JP2003039141A - Electromagnetic stirrer for molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the flow of a molten metal in a continuous casting apparatus for a metal and to operate the apparatus in a mutually connected manner with two electromagnetic stirrers to prevent segregation of the center of a slab section and improve quality. To produce metal slabs. SOLUTION: In a continuous casting apparatus for metal, two electromagnetic stirring means 61a installed outside a mold 3 for controlling the flow of molten metal and for flowing the molten metal 1 by electromagnetic induction in the mold 3 are provided. 61b, 62a, 62
b, the electromagnetic stirring means 61a and 61b are arranged on the meniscus surface 5, and the other electromagnetic stirring means 62a and 62b are positioned immediately below the mold or at a position where the metal slab is drawn out. By arranging and operating in tandem with each other to enhance the effect of electromagnetic stirring, segregation of the center of the slab section is prevented, center cracks and the like are prevented, and the quality of the product is improved.

Description

Detailed Description of the Invention

[0001]

The present invention relates to continuous casting,
Regarding an electromagnetic stirrer used to control the flow of molten metal,
In particular, it relates to the improvement.

[0002]

2. Description of the Related Art FIG. 11 is a sectional view of an apparatus used for continuous casting of a conventional metal slab, and FIG. 12 is a plan view of the apparatus shown in FIG. 11 and 12, 1 is a molten metal, 2 is a dipping nozzle, 3 is a mold, 4 is a solidification shell, 5 is a meniscus surface, 10 is a mold long side, and 11 is a mold short side.

In FIG. 11, the molten metal 1 is injected into the mold 3 from the immersion nozzle 2, but the molten metal 1 is gradually cooled from the wall surface of the cooled mold 3 to form a solidified shell 4, and this solidified shell 4 is formed. 4 is pulled out and becomes a metal slab. On the other hand, in FIG. 12, the immersion nozzle 2 is provided at the center of the horizontal surface of the mold, and the molten metal 1 in the mold is discharged from the nozzle port and flows as shown by the arrow in FIG. 11, and the meniscus surface (the upper surface of the molten metal). Figure 5 within 5
1 and FIG. 12, a reverse flow from the mold short side 11 to the immersion nozzle 2 is generated as shown by a solid arrow.

In the apparatus used for continuous casting of metal slabs as described above, if the temperature of the molten metal on the mold wall surface at the same height is not uniform, vertical cracking of the solidified shell 4 is likely to occur. To prevent this vertical cracking, flowing molten metal in the meniscus surface 5 and using an electromagnetic stirring method as a means for flowing molten metal are described in JP-A-1-228645. .

FIG. 13 shows a conventional electromagnetic stirrer described in this publication. In FIG. 13, 6a and 6b are electromagnetic stirring coil portions, 10a and 10b are mold long sides, and 11a and 11b are mold short sides. This conventional electromagnetic stirrer has a mold long side 10
electromagnetic stirring coil portion 6a provided along a and 10b
And 6b, a uniform electromagnetic stirring thrust is applied to the molten metal in the mold 3 to generate a circulating flow along the wall surface of the mold in the molten metal. That is, the electromagnetic stirring coil portion 6a includes a plurality of magnetic cores 12a arranged along the long side 10a of the mold, and a coil 14a wound around a slot 13a formed in the magnetic core 12a. The stirring coil portion 6b is also similarly configured. The respective coils 14a and 14b are connected to the three-phase power source 8 via the respective connection boxes 7a and 7b. The connection shown in FIG. 13 shows a typical example. As a result, the moving magnetic field type electromagnetic stirring thrust is applied to the meniscus surface 5.
It is uniformly given to the molten metal inside as shown by the arrow.

Japanese Unexamined Patent Publication No. 1-228645 shown in FIG.
In the electromagnetic stirrer described in the publication, when the frequency of the three-phase power supply 8 is set to 2 Hz and the current is set to 400 A, the thrust distribution in the meniscus plane 5 is calculated by simulation using general-purpose electromagnetic field numerical analysis software. 10
The long-side component of the thrust along a and 10b is substantially constant at each position on the long side. However, in this device, since the electromagnetic stirring force is uniformly applied to the molten metal along the long side of the mold, the rotating flow of the molten metal in the meniscus plane that is actually obtained is such that the reversal flow and the electromagnetic stirring force overlap. As indicated by the dotted arrow in FIG. 12, the flow was strong when going from the mold short side 11 to the immersion nozzle 2, and weak when going from the immersion nozzle 2 to the mold short side 11.

On the other hand, on the meniscus surface,
1000μφ Al₂O₃And SiO ₂Such as non-metallic intervention
Objects and powder are floating, but the rotating flow of molten metal is uneven.
If there is stagnation, the non-metallic inclusions will collect in the stagnation part.
It is piled up and powder is caught. These non money
When the molten metal changes to solid due to metal inclusions and powder
Air bubbles such as CO, and the powder is in the metal
Seizure that causes breakout
It's easy to do. Therefore, the electromagnetic stirring device in the mold described above,
Uniform temperature of molten metal on mold walls at the same height
Although it is useful for preventing vertical cracking of the solidified shell 4,
Not enough to stop.

Therefore, the following improvements have been made. That is, FIG. 14 is a view of a known continuous cast part of an improved metal slab as seen from the meniscus surface, and melts it from the dipping nozzle 2 provided in the center of the cross section of the mold 3 having a rectangular cross section. Metal is poured into the mold 3. Electromagnetic stirring coil portions 6a and 6b are provided along the long sides 10a and 10b of the mold. By adjusting the distribution of the electromagnetic stirring thrust by the electromagnetic stirring coil portions 6a and 6b, the molten metal in the meniscus surface 5 is It provided a uniform rotating flow along the mold.

That is, in FIG. 14, the electromagnetic stirring coil portion 6a is
Let P be the electromagnetic stirring thrust applied from the mold short side 11a to the immersion nozzle 2 and Q be the electromagnetic stirring thrust applied from the immersion nozzle 2 to the mold short side 11b. The mold short side 11 provided along the mold long side 10b.
When the electromagnetic stirring thrust from b toward the immersion nozzle 2 is R and the electromagnetic stirring thrust from the immersion nozzle 2 toward the mold short side 11a is S, thrust P and thrust Q are different from thrust R and thrust S in opposite directions. Yes, the thrust Q is made larger than the thrust P, and the thrust S is made larger than the thrust R. By distributing the electromagnetic stirring thrust in this way and adjusting the magnitude of the thrust, a uniform rotating flow clockwise as viewed from above was given to the molten metal in the meniscus plane. On the other hand, in the same figure, by making the electromagnetic stirring thrust in the opposite direction, making the thrust P larger than the thrust Q and making the thrust R larger than the thrust S,
A uniform counterclockwise rotating flow could be given. Such electromagnetic stirring thrust was realized by an electromagnetic coil and a three-phase AC current source based on the principle of a three-phase linear motor. In other words, such an action is performed by setting the proper frequency, voltage, current, and other electromagnetic stirring conditions according to the operating conditions of continuous casting so that the molten metal in the meniscus surface 5 is uniformly rotated along the mold side. It was the one that gave the flow.

In continuous casting of metal slab, the molten metal discharged from the dipping nozzle collides with the short side of the mold and becomes a reverse flow, and as shown in FIG. 12, within the meniscus surface 5,
As shown by the solid line arrow, the flow is from the mold short side 11 to the immersion nozzle 2. However, due to such a known improvement,
As shown in FIG. 14, in the meniscus surface 5, the electromagnetic stirring thrust Q from the immersion nozzle 2 toward the mold short side 11 is obtained.
And S are made larger than the electromagnetic stirring thrusts P and R directed from the mold short side 11 toward the immersion nozzle 2, thereby imparting a uniform clockwise flow to the molten metal in the meniscus surface 5 as described above. It goes without saying that, in the steady state, the counterclockwise rotational flow can be given by reversing the thrust relationship. As a result, the molten metal in the meniscus surface 5 is given an appropriate electromagnetic stirring thrust in consideration of the reverse flow, so that the molten metal uniformly rotates and flows along the mold walls 10a, 11b, 10b, 11a. Therefore, in the steady state, the molten metal does not settle, the accumulation of non-metallic inclusions in the molten metal and the entrainment of powder on the meniscus surface 5 are prevented, and a metal slab without surface defects such as vertical cracks is obtained. You can

The above-mentioned operation is realized by the circuit connection shown in FIG. That is, the electromagnetic stirring thrust is distributed as described above by the connection of FIG. 15, the thrust Q is larger than the thrust P, and the thrust S is larger than the thrust R.
A clockwise rotating uniform flow is applied to the molten metal in the meniscus plane, the electromagnetic stirring thrust is reversed, and the thrust P is larger than the thrust Q and the thrust R is larger than the thrust S. As a result, a counterclockwise uniform rotating flow can be provided. In FIG. 15, 6a and 6b are electromagnetic stirring coil units, 7a and 7b are wiring boxes, 8 is a three-phase inverter, 9 is a command box, 10a,
10b is a long side of the mold, and 14a and 14b are coils.

In the above electromagnetic stirrer, as shown in FIG. 15, on the long side 10a of the mold, the coil 14a of the electromagnetic stirrer coil portion 6a and the connection box 7 which is a connecting means.
The circuit composed of the wiring of a is divided into A and B.
On the other hand, on the side of the long side 10b of the mold, the circuit composed of the coil 14b of the electromagnetic stirring coil portion 6b and the wiring of the connection box 7b which is the connecting means is divided into C and D. The circuits A and C and the circuits B and D are point-symmetric with respect to the immersion nozzle 2, the circuits A and B are parallel to each other and have different impedances, and the circuits C and D are also parallel to each other. They have different impedances. As shown in FIG. 16, the circuit of the device shown in FIG. 15 has a circuit A and a circuit C which are Y-connection (star connection) and circuit B.
The circuit D and the circuit D are Δ-connected (annular connection), and the impedance of each circuit is larger in the circuit A and the circuit C than in the circuit B and the circuit D. Therefore, as shown by the arrow in the meniscus surface 5 of FIG. 15, the electromagnetic stirring thrusts along the two mold long sides 10a and 10b are opposite to each other, and the electromagnetic stirring in the direction from the immersion nozzle 2 to the mold short side is performed. The thrust is larger than the electromagnetic stirring thrust in the direction from the short side of the mold to the immersion nozzle 2. Therefore, in the command box 9, an appropriate frequency according to the operating condition of continuous casting,
By setting electromagnetic stirring conditions such as voltage and current, a uniform rotating flow along the mold is given to the molten metal in the meniscus surface 5.

As described above, in the continuous casting of the metal slab, the molten metal discharged from the dipping nozzle collides with the short side 11 of the mold and becomes a reverse flow, and within the meniscus surface 5, the dipping nozzle 2 from the short side 11 of the mold. A flow is generated toward. However, according to the conventional improved electromagnetic stirring device, as shown in FIG. 14, the electromagnetic stirring thrusts Q and S from the dipping nozzle 2 toward the mold short side 11 in the meniscus surface 5 are dipped from the mold short side 11 by immersion. By making the electromagnetic stirring thrusts P and R toward the nozzle 2 larger, a uniform clockwise rotating flow can be given to the molten metal in the meniscus surface 5. In this case, the electromagnetic stirring condition is adjusted by setting the condition of the power source such as frequency, voltage and current by setting the command box 9, and the impedance of each circuit configured by the electromagnetic stirring coil unit 6 and the wiring boxes 7a and 7b. It can be adjusted by setting. In such an improvement, the molten metal in the meniscus surface is given an appropriate electromagnetic stirring thrust considering the reversal flow, and the molten metal uniformly rotates along the mold wall, so that there is no stagnation of the molten metal. Accumulation of non-metallic inclusions in the molten metal, entrapment of powder on the meniscus surface, etc. are prevented, and a metal slab without surface defects such as vertical cracks can be obtained.

In the modification shown in FIG. 15, the frequency of the three-phase power source is 2 Hz, the current is 525 A, the current density in the circuits A and C is 2.248 × 10 ⁶ AT / m ² , and the current density in the circuits B and D is 3. The distribution of the electromagnetic stirring thrust in the meniscus surface 5 when 893 × 10 ⁶ AT / m ² is obtained is as follows:
The thrust component from the immersion nozzle 2 to the immersion nozzle 2 was small, and the thrust component from the immersion nozzle 2 to the mold short side 11 was large. Therefore, when electromagnetic stirring is performed by such a device, a small thrust force is applied in the same direction as the reverse flow of the molten metal in the meniscus surface, and a large thrust force is applied in the opposite direction, so that uniform thrust along the mold is ensured. A rotating flow is obtained, the molten metal flow is free from stagnation, and a metal slab having no surface defects is obtained.

In continuous casting of metal slabs, the discharge flow rate of the molten metal may vary from discharge port to discharge port of the dipping nozzle 2 due to non-metallic inclusions in the molten metal adhering to the discharge port. . In this case, since the flow of the molten metal in the meniscus plane continuously changes, a uniform rotating flow cannot be stably obtained by applying the uniform electromagnetic stirring thrust as described above. In addition to rotation, it is also desired to apply various forms of thrust to the molten metal in the meniscus surface, such as braking and acceleration against the reverse flow. However, the above electromagnetic stirring is performed using a three-phase one-power source, and it has been difficult to continuously change the thrust force with respect to the continuously changing flow of the molten metal. Further, the electromagnetic stirring thrusts along the long sides 10 of both molds interfere with each other to generate thrust vortices, which may cause surface defects such as vertical cracks in the stagnation shell.

Therefore, in continuous casting of a metal slab such as steel, the molten metal in the mold is uniformly rotated in the meniscus plane, or an appropriate thrust distribution for braking or accelerating the reverse flow is imparted. In addition, even when the flow of the molten metal continuously changes, the electromagnetic stirring thrust can be continuously changed, and the problem due to the vortex of the stirring thrust can be solved to obtain a metal slab with excellent surface properties. is necessary. Such a requirement is satisfied by a device including a wiring box that connects the two electromagnetic stirring coil units to each of the power sources and a power source control unit corresponding to each power source. That is, each electromagnetic stirring coil unit is a moving magnetic field type in which a plurality of magnetic poles are arranged along the long side of the mold, and a coil is wound around each magnetic pole. The circuit composed of this coil and the wiring of the wiring box is divided into two parts, respectively, and any two units of the divided four circuits are respectively connected to different power sources, or the above four circuits are connected. Are connected to different power sources.

FIG. 17 is an explanatory view showing a cross section of the continuous casting apparatus for a metal slab according to the multi-power source system as seen from the meniscus surface, and an example of wiring of the electromagnetic stirring coil section. At the center of the cross section of the mold 3 having a substantially rectangular cross section, molten metal is injected from the immersion nozzle 2 provided therein. Further, since the electromagnetic stirring coil portions 6a and 6b are provided along the two long sides 10a and 10b of the mold, respectively, the meniscus surface 5 is generated by the respective electromagnetic stirring thrusts.
The flow of molten metal is controlled within. In the device shown in FIG. 17, two power sources, a first power source 24 and a second power source, are used.
The power supply 25 is used. Two electromagnetic stirring coil parts 6a,
The circuit that connects each coil 14 of 6b to each power source is divided into two, and a total of four divided circuits A, B, C, and D.
Any two of the combinations of two separate power supplies 2
4 and 25 are connected. Depending on the coil of each circuit,
The electromagnetic stirring thrust is controlled. Specifically, there are three combinations, and these three combinations are implemented by switching the switch box 21. During operation, the switches may be changed as appropriate, or the combination may be set in advance without using the switch box 21.

That is, according to the above-mentioned known improvement method, a uniform rotating flow of clockwise or counterclockwise given by the electromagnetic stirring thrust and a reverse flow of molten metal discharged from the immersion nozzle are synthesized. Steadily results in a uniform molten metal flow. On the other hand, in the continuous casting of the metal slab obtained from the molten metal, the molten metal descends obliquely downward as shown in FIG. 18, and the metal slab is generated at the lower end thereof. In FIG. 18, 1 is a molten metal, 2 is a nozzle, 2
a, 2b are nozzle ejection ports, 3 are molds, 4 are solidification shells, 5 are meniscus surfaces, 100 is solidification interface, 1 is
01 is a crater end. In FIG. 18, the molten metal 1 injected into the mold 3 from the nozzle ejection ports 2a and 2b descends obliquely downward, and a metal slab is generated. The molten metal is partially cooled at the tip of the metal slab, and depending on the conditions, it solidifies at a temperature lower than its melting point, but there is a place where cooling does not proceed, so a temperature higher than its melting point. There is also a portion that is kept molten and remains molten. In such a state, a high temperature portion and a low temperature portion coexist, center segregation of the slab cross section occurs, and the quality of the metal slab is deteriorated due to center cracking or the like.

[0019]

The electromagnetic stirring imparts a uniform rotating force to the molten metal in the clockwise or counterclockwise direction. Therefore, at the position where the coil portion of the electromagnetic stirring device is arranged, the molten metal The temperature is kept uniform within the same level plane. However, as the molten metal is drawn obliquely downward, the cooling conditions are not uniform in the oblique downward direction, so cooling progresses and the temperature of the metal falls below the melting point and solidifies, The cooling progresses slowly and the temperature of the metal is kept above the melting point and remains in a liquid state. In such a state, the quality of the slab is not uniform, so the uniformity of composition is lost and vertical cracks occur.
This is a factor that deteriorates reliability, which is not preferable in terms of both quality and reliability. The present invention, when the molten metal is drawn obliquely downward, since the cooling conditions are not uniform just below the mold and obliquely below, it is an object to solve the quality deterioration based on the temperature difference generated in the molten metal. To do.

[0020]

An electromagnetic stirrer for molten metal according to the present invention is provided with an immersion nozzle for injecting molten metal in its upper part, and the molten metal injected from said immersion nozzle is cooled inside. The solidified shell formed by being gradually cooled by the wall surface is installed on the outside of the mold for producing a metal slab when being drawn obliquely downward from below, and of the molten metal injected from the immersion nozzle into the mold. In order to make the temperature distribution on the mold wall uniform, the electromagnetic induction is applied entirely or selectively in the meniscus plane of the molten metal, and the linear motor causes the molten metal to flow clockwise or counterclockwise. First electromagnetic stirring means for causing the first electromagnetic stirring means and the first electromagnetic stirring means arranged below the position where the first electromagnetic stirring means is arranged. Is characterized in by being configured and a second electromagnetic stirring means is controlled to operate in tandem.

Further, in the above-mentioned molten metal electromagnetic stirring device, the operation in which the first and second electromagnetic stirring means are connected to each other is performed by the molten metal flow inside the first electromagnetic stirring means and the second electromagnetic stirring means. The electromagnetic stirring means is provided with a control means for performing sequence control so that the molten metal flow is in the state of forward rotation, reverse rotation, or forward / reverse inversion with each other.

Further, in each of the molten metal electromagnetic stirring devices described above, the second electromagnetic stirring means is arranged such that the position where the second electromagnetic stirring means is arranged is directly below the nozzle ejection port provided in the mold. It is characterized by being a thing.

[0023]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of an electromagnetic stirring apparatus for molten metal according to the present invention. Figure 1
, 1 is molten metal, 2 is immersion nozzle, 2a, 2b
Is a nozzle ejection port, 3 is a mold, 4 is a solidification shell, 5 is a meniscus surface, 61a and 61b are coil portions of the first electromagnetic stirring means, and 100 is a solidification interface. In FIG. 1, the molten metal ejected from the nozzle ejection ports 2 a and 2 b and injected into the mold 3 as indicated by the arrow flows toward the solidified shell 4 formed on the inner wall of the mold 3 and then flows into the solidified shell 4. Along the upper and lower sides of the mold 3.
The upward flow of the molten metal is directed to the meniscus surface 5 along the solidified shell 4 formed on the wall surface of the mold 3. On the other hand, the downward flow of the molten metal 1 is gradually cooled and becomes a product. That is, the molten metal 1 moves downward while being cooled.

The coil portions 61a and 61b of the first electromagnetic stirring means shown in FIG. 1 are arranged in the mold 3 at the position level of the meniscus surface 5. On the other hand, the coil portions 62a and 62b of the second electromagnetic stirring means are arranged at the position level of the nozzle ejection ports 2a and 2b of the nozzle 2 immersed in the mold 3. Coil portions 61a, 61b of the first electromagnetic stirring means
A view cut from AA and seen from the top has a shape similar to that of the coil portions 6a and 6b of the conventional electromagnetic stirring device.
The operation is the same mode as the coil portions 6a and 6b of the conventional electromagnetic stirring device. That is, the nozzle 2 is provided in the mold 3, and the molten metal 1 is filled with the nozzle 2
Since it is jetted from a and 2b, a molten metal flow is generated and affects the molten metal flow due to electromagnetic stirring. For this reason, as described in the related art, the coil portions 61a and 61b of the electromagnetic stirring means are divided into two, and the stirring force is made different between the left side and the right side of the nozzle 2 so that the combined stirring force becomes uniform. Is being adjusted. On the other hand, the coil portions 62a and 62b of the second electromagnetic stirring means are arranged at a position level corresponding to directly below the ejection openings 2a and 2b of the nozzle 2, and the nozzle portions are similar to the coil portions 61a and 61b of the first electromagnetic stirring means. It is affected by the molten metal flow ejected from No. 2. Therefore, also in this case,
Improvements similar to those of the coil portions 61a and 61b of the first electromagnetic stirring means are added to adjust the combined stirring force to be uniform.

FIG. 2 illustrates a control system of the electromagnetic stirring means of FIG. That is, in the electromagnetic stirrer for molten metal shown in FIG. 1, the coil portion 61 of the first electromagnetic stirrer is used.
While cutting a and 61b with AA and seeing from the upper surface,
The coil portions 62a and 62b of the second electromagnetic stirring means are BB
FIG. 2 is a view showing the control system by cutting it at a top view. In FIG. 2, 2 is a nozzle, 3 is a mold, 10 is a long side of the mold 3, 11 is a short side of the mold 3, 61a and 61b are coil parts of the first electromagnetic stirring means, and 62a and 62b are second parts. Of the electromagnetic stirring means, 200 is a control means for the first and second electromagnetic stirring means, 201 is a power source for the first and second electromagnetic stirring means, and 202 is an operation of the electromagnetic stirring means with respect to the control means 200. It is a command signal generator for instructing conditions and operation sequences.

In FIG. 2, when a uniform electromagnetic stirring force is applied along the long side 10 of the mold in the mold 3 adjacent to the coil portions 61a and 61b of the first electromagnetic stirring means, the molten metal rotates. The flow is superposed by the reversal flow caused by the jet of molten metal and the electromagnetic stirring force, and is strong when going from the mold short side 11 to the nozzle 2 as shown by the dotted arrow, and the nozzle 2
There is a weak flow from the mold to the short side 11 of the mold. However, in the portions immediately below the nozzle ejection ports 2a and 2b, the flow of the molten metal 1 accompanying the ejection of the molten metal 1 is in the direction opposite to the meniscus surface 5, as can be seen from FIG. Therefore, when a uniform second electromagnetic stirring force is applied along the long side 10 of the mold, the rotating flow of the molten metal overlaps the jet flow accompanying the jetting of the molten metal and the electromagnetic stirring force. As shown in, the flow is weak when going from the mold short side 11 to the nozzle 2, and is strong when going from the nozzle 2 to the mold short side 11.

As described above, regarding the operation of the first electromagnetic stirring means, the flow of the molten metal 1 is on the left side of the nozzle 2 and on the coil portion 61a side (first region) of the long side 10 of the mold. 2 on the right side of the mold long side 10 on the coil portion 61a side (second region), on the left side of the nozzle 2 on the long side mold 10 side of coil 61b (third region) on the right side of nozzle 2. However, it differs on the coil portion 61b side (fourth region) of the long side 10 of the mold. Therefore, it is necessary to control the molten metal flow for each of these four divided regions, and such control for each divided region can be performed in the same manner as the conventional method. That is,
The stirring force represented by the dotted line in the first region is more than the second stirring force.
The stirring force represented by the dotted line is increased in the region of 3 and the stirring force represented by the dotted line in the third region is made larger than the stirring force represented by the dotted line in the 4th region so that they are equal to each other. If
A uniform molten metal flow in the clockwise direction can be obtained.

On the other hand, the operation of the second electromagnetic stirring means can be similarly considered. That is, the flow of the molten metal 1 is on the left side of the nozzle 2 and on the coil part 62a side of the mold long side 10 (first region), and on the right side of the nozzle 2 and the coil part 62a side of the mold long side 10 side. (Second region), the left side of the nozzle 2 and the coil portion 62b side of the mold long side 10 (third region), and the right side of the nozzle 2 and the coil portion 62b side of the mold long side 10 (the third region). 4 area). Similar to the coil portion of the first electromagnetic stirring means, the coil portion of the second electromagnetic stirring means can be controlled in each of the four divided regions in the same manner as the conventional method. That is, the stirring force in the first region is made larger than the action of the molten metal flow to give a rightward stirring force represented by a dotted line, and the rightward stirring force represented by a dotted line in the second region is applied. Adjust to equalize the rightward stirring force represented by the dotted line in the first region, and make the stirring force greater than the action of the molten metal flow in the fourth region to the leftward stirring represented by the dotted line. If a force is applied and the leftward stirring force represented by the dotted line in the third region is adjusted to be equal to the leftward stirring force represented by the dotted line in the fourth region, the clockwise uniformity is obtained. A different molten metal stream can be obtained.

Since the rotational force due to the stirring force of the first and second electromagnetic stirring means is clockwise, the stirring force of the four regions of the first electromagnetic stirring means and the second electromagnetic stirring means are the same. By controlling the stirring force of the above four areas by the control means 200, the effect of rotation by the stirring force of the first and second electromagnetic stirring means can be synergized. By controlling in this way, the rotating flow due to the stirring force of the first electromagnetic stirring means can be adapted to the rotating flow due to the stirring force of the second electromagnetic stirring means, so that the stirring force is equivalent to one electromagnetic stirring means. A large stirring effect is generated as compared with the case of using or the independent operation of the two electromagnetic stirring means.

Here, it is assumed that the flow of the molten metal in the clockwise direction is the normal state and the flow of the molten metal in the counterclockwise direction is the reverse state. Since the flow of the molten metal inside the first and second electromagnetic stirring means is controlled by the voltage, frequency, phase, etc. of the polyphase AC power applied to the coil portion of each electromagnetic stirring means,
In the control means 200, the coil portion 61 of the first electromagnetic stirring means is used.
a, 61b, and the coil portion 62 of the second electromagnetic stirring means
The voltage, frequency, phase, etc. of the polyphase AC power applied to a and 62b are adjusted as appropriate for optimization. When optimized, the electromagnetic stirrer has the following four operation modes depending on the polyphase AC power applied to each coil unit.

That is, in the above-mentioned operation mode, the first electromagnetic stirring means is in the normal rotation state and the second electromagnetic stirring means is in the normal rotation state. This is the first operation mode. Second
In the operation mode of 1, the first electromagnetic stirring means is in the normal rotation state and the second electromagnetic stirring means is in the reverse rotation state. In the third operation mode, the first electromagnetic stirring unit is in the reverse rotation state and the second electromagnetic stirring unit is in the normal rotation state. In the fourth operation mode, the first electromagnetic stirring means is in the reverse rotation state and the second electromagnetic stirring means is in the reverse rotation state. These four operation modes are shown together in FIG. In the first and second electromagnetic stirring means, the command signal generating section 202 is, for example, the control means 20.
It is possible to issue an operation mode command as shown in FIG. The command as shown in FIG. 5 can be sent by program control,
It can be arbitrarily set by reading a command to the command signal generator 202.

As described above, in the second electromagnetic stirring means, the coil portion is attached directly below the nozzle, but the jetting of the molten metal from the nozzle can be used as a sink, but it can be attached at other positions. That is, in the case where the coil portion of the second electromagnetic stirring means is arranged immediately below the mold, the weight of the mold is reduced and the replacement of the mold is facilitated. FIG. 6 is an explanatory diagram showing the second embodiment of the present invention. In FIG. 6, the coil portion of the first electromagnetic stirring means is arranged on the meniscus surface of the mold, and the coil portion of the second electromagnetic stirring means is arranged immediately below the mold. In FIG. 6, 1
Is molten metal, 2 is a nozzle, 2a and 2b are nozzle ejection ports,
3 is a mold, 4 is a solidified shell, 5 is a meniscus surface, 6
Reference numerals 1a and 61b are coil portions of the first electromagnetic stirring means, and 62a and 62b are coil portions of the second electromagnetic stirring means.

In FIG. 6, the molten metal 1 ejected from the nozzle is drawn downward in the mold 3, but on the meniscus surface, the flow of the ejected molten metal 1 and the stirring force of the first electromagnetic stirring means are added. And stirring is performed. The molten metal 1 ejected from the nozzle ejection ports 2 a and 2 b moves upward along the side wall of the mold 3 and moves on the meniscus surface 5 toward the nozzle 2. Therefore, it is considered that the influence of the nozzle 2 need not be taken into consideration in the coil portions 62a and 62b of the second electromagnetic stirring means. Therefore, in the second embodiment, the connection of the coil portions of the first and second electromagnetic disrupting means is as shown in FIG.
As shown in. In FIG. 7, 2 is a nozzle, 3 is a mold, 10 is a long side of the mold 3, 11 is a short side of the mold, 61a and 61b are coil portions of the first electromagnetic stirring means, and 62a and 62b are second sides. A coil part of the electromagnetic stirring means, 200 is a control means, 201 is a power source, 202
Is a command signal generator.

In the second embodiment shown in FIG. 7, the first electromagnetic stirring means operates in the same manner as in the first embodiment shown in FIG. Therefore, the molten metal flow is a synergistic effect of the molten metal flow ejected from the nozzle 2 and the molten metal flow caused by electromagnetic stirring. On the other hand, the second electromagnetic stirring means considers that the influence of the molten metal flow ejected from the nozzle 2 can be ignored, and handles only the molten metal flow by electromagnetic stirring. Therefore,
The control means 200 is the coil portion 61 of the first electromagnetic stirring means.
When controlling a and 61b, each coil part 6
1a and 61b are divided into two, and each unit consisting of a total of 4 units is controlled. The control is similar to that in FIG. On the other hand, the coil portion 62 of the second electromagnetic stirring means
In a and 62b, a simple control method for generating a uniform molten metal flow is adopted.

In this case, as the operation modes of the first and second electromagnetic stirring means, the four operation modes shown in FIG. 4 in the first embodiment are applied. That is, when the first electromagnetic stirring unit is in the normal rotation state, the second electromagnetic stirring unit has a forward rotation state and a reverse rotation state, while when the first electromagnetic stirring unit is in the reverse rotation state, the second electromagnetic stirring unit is in the second rotation state. The electromagnetic stirring means has a normal rotation state and a reverse rotation state. These operation modes can be realized by the device including the control means, the power supply, and the command signal generating section described above.

FIG. 8 is an explanatory view showing a third embodiment of the present invention, in which the coil portion of the second electromagnetic stirring means is mounted below the mold 3. In FIG. 8, 1 is a molten metal,
Reference numeral 2 is a nozzle, 2a and 2b are nozzle ejection ports, 3 is a mold, 4 is a solidified shell, 61a and 61b are coil portions of the first electromagnetic stirring means, 62a and 62b are coils of the second electromagnetic stirring means, respectively. Part 100 is a solidification interface. The control mode by the first and second electromagnetic stirring means is almost the same as that shown in FIG.

In this way, since the molten metal concentrates in the central portion as the metal slab is produced, the action of the second electromagnetic stirring means becomes weak in the above case. Therefore, FIG. 9 is an explanatory view showing a fourth embodiment in which the coil portion of the second electromagnetic stirring means is arranged between the rolls. Figure 9
8 is compared with FIG. 8, the coil portion 6 of the second electromagnetic stirring means is compared.
The effect of moving 2a and 62b on the molten metal is increased.

FIG. 10 is an explanatory view showing the positional relationship between the coil portions 62a and 62b of the electromagnetic stirring means and the molten metal in FIG. 9, and the coil portion of the second electromagnetic stirring means is indicated by BB in FIG. FIG. In FIG. 10, 1 is a metal slab, 62a and 62b are coil parts of the second electromagnetic stirring means, and 100 is a solidification interface. As can be seen from FIG. 10, the coil portions 62a, 6 of the second electromagnetic stirring means
2b is close to the metal slab.

[0039]

As described above, according to the present invention, the first and the first for stirring the molten metal on the outside of the mold for producing the metal slab are provided with the immersion nozzle for injecting the molten metal. Since it is equipped with 2 electromagnetic stirring means,
The stirring effect of the molten metal can be increased, the uniformity of the metal slab used as a product can be improved, and problems in quality control such as unevenness in quality can be significantly improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of an electromagnetic stirrer for molten metal according to the present invention.

FIG. 2 is an explanatory diagram showing a control system of the electromagnetic stirring means of FIG.

FIG. 3 is an explanatory diagram showing a flow of molten metal in a mold.

FIG. 4 is an explanatory diagram showing an operation mode in which operations of first and second electromagnetic stirring means are combined.

FIG. 5 is an explanatory diagram showing an example of a command of a command signal generation unit.

FIG. 6 is an explanatory view showing a second embodiment of the electromagnetic stirrer for molten metal according to the present invention.

7 is an explanatory diagram showing a control system of the electromagnetic stirring means in FIG.

FIG. 8 is an explanatory view showing a third embodiment of the electromagnetic stirring apparatus for molten metal according to the present invention.

FIG. 9 is an explanatory view showing a fourth embodiment of the electromagnetic stirring apparatus for molten metal according to the present invention.

10 is an explanatory diagram showing a positional relationship between a coil portion of the electromagnetic stirring means shown in FIG. 9 and a molten metal.

FIG. 11 is a sectional view of an apparatus used for continuous casting of a conventional metal slab.

FIG. 12 is a plan view of the apparatus shown in FIG. 11 as seen from the AA plane.

FIG. 13 is an explanatory diagram showing a conventional electromagnetic stirring device.

FIG. 14 is an explanatory view of a continuous casting portion of a conventional improved metal slab as viewed from above the meniscus surface.

FIG. 15 is a circuit connection diagram for realizing the operation shown in FIG.

16 is a wiring diagram of a power supply supplied to the circuit shown in FIG.

FIG. 17 is an explanatory view of a continuous casting device for a metal slab according to the multiple power source system, as viewed from the meniscus surface.

FIG. 18 is an explanatory diagram showing a process of producing a metal slab.

[Explanation of symbols]

1, 8 ... Molten metal 2 ... Nozzles 2a, 2b ... Nozzle mouth 3 ... Mold 4 ... Solidification shell 5 ... Meniscus surface 6, 6a, 6b, 61a, 61b, 62a ... Coil portions 7a, 7b of electromagnetic stirring means ... Wiring Box 8 ... 3-phase inverter 9 ... Command boxes 10, 10a, 10b ... Mold long sides 11, 11a, 11b ... Mold short sides 14a, 14b ... Coil 21 ... Switch box 22 ... Control box 23 ... Sensor 100 ... Solidification interface 101 ... Crater end 200 ... Control means 24, 25, 201 ... Power source 202 ... Command signal generator

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI Theme Coat (reference) B22D 11/115 B22D 11/115 R (72) Inventor Naohisa Honda 1-1 Hibahata-cho, Tobata-ku, Kitakyushu, Fukuoka No. New Nippon Steel Co., Ltd. F term in Yawata Works (reference) 4E004 AA09 GB01 GB02 GB03 MB12 MB13

Claims (3)

[Claims] 1. A solidified shell, which is provided with an immersion nozzle for injecting a molten metal in an upper part thereof, and is formed by gradually cooling the molten metal injected from the immersion nozzle from a cooled inner wall surface, on the inner wall surface. Including the temperature of the molten metal injected into the mold from the immersion nozzle inside the mold to generate a metal slab when the solidified shell is drawn obliquely downward from below. In order to make the distribution even, in order to cause the molten metal to flow clockwise or counterclockwise by the action of its linear motor by giving electromagnetic induction in the meniscus plane of the molten metal entirely or selectively. Of the first electromagnetic stirring means, and the first electromagnetic stirring means is arranged below the position where the first electromagnetic stirring means is arranged, and is connected to the first electromagnetic stirring means. An electromagnetic stirring device for molten metal, comprising: a second electromagnetic stirring means controlled to operate as described above. 2. The electromagnetic stirrer for molten metal according to claim 1, wherein the mutually linked operations of the first and second electromagnetic stirrers melt inside the first electromagnetic stirrer. It is characterized by comprising control means for performing sequence control so that the metal flow and the molten metal flow inside the second electromagnetic stirring means are respectively in a normal rotation, reverse rotation, or forward / reverse inversion state. Electromagnetic stirrer for molten metal. 3. The electromagnetic stirring device for molten metal according to claim 1 or 2, wherein the second electromagnetic stirring means has a position where the second electromagnetic stirring means is disposed in a nozzle ejection port provided in the mold. An electromagnetic stirring device for molten metal, characterized in that it is arranged directly below.