JP3130515B2 - Method and apparatus for continuous casting of molten metal - 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 continuously casting molten metal. The present invention relates to a method for continuously changing the amplitude, frequency or phase of an alternating current to be applied so that electromagnetic force can be separated from a mold by electromagnetic waves. The present invention relates to a method and an apparatus for continuous casting while suppressing the instability of initial solidification and imparting a lubricating action and a surface property improving action between a mold and a molten metal.

[0002]

2. Description of the Related Art In continuous casting, powder is generally added to the upper surface of a molten metal pool in a mold, and the powder melted by heat from the molten metal forms a mold wall vibrating up and down;
These gaps flow due to the relative movement of the solidified shell being withdrawn at a constant speed. The meniscus and the tip of the solidified shell are deformed by the dynamic pressure generated when the molten powder flows. Since this deformation is repeated at the cycle of the mold oscillation, periodic wrinkles called oscillation marks are formed on the slab surface.

[0003] Here, it is known that formation of a regular oscillation mark of a normal depth contributes to casting operation and stabilization of the surface quality of a slab. On the other hand, if the depth of the oscillation mark is too deep, there is a possibility that a slab surface defect is caused. In addition to the problem that the mark itself is too deep, for example, in the case of continuous casting of austenitic stainless steel, positive segregation of Ni occurs in the mark valley, and the surface of the slab needs to be ground, or Even in the case of steel or the like, a phenomenon such as an increase in trapping of bubbles and inclusions in the mark portion is observed with the formation of the mark, and the yield may be reduced in some cases.

On the other hand, conventionally, in continuous casting of cast pieces having a small sectional area such as billets, repseed oil has been used instead of powder. Without using the immersion nozzle, in the continuous casting of this small cross-section slab to be poured,
This is because powder that causes entrainment by the injection flow cannot be used. It is known that this repseed oil burns in the meniscus and turns into graphite to prevent the solidified shell from burning to the mold wall. However, as a result, it is difficult to obtain clear oscillation marks regularly generated on the surface of the cast slab, and the stability of the casting operation and slab quality is inferior to that of powder casting. .

As a method for controlling the above-mentioned initial solidification, conventionally, as described in JP-A-52-32824, a molten metal 2 and a lubricant 4 are injected into a water-cooled mold 1 which vibrates at a constant cycle. Then, in a continuous casting method by continuously drawing downward, alternating current is continuously applied to an electromagnetic coil 5 provided around a mold as shown in FIG.
There has been proposed a method of improving the surface properties of a slab by raising the molten metal 2 in a convex shape using an electromagnetic force generated by an AC electromagnetic field. Also, Japanese Patent Application Laid-Open No. 64-83
No. 348, when applying an electromagnetic force to the molten metal in the mold by an electromagnetic coil, by applying an alternating magnetic field in a pulsed manner as shown in FIG. 2, the electromagnetic force is intermittently applied, In powder casting, a method for further improving the surface properties has also been proposed.

As shown in the above-mentioned Japanese Patent Application Laid-Open No. 52-32824, the surface properties of a slab are improved by continuously applying an electromagnetic force to a molten metal in a mold by an electromagnetic coil. . However, the applied electromagnetic field not only changes the meniscus shape, but also heats the molten metal to be solidified in the mold, and the initial solidification may not always proceed stably. Also, Japanese Patent Application Laid-Open
As shown in JP-A-83348, by intermittently applying an electromagnetic force to the molten metal in the mold by an electromagnetic coil, the flow of powder between the solidified shell and the mold wall is further promoted, and Surface properties have been improved. However, in the case of a rapid on / off pattern as shown in FIG. 2, a case where a wave is generated on the surface of the molten metal pool is seen. This wave remained even during the non-energization period, resulting in disturbance of the molten metal pool meniscus, hindering the effect of the application of electromagnetic force, and in extreme cases, causing powder capture in the solidified shell. . On the other hand, in a continuous casting process that does not use a lubricant such as powder that flows between the solidified shell and the mold as a liquid at the meniscus, the operation and the surface properties of the cast slab are determined using powder. It was necessary to improve it to the same level as when casting.

[0007]

Conventionally, the applied electromagnetic force also acts on the molten metal and acts in the direction of reducing the contact pressure between the metal and the mold, that is, in the direction of reducing the contact resistance between the two. However, when this force was increased to stabilize the initial solidification, the calorific value of the mold and the metal also increased, and as a result, stabilization was not obtained.

The present invention solves the problems of such a conventional casting method by applying an electromagnetic force, suppresses the instability of initial solidification, and stably obtains an effect of improving lubrication and an effect of improving slab surface properties. To provide a continuous casting method for molten metal.

[0009]

The gist of the present invention for solving the above-mentioned problems is as follows. (1) An alternating current is applied to a solenoid-shaped electromagnetic coil installed so as to surround the continuous casting mold wall or a solenoid-shaped electromagnetic coil embedded in the side wall of the mold, and the molten metal is injected into the mold and solidifies. In the method of continuous casting while applying an electromagnetic force acting in a direction to separate from the mold wall to the molten metal side, the alternating current to be applied, amplitude modulation,
A frequency modulation or phase modulated current, its waveform is observed as a set waveform comprising a plurality of small wave,
A continuous casting method for molten metal, characterized by gradually and periodically changing the amplitude or waveform of the aggregated waveform to improve lubrication and slab surface properties.

(2) Instead of periodically increasing or decreasing the amplitude of the alternating current flowing through the electromagnetic coil, (1) applying a modulated current to the electromagnetic coil, and (2) generating a signal wave of the modulated current. The frequency fs is set to be the same as the frequency fm of the mold vibration. (3) The frequency fc of the carrier of the modulation current and the frequency fm of the mold vibration are set to 0.69 ≦ 1n (fc / fm) ≦
9. The method for continuous casting of molten metal according to (1), wherein the method is set to a range of 9.90.

[0011]

[0012]

(3) Amplitude modulation and frequency modulation of the continuous casting mold and the solenoid-shaped electromagnetic coil installed so as to surround the continuous casting mold or the solenoid-shaped electromagnetic coil embedded in the side wall of the continuous casting mold and the electromagnetic coil Alternatively, a continuous casting apparatus for molten metal for carrying out the method according to (1) or (2) , comprising a power supply or a waveform generator for supplying a phase-modulated alternating current.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first aspect of the present invention is to apply an alternating current whose amplitude, frequency or phase waveform periodically changes to a solenoid-shaped electromagnetic coil installed on the outer periphery of a continuous casting mold wall which vibrates at a constant cycle. Supplying, and consequently, applying to the molten metal injected into the mold, an electromagnetic force that varies in response to the alternating current.

In the present invention, in the continuous casting process of molten metal, as shown in the schematic view of the principle of generating electromagnetic force in FIG. 7A, a solenoid-shaped electromagnetic coil 5 arranged so as to surround a continuous casting mold, or in which the solenoidal electromagnetic coil which is embedded in the side wall of the mold and energizing the alternating current, continuous casting while applying an electromagnetic force 14 in the molten metal 2 to the injected into the mold solidification starting cents to, induced an induction current 16 The direction of the electromagnetic force 14 is determined by the direction of the magnetic field 15 , and in the present invention, the molten metal 2 always acts on the mold 1 in a direction that tends to separate the molten metal 2 from the mold wall.

At this time, the application period of the electromagnetic force is synchronized with the vibration period of the mold, and the application time is set as the negative strip period so that a uniform oscillation mark is formed on the surface of the slab in the circumferential direction. A cast slab having a surface property can be obtained. When the application time of the electromagnetic force is the positive strip period, the formation of oscillation marks on the surface of the slab is suppressed, and a slab with a smooth surface can be obtained.

Second, a periodically changing alternating current is supplied to a solenoid-shaped electromagnetic coil installed on the outer periphery of the continuous casting mold wall without vibration, and the molten metal injected into the mold is adapted to the alternating current. And applying a changing electromagnetic force to form a mark equivalent to an oscillation mark on the slab surface. In these first and second methods, specific means for supplying an alternating current that periodically changes to the electromagnetic coil and applying an electromagnetic force that changes according to the alternating current to the molten metal injected into the mold. There are the following three types.

A pulse-like alternating current was supplied to the electromagnetic coil so that one period of the electromagnetic field waveform was an intermittent magnetic field formed by an alternating magnetic field application period and a non-application period, and was injected into the mold. An electromagnetic force is intermittently applied to the molten metal. An alternating current whose amplitude varies with magnitude is supplied to the electromagnetic coil so that there is no non-application period of the alternating magnetic field in one cycle of the electromagnetic field waveform, and the alternating current is supplied to the molten metal injected into the mold. Of the electromagnetic force that varies in accordance with the amplitude of.

An alternating current whose frequency changes with a high or low value is supplied to the electromagnetic coil so that there is no non-application period of the alternating magnetic field in one cycle of the electromagnetic field waveform. An electromagnetic force that changes according to the frequency of the alternating current is applied. Above, regardless of whether powder is used or not, the intended stable control can be achieved by changing the AC current applied to the electromagnetic coil with the following characteristics.

Instead of periodically increasing or decreasing the amplitude of the alternating current applied to the electromagnetic coil, a modulated current is applied to the electromagnetic coil, and the frequency of the signal wave of the modulated current is the same as the frequency of the template vibration. And the frequency fc of the carrier of the modulation current and the frequency fm of the template vibration are set to 0.69 ≦ 1n.
(Fc / fm) ≦ 9.90. As the modulation current, amplitude modulation, frequency modulation, or phase modulation is selected. If there is no mold vibration, a frequency of 1 to 5 Hz normally used for mold vibration is selected as fc.

In the amplitude modulation, the amplitude of an AC waveform can be changed by a circuit for modulating the amplitude of a carrier wave by an input signal, utilizing the nonlinearity of a diode; or a circuit by a transistor. In the frequency modulation, the instantaneous frequency is changed periodically or randomly by a control operation. Related to this is that the phase angle of the carrier changes from the reference phase by a value proportional to the instantaneous value of the modulated wave.

In continuous casting of a molten metal, the effect of promoting the inflow of powder by applying an electromagnetic force to the initially solidified portion and the effect of improving the surface properties of a slab are described in detail in Japanese Patent Application Laid-Open No. 64-83348. That is, as shown in FIG. 3A, the gap between the solidified shell 6 and the tip thereof is increased by the electromagnetic force being turned on. Subsequently, when the electromagnetic force is turned off, FIG.
As shown in (b), the tip of the solidified shell 6 is pushed back to the mold wall side by the static pressure P of the molten metal 2, but this on / off is periodically performed, so that the solidified shell 6 has the shape shown in FIG. As shown in (1), a constriction occurs, and this constriction is repeated, and the supply of powder as a lubricant between the mold wall and the solidified shell is promoted. The present inventors, by a casting experiment using a low-melting alloy, continuous conduction, and the waveform of the alternating current to be conducted is observed as a collective waveform composed of a plurality of small waveforms, the amplitude or waveform of this collective waveform is gradual, And while verifying the periodically changing application effect of the electromagnetic force due to the periodically changing energization as described above, simple continuous energization, or the waveform of the alternating current to be energized as a collective waveform consisting of multiple small waveforms It has been observed that in casting with a magnetic field obtained by applying a current that gradually and periodically changes the amplitude or waveform of this collective waveform, defects relating to initial solidification instability are generated on the surface of the slab. In other words, in the case of simple continuous energization, the current induced in the molten metal contributing to the meniscus shape change heats the molten metal to be solidified and does not sufficiently advance solidification, resulting in insufficient powder inflow. Or become
The slab surface property was sometimes deteriorated.

On the other hand, as shown in FIG. 2, the non-energization period t _off
In the case of a simple pulse-shaped energization consisting of the energization period t _on , when the energization is stopped, the instantaneous value becomes 0 from the maximum value, so that this sudden meniscus shape change causes a wave on the molten metal pool meniscus surface, The resulting disturbance caused the powder to be entrained in the molten metal and caught by the solidified shell, resulting in surface defects.

The present inventors have observed the waveform of alternating current to be applied to the electromagnetic coil as shown below as an aggregated waveform composed of a plurality of small waveforms. The amplitude or waveform of the aggregated waveform is gradually reduced. The above problem was solved by using a periodically changing alternating current that changes periodically. FIG. 4 shows the outline of the apparatus used in the present invention. An electromagnetic coil 5 is arranged around the mold 1, and a predetermined alternating magnetic field can be periodically applied to the electromagnetic coil. Using this apparatus, a general medium carbon steel billet was continuously cast. Casting speed is 2.5m / min, mold section size is 130
mm × 130mm, mold oscillation stroke ± 4m
m, and the oscillation frequency was 190 cpm. The casting was carried out while supplying a small amount of repseed oil by transmitting the copper plate from above the mold copper plate.

The present inventors have confirmed the following in the investigation and study of the initial coagulation. That is, the powder is in a molten state in the meniscus part in the mold and has a viscosity of a certain value or more, so the mold vibration is transmitted to the meniscus as dynamic pressure, and as a result, regular meniscus deformation and molten steel overflow are promoted. . This regular deformation of the meniscus and the overflow of the molten steel lead to the formation of regular and clear oscillation marks.

On the other hand, as shown in FIG. 5, when the molten metal is continuously cast without using the powder, the vibration of the mold is not reliably transmitted to the meniscus portion of the molten metal. For example, the repseed oil 9 used for casting a small-section slab such as a billet does not contribute to lubrication as a liquid. The oil added in a small amount along the copper plate of the continuous casting mold 1 gently burns until reaching the meniscus 3 and turns into graphite, thereby contributing to the prevention of seizure of the solidified shell on the mold wall. However, there is no medium to transmit mold vibrations to the solidifying meniscus. Therefore, regular oscillation marks are hardly formed on the slab surface, and in many cases, good slab surface properties cannot be obtained.

However, an oscillation mark is formed on the billet surface cast using the repseed oil, though it is not clear. As a mark formation mechanism in this case, it is conceivable that the tip of the shell undergoes deformation, particularly during the descent period of the mold, due to the oscillation of the mold wall slightly deformed in the meniscus. Since it differs depending on the state of contact with the mold and the deformation of the mold wall is not always uniform in the circumferential direction, in this case, it is formed on the surface of the slab 11 as shown in FIG. 6, and the casting operation and the obtained slab surface quality It was not stable and good.

On the other hand, the present inventors previously applied a pulse as shown in FIG. 2 to an electromagnetic coil installed around a continuous mold for the purpose of promoting powder supply between the solidified shell and the mold wall. Invented a method of applying an alternating magnetic field intermittently to the solidification start site of the molten metal meniscus in the mold by applying an AC current in a shape, and repeatedly applying an electromagnetic force in a direction repelling from the mold to the same portion, This is disclosed in
It was disclosed in Japanese Patent Application Laid-Open No. 4-83348. In a subsequent study, the authors observed that the waveform of the alternating current to be applied was observed as an aggregated waveform consisting of multiple small waveforms, and the application of a magnetic field by energization that gradually and periodically changed the amplitude or waveform of this aggregated waveform was observed. In the case where no lubricant is used, or when a substance that does not exist as a liquid in the meniscus such as repseed oil is used, the initial solidification, which was conventionally unsatisfactory due to poor control of the mold deformation, is greatly improved and improved. I found something new that could be done.

That is, the waveform of the alternating current flowing through the meniscus is observed as an aggregated waveform composed of a plurality of small waveforms, and a coagulation start site is formed by applying a magnetic field that gradually and periodically changes the amplitude or waveform of the aggregated waveform. Generates an electromagnetic force that changes periodically. Therefore, even when a substance that transmits mold vibration to the solidified shell, such as powder, cannot be used, the waveform of the alternating current to be applied is observed as a collective waveform composed of a plurality of small waveforms. By applying a repulsive magnetic field that changes slowly and periodically, periodic shell deformation and overflow of the molten metal are surely generated, and regular oscillation marks are formed. It is possible to secure directional stability.

In particular, when a repulsive magnetic field is applied during the negative strip period when the mold descending speed exceeds the casting speed,
Oscillation marks can be generated reliably,
This mode is most efficient for the casting operation and the stabilization of the slab surface properties. On the other hand, when the repulsive magnetic field is applied during the negative strip period during the vibration of the mold, the generation of the oscillation mark is suppressed, and a slab with a smooth surface can be obtained. However, in this case, it does not necessarily lead to stabilization of the initial solidification, so that attention must be paid to casting at a reduced casting speed.

When performing continuous casting by applying a mechanical vibration to the mold, the waveform of the alternating current for applying the alternating current to the electromagnetic coil is observed as a collective waveform composed of a plurality of small waveforms.
By applying an electromagnetic force to the molten metal in the mold periodically to apply the amplitude or waveform of the collective waveform in a gradual and periodic manner, the mold and the slab contact in the initial solidification part. The pressure can be reduced periodically, but by setting the repetition frequency ft of the amplitude of the applied current to be the same as the frequency fm of the mold vibration,
Electromagnetic force acts at the same cycle as the vibration of the mold, and it is possible to control the breakage of the solidified shell and the overflow of the molten metal, which cause oscillation marks.

When continuous casting is performed by applying mechanical vibration to the mold, the waveform of the alternating current to be applied is observed as a collective waveform composed of a plurality of small waveforms with respect to the vibration frequency fm of the mold. If the frequency fp of the alternating current that changes the amplitude of the waveform or the waveform slowly and periodically is inappropriate, a standing wave is generated in the meniscus of the molten metal, and the meniscus becomes unstable or solidifies. However, as a result of various studies, by setting fm and fp in the range of 0.69 ≦ 1n (fp / fm) ≦ 9.90, interference of the level vibration at the meniscus was generated. And coagulation can be stabilized. The reason why the lower limit of the value of fp / fm exists as described above is to stabilize the meniscus, and the reason that the upper limit exists is due to thermal restrictions for stably developing the solidified shell. It is.

In the coil current for generating a periodic electromagnetic force, the waveform of the alternating current to be applied is observed as an aggregated waveform composed of a plurality of small waveforms, and the amplitude or the waveform of the aggregated waveform is reduced gradually and periodically. It can also be realized by modulated current such as amplitude modulation, frequency modulation, phase modulation, etc. In this case, the waveform of the alternating current flowing at the frequency fs of the signal wave of the modulation current is observed as an aggregated waveform composed of a plurality of small waveforms, and the amplitude or the waveform of the aggregated waveform is gradually and periodically changed. Since the frequency corresponds to the repetition frequency ft of the magnitude of the current amplitude and the frequency fc of the carrier corresponds to fp, the frequency of the signal wave is set to be the same as the frequency of the template vibration, and the frequency fc of the carrier and the frequency fm of the template vibration are set. 0.69 ≦ 1n (fc /
fm) ≦ 9.90, the above-described waveform of the alternating current to be applied is observed as an aggregated waveform composed of a plurality of small waveforms, and the amplitude or waveform of the aggregated waveform is gradually and periodically changed. The same operation as when a changing AC current is applied can be obtained.

This control can be used to provide a lubrication assisting action equivalent to mechanical vibration by an electromagnetic field even when mold vibration is not performed. In this case, since fm does not exist, about 1 to 5 Hz which is usually used as fm is selected as fc.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be specifically described below with reference to embodiments. FIG. 7B is a schematic diagram illustrating an example of the device of the present invention. In the present device, a waveform generator 19 is provided in a power supply device 20 for driving the electromagnetic coil 5, and thereby an exciting current 17 is applied to the coil. First, casting was performed at a speed of 150 cm / min without applying a current to the electromagnetic coil of the apparatus of FIG. 7B. The cast slab obtained as a result of the casting had periodic irregularities due to the vibration of the mold on the surface, and the surface roughness was 320 μm on average. Further, a lateral crack along the oscillation mark occurred on a part of the surface of the slab. Next, using the apparatus shown in FIG. 7B, casting was performed by continuously applying an alternating current having a frequency of 60 Hz and a peak value of 3000 A. The resulting slab had defects caused by hot water wrinkles and powder entrapment, and the surface and subcutaneous properties of the slab were rather deteriorated than when no electromagnetic force was applied. This is because a molten mixture was generated in the mixture and the meniscus was destabilized.

Therefore, as an embodiment of the present invention, an alternating current having a frequency of 60 Hz and a peak value of 3000 A is applied to the exciting coil.
This was performed on the vibration-modulated AC waveform shown in FIG. When such excitation is performed, the electromagnetic force acting on the molten steel in the mold has a high frequency component of 60 Hz averaged, and the electromagnetic force periodically changes every 0.25 seconds. The timing of the application of the electromagnetic force was controlled so as to be in the rising phase of the mold, and the casting was performed at a speed of 150 cm / min. On the surface of the obtained cast slab, periodic irregularities were reduced, and the surface roughness was 120 μm on average, which was about 3 μm as compared with the case where no electromagnetic force was applied.
Reduced by a factor of one.

Further, there is an effect that generation of defects below the surface is suppressed. Furthermore, when casting was performed at a casting speed of 200 cm / min, the casting was performed stably, and the surface and subcutaneous properties of the slab were the same as those at a casting speed of 150 cm / min. Next, the timing of the application of the electromagnetic force was set in the mold descent period, and the casting was carried out under the same conditions as the other conditions, and a slab having a surface roughness of 150 μm was obtained.
Moreover, the occurrence of lateral cracks on the slab surface could be suppressed.
Furthermore, as a current to be applied to the excitation coil, a frequency-modulated current or a phase-modulated current was selected and casting was performed.As a result, a cast piece having the same surface properties as when the excitation current was applied was obtained. did it. FIG. 9 shows a frequency-modulated AC waveform.

[0038]

As is clear from the embodiment, in continuous casting of molten metal without using a lubricant, the electromagnetic force is applied in a pulsed manner so as to be synchronized with the mold vibration or even when the mold vibration is not performed. By performing continuous casting while applying voltage, clear oscillation marks can be formed on the slab surface, and the slab quality and the stability of the casting operation have been improved.

[0040]

As described above, the present invention relates to a process for achieving an improvement in lubrication and an improvement in slab surface quality by applying an electromagnetic force to a molten metal meniscus portion which starts solidification to increase powder inflow. The waveform of the alternating current flowing through the electromagnetic coil installed so as to surround the meniscus in the mold is observed as an aggregated waveform composed of a plurality of small waveforms, and the amplitude or waveform of this aggregated waveform is gradually and periodically changed. It is characterized by the following. As a result, the initial solidification can be stably advanced, and lubrication and slab surface quality can be significantly improved while preventing powder entrainment caused by meniscus disturbance.

Further, the waveform of the alternating current flowing through the meniscus portion of the molten metal which starts solidification is observed as an aggregated waveform composed of a plurality of small waveforms, and the amplitude or waveform of the aggregated waveform is gradually and periodically changed. By performing the casting while applying the changing electromagnetic force, the repetition of the continuous solidification of the initial solidification can be progressed regularly even when the lubricant is not used. As a result, a clear oscillation mark was formed on the slab surface, and it was possible to greatly improve the slab surface properties and casting stability.

[Brief description of the drawings]

FIG. 1 is a diagram showing a positional relationship between an electromagnetic coil, a molten metal meniscus, and powder incorporated in a continuous casting mold.

FIG. 2 is a diagram illustrating a mode of applying a pulse-like electromagnetic field that has been conventionally proposed.

3A is a deformed meniscus shape when an electromagnetic force is applied, FIG. 3B is a static meniscus shape when an electromagnetic force is not applied, and FIG. 3C is a solidified shell when an electromagnetic force is repeatedly applied and not applied. It is a figure showing the shape of.

FIG. 4 is a diagram showing a positional relationship between a continuous casting mold, a meniscus, and an electromagnetic coil according to the present invention.

FIG. 5 is a diagram showing a conventional process for performing continuous casting of molten metal with repseed oil.

FIG. 6 is a view showing a surface state of a billet slab cast by the conventional process of FIG. 1;

FIG. 7A is a diagram showing the principle of the electromagnetic force of the present invention.
(B) is a figure which shows the outline | summary of an apparatus.

FIG. 8 is a diagram showing an example of an amplitude-modulated AC waveform according to the present invention.

FIG. 9 is a diagram showing an example of a frequency-modulated AC waveform of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mold 2 ... Molten metal 3 ... Meniscus 4 ... Powder 5 ... Electromagnetic coil 6 ... Solidified shell 7 ... Pouring nozzle 8 ... Meniscus when an electromagnetic field is applied 9 ... Repseed oil 10 ... Oscillation mark 11 ... Electromagnetic field Cast slab not applied 12 ... Oscillation mark of intermittent magnetic field 13 ... Cast slab of intermittent magnetic field 14 ... Electromagnetic force 15 ... Induction magnetic field 16 ... Induction current 17 ... Excitation current 18 ... Electromagnetic force induced flow 19 ... Waveform generator 20 ... Power supply device 21 ... Instructed excitation current waveform 22 ... Oscillation

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenzo Sawada 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Kiyoshi Wajima 20-1 Shintomi, Futtsu-shi, Chiba New Japan (72) Inventor Shisei Asai 112, Yakushiyama, Narumi-cho, Midori-ku, Nagoya City, Aichi Prefecture (72) Inventor Kensuke Sasa 15-43 (72) Inventor Li Jiao-gu, China 116024 Dariens Gaengjin-dich Dalian Ri-Gondache-Zalyshinet (56) References JP-A-4-344861 (JP, A) JP-A 64-83348 (JP, A) Patent flat 2-274351 (JP, a) JP Akira 52-32824 (JP, a) WO 96/5926 (WO, A1) (58 ) investigated the field (Int.Cl. ^7, B name) B22D 11/115 B22D 11/07

Claims (3)

(57) [Claims] 1. An alternating current is applied to a solenoid-shaped electromagnetic coil installed so as to surround a wall of a continuous casting mold or a solenoid-shaped electromagnetic coil embedded in a side wall of a casting mold, and is injected into the casting mold and solidified. In a method of continuously casting a metal while applying an electromagnetic force acting in a direction to separate the metal from the mold wall toward the molten metal, an alternating current to be applied may be subjected to amplitude modulation, frequency modulation, or position modulation.
A phase modulated current, its waveform is observed as a set waveform comprising a plurality of small waveform, slowly the amplitude or waveform of the set waveform, and periodically changed, the lubrication and the cast slab surface quality A method for continuous casting of molten metal, characterized in that it is improved. 2. Instead of periodically increasing or decreasing the amplitude of the alternating current flowing through the electromagnetic coil, (1) applying a modulated current to the electromagnetic coil, (2) frequency of a signal wave of the modulated current fs is set to be the same as the frequency fm of the template vibration. (3) The frequency fc of the carrier of the modulation current and the frequency fm of the template vibration are set in the range of 0.69 ≦ 1n (fc / fm) ≦ 9.90. The method for continuously casting molten metal according to claim 1, wherein: 3. A continuous casting mold, a solenoid-shaped electromagnetic coil installed to surround the continuous casting mold or a solenoid-shaped electromagnetic coil embedded in a side wall of the continuous casting mold, and amplitude modulation and frequency modulation applied to the electromagnetic coil. 3. A continuous casting apparatus for molten metal for carrying out the method according to claim 1, further comprising a power supply or a waveform generator for supplying a phase-modulated alternating current.