KR100950396B1 - Device for detecting the slag injection using the vibration sensor attached to long nozzle - Google Patents

Abstract

The present invention relates to a slag outflow detection device using a vibration sensor, and more particularly, the slag remaining in the ladle into the tundish at the end of the process of injecting the molten steel into the tundish in the continuous casting process of molten steel It relates to a slag outflow detection device using a long nozzle-type vibration sensor for detecting the inflow.

Slag outflow detection device using a long nozzle-type vibration sensor of the present invention, in the device for detecting that the slag contained in the molten steel outflow into the tundish from the ladle containing the molten steel, to fix the long nozzle 11 The vibration sensor 32 which is installed on the outer surface of the long nozzle mounting device 31 and detects the vibration of the long nozzle 11 according to the movement of molten steel and slag, and the vibration signal detected by the vibration sensor 32 as electromotive force. By using the vibration / electromotive force converter 33 and the electromotive force value output from the vibration / electromotive force converter 33 to calculate the moving average value according to two different time and stores the vibration level value according to the type of molten steel The vibration analyzer 35 detects and outputs a vibration when the vibration falls below the basic limit value, and receives an output signal from the vibration analyzer 35 to instruct a slag outflow value and generate an alarm. The slag outflow indication and the alarm 37 is included.

Molten steel, slag, detection, detection, long nozzle, vibration sensor, ladle, tundish

Description

Device for detecting the slag injection using the vibration sensor attached to long nozzle}

1 illustrates a process of producing cast steel by introducing molten steel into a tundish in a conventional ladle;

Equipment configuration,

2 is a state diagram of the installation of a eddy current sensor for detecting a conventional slag outflow,

3 is a detection principle diagram of a eddy current sensor for detecting a conventional slag outflow,

4 is a block diagram of a slag outflow detection device using a vibration sensor according to the present invention,

5 is a block circuit diagram of the vibration analyzer of FIG.

FIG. 6 is a graph showing an output voltage waveform of the vibration / electromotive force converter of FIG. 4;

7 is a graph showing a pattern of change of vibration level during slag outflow;

8 is a graph illustrating a slag detection signal determination method in a vibration analyzer;

9 is a graph showing the vibration level ratio at the time of detecting slag outflow in the vibration analyzer.

* Description of the symbols for the main parts of the drawings *

1: ladle 2: tundish

3: mold 4: player drawing roll

5: cast 11: long nozzle

12: Vortex sensor 13: molten steel                 

15: firebrick 17: ladle

21: Primary coil 23: Secondary coil

25: magnetic field 31: long nozzle

33: vibration / electromotive transducer 35: vibration analyzer

37: Slag outflow indicator and alarm 43: A / D conversion and noise filter

45: short time moving average processing circuit 46: long time moving average processing circuit

47: division operation unit 49: (vibration deterioration state) continuous determination circuit

51: detection circuit 53: D / A conversion and output

55: indicator and alarm 57: long nozzle control device

The present invention relates to a slag outflow detection device using a vibration sensor, and more particularly, the slag remaining in the ladle into the tundish at the end of the process of injecting the molten steel into the tundish in the continuous casting process of molten steel It relates to a slag outflow detection device using a long nozzle-type vibration sensor for detecting the inflow.

The molten metal refined in the converter of the steelmaking process (hereinafter referred to as "molten steel") is a long nozzle 11 vertically connected to the lower part of the ladle 1 with a tundish 2 for the next continuous casting operation from the ladle 1. It is injected (poured) through. In general, since slag which is an impurity is mixed in molten steel, slag is included and moved together at the end of injecting molten steel from the ladle 1 to the tundish 2.

The slag mixed in the molten steel is mixed with the mold of the continuous casting machine and remains as an internal defect in the cast piece 5 which is cast while passing through the roller which is a player. Therefore, preventing the slag from flowing into the tundish 2 is a very important factor in improving the quality, and an apparatus for blocking the injection port of the long nozzle 11 is used immediately upon detecting the injection point of the slag. Reference numeral 3 is a mold.

2 is a schematic installation state diagram of a vortex type sensor used in a detection apparatus for detecting an inflow state of a conventional slag.

Referring to (a) (b) of Figure 2, the vortex type sensor 12 is provided in an annular shape on the upper side of the long nozzle 11 that is the molten steel outflow portion connected to the bottom of the ladle (1). The eddy current sensor 12 is installed on the outer circumferential surface of the long nose 11 so as to surround the surface through which molten steel passes, as shown in (b) of FIG. 2, to detect a moving state of the molten steel 13. Reference numeral 15 denotes a firebrick and 17 a ladle shell.

As shown in (a) of FIG. 3, the eddy current sensor 12 is composed of primary and secondary coils 21 and 23 located outside the long nozzle 11, and the primary coil 21 When AC current is flowed through, induced electromotive force is generated according to the flow of molten steel. The induced electromotive force is induced in the secondary coil 23 and becomes a secondary voltage. The absolute value of the secondary voltage changes depending on the components of the molten steel. That is, if only molten steel is included in molten steel, the magnetic field is reduced compared to slag, and a voltage difference is generated according to the amount of molten steel and slag mixed, and a detection signal is generated accordingly.                         

In other words, by detecting the amount of slag contained in molten steel by electromagnetic field measurement principle, slag has less electrical conductivity than molten steel, so there is less eddy current in slag. Thus, slag and molten steel are distinguished by this difference. The detection state of the magnetic field according to the molten steel or the mixed state of the molten steel and the slag is shown in FIGS. 3B and 3C, respectively.

However, the problem of the detection device using the vortex type sensor is that a failure of the connection contact portion of the signal connector occurs due to vibration and local shock, and the nozzle of the sensor portion during the repair of the fireproof brick of the ladle at the ladle repair station. By applying an impact to the vortex type sensor installed in the cassette, the sensor malfunctions due to the deformation of the sensor, the characteristic change of the internal coil of the sensor, and the influence of noise, resulting in a decrease in the operation rate of the slag detection equipment, resulting in poor quality. Therefore, there is a problem such as the need for regular cleaning and continuous preventive inspection of the sensor area, a lot of time for maintenance and maintenance.

In addition, the vortex type sensor is indirectly exposed to high temperature molten steel, which causes frequent breakage or degradation of the sensor, which leads to an increase in manufacturing cost.In addition, maintenance load increases due to long time of replacement time due to sensor failure. As a result, the facility operation rate is lowered, causing the deterioration of quality due to the slag outflow and the operation load rate due to the manual operation of the driver. There is a problem such as a rise.

Moreover, since the slag outflow limit is set to a fixed value regardless of the steel type of molten steel, the flow becomes unstable during inflow of molten steel or dispersion of the electromotive force generated when the slag passes as the size and shape of the inflow nozzle changes. Therefore, undetected or misdetected slag often occurs.

The electromotive force at the time of passing a slag fluctuates in the range of 20%-100% of the electromotive force value with respect to 100% of slag by the confusion of the molten steel which flows in. In this case, if the threshold is set high, the slag actually passes through the tap, but the slag cannot be detected. If the threshold is set low, the slag is judged as slag even though the slag is not actually passing through the tap. There were problems such as causing false detection to be detected.

The present invention is to solve the above problems, the object is to detect that the slag remaining in the ladle flow into the tundish at the end of the process of injecting the molten steel into the tundish in the continuous casting process of molten steel It is to provide a slag outflow detection device using a long nozzle mounted vibration sensor for.

Another object of the present invention is to produce a high-quality cast steel by performing an accurate detection irrespective of the type of steel when the slag outflow, and a long nozzle-type vibration sensor that can improve the manufacturing process by reducing the inspection time of the equipment It is to provide a slag outflow detection device used.

The slag outflow detection device of the present invention for achieving the above object, in the device for detecting that the slag contained in the molten steel outflow into the tundish from the ladle containing the molten steel, the outside of the long nozzle mounting device for fixing the long nozzle Vibration sensor installed on the surface to detect the vibration of the long nozzle according to the movement of the molten steel and slag, vibration / electromotive force converter for converting the vibration signal detected from the vibration sensor into electromotive force, electromotive force output from the vibration / electromotive force converter A vibration analyzer that calculates a moving average value according to two different time values using the value, stores vibration level values according to the type of molten steel, and detects and outputs a vibration when the vibration falls below a basic limit value; Slag outflow indicator and alarm that indicates the slag outflow value from the output signal and generates an alarm It includes.

In addition, the vibration analyzer of the present invention, the A / D conversion and noise filter for converting the voltage signal corresponding to the vibration to digital and remove the noise, and the predetermined process using the signal output from the A / D conversion and noise filter By using a short time moving average processing circuit and a long time moving average processing circuit for calculating a moving average value according to time, a calculating unit for dividing the value output from the long time moving average processing circuit, and an output value output from the calculating unit. Vibration reduced state continuous judging circuit for judging whether vibration continues to fall when slag flows out; detection circuit for detecting vibration lowered state using a signal output from the vibration reduced state continuous judging circuit; D / A converter and output device that converts the output signal to analog and output the long nozzle Long nozzle and a control device.

Hereinafter, a slag leak detection apparatus using the long nozzle-mounted vibration sensor according to the present invention will be described in detail with reference to the accompanying drawings.

The present invention continuously measures the moving average value according to two different times of the vibration level generated by the molten steel injected into the tundish in the ladle long nozzle used as air blocking and injection sealing pipe for molten steel. An apparatus for detecting the outflow of slag on the basis of the change of the vibration level according to the specific gravity difference of the slag, the detection principle of the vibration level is as follows.

Referring to FIG. 4, the molten steel in the ladle 1 falls freely by gravity through the molten steel injection long nozzle 11 and collides with the hot water surface in the tundish 2. Although not shown in detail, the long nozzle 11 is conventionally provided with a control device for blocking the opening surface of the long nozzle 11. Due to the free fall collision of the molten steel, an impact is applied to the distal end of the long nozzle 11 pipe, and the impact is excited to generate vibration.

Particularly, when the slag flows out instead of the molten steel, the specific gravity of the slag is only about one third of the molten steel, and thus the excitation force transmitted to the long nozzle pipe caused by the fluid collision is reduced due to the specific gravity difference. The vibration level occurring at the is reduced than that due to the molten steel. Therefore, the inflow of slag can be detected by measuring the reduction degree of vibration level.

The vibration level is measured using the charge type vibration sensor 32 provided in the long nozzle mounting device 31. The vibration signal measured by the vibration sensor 32 is converted into a voltage value by the vibration / electromotive force converter 33 and input to the vibration analyzer 35.

An example of the conversion by the vibration / electromotive force converter 33 is shown in FIG. Referring to the graph, it can be seen that the electromotive force rises to about 75mV at the time of about 70 seconds when a small amount of slag is mixed with molten steel when the slag is discharged at the end of the molten steel injection. As described above, the vibration signal is converted into electromotive force and outputted according to the outflow of the slag.

The determination of the measured vibration level is performed by the vibration analyzer 35 as follows. When the molten steel is injected from the ladle 1, the vibration level generated by the long nozzle 11 is continuously measured using the vibration sensor 32. Then, the moving average processing is performed on the vibration values for two different time intervals (short time and long time) for averaging the magnitudes of the measured vibration levels. The average after the moving average process determines that the slag has leaked when the value A / B divided by the magnitude B of the long-term averaged vibration level becomes smaller than the predetermined value, that is, the limit value. Further, it is determined that the slag has been leaked when the time detected to be smaller than the predetermined threshold value continues the predetermined time T.

Two times (short time, long time) of moving average processing the vibration level is divided into at least two kinds of average time (short time, long time) without using the data as it is when the vibration signal is input from the vibration sensor 32 For each time, the moving average processing is performed for one second for a short time and for five seconds for a long time to perform arithmetic processing.

Since the present invention detects the outflow of slag by using the lowering of the vibration signal applied to the long nozzle 11, the matters to be considered in detecting the vibration level are as follows. (1) The vibration value at the time of slag outflow contained in the molten steel is not always limited. This is because the vibration level itself changes accordingly because the situation of the flow in the long nozzle pipe changes depending on the operating state (for example, the opening degree of the long nozzle, the quantity of molten steel in a tundish, etc.) which a measurement progresses.

(2) There are a plurality of patterns of vibration level change (flow of how the vibration level changes continuously) when slag flows out. An example of such a pattern of change in vibration level is shown in the graph of FIG. FIG. 7A illustrates a case where the vibration level drops rapidly when the slag is discharged from a stable state, and FIG. 7B illustrates a case where the vibration level gradually decreases, and FIG. 7C shows an unstable vibration state (vibration). The case where the slag outflow occurs while the level rises and falls repeatedly is shown, respectively. Therefore, when attempting to detect the slag outflow automatically should be applicable to all the vibration patterns as described above.

In view of this point, the decrease in vibration level is evaluated as the rate of change of the average vibration level of slag injection. By doing so, even if the vibration level is different for each ladle, the rate of change has the advantage of determining the outflow of slag without being affected by the operating conditions. In addition, in order to avoid unstable misdetection, it is determined that the slag is outflowed when the deterioration state of the change rate continues for a predetermined time.

The detection state of the slag outflow of the vibration level of the present invention will be described with reference to FIG. FIG. 8A is a graph showing a change with time of the vibration level generated in the long nozzle 11. In FIG. 8A, the change in the vibration level due to the slag outflow is shown at the time point C. However, since the reference vibration level cannot be grasped, the amount of change in the vibration level cannot be quantified and the slag based on the signal of the vibration level It is very difficult to detect an outflow.                     

FIG. 8B is a graph showing a continuous change of the vibration level after moving average processing the vibration level signal of FIG. 8A for each short time t1. FIG. 8C is a graph showing the continuous change of the vibration level after moving average processing the vibration level signal of FIG. 8A every time (time longer than t2 and t1).

The change in the vibration level by performing the moving average processing in FIGS. 8B and 8C is apparent from FIG. 8A but is based on the signal of the vibration level in FIG. 8A. As can be seen, it is difficult to quantify the amount of change in vibration level, and it is difficult to detect the slag outflow based on the averaged signal level.

FIG. 8D is a value obtained by dividing the averaged vibration level A of FIG. 8B by the averaged vibration level B of FIG. 8C for each corresponding time in order to quantify the amount of change in the vibration level (A / This graph shows the continuous change of B).

In Fig. 8 (d), the value of (A / B) is changed around 1 when the vibration level is changing with a constant value, for example, when only molten steel is flowing out, and the slag is It can be seen that when outflow, the vibration level decreases from one.

According to the signal processing method described above, the absolute value of the vibration level is standardized by using the difference of the vibration level caused by the difference in the time division of the moving average (a plurality of values are collected and averaged). Irrespective of this, it is possible to quantify the amount of change in the vibration level. For example, in FIG. 8 (d), the reduction of the vibration level due to the outflow of slag at the time of C is set to a threshold value of 0.8.

5 is a block diagram of a vibration analyzer 35 that performs the signal processing of the vibration level as described above. As shown, an A / D conversion and noise filter 43 for digitally converting a voltage (electromotive force) signal corresponding to vibration and removing noise, and a signal output from the A / D conversion and noise filter 43. A short time moving average processing circuit 45 and a long time moving average processing circuit 46 for calculating a moving average value according to a predetermined processing time using the above, and values output from the long time moving average processing circuits 45 and 46. A calculation unit 47 for dividing and calculating a signal, a vibration lowering state continuous judging circuit 49 for judging whether the vibration continues to fall upon the outflow of slag using the output value output from the calculation unit 47, and the vibration A detection circuit 51 for detecting a vibration lowering state using a signal output from the low state sustain determination circuit 49, and a D / A conversion for converting the signal output from the detection circuit 51 into analog and outputting the analog signal;It includes a ryeokgi 53, the D / A conversion and output unit long nozzle control device 57 for cutting off the long nozzle 11 by the signal output from the 53.

The signal input to the vibration analyzer 35 is a signal obtained by converting the vibration detected from the vibration sensor 32 into electromotive force. The vibration signal is input to the A / D conversion and the noise filter 43 to extract only the signal in the frequency band of 10 to 1000 Hz. The vibration signal is transmitted to the short time moving average processing circuit 45 and the long time moving average processing circuit 46, respectively. The short time moving average processing circuit 45 performs the average value (A, B) of the vibration signal in the unit of 1 second and the long time moving average processing circuit 46 in the unit of 5 seconds. However, it is apparent that the short time and long time are not limited to the numerical values.

The two vibration levels A and B averaged as described above are transmitted to the division calculating unit 47, and the vibration level A averaged by the short time moving average processing circuit 45 is averaged by the long time moving average processing circuit 46. The division operation processing divided by the vibration level B is performed.

The (A / B) value output from the division calculating unit 47 is transmitted to the vibration deterioration state determination circuit 49, and when the value of (A / B) is longer than the time T which is longer than or equal to the predetermined value, the detection circuit 51 The signal is sent to the slag outflow value indication and alarm device 55 and the long nozzle controller 57, and the long nozzle controller generates a long nozzle shutoff signal to block the slag that flows out.

And it is comprised so that the slag outflow signal may be output when the conditions of both A / B and T in the vibration analyzer 35 are satisfied, or it may be output when only the conditions of A / B are satisfied. In order to avoid false detection when the vibration is unstable, both A / B and T conditions must be established. However, when the vibration level is stable, there is no fear of false detection. In order to improve the performance, the output is performed only under the condition of A / B. In this case, the determination of the stability and instability of the vibration may be performed automatically, the slag outflow instruction and the recording trend of the alarm 37 may be checked, and the operator may judge and select it.

FIG. 9B is an example showing the change of the vibration level ratio (value of A / B) when the slag outflow is detected as described above, and FIG. 9 (A) shows the vibration level before performing the moving average process. Indicates a continuous change of.

In FIG. 9B, the ratio of vibration levels at time C decreases to a limit of 0.08, and the slag outflow is detected. When this vibration signal was recorded, the driver was injured on the molten steel in the tundish at the same time and confirmed to the neck side, but such a slag outflow was detected two seconds after the time of C.

Table 1 below is an example of dividing the detection limit value of the vibration level for each steel type of molten metal. The vibration level is slightly larger because the flow rate of molten steel is severe at the time of continuous casting, and the average value of vibration is slightly smaller when normal casting is made, and the slag is higher than the vibration level when pure molten steel is injected. When outflowing, the vibration level value appears very small, so that the timing can be detected accurately. Such detection limit values are stored and used in the detection apparatus as a table.

According to the present invention, it is possible to accurately determine the timing of the slag outflow even if the vibration level is different for each steel grade of the molten steel, and also has a low probability of misdetecting the slag outflow, is cast by minimizing the slag outflow It can improve the quality of cast steel.

Claims (2)

In the device for detecting the outflow of the slag contained in the molten steel from the ladle receiving the molten steel into the tundish, the molten steel and the slag is installed on the outer surface of the long nozzle mounting device 31 for fixing the long nozzle 11 Vibration sensor 32 for detecting the vibration of the long nozzle 11 according to the vibration, vibration / electromotive force converter 33 for converting the vibration signal detected from the vibration sensor 32 to electromotive force, and the vibration / electromotive force converter ( Using the electromotive force value output from 33), it calculates the moving average value according to two different times, stores the vibration level value according to the type of molten steel, and detects and outputs the vibration when the vibration falls below the basic limit value. And a slag outflow instruction and alarm (37) for receiving an output signal from the vibration analyzer (35) and indicating a slag outflow value and generating an alarm. Slag outflow detection apparatus using a nozzle-mounted vibration sensors. The method of claim 1, The vibration analyzer 35 includes: an A / D conversion and noise filter 43 for digitally converting a voltage (electromotive force) signal corresponding to vibration and removing noise from the A / D conversion and noise filter 43. From the short time moving average processing circuit 45 and the long time moving average processing circuit 46 which calculates a moving average value according to a predetermined processing time using the output signal, from the long time moving average processing circuits 45 and 46, respectively. An arithmetic operation unit 47 for dividing the output value, and a vibration lowering state continuous determination circuit 49 for judging whether or not the vibration continues to fall upon the outflow of slag by using the output value output from the operation unit 47; And a detection circuit 51 for detecting the vibration reduction state by using the signal output from the vibration reduction state continuous determination circuit 49, and D / A for converting the signal output from the detection circuit 51 to analog and outputting it. A side And a long nozzle control device 57 for blocking the long nozzle 11 by an output unit 53 and a signal output from the D / A conversion and the output unit 53. Slag outflow detection device using vibration sensor.

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