JP2000351053A - Method for continuously casting molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous casting method for molten metal in which a cast slab having good surface quality can stably be cast at a high speed. SOLUTION: A conductive coil 3 is vibrated in the casting direction and, high frequency current modulated by an effective value synchronously with the vibrating frequency of the conductive coil 3 is supplied into the conductive coil 3. The resonance frequency is measured at a specified phase of the high frequency current modulated by the effective value, and the supplying speed of the molten metal is adjusted with a molten metal supply control unit 18 so that te detected resonance frequency at the upper end position in the vibrating range of the conductive coil 3 becomes a preset value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method of molten metal, and more particularly, to a method of applying an electromagnetic force to the vicinity of an initial solidified shell in a mold using an energizing coil provided on the outer periphery of the mold. It relates to a continuous casting method.

[0002]

2. Description of the Related Art Generally, in a continuous casting method of molten metal,
By applying micro-vibration called oscillation to the mold, molten powder is caused to flow into a gap between the mold and the solidified shell to prevent seizure between the mold and the solidified shell.
Further, the inflow state of the molten powder affects the improvement of the surface quality of the slab, the increase of the casting speed, the stability of the casting, and the like.
Therefore, in recent years, a method has been adopted in which an electromagnetic force is applied to the vicinity of the initial solidified shell of the molten metal in the mold to promote the inflow of the molten powder.

Japanese Patent Application Laid-Open No. Hei 8-206799 proposes a method in which an energizing coil arranged on the outer periphery of a mold is vibrated along a casting direction and casting is performed while modulating an effective value of a high-frequency current to be applied into a rectangular wave. ing. The action of the electromagnetic force squeezes the molten metal toward the center of the mold, widens the gap between the mold and the solidified shell, and promotes the inflow of the molten powder.

In this method as well, it is important to keep the molten metal level in the mold constant. That is,
By performing casting while maintaining a constant level of the molten metal, it is possible to prevent powder from being entangled in the molten metal in the mold and occurrence of wrinkles on the slab surface due to undulation of the molten metal level. In order to perform casting while maintaining a constant level of the molten metal, it is necessary to detect the level of the molten metal. Sensors utilizing the action of (1) are widely used.

[0005] However, the above-mentioned Japanese Patent Application Laid-Open No. 8-206799 has been disclosed.
According to the method proposed in Japanese Patent Application Publication No. 2000-209, it is impossible to use this eddy current sensor due to the principle of measurement that measures the electromotive force of the detection coil in order to apply electromagnetic force due to high-frequency current to the molten metal in the mold. There's a problem.

Japanese Patent Application Laid-Open No. Hei 7-230060 discloses a method for supplying molten metal into a mold such that the resonance frequency of a high-frequency current applied to an energizing coil disposed on the outer periphery of the mold has a predetermined value. Methods for adjusting the amount have been proposed. The principle of the measurement is that when the level of the molten metal in the mold changes, the self-inductance including the mold and the molten metal changes, and as a result, the inductance of the circuit changes. It is based on the principle of electromagnetism that the resonance frequency of a high-frequency current to be applied changes. That is, in this method, since there is a correlation between the resonance frequency of the high-frequency current and the level of the molten metal, the resonance frequency of the high-frequency current is set to a predetermined value and the level of the molten metal is kept constant.

The method for measuring the level of the molten metal proposed in Japanese Patent Application Laid-Open No. 7-230060 is described in Japanese Patent Application Laid-Open No.
When applied to the method proposed in JP-A-06799 to promote the flow of molten powder into the gap between the mold and the solidified shell by electromagnetic force, there is a problem in that the level of the molten metal cannot be measured with high accuracy. That is, in the method proposed in Japanese Patent Application Laid-Open No. 8-206799, the effective value of the high-frequency current to be supplied is modulated, so that the inductance and resonance frequency of the circuit change according to the modulated effective value. Therefore, the level signal fluctuates in the same cycle as the modulation cycle of the high frequency power supply.

Further, when the energizing coil is vibrated in the casting direction in order to promote the inflow of powder, as in the method proposed in Japanese Patent Application Laid-Open No. 8-206799, the molten metal surface level and the energizing coil , The inductance and the resonance frequency change. Therefore, there is a problem that a disturbance signal is superimposed on the molten metal level signal in the same cycle as the vibration cycle of the current-carrying coil, and a stable molten metal level detection signal cannot be obtained.

[0009]

As described above, in order to improve the slab surface quality, increase the casting speed, and stabilize the casting, the electromagnetic force near the initial solidification shell of the molten metal in the mold is increased. The conventional method of promoting the inflow of the molten powder by causing the following has the following problems. That is, a high-frequency current is applied to an energizing coil disposed on the outer periphery of the mold, and an electromagnetic force is applied to the vicinity of the solidified shell of the molten metal in the mold to perform casting (hereinafter, may be simply referred to as an electromagnetic field casting method). )
In addition, in the method of vibrating the energizing coil along the casting direction and performing the casting while modulating the effective value of the energized high-frequency current into a rectangular wave (hereinafter sometimes simply referred to as an output modulation method), At present, there is no method for accurately detecting the surface level, and the operation is performed while observing the surface level visually or the like. Therefore, not only is it difficult to perform a stable continuous casting operation, but also a sufficient level of electromagnetic force cannot be obtained due to fluctuations in the level of the molten metal. In addition, unstable fluctuations in the level of the molten metal have an adverse effect on the quality of the slab, such as the occurrence of powder entrainment.

The present invention relates to a continuous casting method of molten metal in which an electromagnetic force is applied by a high-frequency current in the vicinity of an initially solidified shell in a mold, wherein an energizing coil is vibrated in a casting direction, and an effective value of an applied high-frequency current is applied. It is an object of the present invention to provide a continuous casting method capable of casting a slab of good surface quality at high speed and stably even when the temperature is modulated.

[0011]

The gist of the present invention resides in a continuous casting method shown in the following (1) and (2). (1) A mold having a plurality of slits penetrating the mold wall, the inside of which is water-cooled, an energizing coil disposed on the outer periphery thereof, a vibrating device for vibrating the energizing coil in a casting direction, and a tundish. A molten metal supply port for supplying molten metal to the mold, and a continuous casting method by a device configured with a molten metal supply control device that adjusts the supply amount of the molten metal, wherein the energizing coil in the casting direction A high-frequency current whose effective value is modulated in synchronization with the oscillation cycle of the energizing coil is applied to the energizing coil, and the resonance frequency detected at the upper end position of the oscillation range of the energizing coil is set to a predetermined value. A continuous casting method for molten metal, wherein the molten metal supply control device adjusts the supply rate of molten metal.

(2) The oscillation cycle of the current-carrying coil and the modulation cycle of the effective value modulated high-frequency current applied to the current-carrying coil are synchronized with the oscillation cycle of the casting direction of the mold, and the mold is raised or the mold is lowered. The continuous casting method for molten metal according to the above (1), in which the energizing coil is raised and a high-frequency current is oscillated at a high output during the period.

The present inventors have solved the above-mentioned problems of the present invention as follows. That is, (a) In the method of the present invention, the resonance frequency of the effective value modulated high-frequency current at a phase corresponding to the upper end position of the vibration range of the energizing coil is measured. The reason is as follows. In other words, the higher the relative position of the level of the metal surface with respect to the current-carrying coil, the smaller the rate of change of the resonance frequency with respect to the change of the level of the metal surface, and the detection accuracy of the resonance frequency deteriorates. Therefore, the resonance frequency detection accuracy is the highest at the upper end position of the vibration range of the energizing coil where the relative position of the metal surface level to the energizing coil is the lowest. Also,
At the upper end position of the vibration range of the energizing coil, the moving speed of the energizing coil is almost zero, and the time change of the resonance frequency signal due to the fluctuation of the height of the energizing coil is minimized, and the detection accuracy is good. Further, the detection time of the resonance frequency signal can be sufficiently secured. In this manner, a resonance frequency with good detection accuracy can be obtained, and the level can be accurately determined based on a calibration curve that indicates a correlation between the level and the resonance frequency that are known in advance. .

(B) Further, the frequency signal processing device controls the molten metal supply control device so that the opening degree of the molten metal supply port is adjusted so that the resonance frequency detected at the upper end position of the vibration range of the energizing coil becomes a predetermined value. Instruct. Thereby, the level of the molten metal can be kept constant.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The molten metal to which the method of the present invention is applied is steel such as ordinary steel, alloy steel, stainless steel, aluminum and its alloys, and copper and its alloys. The method of the present invention can be applied to other metals or alloys thereof that can be continuously cast.

FIG. 1 is a diagram showing an example of an apparatus configuration when the method of the present invention is applied. The molten metal 5 is supplied from the tundish 20 into the mold 2 through the molten metal supply port 19 and the immersion nozzle 4. Mold powder 6 is added to the surface of the molten metal in the mold. The molten powder 8 melted by the heat of the molten metal flows into a gap between the mold and the solidified shell 7.

The mold 2 is provided with a plurality of slits 1 penetrating the mold wall, and a mold vibration device 9 and a mold displacement detector 10 are arranged. The mold vibrating device may be any device that can apply a vibration such as a normal sine wave, such as a structure including a motor and an eccentric cam, and a stepping cylinder. The mold displacement detector may be a detector having a response speed that can follow the mold vibration, such as a contact displacement meter or a non-contact displacement meter using a laser beam.

The energizing coil 3 provided on the outer periphery of the mold may be made of water-cooled copper. The energizing coil driving device 14 synchronizes with the oscillation cycle of the mold with an amplitude of several mm to several tens mm in the casting direction. Vibration is applied. The position of the energizing coil that vibrates is detected by the energizing coil position detector 21.

FIG. 2 is a block diagram showing the flow of signal processing. The template displacement signal detected by the template displacement detector 10 is input to the trigger pulse generator 11. The trigger pulse generator detects a specific phase of each cycle of the mold vibration based on the input information on the position of the mold and outputs a trigger pulse signal. The output trigger pulse signal is input to the waveform generator 12. The waveform generator outputs pulse signals for output modulation, vibration control, and frequency measurement to the high-frequency current effective value modulator 15, the energizing coil vibration controller 13, and the frequency signal processor 17, respectively.

The pulse signal for output modulation is input to the high-frequency current effective value modulator 15, which modulates the effective value of the high-frequency current output from the high-frequency power supply based on the pulse signal. .

A pulse signal for controlling the energized coil vibration is input to the energized coil vibration control device 13. The energizing coil vibration control device synchronizes the oscillation cycle of the energizing coil with the oscillation cycle in the casting direction of the mold based on the pulse signal and the energizing coil position signal detected by the energizing coil position detector 21, and Control is performed so as to raise the current-carrying coil during the rising period or to raise the current-carrying coil during the falling period of the mold.

The pulse signal for frequency measurement is input to the frequency signal processing device 17 together with the frequency signal from the high frequency power supply 16 that has been subjected to RMS modulation. This frequency signal processing device measures the resonance frequency at a specific phase of the RMS-modulated high-frequency current, and the resonance frequency detected at the upper end position of the vibration range of the energizing coil becomes a predetermined value. Thus, the molten metal supply control device 18 outputs a molten metal level signal for instructing the opening degree of the molten metal supply port.

Further, the method of the present invention will be specifically described below. In the method of the present invention, the resonance frequency at a specific phase of the effective value modulated high-frequency current is measured, and the resonance frequency detected at the upper end position of the vibration range of the energizing coil is set to a predetermined value. The opening degree of the molten metal supply port is controlled so that the same result can be obtained by measuring the inductance as a signal value using an inductance detector instead of the resonance frequency. Hereinafter, a description will be given on the assumption that a measurement target is a resonance frequency.

The displacement signal of the mold detected by the mold displacement detector is input to the waveform generator via the trigger pulse generator. The waveform generator outputs respective pulse signals for output modulation, vibration control, and frequency measurement.

FIG. 3 is a diagram showing examples of signals input and output by the trigger pulse generator and the waveform generator. FIG.
(A) is the displacement signal of the mold input to the trigger pulse generator, FIG. 3 (b) is the trigger pulse signal output from the trigger pulse generator, and FIG. 3 (c) is the output from the waveform generator. Pulse signal for controlling the vibration of the energized coil, Fig. 3
(D) is a pulse signal for high-frequency current output modulation, FIG.
(E) is a figure which shows the pulse signal for resonance frequency measurement, respectively. These pulse signals for modulation, control, and measurement are output with a predetermined time difference (phase difference) added to the trigger pulse signal output at a specific phase of the mold vibration.

FIG. 4 is a diagram showing the resonance frequency when the current-carrying coil is raised during the rising period of the mold and high-frequency current is oscillated at high output. FIG. 5 is a diagram showing the resonance frequency when the current-carrying coil is raised during the falling period of the mold and high-frequency current is oscillated at high output. FIG. 4 and FIG.
Since only the displacement relationship between the mold and the current-carrying coil is different, the case of FIG. 4 will be described below as a representative example.

FIG. 4A shows a waveform of a displacement signal of the mold, and shows an example in which the mold oscillates in a casting direction with a sine wave at a cycle of 2 Hz. The center point of the amplitude in the rising phase of the mold,
The phase of the sine wave is 0 degree and 360 degrees. Although not shown in FIG. 4, as shown in FIG.
60 degrees is the phase at which the trigger pulse signal is output from the trigger pulse generator. The following are the phases 0 to 360
Explain the phenomenon between degrees.

FIG. 4B shows a waveform of a displacement signal of the energizing coil. The phase of the displacement signal of the energizing coil is the same as the phase of the waveform of the displacement signal of the mold. FIG. 4C shows the waveform of the high frequency current effective value. The phase of the high-frequency current effective value is
0-90 degrees and 270-36 corresponding to the mold rise phase
0 degrees is a high output, and 90 to 270 degrees is a low output.

FIG. 4D shows the waveform of the resonance frequency signal as it is input from the high frequency power supply to the frequency signal processing device. The behavior in which the resonance frequency changes with time (phase) due to the superposition of the fluctuation component caused by the vibration of the energizing coil. With such a resonance frequency that changes with time, accurate detection of the level of the molten metal cannot be performed.

FIG. 4E shows a resonance frequency measuring pulse signal output from the waveform generator. The pulse signal for measuring the resonance frequency is a rectangular pulse signal for detecting at 85 to 95 degrees and performing a hold process at 0 to 85 degrees and 95 to 360 degrees, and is input to the frequency signal processing device.
Hold processing circuit of frequency signal processing device (shown in FIG. 2)
Then, the resonance frequency signal is detected in the phase of 85 to 95 degrees, and in other phases, the process of holding the resonance frequency signal detected at the phase of 95 degrees as it is is performed.

FIG. 4 (f) shows the waveform of the resonance frequency signal processed as described above. Thereafter, the processed resonance frequency signal is converted by a signal conversion circuit (shown in FIG. 2) of the frequency signal processing apparatus based on a calibration curve indicating a correlation between the level of the molten metal surface and the resonance frequency which is known in advance. The molten metal level signal is converted into a surface level signal, and the converted molten metal level signal is input from the frequency signal processing device to the molten metal supply control device. The molten metal supply control device adjusts the opening of the molten metal supply port based on the input molten metal level signal, and adjusts the flow rate of the molten metal so that the detected molten metal level signal becomes a predetermined value. Control.

In this way, the level of the molten metal can be accurately obtained, and the level of the molten metal can be kept constant.

According to the method of the present invention, when measuring the resonance frequency at a specific phase of the RMS-modulated high-frequency current,
The resonance frequency detected at the upper end position of the vibration range of the energizing coil is measured. The upper end position of the vibration range is a 90 ° phase of a sine wave indicating that the position of the energizing coil has a maximum, or an energizing coil in which the fluctuation of the energizing coil position (moving speed of the energizing coil) is zero or nearly zero near the phase. Means position,
At this position, 1% (3.6 degrees) to 10% of the oscillation period
The detection time of the frequency signal is provided at a time corresponding to% (36 degrees). In the example of FIG. 4 and FIG.
% (10 degrees). Accordingly, in FIG. 4, the phase is 85 to 95 degrees, and in FIG.
It is provided at 275 degrees.

Further, in the method of the present invention, the oscillation cycle of the energizing coil and the effective value modulation cycle of the high-frequency current applied to the energizing coil are synchronized with the oscillation cycle of the mold, and the energizing cycle is performed during the rising or falling period of the mold. It is desirable to raise the coil and oscillate a high-frequency current with high output. High-power oscillation refers to temporarily modulating the output of a high-frequency current to a higher order so as to enhance the effect of the electromagnetic force only at a specific time. The low output oscillation is to temporarily modulate the high frequency current to the lower side. At the time of the low output oscillation, a current of about 1 to 25% of the current value at the time of the high output oscillation is supplied to the energizing coil. I do. In this way, by performing the effective value modulation to the high output side and raising the energizing coil,
It is desirable to match the time when the electromagnetic force is gradually applied to the solidified shell with either the rising period of the mold or the falling period of the mold. The reason will be described below.

During the rising period of the mold, the relative speed between the mold and the slab becomes maximum. At this time, the molten powder does not easily flow into the gap between the solidified shell and the mold. This is because the inflow of the molten powder is suppressed by the rise of the mold. Further, during the lowering period of the mold, there is a so-called negative strip period in which the lowering speed of the mold is faster than the drawing speed of the slab. At this time, the molten powder does not easily flow into the gap between the solidified shell and the mold. This is because the lowering speed of the mold is faster than the inflow speed of the molten powder.

Therefore, by synchronizing the cycle with the rising period of the mold or the falling period of the mold and modulating the effective value of the high-frequency current supplied to the energizing coil and raising the energizing coil, the electromagnetic force acting on the solidified shell is obtained. Power gradually increases,
The gap between the solidified shell and the mold can be widened to promote the inflow of the molten powder.

Further, when the energizing coil is lowered, the effective value of the high-frequency current applied to the energizing coil is modulated to a low output side, and the electromagnetic force acting on the solidified shell is substantially invalidated. It is possible to prevent the molten powder flowing into the gap with the mold from flowing backward.

In the method of the present invention, a position 0 to 50 mm higher than the upper end position of the current-carrying coil at the center of the vibration range,
It is desirable to control the level of the molten metal. This is because the electromagnetic force can be applied to the initially solidified shell most effectively.

In FIG. 1, the molten metal supply port of the sliding gate is used as the molten metal flow rate adjusting means, but the method is not particularly limited. For example, flow rate adjusting means such as a rod stopper may be used. In addition, these flow controls are based on the so-called PI (2)
Existing process controllers such as motion controllers), PIDs (three motion controllers) are sufficient.

[0040]

EXAMPLE A continuous casting experiment of molten steel was performed using a continuous casting apparatus having the apparatus configuration shown in FIG. Table 1 shows the chemical composition of the tested medium carbon steels. In each of the tests of the examples and the comparative examples, continuous casting was performed.

[0041]

[Table 1]

Example 1 Table 2 shows the casting conditions for the test. Table 3 shows the chemical composition of the used mold powder.

[0043]

[Table 2]

[0044]

[Table 3]

A circular slab having a diameter of 266 mm was formed at a speed of 2 m.
/ Min. In the upper part of the mold, 30 slits having a width of 0.25 mm penetrating the mold wall are provided in the casting direction. The position of the slit is 20m below the upper end of the mold wall.
From the position of m, the position was 220 mm in height. The molten steel level in the mold was set at a position about 100 mm below the upper end of the mold. The vibration condition of the mold is vibration frequency 2
Hz and a sine wave waveform with an amplitude of ± 3 mm.

The energizing coil was wound three turns around the mold, the coil height was 40 mm in the casting direction, and the upper end of the stationary energizing coil was placed at a position about 125 mm below the upper end of the mold. The vibration condition of the current-carrying coil is a vibration frequency of 2 Hz and an amplitude of ± 16 mm. For the energizing coil,
A current of 4500 A was applied at a high frequency of 20 kHz.

The output modulation is performed when the output is 100
%, Output 15% at low output, duty ratio (1
(High signal level time ratio in the cycle) 50%, and the frequency was modulated at 2 Hz which is the same as that of the mold and the energizing coil.

The resonance frequency is measured at the upper end of the vibration range of the current-carrying coil during a period of 85 to 95 degrees with respect to the phase of the vibration of the sinusoidal waveform of the mold.
The resonance frequency signal detected at the phase of 5 degrees was held.

During the rising period of the mold, output control for modulating the high-frequency current to the high output side and energizing coil vibration operation for causing the energizing coil to move upward were performed.

The obtained slab had good surface properties,
No defects, such as burn-in, which could be attributed to insufficient powder inflow, were found. The surface level during casting was stable, and there was no change in the surface level that hindered stable operation. Also, when the thickness of the powder film collected just below the mold was measured, the average was 1.35 mm.
Thus, it was confirmed that sufficient powder inflow was performed.

By applying the method of the present invention, it can be seen that stable casting level control is possible even in the continuous casting method in which the effective coil of the energized coil is vibrated and the high-frequency current applied to the energized coil is modulated. Was.

(Embodiment 2) In Embodiment 2, the output control for modulating the high frequency current to the high output side during the falling period of the vibrating mold, and the energizing coil vibration operation such that the energizing coil moves upward. Was done. The measurement of the resonance frequency is performed at the upper end of the vibration range of the current-carrying coil during a period of 265 to 275 degrees with reference to the phase of the vibration of the sine wave waveform of the mold. The detected resonance frequency signal was held. The phase of the high-frequency current at the time of high output is 80 to 260 degrees. Other test conditions were the same as in Example 1.

The obtained slab had good surface properties, cracks,
No defects, such as burn-in, which could be attributed to insufficient powder inflow, were found. The surface level during casting was stable. In addition, the thickness of the powder film recovered directly below the mold was 1.26 mm on average, and it was confirmed that sufficient powder inflow was performed.

Comparative Example 1 In Comparative Example 1, the detected resonance frequency signal was tested without performing the hold processing in the hold processing circuit. Other test conditions were the same as in Example 1.

Immediately after the casting is started, the fluctuation of the resonance frequency signal causes the molten metal level signal to be synchronized with the mold oscillation cycle.
It fluctuated by 0 mm or more. The molten metal supply control device adjusted the opening degree of the gate so as to respond to the fluctuation of the molten metal level signal, so that the amount of molten steel flowing into the mold changed periodically. Therefore, the level of the molten steel in the mold subsequently fluctuated greatly, making it difficult to automatically control the level of the molten steel, and the casting operation was stopped halfway. Before the casting operation was stopped, periodic wrinkles were observed on the surface of the cast slab corresponding to the change in the level of the molten metal. Further, pinhole defects and powder defects due to entangled powder were observed in the surface layer of the slab. Further, the thickness of the powder film collected directly below the mold was 0.65 mm on average, and it was found that sufficient inflow of the powder was not performed.

[0056]

According to the method of the present invention, even when the energized coil is vibrated in the casting direction and the effective high-frequency current is modulated, the slab having good surface quality can be produced at high speed. Casting can be performed stably.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an apparatus configuration when a method of the present invention is applied.

FIG. 2 is a block diagram illustrating a flow of signal processing.

FIG. 3 is a diagram illustrating examples of signals input and output by a trigger pulse generator and a waveform generator.

FIG. 4 is a diagram showing a resonance frequency when a current-carrying coil is raised during a rising period of a mold and a high-frequency current is oscillated at a high output.

FIG. 5 is a diagram showing a resonance frequency when a high-frequency current is oscillated at a high output while a current-carrying coil is raised in a falling period of a mold.

[Explanation of symbols]

1: Slit 2: Mold 3: Electric coil 4: Dipping nozzle 5: Molten metal 6: Mold powder 7: Solidified shell 8: Melt powder 9: Mold vibrating device 10: Mold displacement detector 11: Trigger pulse generator 12: Waveform Generator 13: energized coil vibration control device 14: energized coil drive device 15: high frequency current effective value modulator 16: high frequency power supply 17: frequency signal processing device 18: molten metal supply control device 19: molten metal supply port 20: tundish 21: Energized coil position detector

Claims (2)

[Claims] 1. A mold having a plurality of slits penetrating through a mold wall, the inside of which is water-cooled, an energizing coil disposed on an outer peripheral portion thereof, a vibrating device for vibrating the energizing coil in a casting direction, and a tank. A continuous casting method using a device comprising a molten metal supply port for supplying molten metal from a dish to the mold and a molten metal supply control device for adjusting a supply amount of the molten metal, wherein the energized coil is cast. A high frequency current whose effective value is modulated in synchronization with the oscillation cycle of the energizing coil is applied to the energizing coil, and the resonance frequency detected at the upper end position of the oscillation range of the energizing coil is predetermined. Wherein the molten metal supply control device adjusts the supply rate of the molten metal so that the molten metal supply value is adjusted. 2. The method according to claim 1, further comprising: synchronizing a vibration cycle of the energizing coil and a modulation cycle of the effective value modulated high-frequency current to be supplied to the energizing coil with a vibration cycle in a casting direction of the mold. 2. The method for continuously casting molten metal according to claim 1, wherein the energizing coil is raised and a high-frequency current is oscillated at a high output.