JP3218953B2 - Continuous casting operation control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a continuous casting operation, and more particularly to a method for controlling the molten steel level at the start of casting when the molten steel level in a mold changes rapidly and at a steady operation thereafter.

[0002]

2. Description of the Related Art There are the following methods for measuring the level of molten steel in a mold and controlling the same in a conventional continuous casting facility. Electromagnetic induction type (eddy current type) level meter: The level of molten steel in the mold is measured and controlled by an electromagnetic induction type level meter. Level measurement and control during steady operation are mainly performed by this method. Electrode method (Japanese Patent Publication No. 3-61536): A plurality of electrodes having different tip positions are installed in a mold, a voltage is applied, and level detection is performed by the molten steel reaching the electrodes and short-circuiting to control the molten steel level. Do. Thermocouple method (Japanese Patent Publication No. 2-51699): A change in the molten steel level in the mold is detected based on a change in the temperature measurement values of a plurality of thermocouples (thermosensitive elements) embedded in the vertical direction of the inner wall of the mold, and the molten steel level is detected. Control. Electromagnetic wave method: Sends electromagnetic waves such as microwaves and millimeter waves into the mold, detects the reflected signal from the molten steel surface, measures the level of molten steel in the mold from the round-trip propagation time of the signal,
Control the molten steel level.

[0003]

The following problems are pointed out in the above prior art. Electromagnetic induction type level meter: In the electromagnetic induction type level meter, the measurable range of the molten steel level is limited to about 100 mm, and it is difficult to measure the level immediately after the start of injecting molten steel into the mold, and sufficient control is performed. Can not do. In addition, the electromagnetic induction type level meter performs calibration work by comparing it with actual hot water as needed during measurement.However, it is difficult to maintain and control the actual level, so accurate calibration may not be possible. Absolute control accuracy may deteriorate. Electrode method: It is impossible to measure the continuous change of the molten steel level in the mold, and there is a possibility of erroneous measurement due to scattering of the molten steel. When the mold has a small sectional area such as a billet, it is difficult to install a plurality of electrodes. Thermocouple method: In detecting the level of molten steel by measuring the temperature of a thermocouple embedded in a mold, sufficient responsiveness cannot be obtained due to a time delay caused by heat conduction. Also,
Continuous measurement of the molten steel level is not possible, and embedding a thermocouple in a mold deteriorates strength and durability. Electromagnetic wave method: It is difficult to install an antenna for transmitting and receiving electromagnetic waves with a small-section mold such as a billet. Furthermore, the equipment is complicated and expensive

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a continuous casting operation control method capable of appropriately controlling the level of molten steel in a mold in a continuous casting operation. With the goal.

[0005]

According to one aspect of the present invention, a method for controlling a continuous casting operation according to one aspect of the present invention includes a method for controlling a first and a second casting in a continuous casting mold at the start of casting of a continuous casting equipment operation.
A predetermined signal is input to the first electrode, a predetermined signal is input to the first electrode, and a predetermined signal transmitted to the second electrode via molten steel injected into the mold and in contact with the first and second electrodes is received. The molten steel level in the mold and its rising speed are measured based on the change of the time delay due to the propagation of the predetermined signal, and when the molten steel level in the mold reaches a specified position, the drawing is started, and the molten steel level in the mold and Based on the rising speed, the drawing speed and the amount of molten steel injected from the tundish are adjusted to control the level of molten steel in the mold, and the operation shifts to a steady operation.

In one embodiment of the present invention, before the start of casting, the first and second two electrodes are vertically inserted until just before the dummy bar in the mold. Even if a signal is input to the first electrode before the start of operation, the signal is not transmitted to the second electrode because the first electrode and the second electrode are insulated from each other. When the operation is started and molten steel is injected into the mold, the molten steel and the first and second electrodes start to contact, and a signal input to the first electrode is applied to the second electrode via the molten steel. Transmitted. As the molten steel level in the mold rises, the time delay due to the propagation of the signal transmitted between the first electrode and the second electrode via the molten steel becomes shorter, and the change in the time delay of this signal is measured. By doing so, the change in the molten steel level in the mold from the start of the injection of the molten steel and the change in the rising speed thereof are continuously calculated and measured. Further, in the present invention, the slab drawing is started according to the measured molten steel level in the mold and the rising speed thereof, and the drawing speed and the molten steel injection amount (the opening degree of the nozzle of the tundish) are controlled so that the inside of the mold is controlled. Is adjusted and the molten steel level converges to a predetermined constant value.

When the molten steel level in the mold reaches the target value, the operation shifts to the steady operation control based on the measured value of the electromagnetic induction type level meter. In the control by the usual electromagnetic induction type level meter, the molten steel level in the mold from the start of hot water to the measurement range of the electromagnetic induction type level meter is not measured, and control is performed after the molten steel level rises in the measurement range, Depending on the rising speed of the molten steel level in the mold, the control of the molten steel level in the mold is delayed, causing the molten steel level to rise above the target level and the molten steel surface to fluctuate, and it takes time to shift to steady operation. In some cases, however, in the present invention, control is performed in accordance with the molten steel level in the mold from the start of the rise of the molten metal and the rising speed thereof to prevent fluctuations of the molten steel surface and the like, and to stably shift to steady operation in the shortest time. It has become possible. In the measurement of the molten steel level according to the present invention, since the electrode in the lower part from the molten steel surface is melted at the time when the electrode enters the molten steel, if there is a vertical change in the molten steel surface, However, the contact between the electrodes is interrupted and signal detection becomes difficult.However, for fine fluctuations, the melting time after intrusion of molten steel is adjusted by adjusting the electrode material and shape, and the contact between the electrodes and the molten steel is reduced. Maintain and measure continuously. In addition, using long electrodes,
Continuous measurement can be performed by sequentially inserting electrodes into the mold with respect to the dissolution and wear of the electrode material.

[0008] A continuous casting operation control method according to another aspect of the present invention is the continuous casting operation control method described above.
Measures the level of molten steel in the mold using an electromagnetic induction level meter
Measure and measure the value of the electromagnetic induction level meter with the electrode
Calibration based on measured molten steel level in mold
After the molten steel level in the mold reaches the steady operation level, the molten steel level in the mold is controlled based on the calibrated measurement value of the electromagnetic induction level meter.

In another embodiment of the present invention, an electromagnetic induction type level meter and electrodes are provided on a mold, and the level of molten steel in the mold from the start of casting (start of molten steel injection) is measured by the electrode type level meter. When the molten steel level reaches within the measurement span of the electromagnetic induction type level meter, the measurement value of the electromagnetic induction type level meter is calibrated by the measurement value of the electrode type level meter, and thereby, the electromagnetic induction type level due to temperature drift etc. Prevents errors in meter readings. Then, after shifting to the steady operation, the drawing speed and the opening of the tundish (TD) nozzle are adjusted based on the calibrated values measured by the electromagnetic induction type level meter, and the accurate absolute value of the molten steel level in the mold is obtained. Perform control.

[0010] Further, according to another aspect of the present invention, there is provided a continuous casting operation control method.
After the transition to the steady operation in the continuous casting operation, the two electrodes are held on the molten steel surface, and a short circuit and signal transmission between the two electrodes due to the molten steel are detected, and the opening of the tundish nozzle is detected by the detection. Is adjusted to prevent overflow of molten steel from inside the mold.

According to another aspect of the present invention, in a continuous operation of continuous casting, the first and second positions are set at arbitrary positions above a steady state molten steel level (steady control level) in a mold.
By installing the electrode and constantly monitoring the presence or absence of signal transmission between the first and second electrodes, a control failure due to a failure of the level meter in a steady operation occurred and the molten steel level in the mold abnormally increased. In this case, by detecting the transmission signal due to the contact between the electrode and the molten steel, it is possible to detect the abnormal rise of the molten steel level and its rising speed, and to prevent the overflow by adjusting the drawing speed or the molten steel injection amount.

[0012] According to a continuous casting operation control method according to another aspect of the present invention, in the above continuous casting operation control method, the first electrode and the second electrode may have a speed substantially equal to a rising speed of a molten steel level at the start of casting. Use a member that melts at

In another aspect of the invention, the first electrode and the second electrode melt at a rate approximately equal to the rate of rise of the molten steel level at the start of casting, so that the melting is too slow and too fast. Evils of both can be avoided. That is, if the melting is too slow, the electrodes are continuously present at the bottom of the mold even at the start of drawing, the electrodes are caught by the solidified shell at the start of drawing, and the electrodes are pulled out of the electrode holder with the start of drawing,
Measurement becomes impossible. Also, if the melting is too early, if the molten metal level fluctuates, the contact between the molten steel and the electrode is cut off, and a situation occurs in which measurement becomes impossible. In the present invention, the above situation is avoided by appropriately setting the melting rate of the electrode.

[0014] In a continuous casting operation control method according to another aspect of the present invention, there is provided the continuous casting operation control method, wherein a method of measuring a time delay of the predetermined signal includes generating a first pseudo-random signal; Generating a second pseudo-random signal having the same signal pattern as that of the first pseudo-random signal but having a slightly different frequency; and multiplying the first pseudo-random signal by the second pseudo-random signal to obtain a first multiplied value. , A step of inputting the first pseudo-random signal to the first electrode, and a step of multiplying the signal transmitted to the second electrode through the molten steel by the second pseudo-random signal to obtain a second pseudo-random signal. A step of obtaining a multiplied value, a step of integrating a first multiplied value to obtain a first integrated value, a step of integrating a second multiplied value to obtain a second integrated value, and a first integrated value And each of the second integral values has a maximum value And a step of measuring the time delay between the time.

In another embodiment of the present invention, the following arithmetic processing is performed to measure a time delay of a predetermined signal. The time series pattern of the first multiplication value is the first pseudo-random signal and the second
The multiplied value when the pulse of each period of the pseudo-random signal coincides with the maximum value indicates the maximum correlation value, and becomes the maximum value. This maximum value occurs in the period T. The period T is represented by the following equation. T = k / Δf (1) Here, k is a constant and represents the number of bits (the number of clocks) constituting one cycle of the first pseudo-random signal M1 and the second pseudo-random signal M2. Δf is the difference between the 1-bit clock frequency f1 of M1 and the 1-bit clock frequency f2 of M2, and is expressed by the following equation. Δf = f1−f2 (2)

The maximum value of the time series pattern of the second multiplication value also occurs in the period T, but the first pseudo random signal M1
Through the electrode, the molten steel, and the second electrode, Td
Since the time is delayed with respect to the second pseudo random signal M2, it is delayed by X time with respect to the maximum value of the second multiplied value as shown in FIG. 8 described later. X is represented by the following equation. X = (Td / Δt) × P2 (3) Δt = P2-P1 (4) Here, P1 is a period of M1, and P2 is a period of M2. Here, since Td changes according to the displacement of the molten steel level, displacement of the molten steel level can be obtained by measuring X from equation (3) and obtaining Td. If the displacement of the molten steel level is known, a reference position can be determined, and the distance from the reference position to the molten steel level can be obtained. In the equation (3), if the value of Δt is made smaller than Td and the value of P2 is made larger,
Can be measured with an enlargement of the value of P2 / Δt times, so that the measurement can be performed with high accuracy. Also, in the measurement by this method, the signal is conducted through the electrode and the molten steel and the reflection method is not used as in the past, so the S / N ratio is large, there is no influence of multiple reflection, and the level of the molten steel is accurately measured. can do.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a diagram showing the configuration of a control device to which a continuous casting operation control method according to an embodiment of the present invention is applied and related equipment. In FIG. 1, reference numerals 1 and 2 denote first and second electrodes, 3 denotes an electrode type level meter, 4 denotes a signal processing device, 5 denotes a drawing speed control device, and 6 denotes a nozzle opening degree adjusting device. 7 is a mold, 8 is a tundish, 9 is a nozzle, 10 is molten steel, 11 is an electrode holding device, 12 is a dummy bar, and 13 is an electromagnetic induction type (eddy current type) level meter. In the present embodiment, the two electrodes 1 and 2 that are installed above the continuous casting mold 7 and vertically inserted into the mold by the electrode holding device 11 are held and installed.
Here, the tips of the electrodes 1 and 2 are connected to the dummy bar 1 in the mold.
Although the position is immediately before the position 2, even if the tips of the electrodes 1 and 2 contact the dummy bar 12, there is no problem in measurement. The electrodes 1 and 2 are made of SUS pipe (diameter 3 mm, wall thickness 0.
1 mm) and the electrode spacing is 30 mm.

The electrode type level meter 3 converts a pseudo random signal generated in the device into a first signal via a coaxial cable.
, And detects a pseudo-damn signal transmitted to the second electrode 2 via the molten steel 10 in the mold 7.
Then, the electrode level meter 3 calculates the molten steel level in the mold from the change in the time delay of the detected pseudo-random signal and the transmission speed of the signal, and further, changes the molten steel level in the mold in a unit time. Calculate the ascending speed from the quantity.

FIG. 2 is a block diagram showing a detailed configuration of the electrode type level meter 3. In the electrode type level meter 3, the first
The clock generator 21 generates a frequency of f1 per clock, and the second clock generator 22 generates a frequency of f2 slightly smaller than f1 per clock. A first pseudo-random signal generator 23 generates a first pseudo-random signal M1 having a period P1, and a second pseudo-random signal generator 24 generates a second pseudo-random signal M2 having the same pattern as M1 and a period P2 slightly different from P1. Occurs. The first pseudo random signal M1 is sent to the first electrode 1. Then, a signal obtained through the second electrode 2 is input to the multiplier 26. The first multiplier 25 includes a first pseudo-random signal generator 23
Is multiplied by M1 that has passed through the transmission line Lc and M2 that has passed through the transmission line La from the second pseudo-random signal generator 4. The second multiplier 26 receives the signal from the first pseudo-random signal generator 23
M1 that has passed through Ld is multiplied by M2 that has passed through transmission line Lb from second pseudo-random signal generator 24.

The first low-pass filter 27 includes a first multiplier 2
A high-frequency component is removed from the output of No. 5, and a time-series pattern having one cycle between the maximum correlation values is output. Similarly, the second low-pass filter 28 removes high-frequency components from the output of the second multiplier 26 and outputs a time-series pattern having one cycle between the maximum correlation values. The operation unit 29 includes the first low-pass filter 27 and the second
The molten steel level is calculated from the time difference between the maximum correlation values of the time series pattern of the low-pass filter 28. The molten steel level obtained in the arithmetic unit 29 is output to the signal processing device 4.
The transmission line is provided with a first electrode 1 and a second electrode 2 partially inserted in molten steel 10 in a mold 7,
Both electrodes 1 and 2 are electrically connected via molten steel 10.

FIG. 3 is a diagram showing the configuration of the first clock generator 21 and the second clock generator 22. The first crystal oscillator 41 has a frequency fa, for example, a crystal oscillator of 30.001 MHz, and the second crystal oscillator 42 has a frequency fb, for example, 30.
The common oscillator 43 is an oscillator having a frequency fc, for example, 1470 MHz. The first mixer 44 is composed of, for example, a balanced modulator and outputs a signal of fc ± fa, and the second mixer 45 is a mixer for outputting a signal of fc ± fb. The first bandpass filter 46 passes fc ± fa of the output of the first mixer 44, and the second bandpass filter 47 passes fc ± fb of the output of the second mixer 45.

30. Output from the first crystal oscillator 41
The 001 MHz signal and the 1470 MHz signal output from the common oscillator 43 are mixed by the first mixer 44 and
Two signals of 500.001 MHz and 1439.999 MHz are output. Among them, the signal of 1500.001 MHz passes through the first band-pass filter 46 and is output as the first clock frequency f1. Similarly, a signal of 30.000 MHz output from the second crystal oscillator 42 and a signal of 1470 MHz output from the common oscillator 43 are mixed by the second mixer 45 to obtain a signal of 1500.000 MHz.
And two signals of 1440 MHz are output and passed through the second band-pass filter 47 so that 15000.00
A second clock frequency f2 of 0 MHz is output. With this configuration, the difference between the frequencies f1 and f2 is accurately maintained at 1 KHz.

The first and second crystal oscillators 41 and 42 corresponding to the local oscillators already have a difference of 1 KHz, and the frequency difference output from the mixers 44 and 45 is as wide as 60 MHz. Therefore, the characteristics of the first and second band-pass filters 46 and 47 do not need to be very steep, and can be realized by a general filter such as a SAW filter or a crystal filter.

FIG. 4 is a diagram illustrating the configuration of the first and second pseudo random signal generators 23 and 24. This figure is a configuration diagram of a 3-bit M-sequence signal generator, and shows a 3-bit case for easy understanding, but a larger bit,
For example, a 7-bit shift register or the like is used. The M-sequence signal generator includes a shift register 50 including a flip-flop synchronized with a clock signal, and a shift register 50.
, And an exclusive logic circuit 51 which inputs the output signal of the immediately preceding stage and outputs the signal to the first stage.

FIG. 5 is a timing chart showing a pseudo random signal (M-sequence signal) when the three-stage shift register shown in FIG. 4 is used. The number of clocks (the number of bits) in one cycle is represented by P = 2 ⁿ -1 where n is the number of stages. In the case of a three-stage shift register, n = 3 and P = 7. The first pseudo-random signal generator 23 shown in FIG.
The 1-bit clock frequency of the pseudo-random signal M1 is f1,
Assuming that the 1-bit clock frequency of the second pseudo-random signal M2 of the second pseudo-random frequency generator 24 is f2, the periods P1 of M1 and the period P2 of M2 are represented by the following equations. P1 = (2 ⁿ -1) / f1, P2 = (2 ⁿ -1) / f2 (5) The time difference Δt in one cycle of the pseudo random signals M1 and M2 is expressed by the following equation. Δt = P2−P1 = (2 ⁿ −1) (f1−f2) / (f1 · f2) (6) Here, f1> f2. As a specific example, f1 = 1500.00
Assuming that 1 MHz and f2 = 1500.000 MHz and the shift register has 7 stages (n = 7), P1 = (2 ⁿ -1) / f1 = (2 ⁷ -1) /1500.001×10 ⁶ = 846666.1022 (Psec) P2 = (2 ⁿ −1) / f2 = (2 ⁷ −1) /1500.001×10 ⁶ = 846666.667 (psec) The difference Δt of one cycle is Δt = P2 from the equation (6). −P1 = 0.0565 (psec), which is obtained as a very small time difference.

FIGS. 6A, 6B, and 6C show multiplier 2
FIG. 5 is an explanatory diagram of correlation values obtained in 5, 26. FIG. 6 (b)
Is an enlarged view of one cycle of pseudo-random signals M1 and M2 of the three-stage shift register shown in FIG. 4 and one bit thereof, and the first bit of M2 and M1 is shifted from the state shifted by one bit by one bit. And then the process of shifting by one bit. FIG. 6C shows the correlation value at this time. FIG. 6 (b)
, One cycle P2 of M2 and one cycle P1 of M1 are shifted by Δt as shown in the equation (6), and one cycle P1 and P2 are composed of 7 bits. Δt / 7, and the last 7th bit is shifted by Δt. Is
The case where M1 and M2 are shifted by 1 bit, the case where M1 and M2 are the most matched, and the case where M1 and M2 are shifted by 1 bit again. FIG.
(C) of FIG. 6B shows the magnitude of the correlation value corresponding to in FIG. 6B on the vertical axis and the time axis on the horizontal axis. This represents the output of the low-pass filters 27 and 28 in FIG. 2, and the vertices of the triangle are the maximum correlation values.

There is a correlation between the pseudo-random signals M1 and M2 when the phases of the periods P1 and P2 match. That is,
If the phases of P1 and P2 are shifted by one bit or more, correlation cannot be obtained. The time ΔT at which M1 and M2 are correlated with each other
Is given by the following equation, where the time per bit of M2 is B2. ΔT = 2 (B2 / Δt) × P1 = 2 (1 / Δf) (7) where B2 = 1 / f2 B2 / Δt indicates the number of M1 periods P1 shifted by 1 bit, and the number of periods P1 Can be obtained by multiplying P1, and this one-bit shift is doubled because there is a shift back and forth. Next, after obtaining the correlation once, a time (correlation cycle) until the correlation is obtained again is obtained.

FIG. 7 is a timing chart showing a phase change of the cycle P1 with respect to the cycle P2. In the figure, Δt is set to a larger value than P1 and P2 for easy understanding.
As shown, from the position of A, Δt is the number included in P2
When P1 is repeated, the relationship between P2 and P1 becomes the position of B, which is the same as the position of A, so T is expressed by the following equation. T = (P2 / Δt) × P1 = (P2 / (P2−P1)) × P1 = (2 ⁿ −1) / Δf (8) Equation (8) represents equation (1) shown above. I have.

FIG. 8 is a timing chart showing the outputs of the first and second low-pass filters 27 and 28 of FIG.
S1 indicates the output of the first low-pass filter 27, and S2 indicates the output of the second low-pass filter 28. In S1 and S2, the maximum correlation value appears in the correlation cycle T. Note that the transmission lines La to Ld in FIG. 2 also represent the lengths of the respective lines,
The transmission line La is transmitted from the second pseudo-random signal generator 24 to the first
The transmission distance to the multiplier 25, the transmission line Lb is the transmission distance from the second pseudo-random signal generator 24 to the second multiplier 26, and the transmission line Lc is from the first pseudo-random signal generator 23 to the first multiplier 25. The transmission line Ld is the distance from the first pseudo-random signal generator 23 to the second multiplier 26 via the first electrode 4 and the second electrode 5. Assuming that La = Lb and Lc = Ld, the phase difference X between S1 and S2 is 0.
However, when Lc ≠ Ld, the phase difference X corresponding to the difference between Lc and Ld is obtained.
Occurs.

FIG. 9 is a view for explaining a change in Ld-Lc when the molten steel level changes. At the level H0: Ld−Lc = L ′ At the level H1: Ld−Lc = 2L + L ′, and when the level is displaced by L, the signal M1 transmitted from the first pseudo random signal generator 23 to the multiplier 26 is multiplied. Vessel 2
5 is transmitted at a time Td (delay time) shown in the following equation, which is later than M1 transmitted to M5. Td = (2L + L ') / V (9) where V = 3 × 10 ⁸ m / sec (speed of light) is the speed at which the signal M1 is transmitted between the electrode and the molten steel.

FIG. 10 is a timing chart showing the relationship between the delay time Td and the phase difference X. At the position A and the position B, the phases of the period P2 and the period P1 coincide with each other. At the position A, the maximum correlation value of S1 occurs, and at the position B, the maximum correlation value of S2 occurs. In the phase difference X, the period P2 and the period P1 are n
The difference between the n P2 and the n P1 is represented by nΔt, and since nΔt is equal to the delay time Td, the following equation holds. Td = nΔt (10) Since n = X / P2, X = (Td / Δt) P2 (11) = Td × f1 / Δf = ((2L + L ′) × f1) / (V × Δf (12) Equation (11) represents Equation (3) shown above. (12)
To determine the molten steel level using the equation, the following is performed. First, a reference level H0 is set. If the level displacement L is set to 0 at H0 and the phase difference X0 at H0 is obtained, (12)
L ′ can be obtained from the equation. Next, the reference level H0
If the phase difference X1 at the level H1 below L is obtained, (1
2) L can be obtained by substituting L 'and X1 into the equation.
When the molten steel level goes above H0, the displacement L is calculated as a negative value.

Here, assuming that the displacement L of the molten steel level changes from L1 to L2, the phase differences X1, X2 at the respective displacements.
Is represented by the following equation. X1 = ((2L1 + L ′) × f1) / (V × Δf) (13) X2 = ((2L2 + L ′) × f1) / (V × Δf) (14) The phase difference change amount ΔX at this time Is expressed by the following equation. ΔX = X2−X1 = (2 (L2−L1) × f1) / (V × Δf) = 2ΔL × f1 / (V × Δf) (15) where ΔL = L2−L1 The phase difference change ΔX and displacement Since it is obtained from the relationship of the difference ΔL, ΔL can be calculated from ΔX. Also ΔL
, The displacement L from the reference level and the molten steel level can also be calculated.

Next, a study will be made by substituting the specific numerical values shown above. The number n of shift register stages of the pseudo random signal generator is 7
It is a step. P = 2 ⁿ -1 = 127 Clock frequency f1 = 1500.001 MHz f2 = 1500.000 MHz Displacement difference ΔL = 1 mm. By substituting the above values into equation (15), ΔX = (2ΔL = f1) / (V × f1) = 2 × 1 × 10 ⁻³ × 1500 × 10 ⁸ / (3 × 10 ⁸ × 1 × 10 ³ ) = 0.00001 (sec) = 10 × 10 ⁻⁶ (sec) Usually, the signal propagation time ΔX ′ per 1 mm is ΔX ′ = 2L / V = (2 × 1 × 10 ⁻³ ) / (3 × 10 ⁸ ) = 6.7 × 10 ^-12 (sec) ΔX / ΔX '= 10 × 10 ^{-6 /} (6.7 × 10 ^-12 ) = 1.5 × 10 ⁶ This reduces the signal transmission time by about 1.5 million times. As a result, the signal processing is easily and accurately performed.

FIG. 11 is a characteristic diagram showing the measurement results of the electrode level meter 3 of FIG. The horizontal axis indicates the molten steel level, and the vertical axis indicates the voltage representing the measured value of the molten steel level. The measurement conditions at this time are f = 1500 MHz, Δf = 1 KHz, and the number of shift resist stages of the pseudo random signal generator is seven. In the experiment, the level or the distance from the reference position could be processed easily and at high speed by taking the phase difference X into a computer and calculating it.

The electrodes 1 and 2 of this embodiment may be made of a metal having a melting point higher than that of the molten metal, or may be automatically fed into the molten metal. If the electrode is made of the same material as the molten metal, it does not affect the components of the molten metal even if it is melted.

When the contents of the electrode type level meter 3 have been clarified from the above description, the description will be continued by returning to FIG. 1 again. In the signal processing device 4, the detection signal of the electromagnetic induction type level meter 13 is also input, and the molten steel level in the mold rises, and the output of the electromagnetic induction type level meter 13 is obtained (when the molten steel level is within the measurement span). ), The output-distance characteristics of the electromagnetic induction type level meter 13 are obtained, and the characteristics are calibrated based on the measurement results of the electrode type level meter 3. After that, the electromagnetic induction type level meter 1
The measured value of the molten steel level in the mold is calculated based on the calibrated output of Step 3.

FIG. 12 shows the measured values of the molten steel level in the mold continuously from the start of casting (at the start of molten steel) by the electrode type level meter 3 according to the present embodiment and the measured values of the electromagnetic induction level meter 13. FIG. Although the measurement value of the electromagnetic induction level meter 13 and the measurement value of the electrode level meter 3 do not initially match, from the time when the measurement value of the electromagnetic induction level meter 13 is calibrated by the measurement value of the electrode level meter 3 The two measured values are the same, and then the electrodes 1, 2
Melts and the measurement by the electrode type level meter 3 becomes impossible, but the measured value of the electromagnetic induction type level meter 13 is calibrated and has high accuracy. In the steady control of the molten steel level, the measured value is Is used.

In the signal processing device 4, the drawing speed control device 5 is provided in accordance with the molten steel level in the mold and the rising speed of the molten steel level measured by the electrode type level meter 3.
And a control signal is sent to the nozzle opening adjusting device 6, and the drawing speed control device 5 controls the rotation speed of the drawing roll 14 based on the control signal, thereby controlling the drawing speed. Further, the nozzle opening adjusting device 6 controls the position of the stopper 15, thereby adjusting the opening of the nozzle 9. Although various methods can be considered as a method for controlling the molten steel level, in the present embodiment,
At the start of the operation, the position of the stopper 15 is controlled and the nozzle 9 is opened at a constant opening to start the injection of molten steel. When the molten steel level in the mold reaches a certain level, the pulling roll 14 is driven to pull out the molten steel. Start. Further, after the start of drawing, the nozzle 9 is moved so that the rising speed of the molten steel level in the mold gradually decreases and the molten steel level converges to a constant value.
Was controlled and the pulling speed was controlled.

(Embodiment 2) FIG. 13 is a view showing a state where a continuous casting operation control method according to another embodiment of the present invention is applied. In this figure, an embodiment for detection of overflow is shown. In actual operation, when the tips of the electrodes 1 and 2 are set at a position several tens mm above the upper limit of the fluctuation of the molten steel surface in the mold in a steady operation state, and a signal is detected by the electrode type level meter 3 In the first embodiment, the extraction speed and the nozzle opening are adjusted by the signal processing device 4, but in this embodiment, in order to confirm the effect, the tip of the electrode 1 or 2 is moved to the upper limit of the fluctuation of the molten steel level in the mold in the steady operation state. It was installed in the vicinity and the output of the electrode level meter 3 was observed.

FIG. 14 is a diagram showing the observation results.
The electrode and the molten steel surface come into contact with each other due to the fluctuation of the molten steel surface during steady operation, and intermittent measurement values are obtained. Even when the level of molten steel in the mold abnormally rises due to a failure of the total 14 or the like, an increase in the level of molten steel was detected, and it was confirmed that overflow could be prevented.

Although an example in which the electrodes 1 and 2 are of a fixed length is shown, long rods are used as the electrodes 1 and 2 and the rods are continuously immersed in molten steel and depending on the wear of the electrodes. By inserting the electrode rod either intermittently or intermittently, not only the molten steel level at the time of hot water rising but also the molten steel level in a steady state may be measured continuously or intermittently.

Further, by calibrating the measurement value of the electromagnetic induction type level meter 13 based on the measurement value of the molten steel level continuously or intermittently measured by the electrode type level meter 3, the electromagnetic induction level in a steady state can be improved. Accurate measurement of molten steel level in absolute value by the system level meter can be performed. In particular,
Temperature drift can be appropriately corrected when the temperature differs between when the bath rises and in the steady state.

(Embodiment 3) In a continuous casting facility, particularly in a small-section mold such as a billet, the rising speed of the molten steel level is high. Therefore, when a metal rod is used as an electrode, it takes a long time for the electrode to melt in the molten steel. Due to the long time, the electrodes may be continuously present at the bottom of the mold even at the start of drawing, the electrodes are caught in the solidified shell at the start of drawing, and the electrodes are pulled out of the electrode holder with the start of drawing, and measurement is performed. It may not be possible. As a countermeasure, a method of adjusting the time until the electrode is melted by narrowing the electrode is considered, but in such a case, the electrode needs to be extremely thin, and the installation of the electrode,
Sufficient strength for holding cannot be obtained. Therefore, in another embodiment of the present invention, a hollow SUS pipe having an outer diameter of 3.0 mm, an inner diameter of 2.0 mm, and a wall thickness of 0.5 mm is used as two electrodes to be inserted into a small-section mold of a continuous casting facility. It was used.

As a result, the time required for the electrode to melt in the molten steel is shortened, and the immersed portion of the electrode in the molten steel is sequentially melted down following the rise in the molten steel level in the mold. Since the electrodes do not exist continuously, the situation in which the electrodes are caught by the shell and the electrodes fall out of the holder and cannot be measured is avoided.
In addition, since the thickness of the electrode pipe is optimally adjusted as described above, the electrode may be 10 mm to 20 mm below the molten metal level when the molten metal level rises.
mm, the contact between the molten steel and the electrode is cut off even if the molten steel level fluctuates when the molten steel rises. Could be done. Further, by using a pipe as the electrode, it was possible to adjust the melting time of the electrode while maintaining the strength of the electrode.

The electrode is not limited to the above-described example of the metal pipe. If the electrode has a suitable flexural rigidity and the melting speed matches the rising speed of the molten steel level, other members such as conductive ( Plastic (containing carbon) may be used.

[0046]

As described above, according to the present invention, the molten steel level in the continuous casting mold at the start of casting and the rising speed thereof are measured, so that the control of the molten steel level in the mold from the start of casting is performed. It is possible to perform it properly, and stable level control is possible throughout the entire operation. Also,
According to the present invention, at the start of casting, the electromagnetic induction level meter is calibrated, and at the time of steady operation, the molten steel level in the mold is accurately measured based on the calibrated electromagnetic induction level meter. Control of molten steel level is possible. Further, according to the present invention, it is possible to detect an abnormal rise in the level of molten steel in the mold during a steady operation and prevent an overflow in advance. Further, according to the present invention, the first
Since the electrode and the second electrode are melted at a speed substantially equal to the rising speed of the molten steel level at the start of casting, the adverse effects of both too slow and too fast melting are avoided,
Continuous measurement is possible even in a small-section mold such as a billet.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device to which a continuous casting operation control method according to an embodiment of the present invention is applied and its related equipment.

FIG. 2 is a block diagram showing a configuration of the electrode type level meter of FIG.

FIG. 3 is a block diagram illustrating a configuration of a clock generator of FIG. 2;

FIG. 4 is a diagram illustrating an example of a pseudo-random signal (M-sequence signal) generation circuit in FIG. 2;

FIG. 5 is a timing chart showing a pseudo random signal by the three-stage shift register of FIG. 4;

FIG. 6 is a timing chart illustrating output of a correlation value.

FIG. 7 is a timing chart illustrating a method of calculating a correlation cycle T.

FIG. 8 is a timing chart showing an output S1 of a first low-pass filter and an output S2 of a second low-pass filter.

FIG. 9 is a diagram illustrating a melting level and a signal transmission distance.

FIG. 10 is an explanatory diagram for calculating a phase difference X;

11 is a characteristic diagram showing an example of measured values of the electrode type level meter of FIG.

12 is a characteristic diagram showing measured values of the electrode type level meter and the electromagnetic induction type level meter in the embodiment of FIG.

FIG. 13 is a view showing a state where a continuous casting operation control method according to another embodiment of the present invention is applied.

14 is a characteristic diagram showing measured values of the electrode type level meter and the electromagnetic induction type level meter in the embodiment of FIG.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroaki Miyahara 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (56) References JP-A-2-142657 (JP, A) JP-A Sho58 JP-A-8-84652 (JP, A) JP-A-3-8545 (JP, A) JP-A-6-315747 (JP, A) Japanese Utility Model Application No. Sho 61-161605 (JP, U) Japanese Utility Model Application No. Sho 49-9808 (JP, U) (Japanese) 49-90614 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B22D 11/18 B22D 11/16 B22D 11/16 104

Claims (5)

(57) [Claims] 1. At the start of casting in a continuous casting facility operation, first and second two electrodes are inserted into a mold,
A predetermined signal is input to the first electrode, a predetermined signal is injected into the mold, and a predetermined signal transmitted to the second electrode via molten steel contacting the first and second electrodes is received. The molten steel level in the mold and its rising speed are measured based on the change in the delay, and when the molten steel level in the mold reaches a specified position, drawing is started, and based on the molten steel level in the mold and its rising speed, A continuous casting operation control method characterized by controlling a molten steel level in a mold by adjusting a drawing speed and a molten steel injection amount discharged from a tundish, and shifting to a steady operation. 2. An electromagnetic induction type level meter in a mold.
Measures the molten steel level, and the measured value of the electromagnetic induction type level meter
Is the molten steel level in the mold measured by the electrode
After the molten steel level in the mold reaches the steady operation level, control the molten steel level in the mold based on the calibrated electromagnetic induction level meter. The method for controlling a continuous casting operation according to claim 1, wherein: 3. After a transition to a steady operation in a continuous casting operation, two electrodes are held on a molten steel surface, and a short circuit and signal transmission between the two electrodes due to the molten steel are detected. The continuous casting operation control method according to claim 1, wherein an overflow of molten steel from inside the mold is prevented by adjusting an opening degree of the dish nozzle. 4. A member that melts at a speed substantially equal to a rising speed of the molten steel level at the start of casting, as the first electrode and the second electrode. The continuous casting operation control method described in the above. 5. A method for measuring a time delay of a predetermined signal, comprising: generating a first pseudo-random signal; and a second pseudo-random signal having the same signal pattern as the first pseudo-random signal but having a slightly different frequency. Generating a random signal; multiplying the first pseudo-random signal by the second pseudo-random signal to obtain a first multiplied value; and applying the first pseudo-random signal to a first electrode Inputting; multiplying the signal transmitted to the second electrode through the molten steel by the second pseudo-random signal to obtain a second multiplied value; integrating the first multiplied value Calculating a first integrated value, and integrating the second multiplied value to obtain a second integrated value. Each of the first integrated value and the second integrated value is a maximum value. Measuring the time delay between certain times It claims 1 to 4 continuous casting operation controlling method wherein a.