in the temperature estimation step.   3. The slab temperature according to claim 1, wherein the correcting step includes a step of correcting a parameter so that an estimated value of a surface temperature at a plurality of positions in a width direction of the slab coincides with a measured value. Estimation method.   The slab temperature according to claim 3, further comprising a step of estimating a distribution state of solidification completion positions in the width direction of the slab based on estimated values of surface temperatures at a plurality of positions in the width direction of the slab. Estimation method. A temperature distribution estimating means for estimating a temperature distribution in a thickness direction of a slab at a first position in a casting direction of a continuous casting machine by heat transfer calculation using a heat transfer model;
Using the relational expression between the temperature of the slab and the velocity of the ultrasonic wave propagating in the thickness direction of the slab, the velocity distribution of the ultrasonic wave in the thickness direction of the slab at the first position in the casting direction from the temperature distribution. And a propagation time estimation means for estimating the propagation time of the ultrasonic wave in the thickness direction of the slab at the first position in the casting direction using the calculated velocity distribution,
A propagation time measuring means for measuring the propagation time of the ultrasonic wave in the thickness direction of the slab at the first position in the casting direction;
Surface temperature estimation means for estimating the surface temperature of the slab at the second position in the casting direction of the continuous casting machine by heat transfer calculation using a heat transfer model;
Surface temperature measuring means for measuring the surface temperature of the slab at the second position in the casting direction;
The thermal conductivity included in the heat transfer model and heat removal in the mold so that the estimated value of the propagation time of the ultrasonic wave matches the measured value, and the estimated value of the surface temperature matches the measured value. Correction means for correcting a value of at least one parameter of a heat transfer coefficient between the mold and the solidified shell and a heat transfer coefficient of the secondary cooling zone;
Temperature estimation means for estimating the temperature of the slab by heat transfer calculation using a heat transfer model with the parameters corrected;
A slab temperature estimation device comprising:

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