JP3214333B2 - Automatic start control method and apparatus for continuous casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic start control method and apparatus for continuous casting of molten steel, and more particularly to an automatic start at the start of casting.

[0002]

2. Description of the Related Art Conventionally, in the continuous casting of molten steel of this kind, the holding time of molten steel in a mold before the start of pulling out a dummy bar is set to achieve an appropriate formation of a solidified shell.
Various control methods for optimal control have been proposed.
For example, in Japanese Patent Application Laid-Open No. 58-84652, based on a predetermined rising pattern of the level of molten metal in a mold, the injection amount of molten steel and the opening target of the sliding nozzle corresponding to the molten steel depth in the tundish are determined. A control method has been proposed in which a value is calculated and the molten steel injection amount is controlled in accordance with the value. However, in this control method,
Since the deviation between the instantaneous level and the predetermined level rise pattern is not controlled by feedback, variations in nozzle characteristics and variations due to malfunctions cannot be covered, and a state that does not match the flow velocity has occurred. .

In Japanese Patent Application Laid-Open No. 62-84862, in order to improve the above control technique, a time required to reach a predetermined intermediate level of the molten metal level is set, and the required time is set. A control method has been proposed in which the opening of the flow control device is opened to a preset emergency processing opening and triggered by the basic opening level when the intermediate confirmation level does not reach the intermediate confirmation level when the time has elapsed.

Japanese Patent Application Laid-Open No. Sho 62-54562 proposes a control method for correcting a run-up pattern when the run-up pattern is shifted at an intermediate confirmation level. Japanese Patent Laid-Open No.
Various proposals have been made in JP-A-2-183951, JP-A-1-170568, JP-A-2-142659, etc., all of which are determined by whether or not the detection level has reached a predetermined level. , The detection level feedback information was discontinuous.

Further, Japanese Patent Application Laid-Open No. 2-142659 discloses a control method in which a plurality of electrodes having different lengths are provided to detect the level of each molten metal. However, the following problems are pointed out in this control method. (1) Capital investment costs increase. (2) The effects of malfunction due to the effects of splash cannot be completely eliminated. (3) Running costs increase. (4) In a continuous billet casting process, it is difficult to attach a plurality of electrodes to a small cross section having a diameter of, for example, 170 mmφ or less due to restrictions on equipment.

[0006]

As described above, the conventional control method does not employ a method of continuously measuring the rising level of the molten metal from time to time and immediately performing feedback control immediately after the start of injection. However, the molten steel in the tundish contains inclusions, and if the molten metal rises immediately after the start of pouring, the inclusions near the upper part of the molten steel in the tundish are caught in the billet after casting. Causes cracks and other defects due to inclusions.
Unless the bathing speed is set to the optimum value, there is a problem that the defective rate increases. This problem was particularly remarkable in continuous casting of a billet having a small cross section and a high run-up speed in the mold immediately after the start of pouring into the mold.

[0007] When a tundish is reused as in the case of continuous casting of a slab, immediately after the start of casting,
Because the nozzle gain fluctuates greatly due to the slag remaining in the tundish, and the discharge flow rate fluctuates, automatic control cannot be stably performed unless feedback control is performed in this control region. Had to be manually operated. But,
In the case of manual operation, over-action tends to occur, and the frequency of nozzle clogging troubles is high.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and detects the level of a molten metal in a mold from immediately after the start of pouring until the level of the molten metal reaches a steady level. It is an object of the present invention to provide a continuous casting automatic start control method and apparatus capable of appropriately controlling the discharge amount.

[0009]

SUMMARY OF THE INVENTION An automatic start control method for continuous casting according to one aspect of the present invention is a method for controlling continuous start of molten steel from immediately after injection of molten steel into a mold until the molten steel level level reaches a steady value. During the measurement, the level is measured by an electrode level gauge using a pseudo-random signal, and based on the change in the level, the rising speed is calculated, and the deviation between the rising speed and the reference speed is calculated. The flow rate of molten steel discharged from the tundish is adjusted based on the
When the steady state value is reached, casting drawing is started. Automatic start control device for continuous casting according to another aspect of the present invention,
A second pseudo-random signal supplied to one of the electrodes and having a slightly different frequency in the same pattern as the first pseudo-random signal; The random signal is multiplied by a first pseudo-random signal to calculate a first multiplied value, and a signal input via the other electrode is multiplied by a second pseudo-random signal to obtain a second multiplied value. Calculate, integrate the first multiplied value and the second multiplied value, measure the level of the molten metal from the time difference between the maximum correlation values respectively generated in the time series pattern of the integrated values, and further measure the level of the molten metal from the change in the level of the molten metal. An electrode-type level gauge that calculates the speed, and the flow rate of molten steel discharged from the tundish is controlled by controlling the opening of the tundish stopper or sliding nozzle based on the deviation between the rising speed and the reference speed. And has a casting control device bath level height to start casting withdrawal upon reaching a constant height.

In the present invention, the stopper or the sliding nozzle of the tundish is fully opened to start pouring molten steel into the mold, and after a certain period of time, the stopper or the sliding nozzle is lowered to a certain opening. After the start of molten steel pouring, the height of the molten steel surface in the mold gradually increases. Then, at this time, the level of the molten steel in the mold is continuously measured using an electrode type level gauge, and further, the level of the molten metal is calculated, for example, at a constant cycle. In order to eliminate the deviation between the rising speed and the reference speed, an opening correction amount of the stopper or the sliding nozzle is obtained,
By outputting an operation command to the stopper or the sliding nozzle, feedback control is performed at regular intervals. Then, when the level of the molten metal reaches a certain level, casting and drawing are started. The above-mentioned reference speed is an optimum rising speed at which no inclusions are generated, and is obtained in advance for each billet diameter size according to operating conditions. In the feedback control, for example, in an embodiment described later, PI
Although control (proportional + integral control) is used, other methods may be used.

According to another aspect of the present invention, there is provided an automatic start control method for continuous casting, wherein the molten steel level is simulated from immediately after the molten steel is injected into a mold in the continuous casting until the molten steel level reaches a steady value. While continuously measuring with the electrode type level gauge using a random signal , the molten steel head which is the height of the molten steel of the tundish is measured, and the molten steel level, the molten steel head and the opening of the stopper or the sliding nozzle at that time are measured. Based on the opening degree and the ratio of the discharge amount to the molten steel head, an estimated value of the nozzle gain is calculated, and a target discharge amount for satisfying a target injection time set in advance based on the molten metal level is calculated. And the opening of the stopper or the sliding nozzle is calculated based on the estimated value of the nozzle gain and the target discharge amount. Par or sliding nozzle
Operate to adjust the flow rate of the molten steel discharged from the tundish, and repeats the above processing for each prescribed operation cycle, the molten metal surface level reaches a certain height, to start casting withdrawal. An automatic start control device for continuous casting according to another aspect of the present invention includes a pair of electrodes inserted into molten steel of a mold, supplies a first pseudo-random signal to one of the electrodes, and A first pseudo-random signal is multiplied by a second pseudo-random signal having a slightly different frequency in the same pattern as the pseudo-random signal to calculate a first multiplied value. Multiplying by a second pseudo-random signal to calculate a second multiplied value;
Integrating a first multiplied value and the second multiplied value respectively;
Electrode level gauge for measuring the level of the molten steel from the time difference between the maximum correlation values generated in the time series pattern of both integral values, means for measuring the molten steel head which is the height of the molten steel in the tundish, And, based on the opening degree of the stopper or the sliding nozzle at that time, the opening degree and an estimated value of the nozzle gain indicating the ratio of the discharge amount to the molten steel head are calculated, and a target set in advance based on the molten metal level The target discharge amount for satisfying the pumping time is calculated, the opening of the stopper or the sliding nozzle is calculated based on the estimated value of the nozzle gain and the target discharge amount, and the stopper or the sliding nozzle is calculated based on the opening. adjust the flow rate of the molten steel discharged from the tundish by operating the and repeat the above process for each prescribed operation cycle , The molten metal surface level reaches a certain height, and a casting control device for starting the casting withdrawal.

In the present invention, when a tundish stopper or a sliding nozzle is opened to an initial opening to start molten steel pouring, the level of the molten metal in the mold rises. At this time, the level of the molten steel in the mold is continuously measured by an electrode type level gauge and the molten steel head of the tundish is measured. Then, for example, a rise value of the molten metal level from the previous time is calculated for each calculation cycle, and a current actual discharge amount is calculated based on the increase value. Next, an estimated value of the current nozzle gain is calculated from the actual discharge amount, the stopper of the molten steel head and the opening of the tundish or the sliding nozzle. Then, the current target discharge amount is obtained from the current bath level and the time left before the target pouring time,
Based on the target discharge amount, the nozzle gain estimation value, and the current molten steel head, the opening degree, for example, the opening area of the stopper or the sliding nose this time is obtained. And, by operating the stopper or the sliding nozzle based on this result and performing feedback control, in particular,
In response to large fluctuations in nozzle gain due to the effect of nodding immediately after the start of casting when reusing a tundish, the flow rate of molten steel discharged from the tundish is optimally controlled, and the target pouring time can be satisfied. In addition, troubles such as nozzle clogging can be prevented.

Further, the electrode type level gauge according to the present invention comprises a first pseudo-random signal generating means for generating a first pseudo-random signal, and a first pseudo-random signal having the same pattern as that of the first pseudo-random signal and having a slightly different frequency. Second pseudo-random signal generating means for generating a second pseudo-random signal, a first electrode connected to the first pseudo-random signal generating means and inserted into the molten steel, and a second electrode inserted into the molten steel A first multiplier for multiplying an output of the first pseudo-random signal generating means and an output of the second pseudo-random signal generating means to output a first multiplied value; and a second electrode connected to the second electrode. , And its output multiplied by the output of the second pseudo-random signal generating means to obtain a second
A second multiplier that outputs a multiplied value of the first, a first integrator that integrates the first multiplied value and outputs a first integrated value, and a second integrated value that integrates the second multiplied value. A second integrator for output;
Calculating means for measuring the level of the molten metal from the time difference between the maximum correlation values respectively generated in the time series pattern of the first integrated value and the second integrated value, and further calculating the level of the molten metal from the temporal change of the level of the molten metal; It has.

Next, the electrode type level gauge will be described. In this electrode type water level meter, the first pseudo-random signal and the second pseudo-random signal have the same pattern and slightly different frequencies. In the time series pattern of the first multiplied value, the multiplied value when the pulse of each cycle of the first pseudo-random signal and the pulse of the second pseudo-random signal match indicates the maximum correlation value, and becomes the maximum value. It occurs at 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 is
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 from the maximum value of the second multiplied value as shown in FIG. 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, the displacement of the molten steel level can be obtained by measuring X from equation (3) to obtain Td. If the displacement of the level is known, a reference position can be determined, and the distance from the reference position to the level can be obtained. Also,
In the equation (3), if the value of Δt is set to a value smaller than Td and the value of P2 is increased, the value of Td can be enlarged and measured by a factor of P2 / Δt. it can. 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 that the S / N ratio is large, there is no influence of multiple reflection, and the molten steel surface level It can be measured accurately. Therefore,
The rising speed can also be accurately measured.

[0017]

DETAILED DESCRIPTION OF THE INVENTION

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of an automatic start control device for continuous casting according to an embodiment of the present invention and related equipment, and FIG. 2 is a timing chart showing a control state thereof. is there. In the present embodiment, when the volume of the mold is small and the time until the molten metal level reaches a steady value is short as in the case of continuous casting of a billet (for example, 10 to 10).
20 seconds). In the control device of FIG. 1, when molten steel is injected from the ladle pan into the tundish 9 and the weight of the molten steel detected by the tundish weighing scale 7 provided on the tundish 9 reaches a certain value (( a)), a command to open the stopper fully is output from the casting control device 3, and the stepping cylinder 4 is driven. When the stepping cylinder 4 is driven, the stopper 8 is fully opened (see FIG. 2B), and the molten steel starts to be injected into the mold 10. Thereafter, when a certain time has elapsed, a command to close the stopper 8 is output from the casting control device 3 to a certain opening, and the stopper 8 is closed to a certain opening (see FIG. 2B).

At this time, the level of the molten steel is continuously measured by using an electrode-type level gauge 2 (see the embodiment described later), and the rate of the molten steel is calculated at regular intervals based on the change. I do. The calculated measured run-up speed is input to the casting control device 3 and compared with an optimum target run-up speed that does not involve inclusions during operation for each billet diameter size that is input in advance to the casting control device. Then, in order to reduce the deviation between the measured value of the rising speed and the target rising speed to zero, the casting controller 3 outputs a stopper opening correction value by, for example, PI (proportional + integral) control, and the stopper 8 is moved to the predetermined opening. (See FIGS. 2B and 2D).

FIG. 3 is a block diagram showing the configuration of the electrode type water level gauge 2. The first clock generator 21 generates a frequency of f1 per clock, and the second clock generator 2
2 generates a frequency f2 slightly less than f1 per clock. The first pseudo-random signal generator 23 generates a first pseudo-random signal M1 having a period P1, and the second pseudo-random signal generator 24 has the same pattern as M1 and a period P2 having a period P1.
A second pseudo-random signal M2 that is slightly different is generated. 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 24. 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 the transmission line Lb from the 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 level of the molten metal is calculated from the time difference between the maximum correlation values of the time-series patterns of the low-pass filter 28, and the rate of rise of the molten metal level is calculated. The transmission line Ld has a first part in which a part is inserted into the molten metal 33 in the mold 10.
An electrode 30 and a second electrode 31 are provided.
Are electrically connected via a molten metal 33.

FIG. 4 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. 5 is a diagram for explaining the configuration of the first and second pseudo random signal generators. This figure is a configuration diagram of a 3-bit M-sequence signal generator, and shows a 3-bit case for easy explanation, but a larger bit, for example, a 7-bit shift register or the like is used. The M-sequence signal generator is provided with a shift register 50 composed of a flip-flop synchronized with a clock signal, and an exclusive logic circuit which inputs the output signal of the last stage and the immediately preceding stage of the shift register 50 and outputs it to the first stage. 51.

FIG. 6 is a timing chart showing a pseudo-random signal when the three-stage shift register shown in FIG. 5 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 1-bit clock frequency of the first pseudo-random signal M1 generated from the first pseudo-random signal generator 23 shown in FIG. 3 is f1, and the 1-bit clock of the second pseudo-random signal M2 of the second pseudo-random frequency generator 24 is Assuming that the frequency 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
1MHz, f2 = 1500.000MHz with and, when the shift register 7 stages with (n = 7), P1 = (2 n -1) / f1 = (2 7 -1) /1500.001×106 = 84666.61022 (Psec) P2 = (2 ⁿ -1) / f2 = (2 ⁷ -1) /1500.001×10 6 = 846666.667 (psec) Further, the difference Δt of one cycle is Δt = P2− P1 is obtained as a very small time difference of 0.0565 (psec).

FIGS. 7A and 7B show multipliers 25 and 2 respectively.
6 is an explanatory diagram of a correlation value obtained in FIG. FIG. 7A is an enlarged view of one cycle of pseudo-random signals M1 and M2 of the three-stage shift register shown in FIG. 5 and one bit thereof.
And the first bit of M1 coincides from the state shifted by one bit and then shifts by one bit. FIG. 7B shows the correlation value at this time. In FIG. 7B, one cycle P2 of M2 and one cycle P1 of M1 are shifted by Δt as shown in equation (6), and one cycle P1 and P2 are composed of 7 bits. In the first bit of one cycle, Δ
At t / 7, the last 7th bit is shifted by Δt. Is M1
And M2 deviate by one bit, indicates the most coincident case, and indicates the case of deviating again by one bit. FIG. 7C shows the magnitude of the correlation value corresponding to in FIG. 7A 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. 3, and the vertices of the triangle have the maximum correlation value.

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. 8 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. 9 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. Transmission lines La to Ld
Represents the length of each line as shown in FIG. The transmission line La is a transmission distance from the second pseudo-random signal generator 24 to the first multiplier 25, the transmission line Lb is a transmission distance from the second pseudo-random signal generator 24 to the second multiplier 26, the transmission line Lc is the transmission distance from the first pseudo-random signal generator 23 to the first multiplier 25, and the transmission line Ld is the transmission distance from the first pseudo-random signal generator 23 via the first electrode 30 and the second electrode 31. This is the distance to the square multiplier. When La = Lb and Lc = Ld, the phase difference X between S1 and S2 becomes 0, but when Lc ≠ Ld, a phase difference X corresponding to the difference between Lc and Ld is generated.

FIG. 10 is a graph showing Ld- when the level of molten steel changes.
It is a figure explaining the change of Lc. 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. 11 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 molten steel level displacement L changes from L1 to L2, the phase differences X1 and X2 at each displacement are represented by the following equations. X1 = ((2L1 + L ′) × f1) / (V × Δf) (13) X2 = ((2L2 + L ′) × f1) / (V × Δf) (14) The phase difference change amount ΔX at this time Is represented 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 ′ = 2 L / 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 As a result, the signal transmission time is delayed by about 1.5 million times. As a result, the signal processing is easily and accurately performed.

FIG. 12 is a characteristic diagram showing the measurement result of the molten metal level according to the present embodiment. The horizontal axis indicates the level of the molten metal, and the vertical axis indicates the voltage representing the level measurement value. The measurement conditions at this time are f = 1500 MHz, Δf = 1 KHz,
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. Then, a temporal change in the level of the molten metal obtained in this way is detected, and the rate of increase is obtained.

It is preferable to use a metal having a higher melting point than the molten metal for the electrode of the present embodiment, or to automatically inject the metal 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. This is the same in the embodiment described later.

(Embodiment 2) FIG. 13 is a block diagram showing a configuration of an automatic start control device for continuous casting according to another embodiment of the present invention and related equipment, and FIG. 14 shows a control state thereof. It is a timing chart. This embodiment is suitable for a case where a tundish is reused as in the case of continuous casting of a slab, or a case where the capacity of a mold is relatively large and a long time is required to reach a molten metal level (for example, 1 minute or more). I have. 13, components having the same reference numerals as those in FIG. 1 indicate the same or corresponding parts, and a description thereof will be omitted.

In the apparatus shown in FIG. 13, when molten steel is poured from the ladle pan into the tundish 9 and the weight detected by the tundish weighing machine 7 reaches a certain value (see FIG. 14A), the casting is performed. A command of the initial opening is output from the control device 3 to the sliding nozzle 12. The sliding nozzle 12 is vibrated in the vicinity of the closed position to prevent nozzle clogging until receiving this command. When the sliding nozzle 12 receives the command, the nozzle is opened according to the command, and the molten steel starts to be injected into the mold 10. At this point, the electrode level is continuously measured using the electrode level gauge 2, and
The measurement result is input to the casting control device 3. First, the casting control device 3 calculates the actual discharge amount from the previous value and the current value of the calculation cycle by the following equation (16).

[0038]

(Equation 1)

Here, Q _i : the current actual discharge amount (g / se)
c) M _w : Mold width (mm) M _T : Mold thickness (mm) ρ: Molten steel density (g / mm ³ ) ML _(i) : Current molten metal level (mm) ML _(i-1) : Previous level (mm) T _C : Operation cycle (sec). Next, the actual nozzle gain is calculated by equation (17) using Q _i obtained by equation (16).

[0040]

(Equation 2)

Where β _i : current actual nozzle gain A _{T (i-1)} : previous sliding nozzle opening area target value (mm ² ) g: gravitational acceleration (mm / s ² ) Hi _i : previous Is the molten steel head (mm). Note that Q _i and ρ are the same as described in the expression (16). The molten steel head Hi _-1 is obtained based on the weight detected by the tundish weighing scale 7 at the timing when the molten metal level ML _(i-1) is measured. Therefore, the means for measuring the molten steel head of the present invention is constituted by the tundish weighing scale 7 and the casting control device 3 in the present embodiment.

Next, the target discharge amount for injecting the remaining mold height to the remaining mold height based on the actual level of the molten metal level in the time remaining until the target pouring time is calculated by the following equation (18). .

[0043]

(Equation 3)

Here, Q _Ti : current target discharge amount [g / se
c] M _D : Mold height (mm) T _M : Target pouring time (sec) M _w , M _T , ρ, M _{L (i)} , and T _C are the same as described in the expression (16).

Next, β _i obtained by equation (17) and (18)
The target value of the opening area of the sliding nozzle is calculated by the following equation (19) based on Q _Ti obtained by the equation.

[0046]

(Equation 4)

[0047] In this A _Ti: opening area target value of the current of the sliding nozzle (mm ²⁾ H _i: a current of the molten steel head (mm). Note that Q _Ti , β _i , ρ, and g are (16) to (1)
8) This is the same as the description of the equation.

The sliding nozzle operation amount corresponding to the current opening area target value A _Ti of the sliding nozzle 12 obtained by estimating the nozzle gain β _i by the above calculation is operated and feedback controlled. The above control is performed for each calculation cycle of the casting control device 3 up to the level of the molten metal that enters the steady level control (see FIG. 14C). And
Thereafter, the steady level control is performed based on the measured value of the molten metal level by the eddy current level meter 6. Immediately before entering the steady level control, a pull-out command is output from the pull-out speed control device 5,
Pulling out of the dummy bar is started (see (d) of FIG. 14).

[0049]

As described above, according to the present invention, the level is continuously measured by the electrode type level gauge, and the level of the level is calculated from the change in the level, and the tundish is calculated based on the level of the level. Since the amount of hot water discharged from is adjusted, the rising speed of the hot water is appropriate. As a result, the rate of occurrence of defective slabs after casting due to the inclusion of inclusions is reduced by about 20%. Also, as in the prior art, proper formation of solidified shells can be achieved, and prevention of breakout can also be achieved. Further, various phenomena occurring in the early stage of casting, for example, a sudden rise in the molten metal surface caused by peeling of the stopper refractory or an overflow caused by a delay in the action of the stopper operation can be prevented beforehand.

Further, according to the present invention, immediately after the start of casting, the level of the molten metal is detected by an electrode-type water level gauge, and the actual nozzle gain is estimated from the measured value and the like, and a stopper or a sliding nozzle is determined based on the result. By controlling the opening of the tundish, feedback control can be performed moment by moment, so that especially when a tundish is reused, the nozzle gain greatly fluctuates due to the effect of nodules remaining in the tundish, and the discharge flow rate fluctuates. Even in such a case, the discharge amount is optimally controlled, and the effect of reducing troubles such as nozzle clogging, seal leakage, and overflow when using a reused tundish is reduced to 1/3 of the frequency before application of the present invention. was gotten.

Further, according to the present invention, by inserting two electrodes into the molten metal and transmitting a signal in the order of the electrode, the molten metal, and the electrode, a change in the level of the molten metal is represented as a change in the transmission distance. The change in the transmission distance is taken as the delay time of the signal, and the delay time is greatly expanded for measurement. Therefore, the level of the molten metal can be accurately measured, and therefore, the rising speed of the molten metal can be measured. Can be measured accurately, so that appropriate control is possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a control system for continuous casting according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a timing chart of automatic start control of continuous casting in FIG. 1;

FIG. 3 is a block diagram showing a configuration of the electrode type water level gauge of FIG.

FIG. 4 is a block diagram illustrating a configuration of a clock generator of FIG. 3;

FIG. 5 is a diagram illustrating an example of a pseudo-random signal (M-sequence signal) generation circuit in FIG. 3;

FIG. 6 is a timing chart showing a pseudo-random signal by the three-stage shift register of FIG. 5;

FIG. 7 is a timing chart illustrating output of a correlation value.

FIG. 8 is a timing chart illustrating a method of calculating a correlation cycle T.

FIG. 9 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. 10 is a diagram illustrating a level of a molten metal and a signal transmission distance.

FIG. 11 is an explanatory diagram for calculating a phase difference X;

FIG. 12 is a characteristic diagram showing an example of measured values in the embodiment.

FIG. 13 is a block diagram showing a configuration of a continuous casting automatic start control device and related equipment according to another embodiment of the present invention.

FIG. 14 is an explanatory diagram showing a timing chart of the automatic start control of the continuous casting in FIG. 13;

[Explanation of symbols]

 2 Electrode level gauge 3 Casting control device 4 Stepping cylinder 5 Drawing speed control device 6 Eddy current level meter 7 Tundish weighing device 8 Stopper 9 Tundish 10 Mold 11 Pulling roll 12 Sliding nozzle

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Akira Ohkado 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (56) References JP-A-62-179859 (JP, A) JP-A No. 2 JP-A-142659 (JP, A) JP-A-2-290657 (JP, A) JP-A-6-238412 (JP, A) JP-A-4-118163 (JP, A) JP-A-2-142657 (JP, A) JP-A-62-220260 (JP, A) JP-A-62-54562 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/16 104 B22D 11/18

Claims (5)

(57) [Claims] (1) Immediately after injection of molten steel into a mold in continuous casting, until the molten steel surface level reaches a steady value.
The electrode level gauge using a pseudo-random signal is used to continuously measure the level of the molten metal, calculate the level of the molten metal based on the change in the level of the molten metal, and calculate the level of the molten metal based on the deviation between the level of the molten metal and the reference velocity. An automatic start control method for continuous casting, wherein a flow rate of molten steel discharged from a tundish is adjusted, and when a molten metal level reaches a certain height, casting drawing is started. 2. A method according to claim 1, further comprising a pair of electrodes inserted into the molten steel of the mold, for supplying a first pseudo-random signal to one of the electrodes, and for reducing the frequency in the same pattern as the first pseudo-random signal. Is multiplied with the first pseudo-random signal to calculate a first multiplied value, and multiplies the signal input via the other electrode by the second pseudo-random signal. Calculating a second multiplied value, integrating the first multiplied value and the second multiplied value, respectively, and measuring the level of the molten metal from the time difference between the maximum correlation values respectively generated in the time series pattern of the two integrated values. An electrode-type water level gauge for calculating a rising speed from the change in the level of the molten metal; and controlling the opening of a stopper or a sliding nozzle of the tundish based on a deviation between the rising speed and a reference speed. A casting control device for adjusting the flow rate of molten steel discharged from the dish and for starting casting when the molten metal level reaches a certain level. apparatus. 3. Immediately after injection of molten steel into a mold in continuous casting, until the molten steel surface level reaches a steady value.
The level of the molten metal is continuously measured by an electrode-type level gauge using a pseudo-random signal, and the molten steel head, which is the height of the molten steel in the tundish, is measured. The molten steel level, the molten steel head and the stopper or sliding at that time are measured. Based on the opening of the nozzle, an estimated value of the nozzle gain indicating the opening and the ratio of the discharge amount to the molten steel head is calculated, and a target injection time set in advance based on the molten metal level is satisfied. To calculate the target discharge amount, and calculate the opening degree of the stopper or the sliding nozzle based on the estimated value of the nozzle gain and the target discharge amount,
A stopper or a sliding nozzle is operated based on this opening to adjust the flow rate of the molten steel discharged from the tundish, and the above-described processing is repeated at predetermined calculation cycles, so that the level of the molten metal is constant. A method for controlling automatic start of continuous casting, characterized in that the casting start is started when the temperature reaches a predetermined value. 4. A pair of electrodes inserted into molten steel of a mold, a first pseudo-random signal is supplied to one of the electrodes, and the frequency is slightly reduced in the same pattern as the first pseudo-random signal. Is multiplied with the first pseudo-random signal to calculate a first multiplied value, and multiplies the signal input via the other electrode by the second pseudo-random signal. Calculating a second multiplied value, integrating the first multiplied value and the second multiplied value, respectively, and measuring the level of the molten metal from the time difference between the maximum correlation values respectively generated in the time series pattern of the two integrated values. An electrode-type water level gauge, a means for measuring a molten steel head, which is the height of the molten steel of the tundish, and, based on the molten steel level, the molten steel head and the opening degree of a stopper or a sliding nozzle at that time, Calculating the estimated value of the nozzle gain indicating the ratio of the discharge amount to the molten steel head and the target discharge amount to satisfy a target injection time set in advance based on the molten metal level, The opening of the stopper or the sliding nozzle is calculated based on the estimated value of the nozzle gain and the target discharge amount, and the flow rate of the molten steel discharged from the tundish is adjusted by operating the stopper or the sliding nozzle based on the opening. And a casting control device for repeating the above-described processing at every predetermined calculation cycle to start casting when the molten metal level reaches a certain height. Control device. 5. An electrode-type water level gauge comprising: a first pseudo-random signal generating means for generating a first pseudo-random signal;
Generating a second pseudo-random signal having a slightly different frequency in the same pattern as the first pseudo-random signal;
A first electrode connected to the first pseudo-random signal generating means and inserted into the molten steel, a second electrode inserted into the molten steel, and the first pseudo-random signal generating means. A first multiplier for multiplying an output of the signal generating means and an output of the second pseudo-random signal generating means to output a first multiplied value, and a first multiplier connected to the second electrode, A second multiplier for multiplying an output of the second pseudo-random signal generating means to output a second multiplied value, and a first multiplier for integrating the first multiplied value and outputting a first integrated value An integrator, a second integrator that integrates the second multiplied value and outputs a second integrated value, the first integrated value and the second integrated value.
5. The automatic start control device for continuous casting according to claim 2, further comprising a calculating means for measuring the level of the molten metal from the time difference between the maximum correlation values generated in the time series pattern of the integral values.