JP2010279957A - Continuous casting machine and method for estimating generation of longitudinal crack of cast slab surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous casting machine capable of detecting temperature dip more accurately with a simple configuration and accordingly estimating accurate generation of a longitudinal crack, and also to provide a method for estimating generation of a longitudinal crack of a cast slab surface. <P>SOLUTION: A temperature dip indexation part 25a respectively calculates total values of variation amounts ΔT<SB>i</SB>respectively calculated at periods when the variation amounts ΔT<SB>i</SB>respectively detected with temperature sensors 21 and 22 continuously indicate a negative value as a temperature dip index K. An upper and lower index multiplication part 25b calculates a multiplication index M by multiplying a temperature dip index K that the temperature dip indexation part 25a calculates about the temperature sensor 21 by a temperature dip index K that the temperature dip indexation part 25a calculates about the temperature sensor 22. A determination part 25c for the generation of the longitudinal crack determines whether a depression is generated on a surface of a cast slab 17 based on the multiplication index M. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a continuous casting machine and a method for predicting occurrence of vertical cracks on a slab surface, and in particular, a continuous casting machine for predicting whether cracks have occurred on the surface of a slab in the process of continuous casting and occurrence of vertical cracks on a slab surface. It relates to the prediction method.

  As a conventional technique for detecting vertical cracks on the surface of a slab, for example, as disclosed in Patent Documents 1 to 3 shown below, a slab is placed at a location spaced a certain distance from the meniscus in the casting direction (drawing direction of the slab). There is a technique for arranging a plurality of thermocouples arranged in the width direction and predicting whether or not an abnormality has occurred on the surface of the slab from the characteristics of the temperature profile in the slab width direction detected by the thermocouple (hereinafter referred to as the slab surface) This is referred to as prior art 1). Specifically, a plurality of thermocouples arranged in the width direction of the slab are fixed to a copper plate in contact with the slab from the meniscus, and a change with time (temperature profile) of the temperature detected by the thermocouple is acquired. At this time, since the depletion of the slab surface, which is the precursor stage of the slab surface vertical crack, occurs, the heat transfer resistance from the slab to the copper plate increases and the copper plate temperature decreases, so this temperature drop (temperature dip) By detecting this, it is possible to predict whether vertical cracks have occurred on the surface of the slab.

  In addition, for example, in Patent Document 4 shown below, the size of a slab surface temperature dip caused by a depletion caused by a vertical crack on the slab surface is detected at two points in the mold casting direction, It is determined whether the dip generated upstream from the covariance obtained from the temperature detected at this point is also detected downstream, and whether or not vertical cracks have occurred on the slab surface based on this determination result Has been disclosed (hereinafter referred to as Conventional Technology 2).

Japanese Patent Laid-Open No. 2-151356 JP 2004-141906 A JP 2004-181466 A Japanese Patent No. 3093586

  However, the temperature dip generated in the copper plate to which the thermocouple is fixed is not limited to the depletion on the surface of the slab, but is caused by, for example, molten steel flow in the mold or local and temporary fluctuations in the thickness of the mold powder film. Also occurs. For this reason, in the said prior art 1, abnormality other than the vertical crack which arose on the slab surface will be detected, and the problem that an efficient and accurate continuous casting process will be prevented.

  In particular, in the technique disclosed in Patent Document 2, a time-series temperature dip of the copper plate temperature when a depletion accompanied by a vertical crack occurs is detected by pattern recognition of the temperature profile. Therefore, in the conventional technique 2, the temperature decrease amount in the first half of the temperature dip (temperature profile falling portion), the temperature decrease rate per unit time and the minimum temperature, and the temperature increase amount in the second half of the temperature dip (temperature profile increasing portion). And the temperature rise rate per unit time is compared with those of the past temperature dip accumulated in the database, the similarity is calculated, and the obtained similarity is used as the evaluation value. It is predicted that a vertical crack has occurred when it falls within a predetermined range.

  However, there are various shapes of the profile of the temperature dip actually generated. For this reason, there is a problem that it is difficult to select the profile shape of the temperature dip stored as a model case. In addition, when trying to predict the occurrence of vertical cracks more accurately, a huge amount of model cases must be accumulated, which increases the size of the database and further increases the amount of data processing required for prediction. Problems will also occur.

  Moreover, in the said prior art 2, although the magnitude | size (dip amount) of the temperature dip obtained with the thermocouple fixed to the copper plate is quantified, at this time, the primary delay temperature of the time series data of the copper plate temperature is calculated, This first order lag temperature is assumed to be a normal copper plate temperature. Further, a difference between the first-order lag temperature and the actually detected temperature is acquired as a dip amount.

  Here, in calculating the primary delay temperature, it is necessary to set a time constant for determining the amount of the primary delay. However, the temperature drop gradient of the temperature dip caused by the depletion of the slab surface due to vertical cracking does not have a constant value, but varies variously. For this reason, for example, if the set time constant is too small with respect to the temperature drop gradient, the calculated first-order lag temperature is close to the actual copper plate temperature where no temperature dip occurs, and as a result, the dip amount of the copper plate temperature is The problem of underestimation occurs. On the other hand, if the set time constant is excessive with respect to the temperature decrease gradient, it takes time until the calculated first-order lag amount decreases according to the actual decrease in the copper plate temperature. There is a problem that a decrease in the average level of temperature is recognized as a temperature dip.

  Furthermore, in the prior art 2, in the process for obtaining the covariance, the dip amount at each of the two points is multiplied. In this process, the error included in the dip amount is squared and enlarged. For this reason, when the occurrence of a vertical crack is predicted using a threshold value for covariance, there is a problem that it is difficult to set the threshold value because the influence of errors is large.

  As described above, the conventional technology cannot accurately recognize the temperature dip with a simple configuration, and if it is attempted to recognize the temperature dip more accurately, the recognition determination parameters and the database structure are increased in size and complexity. There was a problem of becoming.

  Therefore, the present invention has been made in view of the above problems, and can continuously detect a temperature dip with a simple configuration, and thereby can predict the occurrence of accurate vertical cracks. It is an object of the present invention to provide a machine and a method for predicting occurrence of vertical cracks on a slab surface.

  In order to achieve such an object, a continuous casting machine according to the present invention includes a mold in which molten steel injected from upstream is drawn in the casting direction from downstream, a first temperature sensor disposed on a side surface of the mold, And a second temperature sensor disposed on a downstream side of the first temperature sensor along the casting direction, using the first temperature sensor at predetermined intervals. A first temperature detecting means for detecting the first temperature and a first temperature difference between the first temperature detected before and after the first temperature difference are calculated, and the first temperature difference is continuously negative during the first period. A first temperature dip indexing means for calculating a first index that indexes the degree of decrease in the first temperature; and a timing at which the first temperature detecting means detects the first temperature every predetermined time. Front in the casting direction Second temperature detection means for detecting the second temperature at a timing delayed by a time obtained by dividing the distance between the first temperature sensor and the second temperature sensor by the casting speed; and the second temperature detected before and after. A second temperature dip index that calculates a second temperature difference between the temperatures, and calculates a second index that indexes the degree of decrease in the second temperature during the second period in which the second temperature difference is continuously negative. Whether or not depletion has occurred on the surface of the slab based on the third index, and a vertical index multiplication means for generating a third index by multiplying the first index and the second index And a vertical crack occurrence determination means for determining the above.

  In the continuous casting machine according to the present invention described above, the first temperature dip indexing means calculates the total value of the first temperature differences calculated during the first period as the first index, and the second temperature The dip indexing means calculates the total value of the second temperature differences calculated during the second period as the second index.

  In the continuous casting machine according to the present invention as described above, the first temperature dip indexing means calculates the total value of the first temperatures calculated during the first period as the first index, and the second temperature dip The indexing means calculates the total value of the second temperatures calculated during the second period as the second index.

  In the continuous casting machine according to the present invention described above, the first temperature sensor includes a plurality of first thermocouples arranged along the width direction of the slab, and the second temperature sensor extends along the width direction. Each of the plurality of second thermocouples arranged downstream of the first thermocouple along the casting direction, and the first temperature detecting means includes the plurality of first thermocouples, respectively. The first temperature dip indexing means calculates the first index for each of the plurality of first thermocouples, and the second temperature detection means detects the plurality of second thermoelectrics. The second temperature is detected for each pair, the second temperature dip indexing means calculates the second index for each of the plurality of second thermocouples, and the up / down index multiplying means is the plurality of first thermocouples. Thermocouple and said plurality of second It is characterized by multiplying the first indicator and the second indicator for each of the first thermocouple and a second thermocouple disposed vertically along the casting direction of the couple.

  The method for predicting the occurrence of vertical cracks on the slab surface according to the present invention includes a mold in which molten steel injected from the upstream is drawn in the casting direction from the downstream, a first temperature sensor disposed on a side surface of the mold, and a side surface of the mold. And a second temperature sensor disposed downstream of the first temperature sensor in the casting direction, and a method for predicting occurrence of vertical cracks on a slab surface in a continuous casting machine, wherein A first temperature detecting step of detecting a first temperature using the first temperature sensor, and calculating a first temperature difference between the first temperatures detected before and after, wherein the first temperature difference continues A first temperature dip indexing step of calculating a first index that indexes the degree of decrease in the first temperature during a negative first period; and the first temperature detecting means at each predetermined time 1 Temperature detection tie A second temperature detecting step for detecting the second temperature at a timing later than the distance obtained by dividing the distance between the first temperature sensor and the second temperature sensor in the casting direction by the casting speed, and before and after A second index that calculates a second temperature difference between the detected second temperatures and indexes the degree of decrease in the second temperature during a second period in which the second temperature difference is continuously negative. A second temperature dip indexing step for calculating, a vertical index multiplying step for generating a third index by multiplying the first index and the second index, and a surface of the slab based on the third index And a vertical crack occurrence determination step for determining whether or not a depletion has occurred.

  In the slab surface vertical crack occurrence prediction method according to the present invention described above, the first temperature dip indexing step calculates the total value of the first temperature differences calculated during the first period as the first index. The second temperature dip indexing step calculates the total value of the second temperature differences calculated during the second period as the second index.

  In the slab surface vertical crack occurrence prediction method according to the present invention described above, the first temperature dip indexing step calculates the total value of the first temperatures calculated during the first period as the first index, In the second temperature dip indexing step, a total value of the second temperatures calculated during the second period is calculated as the second index.

  In the slab surface vertical crack occurrence prediction method according to the present invention described above, the first temperature sensor includes a plurality of first thermocouples arranged along the width direction of the slab, and the second temperature sensor includes: A plurality of second thermocouples arranged along the width direction, each disposed downstream of the first thermocouple along the casting direction, wherein the first temperature detecting step comprises The first temperature is detected for each of the first thermocouples, the first temperature dip indexing step calculates the first index for each of the plurality of first thermocouples, and the second temperature detection step includes the steps of: The second temperature is detected for each of a plurality of second thermocouples, the second temperature dip indexing step calculates the second index for each of the plurality of second thermocouples, and the up / down index multiplying step includes: Of the plurality of first thermocouples and the plurality of second thermocouples, the first index and the second index for the first thermocouple and the second thermocouple respectively arranged vertically along the casting direction. It is characterized by multiplying.

  According to the present invention, it is possible to predict whether or not depletion has occurred based on the degree of temperature drop during a period in which the temperature change direction is negative. Thus, it is possible to realize a continuous casting machine and a method for predicting occurrence of vertical cracks on a slab surface, which can accurately predict the occurrence of vertical cracks.

FIG. 1 is a schematic diagram showing a schematic configuration example of a continuous casting machine according to an embodiment of the present invention. 2 is a partial perspective view showing a schematic configuration example of a mold and a temperature sensor in the continuous casting machine of FIG. FIG. 3 is a flowchart showing a schematic flow of slab surface vertical crack occurrence prediction processing according to an embodiment of the present invention. FIG. 4 is a flowchart showing a schematic flow of the temperature dip indexing process according to the embodiment of the present invention. FIG. 5 is a flowchart showing a schematic flow of the up / down index multiplication processing according to the embodiment of the present invention. FIG. 6 is a flowchart showing a schematic flow of vertical crack occurrence determination processing according to an embodiment of the present invention. FIG. 7 shows the relationship between the thermocouple in the upstream temperature sensor and the thermocouple in the downstream temperature sensor for a portion where no vertical cracking is obtained, which is obtained by an experiment using the continuous casting machine according to the embodiment of the present invention. It is a figure which shows the time-dependent change (temperature profile) of the temperature detected by each. FIG. 8A is a diagram showing a change (profile) with time of a change amount obtained from a temperature profile obtained from the upstream thermocouple shown in FIG. FIG. 8B is a diagram illustrating a change with time (profile) of the amount of change obtained from the temperature profile obtained from the downstream thermocouple shown in FIG. FIG. 9A is a diagram showing a temporal change (profile) of the temperature dip index K obtained for the upstream thermocouple shown in FIG. 8A. FIG. 9B is a diagram showing a temporal change (profile) of the temperature dip index K obtained for the downstream thermocouple shown in FIG. 8B. FIG. 10 shows the time-dependent change (profile) of the multiplication index obtained by multiplying the temperature dip index for the upstream thermocouple shown in FIG. 9A and the temperature dip index for the downstream thermocouple shown in FIG. 9B. FIG. FIG. 11 shows a thermocouple in an upstream temperature sensor and a thermocouple in a downstream temperature sensor for a site where a vertical crack obtained by an experiment using a continuous casting machine according to an embodiment of the present invention is found. It is a figure which shows the time-dependent change (temperature profile) of the temperature detected by (1). FIG. 12A is a diagram showing a change with time (profile) of the amount of change obtained from the temperature profile obtained from the upstream thermocouple shown in FIG. FIG. 12B is a diagram showing the change (profile) with time of the change amount obtained from the temperature profile obtained from the downstream thermocouple shown in FIG. FIG. 13A is a diagram showing a temporal change (profile) of the temperature dip index K obtained for the upstream thermocouple shown in FIG. 12A. FIG. 13B is a diagram showing a temporal change (profile) of the temperature dip index K obtained for the downstream thermocouple shown in FIG. 12B. FIG. 14 shows a time-dependent change (profile) of the multiplication index obtained by multiplying the temperature dip index for the upstream thermocouple shown in FIG. 13A and the temperature dip index for the downstream thermocouple shown in FIG. 13B. FIG.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, each drawing only schematically shows the shape, size, and positional relationship to the extent that the contents of the present invention can be understood. Therefore, the present invention is illustrated in each drawing. It is not limited to only the shape, size, and positional relationship. Moreover, the numerical value illustrated below is only a suitable example of this invention, Therefore, this invention is not limited to the illustrated numerical value.

  FIG. 1 is a schematic diagram illustrating a schematic configuration example of a continuous casting machine 10 according to the present embodiment. As shown in FIG. 1, the continuous casting machine 10 according to the present embodiment includes a tundish 12 into which molten steel 11 is poured from a ladle (not shown), and an intervention poured from the tundish 12 through an immersion nozzle 14. A copper mold 15 that semisolidifies the molten steel 11 after removal of the object until the solidified shell 19 on the surface grows into dendrites, and a semi-solid state drawn vertically downward (casting direction D1) from the mold 15. Predicts whether or not depletion that causes vertical cracking has occurred on the surface of the slab support roll 16 that transports the slab 17 to the horizontal direction and the surface of the slab 17 that translates in the casting mold D1 in the casting direction D1. And a slab surface vertical crack occurrence prediction device 20 that issues a command to an operator based on the prediction result.

  A sliding nozzle 13 is provided between the tundish 12 and the immersion nozzle 14 for adjusting the amount of molten steel 11 poured per unit time from the immersion nozzle 14 to the mold 15. Further, the inside of the slab 17, that is, the region surrounded by the solidified shell 19 in the cross section, maintains the state of the unsolidified phase 18 until the slab 17 is conveyed in the horizontal direction by the slab support roll 16. Thereafter, the slab 17 conveyed in the horizontal direction is cut into an appropriate length by a gas cutter (not shown). Thereby, the target slab is manufactured. The manufactured slab is sequentially sent to subsequent processes such as a rolling process.

  On the other hand, as shown in FIG. 1, the slab surface vertical crack occurrence prediction device 20 includes a plurality of temperature sensors 21 and 22 arranged in two rows along the casting direction D <b> 1 in the mold 15, and the temperature sensors 21 and 22. A temperature detector 24 that detects a temperature from a detected value (corresponding to an electromotive force of a thermocouple described later), and the temperature and process data 26 at the positions of the temperature sensors 21 and 22 input from the temperature detector 24. Slab surface vertical crack occurrence prediction processing including temperature dip indexing processing, vertical index multiplication processing, vertical crack occurrence determination processing, and the like, and slab surface vertical crack occurrence prediction by the signal processor 25 And an information processing device 27 that issues a slab maintenance command and a slab conveyance command to the next process such as refining and hot rolling based on the processing result.

  FIG. 2 is a partial perspective view showing a schematic configuration example of the mold 15 and the temperature sensors 21 and 22 in the continuous casting machine 10 of FIG. As shown in FIG. 2, the temperature sensor 21 includes a plurality of thermocouples 21 a to 21 n (n is an integer of 2 or more), and is disposed at a position at a predetermined depth from the side surface or the side surface of the copper mold 15. The thermocouples 21a to 21n are arranged at equal intervals along the width direction D2 of the slab 17 in the vicinity of the molten metal surface (meniscus 17a) of the molten steel 11 injected into the mold 15, and the mold 15 at each arrangement position. An electromotive force is generated according to the temperature. In addition, the temperature sensor 21 is arrange | positioned downstream from the lowest position of the height direction in which the meniscus 17a can exist.

  On the other hand, the temperature sensor 22 includes a plurality of thermocouples 22a to 22n (n is an integer equal to or greater than 2), and is a position downstream of the temperature sensor 21 on the side surface of the copper mold 15, and the side surface of the mold 15 or It is arrange | positioned in the position of predetermined depth from the side surface. The thermocouples 22a to 22n are arranged at equal intervals along the width direction D2 of the slab 17, and generate an electromotive force according to the temperature of the mold 15 at each arrangement position.

  The thermocouples 21a to 21n in the upstream temperature sensor 21 and the thermocouples 22a to 22n in the downstream temperature sensor 22 are associated one-on-one with each other. For example, the thermocouple 21a is associated with the thermocouple 22a. Further, the thermocouples 21a to 21n and the thermocouples 22a to 22n that are in a corresponding relationship are respectively located on straight lines parallel to the casting direction D1.

  The potential differences generated in the thermocouples 21a to 21n and 22a to 22n are input to the temperature detector 24 via the signal lines 23, respectively. The temperature detector 24 periodically or constantly detects the temperatures at the positions where the thermocouples 21a to 21n and 22a to 22n are fixed from the electromotive force input via the signal line 23, and detects the detected temperature information ( (Hereinafter simply referred to as temperature) is input to the signal processor 25.

  The process data 26 is also input to the signal processor 25. In the present embodiment, the process data 26 is so-called casting conditions such as casting speed and mold width. Therefore, it is possible to use a predetermined parameter for the process data 26.

  The signal processor 25 includes a temperature dip indexing unit 25a that executes a temperature dip indexing process that will be described later, a vertical index multiplier 25b that executes a vertical index multiplication process that will be described later, and a vertical crack that executes a vertical crack occurrence determination process. The slab surface vertical crack occurrence prediction process for predicting whether or not a vertical crack has occurred on the surface of the slab 17 is executed by each part executing each process including the occurrence determination unit 25c. Since the slab surface vertical crack occurrence prediction process will be described later, detailed description is omitted here.

  The result predicted by the signal processor 25 is input to the information processing device 27. Based on the input prediction result, the information processing device 27 performs various processes such as a slab care command for instructing care of the slab 17 by an operator and a slab transport destination command for designating a transport destination of the slab 17. Execute.

  Next, the slab surface vertical crack occurrence prediction process according to the present embodiment will be described in detail with reference to the drawings. FIG. 3 is a flowchart showing a schematic flow of slab surface vertical crack occurrence prediction processing according to the present embodiment. As shown in FIG. 3, in the slab surface vertical crack occurrence prediction process according to the present embodiment, the signal processor 25 includes a temperature dip indexing process (step S <b> 101), a vertical index multiplication process (step S <b> 102), The crack occurrence determination process (step S103) is sequentially executed. Thereafter, the signal processor 25 determines whether or not to end the operation (step S104). When the signal processor 25 ends (Yes in step S104), the slab surface vertical crack occurrence prediction process ends. On the other hand, when not complete | finished (No of step S104), it returns to step S101. The operation end of the signal processor 25 is input by operating an operation panel (not shown) by an operator, for example.

  Next, the temperature dip indexing process (step S101), the vertical index multiplication process (step S102), and the vertical crack occurrence determination process (step S103) executed in the slab surface vertical crack generation prediction process of FIG. Will be described in detail. FIG. 4 is a flowchart showing a schematic flow of the temperature dip indexing process (step S101) according to the present embodiment. FIG. 5 is a flowchart showing a schematic flow of the vertical index multiplication processing (step S102) according to the present embodiment. FIG. 6 is a flowchart showing a schematic flow of the vertical crack occurrence determination process (step S103) according to the present embodiment.

  As shown in FIG. 4, in the temperature dip indexing process (step S101), the temperature dip indexing unit 25a first determines whether or not a predetermined time has passed (step S111), and when the predetermined time has passed. (Yes in step S111), temperatures corresponding to the electromotive forces of the thermocouples 21a to 21n and 22a to 22n disposed between the meniscus 17a in the copper mold 15 and the mold outlet 15a are input from the temperature detector 24. (Step S112). The temperature detector 24 periodically signals the temperature corresponding to the electromotive force of each of the thermocouples 21a to 21n and 22a to 22n at every predetermined time interval (hereinafter referred to as the discretization measurement time). Input to the processor 25 (first / second temperature detection step). If the predetermined time has not elapsed (No in step S111), the temperature dip indexing unit 25a waits for the operation until the predetermined time elapses.

  Next, the temperature dip indexing unit 25a calculates the temporal behavior of the temperatures at the fixed positions of the thermocouples 21a to 21n and 22a to 22n from the input temperature (step S113), and from the calculated temporal behavior, The temperature dip index K for recognizing the temperature dip caused by the depletion (hereinafter, including the vertical crack formed by the growth of the depletion) generated in the mold 15 is determined for each fixed position of the thermocouples 21a to 21n and 22a to 22n. (Step S114: first / second temperature dip indexing step). Thereafter, the temperature dip indexing unit 25a returns to the slab surface vertical crack occurrence prediction process of FIG.

In the temperature dip indexing process, specifically, the temperature dip indexing unit 25a first uses the input temperatures of the thermocouples 21a to 21n and 22a to 22n, and then uses the thermocouples 21a to 21n. And the amount of change of the temperature for every predetermined time interval which occurred in 22a-22n is calculated. Here, in any of the thermocouples 21a to 21n and 22a to 22n, a change amount ΔT _{i of the} temperature generated between the discrete measurement time t _i-1 and the discrete measurement time t _i (predetermined time interval). is, T _i-1 of the temperature at discrete measuring times t _i-1, the temperature at discrete measuring times t _i When T _i, can be determined by formula 1 below.

Next, the temperature dip indexing unit 25a determines whether or not the temperature change amount ΔT _i obtained by Equation 1 is in the temperature decreasing direction (ΔT _i <θ). By using the following equation 2, the temperature change amount integrated up to the previous discretization time t _i-1 (hereinafter referred to as the change integration amount ΣΔT _i-1 ) is converted into the discretization time t _i. The temperature variation ΔT _{i at} is added. Θ is a threshold value set in advance to determine whether or not the temperature is decreasing, and is normally set to “0 (zero)”. Therefore, in the present embodiment, the fact that the temperature change amount ΔT _i is in the temperature decreasing direction (ΔT _i <θ) means that the change amount ΔT _i is negative.

Further, the temperature dip indexing unit 25a, when the change amount ΔT _i of the temperature obtained by the above equation 1 is in the temperature maintaining direction or the temperature increasing direction (ΔT _i ≧ θ), the change accumulated so far. The integrated amount ΣΔT _i−1 is reset to zero as shown in the following Expression 3.

As described above, in the temperature dip indexing process, the temperature dip indexing unit 25a changes the temperature (first / second temperature) detected by each of the thermocouples 21a to 21n and 22a to 22n per predetermined time. A temperature dip index (first / second temperature index) that indexes the degree of temperature dip (degree of temperature drop) during a period (first / second period) in which ΔT _i (first / second temperature difference) is continuously negative. 2nd index) is calculated. Thereby, in this Embodiment, it becomes possible to recognize the temperature dip which the temperature produced in the casting_mold | template 15 falls continuously as a temperature dip irrespective of the difference in the concave shape of the temperature profile. Note that “regardless of the difference in the concave shape of the temperature profile” means “not affected by the fact that the magnitude of the temperature drop gradient of the temperature dip can take various values”. Further, the calculated temperature dip index K is input to the vertical index multiplication unit 25b.

  Next, the vertical index multiplication process (step S102) will be described. In the present embodiment, the slab 17 having a horizontal cross section formed in the mold 15 is translated toward the mold outlet 15a by drawing in the casting direction D1. As described above, the thermocouples 21a to 21n in the temperature sensor 21 are associated with the thermocouples 22a to 22n in the downstream temperature sensor 22 on a one-to-one basis. Specifically, the thermocouples 21a to 21n in the upstream temperature sensor 21 are thermocouples 22a located on a straight line parallel to the casting direction D1 starting from each thermocouple 21a to 21n in the downstream temperature sensor 22. To 22n, respectively, in a one-to-one correspondence.

  Therefore, the part which passed the vicinity of each thermocouple 21a-21n in the slab 17 each passes the vicinity of the thermocouple in the corresponding relationship among the thermocouples 22a-22n arrange | positioned downstream later. For this reason, the temperature change detected by each of the upstream thermocouples 21a to 21n is also detected by the thermocouple having the corresponding relationship among the downstream thermocouples 22a to 22n. That is, the temperature dip caused by the depletion of the surface of the slab 17 detected in each of the thermocouples 21a to 21n in the upstream temperature sensor 21 is also applied to the thermocouples 22a to 22n that have a corresponding relationship in the downstream temperature sensor 22 later. Detected.

Furthermore, the time at which the temperature dips due to depletion of the slab 17 surface either thermocouples 21a~21n upstream of the temperature sensor 21 is detected (for convenience of explanation, the time and the time t _i), The time difference τ (= t _{i + τ} −t _i ) with respect to the time t _{i + τ} detected by the thermocouple 22 a to 22 n in the thermocouple 22 a to 22 n in the downstream temperature sensor 22 where the temperature dip due to the same depression is the temperature This is equal to the time (L / V) obtained by dividing the distance L in the casting direction D1 between the sensors 21 and 22 by the drawing speed V of the slab 17 (τ = L / V).

Therefore, in the up / down index multiplying process (step S102) according to the present embodiment, as shown in FIG. 5, the up / down index multiplying unit 25b receives a temperature dip from the temperature dip indexing unit 25a as a result of the temperature dip indexing process. An index K is input (step S121), and the temperature dip at time t _i calculated for each of the thermocouples 21a to 21n in the upstream temperature sensor 21 by using the following equation 4 for the input temperature dip index K: The temperature dip index K (= ΣΔT ^U _{i + τ} ) at the time t _{i + τ} of the thermocouple corresponding to the index K (= ΣΔT ^U _i ) of the temperature dip index K calculated for each of the downstream thermocouples 22a to 22n. (Multiplication) (step S122: vertical index multiplication step). Thereafter, the vertical index multiplying unit 25b returns to the slab surface vertical crack occurrence prediction process of FIG. In Equation 4 below, M is an index calculated by multiplication (hereinafter referred to as a multiplication index). Further, ΣΔT ^U _i is calculated in a temperature dip indexing unit 25a, the temperature dips index K of each upstream thermocouple 21a~21n at time _{t i, ΣΔT} ^D _{i + τ,} like temperature dip indicator unit 25a Is the temperature dip index K for each of the downstream thermocouples 22a to 22n at time ti _{+ τ} .

  The multiplication index M obtained as described above is input to the vertical crack occurrence determination unit 25c. The vertical crack occurrence determination unit 25c may perform depletion on the surface of the slab 17 by executing the vertical crack generation determination process (step S103: vertical crack generation determination step) using the input index M. Predict whether or not there is.

  Specifically, as shown in FIG. 6, when the vertical crack occurrence determination unit 25c inputs the multiplication index M from the vertical index multiplication unit 25b (step S131), the input multiplication index M is set in advance. It is determined whether or not it is greater than or equal to the threshold value φ (step S132), and if it is equal to or greater than the threshold value φ (Yes in step S132: M ≧ φ), it causes vertical cracks on the surface of the slab 17 or causes of this. A prediction result that depletion may occur is generated (step S133). On the other hand, when it is less than the threshold value φ (No in step S132: M <φ), the vertical crack occurrence determination unit 25c predicts that there is no vertical crack on the surface of the slab 17 or depletion that causes the occurrence of the vertical crack. A result is generated (step S134). In addition, after step S133 or S134, the vertical crack occurrence determination part 25c returns to the slab surface vertical crack occurrence prediction process of FIG.

  By executing the slab surface vertical crack occurrence prediction process as described above, in this embodiment, the temperature dip generated in the mold 15 does not depend on complicated logic using a large number of determination parameters, and It is possible to accurately recognize without depending on the difference in the profile shape of the dip. As a result, even a temperature dip having a shape different from the profile shape of the temperature dip generated in the past can be accurately recognized.

  Next, an example of the experimental result obtained by the slab surface vertical crack occurrence prediction process according to the embodiment will be described in detail with reference to the drawings. In carrying out this experiment, the use of the continuous casting machine 10 was set to the specifications shown in Table 1 below, and steels having the component ranges shown in Table 2 below were used to produce the target product (slab).

  In this experiment, the temperature sensor 21 is disposed at a height of 229 mm downstream from the molten metal surface (meniscus 17a) on the side surface of the mold 15 along the casting direction D1, while the temperature sensor 22 is disposed on the molten metal surface (side surface of the mold 15). It was arranged at a height of 517 mm downstream from the meniscus 17a) along the casting direction D1. Further, the thermocouples 21a to 21n and 22a to 22n of the temperature sensors 21 and 22 are embedded to a depth of 10 mm from the side surface of the mold 15, and the distance between the thermocouples 21a to 21n and 22a to 22n in the width direction D2 is 88 mm, respectively. did.

  Furthermore, in this experiment, the temperature was detected at intervals of 1 second from the thermocouples 21a to 21n and 22a to 22n. Furthermore, in this experiment, the temperature detection timing for the temperature sensor 21 is delayed from the temperature detection timing for the temperature sensor 21 by the time τ (= L / V) described above.

  First, the cast slab surface is visually searched to identify the slab in which the vertical crack is found, and the slab surface vertical crack occurrence prediction according to the present embodiment for the portion where no vertical crack has occurred in this slab. We examined what value the prediction result of the process takes. FIG. 7 shows the result of this verification, that is, one of the thermocouples in the temperature sensor 21 (hereinafter, this thermocouple is denoted by 21c) and the temperature sensor 22 for a portion where no vertical crack has occurred. It is a figure which shows the time-dependent change (temperature profile) of each detected with the thermocouple (henceforth the code | symbol of this thermocouple is set to 22c) corresponding to the thermocouple 21c of this. However, in FIG. 7, the horizontal axis is represented by the casting length. The casting length refers to the length from the tip of the cast slab 17. Here, if the casting speed V is constant, the casting length can be represented by the time from the start of casting and the casting speed V. In FIG. 7, a line L1 indicates a temperature profile detected by the thermocouple 21c disposed upstream, and a line L2 indicates a temperature profile detected by the thermocouple 22c disposed downstream.

Subsequently, with respect to the temperature of the profile shown in FIG. 7, the interval from the continuous discrete measurement time t _i-1 to the discrete measurement time t _{i is obtained} by using Equation 1 used in the temperature dip indexing process described above. A change amount ΔT _i of the temperature generated at (predetermined time interval) is obtained. FIG. 8A is a diagram showing a temporal change (profile) of the change amount ΔT ^U _i obtained from the temperature profile obtained from the upstream thermocouple 21c. Figure 8B is a diagram showing changes over time of the amount of change [Delta] T ^D _i obtained from the temperature profile obtained from the downstream thermocouple 22c (profile). However, in FIGS. 8A and 8B, the horizontal axis is represented by the casting length.

Furthermore, using Equation 2 used in the above-described temperature dip indexing process, the temperature variation ΔT ^U _i in the thermocouple 21c shown in FIG. 8A and the temperature variation ΔT ^D in the thermocouple 22c shown in FIG. 8B. The temperature dip index K at each thermocouple 21c and 22c is calculated from _i . FIG. 9A is a diagram showing a temporal change (profile) of the temperature dip index K obtained for the upstream thermocouple 21c. FIG. 9B is a diagram showing a temporal change (profile) of the temperature dip index K obtained for the downstream thermocouple 22c. However, in FIGS. 9A and 9B, the horizontal axis is represented by the casting length.

  Furthermore, the temperature dip index K for the thermocouple 21c shown in FIG. 9A is multiplied by the temperature dip index K for the thermocouple 22c shown in FIG. 9B by using Equation 3 used in the temperature dip indexing process described above. Thus, a multiplication index M for recognizing the occurrence of the temperature dip is calculated. FIG. 10 shows a time-dependent change of the multiplication index M obtained by multiplying the temperature dip index K for the upstream thermocouple 21c shown in FIG. 9A and the temperature dip index K for the downstream thermocouple 22c shown in FIG. 9B. It is a figure which shows a change (profile). However, in FIG. 10, the horizontal axis indicates the casting length.

As shown in FIG. 10, in the temporal change (profile) of the multiplication index M at a site where no vertical crack was found by visual search, a temporary peak of the multiplication index M appears, but the peak value is It was a relatively small value of about 10 [° C. ² ] or less.

  Next, it was verified what value the prediction result of the slab surface vertical crack occurrence prediction process according to the present embodiment takes for the part where the vertical crack was found by visual search. FIG. 11 shows the result of this verification, that is, one of the thermocouples in the temperature sensor 21 (hereinafter, the thermocouple is referred to as 21d) and the temperature sensor 22 for the portion where the vertical crack has occurred. It is a figure which shows the time-dependent change (temperature profile) of the temperature detected with each of the thermocouple (henceforth the code | symbol of this thermocouple is set to 22d) corresponding to the thermocouple 21d of this. However, in FIG. 11, the horizontal axis represents the casting length. In FIG. 11, a line L3 indicates a temperature profile detected by the thermocouple 21d disposed upstream, and a line L4 indicates a temperature profile detected by the thermocouple 22d disposed downstream. Further, in FIG. 11, a point P1 indicates the position in the casting direction D1 from the tip of the slab 17 at the vertical crack occurrence point viewed from the thermocouple 21d when the time axis of the upstream thermocouple 21d is a reference. P2 indicates the position (= 203.07 + 1.5 + 0.229 = 204.799 [m]) of the upstream thermocouple 21d corresponding to the vertical crack occurrence position (position of 1.5 m upstream from the mold outlet 15a). Furthermore, in FIG. 11, a point P3 indicates a position in the casting direction D1 from the tip of the slab 17 at the longitudinal crack portion viewed from the downstream thermocouple 22d when the time axis of the upstream thermocouple 21d is used as a reference. , Point P4 indicates the position (= 203.07 + 1.5 + 0.517 = 205.087 [m]) of the downstream thermocouple 22d corresponding to the vertical crack occurrence position (position 1.5 m upstream from the mold outlet 15a). .

Subsequently, with respect to the temperature of the profile shown in FIG. 11, the interval from the continuous discrete measurement time t _i-1 to the discrete measurement time t _{i is obtained} by using Equation 1 used in the temperature dip indexing process described above. A change amount ΔT _i of the temperature generated at (predetermined time interval) is obtained. FIG. 12A is a diagram showing a temporal change (profile) of the change amount ΔT ^U _i obtained from the temperature profile obtained from the upstream thermocouple 21d. Figure 12B is a diagram showing changes over time of the amount of change [Delta] T ^D _i obtained from the temperature profile obtained from the downstream thermocouple 22 d (profile). However, in FIGS. 12A and 12B, the horizontal axis is represented by the casting length.

Furthermore, using equation 2 used in the temperature dip indexing process described above, the amount of temperature change ΔT ^U _i in the thermocouple 21d shown in FIG. 12A and the amount of temperature change ΔT ^D in the thermocouple 22d shown in FIG. 12B. The temperature dip index K at each thermocouple 21d and 22d is calculated from _i . FIG. 13A is a diagram showing a temporal change (profile) of the temperature dip index K obtained for the upstream thermocouple 21d. FIG. 13B is a diagram showing a temporal change (profile) of the temperature dip index K obtained for the upstream thermocouple 22d. However, in FIGS. 13A and 13B, the horizontal axis is represented by the casting length.

  Furthermore, the temperature dip index K for the thermocouple 21d shown in FIG. 13A is multiplied by the temperature dip index K for the thermocouple 22d shown in FIG. 13B by using Equation 3 used in the temperature dip indexing process described above. Thus, a multiplication index M for recognizing the occurrence of the temperature dip is calculated. FIG. 14 shows a time-dependent change (profile) of the multiplication index obtained by multiplying the temperature dip index K for the thermocouple 21d shown in FIG. 13A and the temperature dip index K for the thermocouple 22d shown in FIG. 13B. FIG. However, in FIG. 14, the horizontal axis is represented by the casting length.

As shown in FIG. 14, the multiplying index M takes a peak value for a site where a vertical crack is found by visual search. Further, the peak value and 52 [° C. ^2] degrees, a very large value compared to the peak value due to factors other than depression shown in FIG. 10 (10 [℃ ^2] or less so).

  From the above, in this embodiment, it is possible to use an index (multiplication index M) that is sufficiently different between a temperature dip due to depletion and a temperature dip due to other than depletion. It is possible to prevent a temperature dip caused by a cause other than the depletion generated on the surface of the piece 17 from being mistaken as a temperature dip caused by the depression.

  Further, in the present embodiment, the temperature dip generated in the mold 15 can be recognized without depending on the temperature dip profile shape accumulated in the database or the like, and thus depends on the difference in the temperature dip profile shape. It is possible to recognize it accurately. That is, even a temperature dip having a shape different from the profile shape of the temperature dip generated in the past can be accurately recognized.

  Furthermore, in this embodiment, since the temperature dip generated in the mold 15 can be recognized without depending on the profile shape of the temperature dip accumulated in the database or the like, a complicated operation using a large number of determination parameters is possible. Regardless of logic, it becomes possible to accurately recognize the temperature dip.

In the above-described embodiment, the temperature dip indexing unit 25a and the first / second temperature dip indexing step (step S114) are the temperatures detected by the thermocouples 21a-21n and 22a-22n (first / Second temperature) change ΔT _i (first / second temperature difference) is calculated for each of thermocouples 21a to 21n and 22a to 22n during a period (first / second period) in which the change is negative continuously. The total change amount ΔT _i (first / second temperature difference) was calculated as the temperature dip index K (first / second index) for each of the thermocouples 21a to 21n and 22a to 22n. It is not limited to this. For example, in each of the thermocouples 21a to 21n and 22a to 22n during a period (first / second period) in which the change amount ΔT _i (first / second temperature difference) is continuously negative with respect to the temperature dip index K. The total value of the detected temperatures (first / second temperature) for each of the thermocouples 21a to 21n and 22a to 22n is calculated as a temperature dip index K (first / second index) for each thermocouple 21a to 21n and 22a to 22n. ). Even when such a temperature dip index is used, the same effects as those of the above-described embodiment can be obtained.

  Moreover, each part (25a, 25b, and 25c) with which the signal processor 25 mentioned above and the slab surface vertical crack generation | occurrence | production prediction process which the signal processor 25 perform are ROM, RAM, CD-ROM (including RW etc.), It may be realized by an information processing unit such as a CPU constituting the signal processor 25 reading and executing a program recorded on a recording medium (not shown) such as a DVD-ROM (including RW), or You may implement | achieve by the chip | tip built in as the hardware which performs the single-surface vertical crack generation | occurrence | production prediction process.

  Further, the above embodiment is merely an example for carrying out the present invention, and the present invention is not limited to these, and various modifications according to specifications and the like are within the scope of the present invention. It is obvious from the above description that various other embodiments are possible within the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Continuous casting machine 11 Molten steel 12 Tundish 13 Sliding nozzle 14 Immersion nozzle 15 Mold 15a Mold exit 16 Slab support roll 17 Cast slab 17a Meniscus 18 Unsolidified phase 19 Solidified shell 20 Slab surface vertical crack generation prediction device 21, 22 Temperature Sensors 21a to 21n, 22a to 22n Thermocouple 23 Signal line 24 Temperature detector 25 Signal processor 25a Temperature dip indexing unit 25b Vertical index multiplication unit 25c Vertical crack occurrence determination unit 26 Process data 27 Information processing device D1 Casting direction D2 Width Direction L1, L2, L3, L4 Lines P1, P2, P3, P4

Claims (8)

A mold in which molten steel injected from the upstream is drawn in the casting direction from the downstream, a first temperature sensor disposed on a side surface of the mold, and a side surface of the mold that is closer to the casting direction than the first temperature sensor. A second temperature sensor disposed downstream of the continuous casting machine,
First temperature detecting means for detecting a first temperature using the first temperature sensor every predetermined time;
A first temperature difference between the first temperatures detected before and after is calculated, and a first temperature drop indexed during a first period in which the first temperature difference is continuously negative First temperature dip indexing means for calculating an index;
It is obtained by dividing the distance between the first temperature sensor and the second temperature sensor in the casting direction by the casting speed rather than the timing at which the first temperature detecting means detects the first temperature every predetermined time. A second temperature detecting means for detecting the second temperature at a timing delayed by a predetermined time;
A second temperature difference between the second temperatures detected before and after is calculated, and the second temperature difference is indexed to the degree of the second temperature drop during a second period in which the second temperature difference is continuously negative. A second temperature dip indexing means for calculating an index;
Vertical index multiplication means for generating a third index by multiplying the first index and the second index;
Vertical crack occurrence determination means for determining whether depletion has occurred on the surface of the slab based on the third index;
A continuous casting machine characterized by comprising: The first temperature dip indexing means calculates a total value of the first temperature differences calculated during the first period as the first index;
The continuous casting machine according to claim 1, wherein the second temperature dip indexing means calculates a total value of the second temperature differences calculated during the second period as the second index. The first temperature dip indexing means calculates a total value of the first temperatures calculated during the first period as the first index;
The continuous casting machine according to claim 1, wherein the second temperature dip indexing means calculates a total value of the second temperatures calculated during the second period as the second index. The first temperature sensor includes a plurality of first thermocouples arranged along the width direction of the slab,
The second temperature sensor includes a plurality of second thermocouples arranged along the width direction, each of which is arranged downstream along the casting direction with respect to the first thermocouple,
The first temperature detecting means detects the first temperature for each of the plurality of first thermocouples,
The first temperature dip indexing means calculates the first index for each of the plurality of first thermocouples,
The second temperature detection means detects the second temperature for each of the plurality of second thermocouples,
The second temperature dip indexing means calculates the second index for each of the plurality of second thermocouples,
The up / down index multiplying means includes a first thermocouple and a second thermocouple respectively arranged up and down along the casting direction among the plurality of first thermocouples and the plurality of second thermocouples. The continuous casting machine according to any one of claims 1 to 3, wherein the first index and the second index are multiplied. A mold in which molten steel injected from the upstream is drawn in the casting direction from the downstream, a first temperature sensor disposed on a side surface of the mold, and a side surface of the mold that is closer to the casting direction than the first temperature sensor. A second temperature sensor disposed downstream of the slab surface vertical crack occurrence prediction method in a continuous casting machine comprising:
A first temperature detecting step of detecting a first temperature using the first temperature sensor every predetermined time;
A first temperature difference between the first temperatures detected before and after is calculated, and a first temperature drop indexed during a first period in which the first temperature difference is continuously negative A first temperature dip indexing step for calculating an index;
It is obtained by dividing the distance between the first temperature sensor and the second temperature sensor in the casting direction by the casting speed rather than the timing at which the first temperature detecting means detects the first temperature every predetermined time. A second temperature detecting step for detecting the second temperature at a timing later by a specified time;
A second temperature difference between the second temperatures detected before and after is calculated, and the second temperature difference is indexed to the degree of the second temperature drop during a second period in which the second temperature difference is continuously negative. A second temperature dip indexing step for calculating an index;
A vertical index multiplication step of multiplying the first index and the second index to generate a third index;
A vertical crack occurrence determination step for determining whether or not depletion has occurred on the surface of the slab based on the third index,
A method for predicting the occurrence of vertical cracks on a slab surface, comprising: The first temperature dip indexing step calculates a total value of the first temperature differences calculated during the first period as the first index;
The slab surface vertical crack according to claim 5, wherein the second temperature dip indexing step calculates a total value of the second temperature differences calculated during the second period as the second index. Occurrence prediction method. The first temperature dip indexing step calculates a total value of the first temperatures calculated during the first period as the first index,
6. The slab surface vertical crack occurrence according to claim 5, wherein the second temperature dip indexing step calculates a total value of the second temperatures calculated during the second period as the second index. Prediction method. The first temperature sensor includes a plurality of first thermocouples arranged along the width direction of the slab,
The second temperature sensor includes a plurality of second thermocouples arranged along the width direction, each of which is arranged downstream along the casting direction with respect to the first thermocouple,
The first temperature detecting step detects the first temperature for each of the plurality of first thermocouples,
The first temperature dip indexing step calculates the first index for each of the plurality of first thermocouples,
The second temperature detecting step detects the second temperature for each of the plurality of second thermocouples,
The second temperature dip indexing step calculates the second index for each of the plurality of second thermocouples,
The up / down index multiplying step includes the first thermocouple and the second thermocouple respectively arranged up and down along the casting direction among the plurality of first thermocouples and the plurality of second thermocouples. The slab surface vertical crack occurrence prediction method according to any one of claims 5 to 7, wherein the first index and the second index are multiplied.

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