Method of controlling injection rate of molten steel, continuous casting method of steel, and control facility

Abstract

To provide a method of controlling the injection rate of molten steel allowing for detecting a melt level with high responsibility.SOLUTION: A method of controlling the injection rate of molten steel in continuous casting of steel includes: a detection step for, at a start of continuous casting of steel, detecting time at which a melt level in a mold reaches a predetermined melt level based on a weight of molten steel poured in the mold; and a control step for controlling the injection rate of molten steel to be poured into the mold from a tundish based on the time detected in the detection step.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for controlling the pouring rate of molten steel at the start of continuous casting of steel using a mold, a method for continuous casting of steel using the method for controlling the pouring rate, and a control facility for controlling the pouring rate.

Background Art

[0002] At the start of continuous casting of steel, a dummy bar is inserted into the mold to close the lower part of the mold, and molten steel is poured thereon. To shift from this state to the steady state of continuous casting of steel, it is necessary to raise the molten metal surface level in the mold to the target molten metal surface level and withdraw the dummy bar at the planned casting speed.

[0003] At the start when the molten steel is first poured into the mold, it is important to accurately grasp the molten metal surface level after the start of pouring of the molten steel and the rising speed of the molten metal surface level. However, the molten metal surface level in the mold and the rising speed of the molten metal surface level always vary due to clogging or the like occurring in the sliding shutter of the tundish. The variation in the rising speed of the molten metal surface level causes the time until the target molten metal surface level is reached to vary, and this variation in time becomes a factor in breakout or deterioration of the quality of the cast slab, hindering stable operation.

[0004] As a technique for controlling the pouring rate of molten steel at the start of continuous casting of steel, Patent Document 1 discloses an auto-start method for continuous casting in which a plurality of thermocouples are embedded in the vertical direction of the mold, and the molten metal surface level in the mold is determined from the surface temperature of the mold measured by the thermocouples. According to Patent Document 1, the rising speed of the molten metal surface is obtained from the determined molten metal surface level, and by controlling the opening degree of the sliding shutter for pouring the molten steel into the mold based on the rising speed, it is said that defects such as overflow of the molten steel, breakout, and cracking of the cast slab can be prevented.

[0005] Patent Document 2 discloses a method for starting continuous casting that corrects the opening pattern of a sliding gate up to a drawing start level based on the time until a reference level lower than the drawing start level of a dummy bar is reached. In Patent Document 2, the molten metal level on the upper side in the mold is detected by a continuous level gauge (eddy current sensor), and the lower side that cannot be detected by the eddy current sensor is detected using a fixed point level gauge (thermocouple), and the opening pattern of the sliding gate is corrected based on the molten metal level. Thereby, it is said that the injection rate of the molten steel is controlled, and problems such as breakout and overflow of the molten metal from the mold can be prevented.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In Patent Documents 1 and 2, it is detected that the molten metal surface in the mold has reached a predetermined molten metal level position from the surface temperature of the mold measured by a thermocouple. However, since there is a delay time due to the heat conduction of the mold copper plate in the thermocouple, there is a problem that the responsiveness of the molten metal level detection is low.

[0008] The present invention has been made in view of such problems of the prior art, and an object thereof is to provide a method for controlling the injection rate of molten steel, a method for continuous casting of steel, and a control facility that can detect the molten metal level with high responsiveness.

Means for Solving the Problems

[0009] The means for solving the above problems are as follows. [1] A method for controlling the injection rate of molten steel in continuous casting of steel, comprising a detection step of detecting, at the start of continuous casting of steel, the time when the molten steel level in the mold reaches a predetermined molten steel level based on the weight of the molten steel injected into the mold, and a control step of controlling the injection rate of the molten steel injected from the tundish into the mold based on the time detected in the detection step and the predetermined molten steel level. A method for controlling the injection rate of molten steel. [2] A method for controlling the injection rate of molten steel in continuous casting of steel, comprising a detection step of detecting, at the start of continuous casting of steel, the time when the molten steel level in the mold reaches the position where the optical fiber type temperature sensor is provided based on the mold temperature measured by the optical fiber type temperature sensor embedded in the mold, and a control step of controlling the injection rate of the molten steel injected from the tundish into the mold based on the time detected in the detection step and the position where the optical fiber type temperature sensor is provided. A method for controlling the injection rate of molten steel. [3] A continuous casting method of steel using the method for controlling the injection rate of molten steel according to [1] or [2]. [4] A control facility for controlling the injection rate of molten steel in continuous casting of steel, comprising a tundish, a mold, and a control device for controlling the injection rate of the molten steel. The tundish has a housing part for accommodating molten steel, a sliding shutter provided at the bottom of the housing part, and a submerged nozzle connected to the sliding shutter for injecting the molten steel into the mold. The mold has a plurality of mold copper plates. The control device has a detection part for detecting the time when the molten steel level in the mold reaches a predetermined molten steel level based on the weight of the molten steel injected into the mold, and an injection rate control part for controlling the injection rate of the molten steel based on the time detected by the detection part and the predetermined molten steel level. A control facility. [5] A control facility for controlling the pouring speed of molten steel in continuous casting of steel, comprising a tundish, a mold, and a control device for controlling the pouring speed of the molten steel. The tundish has a housing portion for accommodating molten steel, a sliding shutter provided at the bottom of the housing portion, and a submerged nozzle connected to the sliding shutter for pouring the molten steel into the mold. The mold has a plurality of mold copper plates and an optical fiber type temperature sensor embedded in at least one of the plurality of mold copper plates. The control device has a detection unit for detecting the time when the molten metal surface in the mold reaches the position where the optical fiber type temperature sensor is provided based on the mold temperature measured by the optical fiber type temperature sensor, and an injection speed control unit for controlling the pouring speed of the molten steel based on the time detected by the detection unit and the position where the optical fiber type temperature sensor is provided.

Advantages of the Invention

[0010] According to the present invention, since the molten metal position is detected using the molten steel weight and the optical fiber type temperature sensor, the molten metal surface position can be detected with high responsiveness. As a result, the time when the molten metal surface reaches the position can be obtained more accurately, and by using this time, the pouring speed of the molten steel at the start of continuous casting of steel can be controlled with high accuracy to the target pouring speed. As a result, breakout due to insufficient cooling, drawing defects due to overcooling, and deterioration of slab quality at the start of continuous casting of steel can be suppressed.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

MODE FOR CARRYING OUT THE INVENTION

[0012] Hereinafter, the present invention will be described through embodiments of the present invention. The following embodiments show a preferred example of the present invention and are not limited by these embodiments.

[0013] FIG. 1 is a schematic cross-sectional view showing an example of a continuous casting facility 10 including a control facility according to the present embodiment. The continuous casting facility 10 includes a tundish 12, a mold 22, pinch rolls 34 provided below the mold 22, a plurality of secondary cooling zones 32, conveying rolls 38, a slab cutter 40, and a control device 60. Above the tundish 12, a ladle 15 for accommodating molten steel 26 is installed, and the molten steel 26 is poured from the bottom of the ladle 15 into the tundish 12.

[0014] The tundish 12 has a housing portion 14 for accommodating molten steel 26, a sliding shutter 16 provided at the bottom of the housing portion 14, and a submerged nozzle 18 connected to the sliding shutter 16 and extending downward. The molten steel 26 accommodated in the housing portion 14 of the tundish 12 is poured into the mold 22 through the sliding shutter 16 and the submerged nozzle 18. The injection rate of the molten steel 26 poured into the mold 22 is controlled by adjusting the opening degree of the sliding shutter 16.

[0015] Figure 2 is a perspective schematic view of the mold 22. As shown in Figure 2, the mold 22 is composed of a plurality of mold copper plates. In this embodiment, the plurality of mold copper plates are, for example, a pair of mold long-side copper plates 44 and a pair of mold short-side copper plates 46. The molten steel 26 injected into the mold 22 is heat-extracted from the inner surface of the mold 22 and solidifies, thereby forming a slab 30 having a solidified shell 28 as an outer shell and the molten steel 26 inside.

[0016] Referring to Figure 1 again. The slab 30 formed in the mold 22 is pulled downward by pinch rolls 34 provided directly below the mold 22. Below the pinch rolls 34, a plurality of slab support rolls 36 adjacent to each other in the casting direction are provided. The slab 30 pulled out below the mold 22 is supported and conveyed by the slab support rolls 36. In the gaps between the slab support rolls 36 adjacent to each other in the casting direction, a plurality of secondary cooling zones 32 in which spray nozzles (not shown) are arranged are installed along the casting direction from directly below the mold 22.

[0017] The slab 30 is cooled while being conveyed by the cooling water ejected from the spray nozzles of the secondary cooling zone 32. While the slab 30 is being conveyed and passing through the plurality of secondary cooling zones 32, the molten steel 26 inside the slab 30 is cooled and solidification proceeds, and the solidification of the slab 30 is completed.

[0018] On the further downstream side in the casting direction, a plurality of conveying rolls 38 for continuously conveying the slab 30 are installed. Above the conveying rolls 38, a slab cutting machine 40 for cutting the slab 30 is provided. After the solidification is completed, the slab 30 is cut to a predetermined length by the slab cutting machine 40 to produce a slab 42.

[0019] The control device 60 oversees the production of the slab 42 by the continuous casting facility 10 described above and controls the operations of each device constituting the continuous casting facility 10. Also, at the start of continuous casting of steel, the control device 60 determines the weight of the molten steel poured from the tundish 12 into the mold 22, and based on the weight of the molten steel, detects the time required until the molten steel surface reaches a predetermined molten steel surface position. Further, the control device 60 controls the injection rate of the molten steel 26 injected from the immersion nozzle 18 based on the detected time. Specifically, the control device 60 uses the predetermined molten steel surface position and the time when the molten steel surface reaches that position to adjust the opening degree of the sliding shutter 16 so that the molten steel surface reaches the position where the drawing of the slab 30 by the pinch roll 34 starts at the target time, and then controls the injection rate of the subsequent molten steel 26. Note that the control facility according to the present embodiment includes the tundish 12, the mold 22, and the control device 60.

[0020] Next, the start of continuous casting of steel will be described. FIG. 3 is a cross-sectional schematic view showing the situation at the start of continuous casting of steel. In the present embodiment, the start of continuous casting of steel means the period from the start of injection of the molten steel 26 into the mold 22 to the start of drawing of the slab 30 by the pinch roll 34 at the initial stage of continuous casting of steel.

[0021] At the start of continuous casting of steel, first, the dummy bar 48 is inserted into the mold 22, and the dummy bar 48 is set at a position where the lower end of the mold 22 is closed by the dummy bar 48. In this state, the molten steel 26 is injected from above the dummy bar 48 using the immersion nozzle 18. The molten steel surface position at which the pinch roll 34 starts drawing the slab 30 is predetermined, and when the molten steel surface reaches that position, the pinch roll 34 starts drawing the slab 30.

[0022] At the start of continuous casting of steel, if the time from the start of pouring the molten steel 26 to the start of pulling out the slab 30 by the pinch rolls 34 is too short, breakouts will occur due to insufficient formation of the solidification shell 28. Also, if the time until the start of pulling out the slab 30 becomes too long, not only will the productivity of continuous casting of steel decrease, but poor pulling out by the pinch rolls 34 and deterioration of the slab quality will also occur.

[0023] Thus, in order to reach the target time at the predetermined molten metal surface position, it is necessary to pour the molten steel 26 into the mold 22 from the immersion nozzle 18 at a predetermined pouring rate. However, at the start of continuous casting of steel, slight clogging is likely to occur in the sliding shutter 16 and the immersion nozzle 18 during the process of the molten steel 26 passing through, and the pouring rate of the molten steel 26 from the immersion nozzle 18 may change from moment to moment. Therefore, it is necessary to grasp such changes in the pouring rate of the molten steel 26 and, when the pouring rate changes, adjust the opening degree of the sliding shutter 16 in response to the change. That is, when the pouring rate decreases, the opening degree of the sliding shutter 16 is increased to increase the pouring rate, and when the pouring rate increases, the opening degree of the sliding shutter 16 is decreased to slow down the pouring rate, and it is necessary to adjust the opening degree of the sliding shutter 16 so that the overall pouring rate at the start reaches the target pouring rate.

[0024] In the control equipment 10 according to the present embodiment, as described above, the weight of the molten steel poured from the tundish 12 into the mold 22 after a predetermined time has elapsed is obtained, and based on the weight of the molten steel, the time when the molten steel in the mold 22 reaches the predetermined molten metal surface position is detected. Then, using the detected time and the molten metal surface position, the opening degree of the sliding shutter 16 is adjusted so that the molten metal surface reaches the molten metal surface position where the pinch rolls 34 start pulling out the slab 30 at the target time, and the subsequent pouring rate of the molten steel 26 is controlled.

[0025] Next, a method for calculating the weight of molten steel poured from the tundish 12 into the mold 22 will be described. FIG. 4 is a diagram for explaining an example of a method for calculating the weight of molten steel poured into the mold 22. Let the initial molten steel weight of the ladle 15 be W 0 (ton), the molten steel weight of the ladle 15 after a predetermined time has elapsed be W t (ton), and the molten steel weight of the tundish 12 after a predetermined time has elapsed be TDW t (ton). Then, the weight of molten steel MDW t (ton) poured into the mold 22 after a predetermined time has elapsed can be calculated by the following formula (1).

[0026] MDW t =(W 0 -W t )-TDWt ···(1)

[0027] FIG. 5 is a graph showing the correlation between the measured value and the calculated value of the weight of molten steel poured into the mold 22. The horizontal axis of FIG. 5 is the measured value (ton) of the weight of molten steel poured into the mold 22, and the vertical axis is the calculated value (ton) of the weight of molten steel poured into the mold 22. As shown in FIG. 5, the calculated value of the weight of molten steel calculated by the above (1) was almost the same as the measured value of the molten steel actually poured into the mold 22. From this result, it was confirmed that the weight of molten steel poured into the mold 22 can be calculated with high accuracy by using the above formula (1).

[0028] By dividing this molten steel weight MDW t by the specific gravity of the molten steel 26, the volume of molten steel poured into the mold 22 after a predetermined time has elapsed can be calculated. By using the calculated volume of molten steel and the correspondence between the molten steel level position in the mold 22 and the volume of molten steel, the molten steel level position can be detected with high responsiveness, and thereby the time from the start of pouring of the molten steel 26 until the molten steel level reaches a predetermined molten steel level position can be detected. Note that the correspondence between the molten steel level position and the volume of molten steel is, for example, a regression formula showing the correspondence between the molten steel level position and the volume of molten steel, and it may be grasped in advance by conducting experiments or the like. Then, by adjusting the opening degree of the sliding shutter 16 based on the molten steel level position and the detected time, the pouring speed of the subsequent molten steel 26 can be controlled to an appropriate pouring speed.

[0029] Next, the control device 60 will be described. FIG. 6 is a schematic diagram showing a configuration example of the control device 60. The control device 60 is a general-purpose computer such as a workstation or a personal computer, for example. The control device 60 includes a control unit 62, an input unit 64, an output unit 66, and a storage unit 68. The control unit 62 is, for example, a CPU or the like, and controls the operation of the continuous casting facility 10 and executes predetermined calculations using the programs and data stored in the storage unit 68. Further, the control unit 62 functions as a detection unit 70 and an injection speed control unit 72 by executing the program read from the storage unit 68.

[0030] The input unit 64 is, for example, a keyboard, a touch panel provided integrally with a display, or the like. The output unit 66 is, for example, an LCD or a CRT display or the like. The storage unit 68 is, for example, an information recording medium such as a rewritable flash memory, a hard disk built-in or connected by a data communication terminal, a memory card, and a reading / writing device thereof. The storage unit 68 stores in advance programs for realizing various functions of the continuous casting facility 10, data used during the execution of the programs, and the like. Further, in the storage unit 68, the above formula (1), the specific gravity of the molten steel 26, the specific gravity of the slab 42, and the correspondence between the molten metal level position in the mold 22 and the volume of the molten steel are input from the input unit 64 in advance and stored in the storage unit 68.

[0031] Next, the processes executed by the detection unit 70 and the injection speed control unit 72 will be described. The detection unit 70 detects the time when the molten metal level reaches a predetermined n-stage molten metal level position in the mold 22 based on the weight of the molten steel injected into the mold 22. The detection unit 70 obtains the initial molten steel weight W of the ladle 15 0 and the molten steel weight W of the ladle 15 t and the molten steel weight TDW of the tundish 12 t at a predetermined sampling rate. These weights are measured by load cells (not shown) provided on the ladle 15 and the tundish 12, and are obtained by calculating the difference between the total weights of the ladle 15 and the tundish 12 including the molten steel 26 and the weights of the ladle 15 and the tundish 12.

[0032] When the detection unit 70 acquires these weights, it reads out the above formula (1), the specific gravity of the molten steel 26, and the correspondence relationship between the molten metal level position in the mold 22 and the molten steel volume from the storage unit 68, and determines the molten metal level position in the mold 22 using these. In this way, the detection unit 70 determines the molten metal level position in the mold 22 at the above sampling rate, and detects the time when the molten metal level position reaches the n-stage molten metal level positions determined in advance. This process is the detection step. The detection unit 70 outputs the detected time and the molten metal level position to the injection speed control unit 72.

[0033] When the injection speed control unit 72 acquires the time and the molten metal level position from the detection unit 70, it adjusts the opening degree of the sliding shutter 16 so that the molten metal level reaches the molten metal level position where the drawing of the slab 30 starts with the pinch roll 34 at the target time, and controls the injection speed of the molten steel 26. Specifically, the injection speed control unit 72 obtains the remaining time until the target time, which is the difference between the target time and the time acquired from the detection unit 70, and specifies the opening degree of the sliding shutter 16 using the remaining time until the target time, the molten metal level position, and the following formulas (2) and (3).

[0034]

Number

[0035]

Number

[0036] In the above formula (3), V S is the injection speed (kg / sec) of the molten steel 26, L is the length (m) of the mold copper plate in the casting direction, and Lv nis the position (m) of the molten steel surface at the nth stage, and TMDV is the remaining time (sec) until the target time. The flow coefficient α is an index of the ease of flow of the molten steel 26 from the immersion nozzle 18, and an appropriate value is set according to the steel type and the number of consecutive uses of the sliding shutter 16. For example, when the sliding shutter 16 is worn out and the molten steel 26 flows more easily, the flow coefficient α is set to 120%, or when a part of the sliding shutter 16 or the immersion nozzle 18 is blocked, the flow coefficient α is set to 80%. Further, the height H of the molten steel 26 in the tundish 12 is obtained from the molten steel weight TDW in the tundish 12 after a predetermined time has elapsed. t is obtained from.

[0037] When the injection speed control unit 72 specifies the opening degree aT of the sliding shutter 16 using the above equations (2) and (3), it adjusts the opening degree of the sliding shutter 16 to the specified opening degree to control the subsequent injection speed of the molten steel 26. This process is the control step. The initial opening degree aT of the sliding shutter 16 when starting the injection of the molten steel 26 into the mold 22 0 is determined by the following equation (4).

[0038]

Equation

[0039] Next, the control process of the injection speed of the molten steel 26 at the start of continuous casting of steel will be described with reference to FIG. 7. FIG. 7 is a flowchart showing the flow of the control process of the injection speed of the molten steel 26 at the start of continuous casting of steel. The flow shown in FIG. 7 starts after the dummy bar 48 is set at the lower end of the mold 22.

[0040] First, the pouring speed control unit 72 calculates the opening degree of the sliding shutter 16 of the tundish 12 using the above formula (4) and determines the initial opening degree aT of the sliding shutter 16 of the tundish 12. 0 (Step S101), the sliding shutter 16 is opened, and the injection of molten steel 26 from the submerged nozzle 18 into the mold 22 begins (Step S102).

[0041] When pouring of molten steel 26 into mold 22 is started, detection unit 70 starts a target time timer (step S103). This target time timer is a timer that indicates the remaining time from the start of pouring of molten steel 26 into mold 22 until the target time for the molten steel surface to reach the pinch roll start position.

[0042] The detection unit 70 detects the initial molten steel weight W 0 , weight of molten steel after a given time has elapsed W t and the weight of molten steel after a certain period of time (TDW) t and calculates the weight of molten steel poured into the mold 22 using the above formula (1). The detection unit 70 also calculates the molten steel level position using the calculated molten steel weight, the specific gravity of the molten steel 26, and the correspondence between the molten steel level position in the mold 22 and the molten steel volume. The detection unit 70 judges whether the calculated molten steel level position has reached a predetermined starting position of the pinch rolls 34 (step S104). If the detection unit 70 judges that the obtained molten steel level position has not reached the starting position of the pinch rolls 34 (step S104: No), it then judges whether the molten steel level position has reached a predetermined n-th stage molten steel level position (step S105). If the detection unit 70 judges that the molten steel level has not reached the n-th stage molten steel level position (step S105: No), it repeatedly executes the processes of steps S104 and S105 until the molten steel level reaches the pinch roll starting position or the n-th stage molten steel level position. The molten metal surface position at which the pinch rolls 34 are started and the molten metal surface position of the nth stage are determined in advance and stored in the storage section 68.

[0043] On the other hand, when the detection unit 70 determines that the soup level has reached the soup level position at the n-th stage (step S105: Yes), it detects the remaining time until the target time from the target time timer (step S106). The detection unit 70 outputs the soup level position at the n-th stage and the remaining time until the target time to the injection speed control unit 72.

[0044] When the injection speed control unit 72 acquires the soup level position at the n-th stage and the remaining time until the target time, it calculates the opening degree aT of the sliding shutter using the above equations (2) and (3), and sets the opening degree of the sliding shutter 16 to the opening degree aT (step S107). After setting the opening degree of the sliding shutter 16, the injection speed control unit 72 returns the process to step S104, and the detection unit 70 executes the processes of step S104 and step S105 again. In step S105, for example, when the soup level reaches the soup level position at the first stage and the processes of step S106 and step S107 are executed, in the subsequent processes, even if the soup level reaches the soup level position at the first stage, the processes of step S106 and step S107 are not executed until the soup level reaches the soup level position at the second stage. That is, the processes of step S106 and step S107 are executed only when the soup level first reaches each n-th stage.

[0045] When the soup level rises and the detection unit 70 determines that the soup level has reached the activation position of the pinch roll 34 (step S104: Yes), the injection speed control unit 72 sets the opening degree of the sliding shutter 16 to the opening degree determined when activating the pinch roll 34 (step S108), activates the pinch roll 34 (step S109), and ends the control process of the molten steel injection speed at the start of continuous casting of steel shown in FIG. 7. In step S104, it may be determined by detecting the soup level with an eddy current sensor (not shown) provided above the mold 22 whether the soup level has reached the pinch roll activation position.

[0046] Thus, in the method and equipment for controlling the pouring rate of molten steel according to this embodiment, the time to reach a predetermined molten metal level is detected based on the weight of the molten steel 26 poured into the mold 22. Therefore, in the method and equipment for controlling the pouring rate of molten steel according to this embodiment, since there is no delay time due to the heat conduction of the mold copper plate, it is possible to detect reaching the molten metal level with high responsiveness and to detect the time to reach the molten metal level more accurately. As a result, the pouring rate of the molten steel 26 can be controlled more accurately so that the molten metal level reaches the position where the pinch roll 34 starts drawing at the target time, and breakout due to insufficient formation of the solidification shell 28, reduction in productivity of continuous casting of steel, drawing defects caused by the pinch roll 34, and deterioration of slab quality can be suppressed.

[0047] Also, by using the weight of the molten steel 26, it is not necessary to provide a thermocouple in the mold 22, which can contribute to cost reduction of the mold 22, and there are no problems of poor contact of the thermocouple or wire breakage due to the molten steel 26, and the time when the molten metal level reaches a predetermined molten metal level can be stably detected.

[0048] In addition, in step S105 of FIG. 7, an example is shown in which it is determined whether or not the molten metal level of the nth stage has been reached and the processes of steps S106 and S107 are executed, but the present invention is not limited to this. When obtaining the molten metal level from the weight of the molten steel, since the molten metal level can be obtained at the sampling rate of the weight of the molten steel, step S105 can be deleted, and the opening degree of the sliding shutter 16 can be continuously adjusted by always executing the processes of steps S106 and S107. Thereby, the opening degree of the sliding shutter 16 can be adjusted in more detail, and the pouring rate of the molten steel 26 can be controlled precisely.

[0049] In the above embodiment, an example is shown in which the molten metal level is obtained from the weight of the molten steel poured into the mold 22, but the present invention is not limited to this. The molten metal level in the mold 22 may be detected using, for example, an optical fiber type temperature sensor embedded in the mold copper plate.

[0050] FIG. 8 is a schematic cross-sectional view showing an example of a mold long-side copper plate in which the fiber optic temperature sensor 50 is embedded. In the mold long-side copper plate 45 shown in FIG. 8, four fiber optic temperature sensors 50 are embedded along the width direction of the mold long-side copper plate 45 at four different positions in the casting direction of the mold long-side copper plate 45.

[0051] The fiber optic temperature sensor 50 is, for example, a fiber optic temperature sensor of the FBG (Fiber Bragg Grating) type. The fiber optic temperature sensor of the FBG type is a temperature sensor that provides a diffraction grating 52 that diffracts a specific wavelength in the optical fiber and detects the temperature using the Bragg diffraction phenomenon in the diffraction grating 52. Further, the interrogator 54 is connected to the end of the fiber optic temperature sensor 50, and while incident light is applied to the sensor, the reflected light from each diffraction grating 52 is analyzed to create temperature data.

[0052] Note that the fiber optic temperature sensor 50 is not limited to the fiber optic temperature sensor of the FBG type, and an OFDR (Optical Frequency Domain Reflectometry) type fiber optic temperature sensor may also be used. The fiber optic temperature sensor of the OFDR type is a method that uses the backscattered light due to Rayleigh scattering, obtains the change in frequency by performing a Fourier transform on the intensity distribution of the backscattered light from a specific range, and obtains the temperature from the change in the frequency.

[0053] As shown in FIG. 8, an optical fiber type temperature sensor 50 is embedded at four predetermined positions, and the temperature of the mold 22 is measured by an interrogator 54. Then, based on the temperature of the mold 22 obtained by the interrogator 54, the time when the molten metal surface in the mold 22 reaches the four-stage molten metal surface position where the optical fiber type temperature sensor 50 is provided may be detected by detecting that the molten metal surface has reached the position. Since the optical fiber type temperature sensor 50 is embedded in the mold copper plate, the delay time due to heat conduction is shorter than that of the thermocouple provided on the back side of the mold copper plate. Therefore, by using the optical fiber type temperature sensor 50, it is possible to detect that the molten metal surface has reached the position with higher responsiveness than the conventional thermocouple, and it is possible to more accurately detect the time until the molten metal surface reaches the position.

[0054] FIG. 9 is a schematic cross-sectional view showing another example of the mold long side copper plate in which the optical fiber type temperature sensor 50 is embedded. In FIG. 9, the same components as those in FIG. 8 are denoted by the same reference numerals, and the description thereof is omitted. In the mold long side copper plate 47 shown in FIG. 9, three optical fiber type temperature sensors 50 are embedded along the casting direction of the mold long side copper plate 45 at three different positions in the width direction of the mold long side copper plate 47.

[0055] In the optical fiber type temperature sensor 50, diffraction gratings 52 can be provided at narrow intervals, so that the temperature can be detected at narrow intervals. Therefore, as shown in FIG. 9, by embedding the optical fiber type temperature sensor 50 along the casting direction, it becomes possible to detect the molten metal surface positions at narrower intervals based on the temperature data obtained by the sensor. As a result, the injection speed of the molten steel 26 can be controlled more precisely, so that the injection speed of the molten steel 26 can be precisely controlled so that the molten metal surface reaches the position where the pinch roll 34 starts pulling at the target time.

Description of Symbols

[0056] 10 Continuous casting equipment 12 Tundish 14 Accommodating part 15 Ladle 16 Sliding shutter 18 Immersion Nozzle 22 Mold 26 Molten Steel 28 Solidification Shell 30 Cast Slab 32 Secondary Cooling Zone 34 Pinch Roll 36 Cast Slab Support Roll 38 Conveyor Roll 40 Cast Slab Cutter 42 Slab 44 Long Side Copper Plate of Mold 46 Short Side Copper Plate of Mold 45 Long Side Copper Plate of Mold 47 Long Side Copper Plate of Mold 48Dummy Bar 60 Control Device 62 Control Unit 64 Input Unit 66 Output Unit 68 Storage Unit 70 Detection Unit 72 Injection Speed Control Unit

Claims

1. A method for controlling the injection rate of molten steel in continuous casting of steel, comprising: At the start of continuous casting of steel, a detection step of detecting the time when the molten steel level in the mold reaches a predetermined molten steel level based on the weight of the molten steel injected into the mold; A control step of controlling the injection rate of the molten steel injected from the tundish into the mold based on the time detected in the detection step and the predetermined molten steel level; A method for controlling the injection rate of molten steel, comprising the above steps.

2. A method for controlling the injection rate of molten steel in continuous casting of steel, comprising: At the start of continuous casting of steel, a detection step of detecting the time when the molten steel level in the mold reaches the position where the optical fiber type temperature sensor is provided based on the mold temperature measured by the optical fiber type temperature sensor embedded in the mold; A control step of controlling the injection rate of the molten steel injected from the tundish into the mold based on the time detected in the detection step and the position where the optical fiber type temperature sensor is provided; A method for controlling the injection rate of molten steel, comprising the above steps.

3. A method for continuous casting of steel, using the method for controlling the injection rate of molten steel according to Claim 1 or Claim 2.

4. A control facility for controlling the injection rate of molten steel in continuous casting of steel, comprising: A tundish; A mold; A control device for controlling the injection rate of the molten steel; The tundish has a housing part for containing molten steel, a sliding shutter provided at the bottom of the housing part, and a submerged nozzle connected to the sliding shutter for injecting the molten steel into the mold. The mold has a plurality of mold copper plates. The control device has a detection part for detecting the time when the molten steel level in the mold reaches a predetermined molten steel level based on the weight of the molten steel injected into the mold, and an injection rate control part for controlling the injection rate of the molten steel based on the time detected by the detection part and the predetermined molten steel level.

5. A control facility for controlling the injection rate of molten steel in continuous casting of steel, comprising: A tundish; A mold; A control device for controlling the injection rate of the molten steel; The tundish has a housing part for containing molten steel, a sliding shutter provided at the bottom of the housing part, and a submerged nozzle connected to the sliding shutter for injecting the molten steel into the mold. ​ ​ The mold has a plurality of mold copper plates and an optical fiber type temperature sensor embedded in at least one of the plurality of mold copper plates. The control device includes a detection unit that detects the time when the molten metal surface in the mold reaches the position where the optical fiber type temperature sensor is provided based on the mold temperature measured by the optical fiber type temperature sensor, and an injection speed control unit that controls the injection speed of the molten steel based on the time detected by the detection unit and the position where the optical fiber type temperature sensor is provided.

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