JP2019078647A - Molten steel temperature measurement method and molten steel temperature measurement device - Google Patents

Abstract

To precisely specify a hot water surface level to perform temperature measurement at a prescribed immersion depth based on the hot water surface level.SOLUTION: A molten steel temperature measurement method for measuring temperature of molten steel in a molten steel ladle 100 comprises the steps of: lowering a temperature measurement probe 3 toward a hot water surface MS of molten steel by a probe lifting and lowering device 7; monitoring a drive current value of the probe lifting and lowering device 7 for lowering the temperature measurement probe 3; determining whether an amount of change in the drive current value is a prescribed first threshold value or larger; and determining that the temperature measurement probe 3 reaches the hot water surface MS when the amount of change is the first threshold value or larger to measure temperature of the molten steel by the temperature measurement probe 3 by lowering the temperature measurement probe 3 up to a prescribed immersion depth with a height of the temperature measurement probe 3 being a standard.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for measuring molten steel temperature in a molten steel pan and a molten steel temperature measurement device.

  In a steelmaking plant, in general, measurement of molten steel temperature in a molten steel pan is carried out in each processing equipment such as waste disposal equipment, dephosphorization furnace equipment, LF equipment and the like. The molten steel temperature is measured by inserting a temperature measurement probe into the molten steel pan from above the molten steel pan. As a device for performing such molten steel temperature measurement, for example, a device shown in Patent Document 1 is known. Patent Document 1 discloses a technique for controlling the tip position of a temperature measurement probe to a target height in a melting steel pan.

JP, 1989-209328, A

  The measurement of the molten steel temperature needs to be performed at a predetermined immersion depth (a predetermined depth further inserted downward from the molten steel surface). Here, each processing in each processing equipment of a steelmaking factory is performed by batch processing for every charge of molten steel pan. Since the level of molten metal in the molten steel pan differs for each charge, it is possible to measure temperature with a predetermined immersion depth even when the level of molten metal is different by any method in the process prior to temperature measurement. It is necessary to specify the hot water level (hot water level).

  As a method of specifying the surface level, it is conceivable to provide a surface level measuring device such as a microwave level meter. However, in the case where a hot-water level measuring device is provided separately from the device related to molten steel temperature measurement, the facility cost increases and the installation space increases. In addition, when another device measures the surface level and the molten steel temperature measuring device measures the temperature at a predetermined immersion depth based on the surface level, a surface level measurement error and position control between the two devices. Since an error easily occurs, temperature measurement at a predetermined immersion depth may not be performed with high accuracy.

  Further, it is also conceivable to specify the surface level by visual observation of the operator without providing the surface level measuring device. However, since there is a distance from the operator's work position to the surface of the metal that can not be determined accurately by visual inspection, it is generally not only visual observation but also information on the surface of the metal surface roughly estimated from the molten steel weight in the pan, etc. It is also necessary to identify the surface level using In this way, when specifying the surface level, the accuracy in specifying the surface level is lower than in the case of using the above-described surface level measuring device, and the temperature at a predetermined immersion depth with high accuracy. I can not measure.

  The present invention has been made in view of the above-described circumstances, and has an object of specifying a level of a molten metal with high accuracy and performing temperature measurement at a predetermined immersion depth based on the level of the molten metal.

  The molten steel temperature measurement method according to one aspect of the present invention is a molten steel temperature measurement method for measuring the temperature of molten steel in a molten steel pan, and a step of lowering a temperature measuring probe toward a molten metal surface by a probe lifting device. A step of monitoring a drive current value of the probe lifting device for lowering the temperature measuring probe, a step of determining whether a change amount of the drive current value is equal to or more than a predetermined first threshold, and When the temperature is higher than the threshold, it is determined that the temperature measuring probe has reached the surface of the hot water, and the temperature measuring probe is lowered to a predetermined immersion depth based on the height of the temperature measuring probe to measure the temperature of molten steel. And the step of

  In the molten steel temperature measurement method according to one aspect of the present invention, the drive current value of the probe lifting device that lowers the temperature measurement probe toward the surface of molten steel is monitored, and the drive current value is equal to or greater than the first threshold. It is determined that the temperature measurement probe has reached the surface of the hot water. In the state where the temperature measurement probe descends in the air, there is no particular resistance load with respect to the temperature measurement probe, so the drive current value of the probe lifting device is relatively small. On the other hand, when the temperature measuring probe reaches the surface of the molten steel, the temperature measuring probe enters into the molten steel having a high specific gravity, and the molten steel acts as a resistance load, and the surface of the molten metal melts slag and the like. Since the precipitates or inclusions are suspended, an impact load is applied when the tip of the temperature measurement probe pierces them, and the above-mentioned drive current value is increased. Therefore, when the temperature measurement probe which has been lowered in the air reaches the surface of the hot water, the drive current value of the probe lifting device rapidly increases. Therefore, as in the molten steel temperature measurement method according to one aspect of the present invention, it is determined that the temperature measurement probe has reached the surface of the molten metal when the amount of change in the drive current value exceeds a predetermined value (first threshold). By doing this, the surface level can be specified with high accuracy. Then, in the molten steel temperature measurement method according to one aspect of the present invention, the temperature measurement probe is further lowered to a predetermined immersion depth based on the determined hot surface level, and the temperature of the molten steel at the predetermined immersion depth is measured. Therefore, temperature measurement can be performed at a predetermined immersion depth based on the hot water level specified with high accuracy. That is, according to the molten steel temperature measurement method according to the present invention, it is possible to realize stable, highly accurate temperature measurement with a constant immersion depth without being affected by the level of the molten metal which differs for each charge.

  Further, in the molten steel temperature measurement method according to one aspect of the present invention, the molten metal level is determined from the change amount of the drive current value of the probe lifting device, so a molten metal level measurement device such as a microwave level meter is separately provided. It is possible to identify the level of the molten metal with high accuracy. By not providing a separate device, it is possible to avoid an increase in equipment cost and an increase in installation space.

  In the step of lowering the temperature measuring probe described above, the lowering speed of the temperature measuring probe is reduced in a predetermined proximity region close to the surface of the molten metal, and the temperature measuring probe is immersed in the surface of molten steel in the molten steel pan at low speed. It is also good. Although the surface level in the molten steel pan varies depending on the charge, the surface level can be generally limited to a specific range. Therefore, the height (region) assumed to be close to the surface is previously set as the proximity region. be able to. Then, in the proximity region, the lowering speed of the temperature measurement probe is reduced, whereby the molten metal level can be specified with higher accuracy when the change amount of the drive current value is determined at predetermined time intervals.

  The step of determining whether the amount of change described above is equal to or greater than the first threshold may be performed only when the temperature measuring probe has reached a predetermined hot water level determination area close to the hot water level by the probe lifting device. . In the hot water level determination area, the hot water level determination range is set in advance before the generally specified hot water level. In the process of lowering the temperature measurement probe, the amount of change in the drive current value may increase even in a state where it does not reach the hot water surface due to some external factors such as acceleration and deceleration at the start of descent and stuck mechanical devices. In this case, there is a possibility that the level may be erroneously detected. When temperature measurement is performed with a relatively small configuration such as a temperature measurement probe, a change in drive current value due to the above-described external factor or the like may more significantly occur. In this respect, the determination of the variation is not performed in the range where the surface level can not be reached, and the determination of the variation is performed only when the temperature measurement probe reaches a predetermined surface determination area, the above-described surface level False detection can be prevented.

  In the step of determining whether the amount of change described above is equal to or greater than the first threshold, it may be determined that the amount of change is equal to or greater than the first threshold when the amount of change for the last 10 milliseconds is equal to or greater than 30 mA. . As described above, when it is determined that the temperature measuring probe has reached the surface when the driving current value changes by 30 mA / 10 milliseconds or more, the surface level can be specified with high accuracy.

  In the molten steel temperature measurement method described above, the difference between the latest value of the drive current value and the average value of the plurality of past values of the drive current value detected before (for example, immediately before) the latest value is predetermined second In the step of measuring the temperature of the molten steel, further including the step of determining whether or not the threshold value is exceeded, the temperature measurement probe when the change amount is the first threshold value or more and the difference is the second threshold value or more It may be determined that the water has reached the surface of the hot water. Thus, in addition to the latest change amount of the drive current value, the condition for determining that the hot water surface has reached that the difference from the average value (time average data) of a plurality of past values is equal to or greater than a predetermined value By doing this, for example, only the latest drive current value becomes a small value due to an external factor or the like, so that the change amount of the drive current value becomes large and it is possible to prevent erroneous detection of the hot metal level etc. . That is, the surface level can be specified with higher accuracy.

  The molten steel temperature measuring device according to one aspect of the present invention is a molten steel temperature measuring device for measuring the temperature of molten steel in a molten steel pan, and includes a temperature measuring probe for measuring the temperature of molten steel and a probe elevation for raising and lowering the temperature measuring probe. The control unit includes a device and a control unit, and the control unit controls the probe lifting device so that the temperature measuring probe is lowered toward the surface of the molten steel, and the change amount of the drive current value of the probe lifting device is predetermined. It is determined that the temperature measurement probe has reached the surface of the hot water if the change amount is equal to or more than the first threshold value, and the height of the temperature measurement probe is determined. Controlling the probe lifting device such that the temperature measuring probe is lowered to a predetermined immersion depth on the basis of

  According to the present invention, the surface level can be identified with high accuracy, and temperature measurement can be performed at a predetermined immersion depth based on the surface level.

It is a schematic diagram which shows schematic structure of the molten steel temperature measuring device which concerns on this embodiment. It is a hardware block diagram of a raising / lowering control apparatus. It is a table | surface which shows the experimental result regarding the relationship between the current value variation | change_quantity for every latest 10 milliseconds, and the surface reached. It is a flowchart which shows the execution procedure of the molten steel temperature measurement method. It is a chart figure which showed an example of a relation of up-and-down speed, probe height, and drive current value in time series. It is a chart figure which showed the other example of the up-and-down speed, the probe height, and the relation of drive current value in time series.

  Hereinafter, embodiments will be described in detail with reference to the drawings. In the description, the same elements or elements having the same function are denoted by the same reference numerals, and redundant description will be omitted.

Molten steel temperature measuring device
First, with reference to FIG. 1, an outline of a molten steel temperature measuring device 1 according to the present embodiment will be described. The molten steel temperature measuring device 1 is a device that measures the temperature of molten steel in the molten steel pan 100. The molten steel temperature measuring device 1 includes a temperature measuring probe 3, a probe lifting device 7, and a lifting control device 50 (control unit).

  The temperature measuring probe 3 is a probe that measures the temperature of molten steel in the molten steel pan 100. The temperature measuring probe 3 is moved up and down by the probe lifting device 7, and descends toward the molten metal hot water surface MS in the molten steel pan 100 in a state where the molten steel pan 100 is set below. The temperature measuring probe 3 is lowered from the surface MS of the molten steel to a predetermined immersion depth (details will be described later) by the probe lifting device 7 and measures the temperature of the molten steel at the predetermined immersion depth. The temperature measurement probe 3 performs measurement at a position where the tip of the probe is inserted into the molten steel from the surface MS of the molten steel pan 100 to a predetermined immersion depth from the viewpoint of measuring the molten steel temperature accurately and with high reproducibility and stability. There is a need to do. The temperature measurement probe 3 outputs a temperature measurement signal indicating the measured temperature to the temperature measurement board 10. The temperature measurement board 10 displays data indicating the temperature measured by the temperature measurement probe 3 to the operator. Further, the temperature measurement board 10 is configured to be communicable with, for example, another communication device, and may transmit data indicating the temperature measured by the temperature measurement probe 3 to the other communication device.

  The probe lifting device 7 is a device for lifting and lowering the temperature measurement probe 3 in accordance with the control of the lifting and lowering control device 50. The probe lifting device 7 holds the temperature measurement probe 3 by a lifting arm (not shown), and the lifting drive motor (not shown) operates according to the drive current supplied from the lift control device 50, thereby lifting the lifting arm Lifts and lowers the temperature measurement probe 3. The probe lifting device 7 has a position detector (not shown) for detecting the position of the temperature measurement probe 3 (specifically, the height of the tip of the temperature measurement probe 3), and the measurement detected by the position detector The position of the temperature probe 3 is output to the lift controller 50. The position detector acquires the displacement of the temperature measurement probe 3 by detecting, for example, the amount of rotation of the elevation drive motor, and based on the initial position of the temperature measurement probe 3 and the displacement, The position (the height of the tip of the temperature measurement probe 3) is identified.

  The elevation control device 50 controls the probe elevation device 7 so that the temperature measurement probe 3 descends toward the molten metal surface MS, and the change amount of the drive current value of the probe elevation device 7 is a predetermined first threshold value. It is determined that the temperature measurement probe 3 has reached the hot water surface MS when the change amount is equal to or more than the first threshold value, and the height of the temperature measurement probe 3 is determined. And controlling the probe lifting device 7 so that the temperature measurement probe 3 is lowered to a predetermined immersion depth as a reference.

  As shown in FIG. 2, the elevation control device 50 is configured by a circuit 51 including one or more processors 53, a memory 54, a storage 55, an input / output port 56, and an input unit 57. The input / output port 56 receives a control signal relating to the input of the operator from the input unit 57, receives a signal including information indicating the height position of the tip of the temperature measuring probe 3 from the probe lifting device 7, Output drive current. The input unit 57 is connected to the input / output port 56 and receives an input from the operator. The input unit 57 is configured of, for example, an operation switch, a keyboard, a mouse, a touch panel, or the like. The input unit 57 may be connected to the input / output port 56 via, for example, a network line.

  The storage 55 records a program for causing the lift control device 50 to execute a process. The storage 55 may be anything as long as it is computer readable. Specific examples include hard disks, nonvolatile semiconductor memories, magnetic disks, optical disks, and the like. The memory 54 temporarily stores the program loaded from the storage 55, the calculation result of the processor 53, and the like. The processor 53 constructs the above-described functional modules by executing a program in cooperation with the memory 54.

  The hardware configuration of the elevation control device 50 is not necessarily limited to one that configures each functional module by a program. For example, each functional module of the elevation control device 50 may be configured by a dedicated logic circuit or an application specific integrated circuit (ASIC).

  Referring back to FIG. 1, a specific configuration example of the elevation control device 50 will be described below. The lift control device 50 includes a lift control unit 61 and a hot water level determination unit 62 as functional modules.

  The elevation control unit 61 controls the probe elevation device 7 so that the temperature measurement probe 3 is lowered toward the molten metal hot water surface MS. Specifically, the elevation control unit 61 supplies a drive current to the elevation drive motor of the probe elevation device 7 and operates the elevation drive motor to lower the elevation arm holding the temperature measurement probe 3.

  The elevation control unit 61 may control the probe elevation device 7 so that the lowering speed of the temperature measurement probe 3 is reduced in a predetermined proximity region close to the molten metal surface MS in the step of lowering the temperature measurement probe 3 . The proximity area is set in advance by an operator, for example. The elevation control unit 61 is configured so that the lowering speed of the temperature measurement probe 3 is reduced when the position of the temperature measurement probe 3 acquired from the position detector of the probe elevation device 7 is included in a predetermined proximity region. The lifting device 7 is controlled. Although the surface level MS in the molten steel pan 100 varies depending on the charge, since the level MS surface in each charge is approximately in a specific range, it is possible to set the above-described proximity region in advance. Moreover, it is possible to set beforehand also about the hot water surface judgment area | region which performs a hot water surface judgment separately from the said proximity | contact area | region which sets a low speed area | region before a probe reaches | attains a hot water surface MS level.

  The elevation controller 61 controls the temperature measurement based on the height of the temperature measuring probe 3 as a reference when the water level judging unit 62 determines that the temperature measuring probe 3 has reached the molten metal's surface MS. The probe lifting device 7 is controlled to lower the probe 3 to a predetermined immersion depth. The predetermined immersion depth is a depth set in advance as a depth at which the molten steel temperature is measured (depth from molten metal surface MS). The elevation control unit 61 determines the position where the molten metal level determination unit 62 determines that the change amount of the drive current value of the probe elevation device 7 is equal to or greater than the first threshold (the temperature measurement probe 3 has reached the molten metal level MS The probe elevating device 7 is controlled so that the temperature measurement probe 3 is lowered from the position (a) by a predetermined immersion depth which is set.

  The molten metal level determination unit 62 monitors the drive current value of the probe lifting device 7 that lowers the temperature measurement probe 3 and determines whether the change amount of the drive current value is equal to or more than a predetermined first threshold. The molten metal level determination unit 62 monitors, for example, the drive current value supplied from the elevation control unit 61 to the elevation drive motor of the probe elevation apparatus 7, and performs the above-described determination at predetermined time intervals (for example, 10 millisecond intervals). The change amount of the drive current value is, for example, a change amount from the drive current value when the determination is made most recently. The predetermined first threshold is, for example, 30 mA. That is, for example, when the determination is performed at intervals of 10 milliseconds, the molten metal surface determination unit 62 determines whether or not the change amount of the drive current value for the latest 10 milliseconds is equal to or more than the first threshold (30 mA). . The hot water surface determination unit 62 determines that the temperature measurement probe 3 has reached the hot water surface MS when the amount of change in the drive current value is equal to or greater than the first threshold value. Such a judgment is, when the temperature measuring probe 3 enters into the molten steel with a high specific gravity (when reaching the surface MS of the molten steel), compared with the case where the temperature measuring probe 3 descends in the air, resistance This is because the load is increased, and the above-described drive current value is increased (that is, the change amount of the drive current value is increased).

The value of the first threshold described above is a value found from an experiment concerning the relationship between the current value change amount of the latest 10 milliseconds and the arrival of the molten metal surface MS. FIG. 3 is a table showing experimental results on the relationship between the current value variation of the last 10 milliseconds and the arrival of the molten metal surface MS. In the experiment, the position of the molten metal surface MS is grasped in advance, and while lowering the temperature measurement probe 3, the amount of change of the driving current value of the nearest 10 milliseconds based on the detected driving current value, and the molten metal surface The relationship with reaching the MS was recorded. In addition, the said experiment was implemented on condition of the following. However, the experimental results are not effective only when conducted under the following conditions, and are effective for molten steel temperature measurement generally performed in the same processing equipment.
・ Laser pot: 250 tons
・ Bore size: 3800 mm
Temperature measuring probe: プ ロ ー ブ 30 mm × 1200 mm
・ Temperature measurement lifting stroke: 6000 mm

  As shown in FIG. 3, in the elapsed time t of 10.82 seconds to 10.85 seconds, the change amount of the drive current value in the last 10 milliseconds is in the range of -2.1 mA to 22.2 mA, and The temperature probe 3 did not reach the hot water surface MS. On the other hand, at the elapsed time t = 10.86 seconds, the change amount of the drive current value in the last 10 milliseconds is 35.2 mA, and at this time, the temperature measurement probe 3 has reached the molten metal surface MS. From the above experimental results, when the change amount of the drive current value in the last 10 milliseconds becomes 30 mA or more, the hot water surface determination unit 62 determines that the change amount is the first threshold or more.

  The specific judgment threshold is set to an optimum value during test operation of the equipment because the weight of the elevating unit and the elevating mechanism of the temperature measuring device differ depending on the application in the steelmaking plant and the scale of the device, etc. The settings may be made in each device based on From this point of view, the setting of the hot water surface determination value may be set as a setting device which can be changed from the outside in consideration of the specification change of the temperature measurement probe and the like.

  The molten metal level determination unit 62 determines whether the change amount of the drive current value is equal to or more than the first threshold value only when the temperature measuring probe 3 has reached a predetermined molten metal level determination area by the probe lifting device 7. You may In other words, the hot water surface determination unit 62 does not have to perform the above determination until the temperature measurement probe 3 reaches the predetermined hot water surface determination region. The hot water level determination area is set except for the area that can not be the hot water level MS level, and is set in advance by, for example, the operator. The hot water level determination area is, for example, a range below the position at which the temperature measuring probe 3 reaches after a predetermined time (for example, 300 milliseconds) has elapsed since the deceleration of the descending speed of the temperature measuring probe 3 described above is started. It is also good. The molten metal level determination unit 62 carries out the above determination only when the position of the temperature measurement probe 3 acquired from the position detector of the probe lifting device 7 reaches a predetermined molten metal level determination area.

  In addition to the determination of whether or not the change amount of the drive current value is the first threshold or more, the hot water level determination unit 62 detects the latest value of the drive current value and the previous value (for example, immediately before) the latest value. It may be determined whether the difference (deviation) of the drive current value with the average value (time-averaged data) of the plurality of past values is equal to or greater than a predetermined second threshold value. In this case, when the amount of change in the drive current value is equal to or greater than the first threshold and the deviation is equal to or greater than the second threshold, the molten metal level determination unit 62 has reached the molten metal level MS It is determined that For example, when the determination is performed at predetermined time intervals, the hot-water level determination unit 62 calculates the time average of the latest value of the drive current value and the drive current value used for the determination of the past seven times (the last seven times). It is determined whether the deviation from the data is equal to or greater than a predetermined second threshold. The predetermined second threshold is, for example, 50 mA.

  In addition, by using a high-speed arithmetic device as the elevation control device 50, the molten metal surface MS judgment (the molten metal surface MS by the change of the drive current of the probe elevation device 7 when the temperature measuring probe 3 enters the molten steel surface MS). Detection) can be realized stably.

[Method of measuring molten steel temperature]
Next, the execution procedure of the molten steel temperature measurement method (molten steel temperature measurement processing) will be described with reference to FIG. As shown in FIG. 4, the lift control device 50 executes steps S1 to S11 in order.

  In step S1, when the molten steel ladle 100 arrives at the measurement position of the molten steel temperature in each processing step of the steelmaking facility, the elevation control unit 61 controls the probe elevation device 7 so that the temperature measuring probe 3 starts to descend. . Specifically, the elevation control unit 61 supplies a drive current to the elevation drive motor of the probe elevation device 7 and operates the elevation drive motor to lower the elevation arm holding the temperature measurement probe 3 to measure the temperature. The temperature probe 3 is lowered toward the hot water surface MS. When the lowering speed of the temperature measurement probe 3 reaches a predetermined speed, the elevation control unit 61 maintains the predetermined speed until the timing of step S4 described later.

  In step S2, the molten metal surface determination unit 62 starts monitoring the drive current value of the probe lifting device 7 that lowers the temperature measurement probe 3. Specifically, the molten metal surface judgment unit 62 monitors the value of the drive current supplied from the elevation control unit 61 to the elevation drive motor of the probe elevation device 7.

  In step S3, the lift control unit 61 determines whether the position of the temperature measurement probe 3 has reached the proximity area. Specifically, the elevation control unit 61 determines whether or not the position of the temperature measurement probe 3 acquired from the position detector of the probe elevation device 7 has reached a predetermined proximity region. If it is determined in step S3 that the position of the temperature measurement probe 3 has not reached the predetermined proximity area, the lift control unit 61 continues to lower the temperature measurement probe 3 at a predetermined speed, and a predetermined time has elapsed. Step S3 is executed again later. When it is determined in step S3 that the position of the temperature measurement probe 3 has reached the predetermined proximity area, the lift control unit 61 executes step S4.

  In step S4, the lifting control unit 61 controls the probe lifting device 7 so that the lowering speed of the temperature measurement probe 3 is reduced. For example, the elevation control unit 61 determines whether or not the temperature measuring probe 3 reaches the above-described surface level determination area (a range where it is determined whether the amount of change in drive current value is equal to or greater than the first threshold). Complete the reduction. When the lowering speed of the temperature measurement probe 3 reaches the reduced speed, the elevation control unit 61 maintains the reduced speed.

  In step S5, the molten metal surface determination unit 62 determines whether or not the position of the temperature measurement probe 3 has reached the molten metal surface determination area. Specifically, the surface judgment section 62 judges whether or not the position of the temperature measurement probe 3 acquired from the position detector of the probe lifting device 7 has reached a predetermined surface judgment area. If it is determined in step S5 that the position of the temperature measurement probe 3 has not reached the predetermined hot water level determination area, the lift control unit 61 continues to lower the temperature measurement probe 3 at a reduced speed. When it is determined that the position of the temperature measurement probe 3 has reached the predetermined hot water level determination area, the hot water level determination unit 62 executes step S6.

  In step S6, the molten metal surface determination unit 62 determines whether the amount of change in the drive current value of the probe lifting device 7 is equal to or greater than a predetermined first threshold value. Specifically, for example, whether or not the change amount of the drive current value supplied from the elevation control unit 61 to the elevation drive motor of the probe elevation device 7 in the last 10 milliseconds is 30 mA or more. Determine When it is determined in step S6 that the change amount of the drive current value is not equal to or more than the first threshold value, the molten metal surface determination unit 62 executes step S7. On the other hand, when it is determined in step S6 that the change amount of the drive current value is equal to or more than the first threshold, the molten metal surface determination unit 62 executes step S8.

  In step S7, the molten metal surface determination unit 62 determines whether a predetermined determination interval (for example, 10 milliseconds) has elapsed. Step S7 is repeatedly performed until a predetermined determination interval passes. If it is determined in step S7 that the predetermined determination interval has elapsed, the molten metal surface determination unit 62 executes step S6 again.

  In step S8, the molten metal level determination unit 62 determines the difference (deviation from the latest value of the drive current value) and the average value (time average data) of the plurality of past values of the drive current value detected before the latest value. ) Is determined to be equal to or greater than a predetermined second threshold. Specifically, for example, the level determination unit 62 determines that the deviation between the latest value of the drive current value and the time-averaged data of the drive current value used for the determination of the past seven times is equal to or more than a predetermined second threshold It is determined whether or not. If it is determined in step S8 that the deviation is not equal to or greater than the second threshold value, the molten metal surface determination unit 62 executes the above-described step S7. On the other hand, when it is determined in step S8 that the deviation is equal to or greater than the second threshold, the molten metal surface determination unit 62 executes step S9.

  In step S9, the molten metal level determination unit 62 measures on the condition that the change amount of the drive current value is equal to or greater than the first threshold and the difference from the time-averaged data is equal to or greater than the second threshold. It is determined that the temperature probe 3 has reached the hot water surface MS.

  In step S10, based on the current height of the temperature measurement probe 3 determined by the elevation control unit 61 that the molten metal surface determination unit 62 has reached the molten metal surface MS, the temperature measurement probe 3 is immersed in a predetermined amount. The probe lifting device 7 is controlled to descend to the depth. That is, the elevation control unit 61 causes the temperature measurement probe 3 to be lowered by the set predetermined immersion depth from the position determined by the water surface determination unit 62 that the temperature measurement probe 3 has reached the water surface MS. To control the probe lifting device 7.

  In step S11, the lift control unit 61 controls the probe lifting device 7 so that the temperature measurement probe 3 stops at a predetermined immersion depth, and measures the molten steel temperature at the predetermined immersion depth in the temperature measurement probe 3. Let it go. By the above-described process, it is possible to measure the temperature of the molten steel at a predetermined immersion depth on the basis of the surface level specified with high accuracy based on the drive current value.

[Operation and effect of this embodiment]
In each processing facility of a steelmaking plant, a temperature measuring probe is inserted into the molten steel, and the temperature measuring probe measures the temperature of the molten steel (temperature at a predetermined position in the molten steel). The molten steel temperature is measured by inserting the temperature measurement probe downward from the surface level by a predetermined immersion depth with reference to the surface level. Here, the surface level in the molten steel pan may be different for each charge. Therefore, in the measurement of the molten steel temperature, it is important to accurately specify the level of the molten metal in the molten steel pan for each charge, and to measure the temperature at a predetermined immersion depth based on the level.

  As a method of specifying the surface level, it is conceivable to provide a surface level measuring device such as a microwave level meter. However, in the case where a hot-water level measuring device is provided separately from the device related to molten steel temperature measurement, the facility cost increases and the installation space increases. In addition, when another device measures the surface level and the molten steel temperature measuring device measures the temperature at a predetermined immersion depth based on the surface level, a surface level measurement error and position control between the two devices. Since an error easily occurs, temperature measurement at a predetermined immersion depth may not be performed with high accuracy. Further, it is also conceivable to specify the surface level by visual observation of the operator without providing the surface level measuring device. However, since there is a distance from the operator's work position to the surface of the metal that can not be determined accurately by visual inspection, it is generally not only visual observation but also information on the surface of the metal surface roughly estimated from the molten steel weight in the pan, etc. It is also necessary to identify the surface level using In this way, when specifying the surface level, the accuracy in specifying the surface level is lower than in the case of using the above-described surface level measuring device, and the temperature at a predetermined immersion depth with high accuracy. I can not measure.

  The molten steel temperature measurement method of the present embodiment for solving such conventional problems is a molten steel temperature measurement method for measuring the temperature of the molten steel in the molten steel pan 100, and the probe elevation device 7 Moving the temperature measuring probe 3 downward, monitoring the driving current value of the probe lifting device 7 moving the temperature measuring probe 3 downward, and determining whether the change amount of the driving current value is equal to or more than a predetermined first threshold And determining that the temperature measurement probe 3 has reached the hot water surface MS if the amount of change is equal to or greater than the first threshold value, and a predetermined value is determined with reference to the height of the temperature measurement probe 3. And d) measuring the temperature of the molten steel with the temperature measuring probe 3 by lowering the temperature measuring probe 3 to the immersion depth.

  In the molten steel temperature measurement method according to the present embodiment, the drive current value of the probe lifting device 7 that lowers the temperature measurement probe 3 toward the molten metal surface MS is monitored, and the drive current value is equal to or greater than the first threshold It is determined that the temperature measurement probe 3 has reached the hot water surface MS. In the state where the temperature measurement probe 3 descends in the air, there is no particular resistance load with respect to the temperature measurement probe 3, so the drive current value of the probe lifting device 7 becomes relatively small. On the other hand, when the temperature measuring probe 3 reaches the molten metal surface MS, the temperature measuring probe 3 enters the molten steel having a high specific gravity, and the molten steel acts as a resistance load, and the metal surface MS Since molten precipitates or inclusions such as slag are suspended, an impact load is applied when the tip of the temperature measurement probe 3 pierces them, and the above-mentioned drive current value is increased. Therefore, when the temperature measurement probe 3 which has been lowered in the air reaches the hot water surface MS, the drive current value of the probe lifting device 7 rapidly increases. In the molten steel temperature measurement method according to the present embodiment, noting such a rapid increase in drive current value, the temperature measuring probe is a molten metal surface when the change amount of the drive current value exceeds a predetermined value (first threshold). It is determined that the Thereby, the surface level MS can be identified with high accuracy. Then, in the molten steel temperature measurement method according to the present embodiment, the temperature measurement probe 3 is further lowered to a predetermined immersion depth based on the determined hot water surface MS level, and the temperature of the molten steel at the predetermined immersion depth is measured. Therefore, temperature measurement can be performed at a predetermined immersion depth based on the hot water level MS specified with high accuracy. That is, according to the molten steel temperature measurement method according to the present embodiment, stable and highly accurate temperature measurement can be realized at a constant immersion depth without being affected by the level of the molten metal level different for each charge.

  Further, in the molten steel temperature measurement method according to the present embodiment, since the molten metal surface MS level is determined from the amount of change in the drive current value of the probe lifting device 7, a molten metal level measurement device such as a microwave level meter is separately provided. It is possible to identify the hot water surface MS level with high accuracy. By not providing a separate device, it is possible to avoid an increase in equipment cost and an increase in installation space.

  The effects of the molten steel temperature measurement method according to the present embodiment described above will be described in more detail with reference to FIG. FIG. 5 is a chart showing an example of the relationship between the elevation speed, the probe height, and the drive current value in time series. As shown in FIG. 5, at time t0, supply of drive current to the probe lifting device 7 by the lifting control device 50 is started, and the temperature measuring probe 3 starts to drop. The lift control device 50 gradually increases the descent speed until the temperature measuring probe 3 reaches a predetermined descent speed (40 m / min in the example shown in FIG. 5), and when the predetermined descent speed is reached at time t1, the predetermined The temperature measuring probe 3 is further lowered while maintaining the lowering speed. Then, while the elevating speed is being reduced from the deceleration start point shown at time t2, the amount of change in the drive current value is rapidly large (larger than the first threshold) at time t3. Accordingly, the elevation control device 50 can determine that the position of the temperature measurement probe 3 at the time t3 is the hot water level MS. As described above, since the change amount of the drive current value rapidly increases when the tip of the probe reaches the hot water surface, the hot water surface MS level can be easily determined by monitoring the drive current value.

  Further, in the molten steel temperature measurement method according to the present embodiment, in the step of lowering the temperature measurement probe 3, the lowering speed of the temperature measurement probe 3 is reduced in a predetermined proximity region close to the molten metal surface MS. Although the surface level MS in the molten steel pan 100 varies depending on the charge, since the surface level MS can be generally limited to a specific range, the height (region) assumed to be close to the surface MS is regarded as the proximity region in advance. It can be set. Then, in the proximity region, the molten metal MS level can be specified with higher accuracy when the amount of change in the drive current value is determined at predetermined time intervals by reducing the falling speed of the temperature measurement probe 3. it can.

  FIG. 6 is a chart showing another example of the relationship between the elevation speed, the probe height, and the drive current value in time series. Although the chart shown in FIG. 6 substantially corresponds to the chart shown in FIG. 5, it is measured in the section from time tx to time ty (section of the proximity area) before time t3 at which the hot water surface MS is reached. The difference is that the falling speed of the temperature probe 3 is reduced (the reduction of the falling speed is completed before time t3). As described above, the falling speed of the temperature measurement probe 3 is reduced before reaching the molten metal surface MS, so that it is possible to more accurately measure the molten metal surface when the arrival of the molten metal surface MS is determined from the change amount of the drive current value. The arrival of the surface MS can be determined. If the lowering speed of the probe is reduced before the temperature measurement probe shown in FIG. 6 reaches the molten metal surface MS, the change in the drive current value is also reduced. The second threshold may be set to, for example, 40 mA or more.

  Further, in the molten steel temperature measurement method of the present embodiment, the step of determining whether the change amount of the drive current value is equal to or more than the first threshold is determined by the probe lifting device 7 by the temperature measuring probe 3. It carries out only when it reaches. In the process of lowering the temperature measurement probe 3, it is conceivable that the amount of change in the drive current value becomes large due to some external factor or the like, even in the state of not reaching the molten metal surface MS. There is a risk of false detection of the level. In this respect, determination of the variation is not performed in the range where the hot water surface MS level can not be achieved, and the above-described hot water is determined only when the temperature measurement probe 3 reaches the predetermined water surface determination region. It is possible to prevent false detection of the surface MS level.

  Further, in the molten steel temperature measurement method of the present embodiment, in the step of determining whether or not the change amount of the drive current value is the first threshold or more, the change is made when the change amount of the last 10 milliseconds becomes 30 mA or more It is determined that the amount is equal to or greater than a first threshold. Thus, based on the experimental results shown in FIG. 3 and the like, it is determined that the temperature measuring probe 3 has reached the molten metal surface MS when the drive current value changes by 30 mA / 10 ms or more, the molten metal surface MS The level can be identified with high accuracy.

  In the molten steel temperature measurement method of the present embodiment, the difference (deviation) between the latest value of the drive current value and the average value of the plurality of past values of the drive current value detected before the latest value is predetermined In the step of measuring the temperature of the molten steel further including the step of determining whether or not it is the second threshold or more, if the variation is the first threshold or more and the deviation is the second threshold or more, It is determined that the temperature probe 3 has reached the hot water surface MS. Thus, in addition to the latest variation of the drive current value, it is determined that the hot water surface MS arrival that the difference from the average value (time average data) of a plurality of past values is equal to or greater than a predetermined value. By doing this, for example, only the latest drive current value becomes a small value due to an external factor or the like, and the amount of change in the drive current value becomes large, preventing erroneous detection of the hot surface MS level, etc. Can. That is, the surface level MS can be specified with higher accuracy.

  DESCRIPTION OF SYMBOLS 1 ... Molten steel temperature measuring device, 3 ... Temperature measurement probe, 7 ... Probe raising / lowering device, 50 ... Elevation control apparatus (control part), 100 ... Melting steel pan, MS ... Hot-water surface.

Claims (6)

A molten steel temperature measuring method for measuring the temperature of molten steel in a molten steel pan,
Lowering the temperature measurement probe toward the surface of the molten steel by a probe lifting device;
Monitoring a driving current value of the probe lifting device for lowering the temperature measurement probe;
Determining whether the amount of change in the drive current value is equal to or greater than a predetermined first threshold value;
When the amount of change is equal to or more than the first threshold value, it is determined that the temperature measurement probe has reached the surface of the hot water, and the temperature measurement is performed to a predetermined immersion depth based on the height of the temperature measurement probe. And d) measuring the temperature of the molten steel by lowering the probe.   In the step of lowering the temperature measuring probe, the lowering speed of the temperature measuring probe is reduced in a predetermined proximity area close to the surface of the hot water, and the temperature measuring probe is immersed in the surface of the molten steel in the molten steel pan at a low speed. The molten steel temperature measurement method according to claim 1.   The step of determining whether the amount of change is equal to or more than the first threshold value is performed only when the temperature measuring probe has reached a predetermined hot water level determination area close to the hot water level by the probe lifting device. The molten steel temperature measurement method according to claim 1 or 2.   In the step of determining whether or not the change amount is equal to or more than the first threshold value, when the change amount of the last 10 milliseconds becomes 30 mA or more, it is determined that the change amount is equal to or more than the first threshold value. The molten steel temperature measurement method according to any one of claims 1 to 3. Determining whether a difference between the latest value of the drive current value and an average value of a plurality of past values of the drive current value detected before the latest value is equal to or greater than a predetermined second threshold value; Further include
In the step of measuring the temperature of the molten steel, the temperature measurement probe has reached the surface of the molten metal when the amount of change is equal to or greater than the first threshold and the difference is equal to or greater than the second threshold. The molten steel temperature measurement method according to claim 3, which is determined as A molten steel temperature measuring device for measuring the temperature of molten steel in a molten steel pan,
A temperature measuring probe for measuring the temperature of the molten steel;
A probe lifting device for raising and lowering the temperature measuring probe;
And a control unit,
The control unit
Controlling the probe lifting device so that the temperature measuring probe is lowered toward the surface of the molten steel;
Determining whether the amount of change in the drive current value of the probe lifting device is equal to or greater than a predetermined first threshold;
When the amount of change is equal to or greater than the first threshold value, it is determined that the temperature measurement probe has reached the surface of the hot water, and the temperature measurement probe is immersed in a predetermined manner based on the height of the temperature measurement probe. Controlling the probe lifting device to descend to a depth, and a molten steel temperature measuring device configured to perform.

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