JP3501997B2 - Method for producing continuous cast slab and electromagnetic stirrer in continuous cast mold - 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 producing a continuously cast slab by applying an alternating magnetic field to molten metal in a continuous casting mold to swirl the molten metal and an electromagnetic stirring device in the continuous casting mold.

[0002]

2. Description of the Related Art In continuous casting for producing steel slabs, in order to reduce inclusion defects on the surface of the slab, crack defects on the surface of the slab, and segregation inside the slab, An electromagnetic stirrer that swirls and stirs the molten steel of No. 2 is widely adopted.

By the way, in continuous casting for producing a slab slab having a rectangular cross section perpendicular to the casting direction and having a large ratio of the long side length to the short side length, the cross section is close to a square or a circle. It is difficult to smoothly swirl molten steel, as compared with continuous casting for producing bloom slabs. This is because when the molten steel in the mold is stirred by electromagnetic stirring, it is due to the difference in the cross-sectional shape of the slab or because the molten steel discharge flow from the immersion nozzle and the stirring flow are likely to interfere with each other. .

Therefore, in continuous casting for producing a slab cast piece, molten steel may be melted at the end in the long side direction of the mold depending on casting conditions such as the width of the cast piece (long side length of the cast piece). There is a problem in that it is easy to settle and the inclusion defects in the surface layer of the slab cannot be sufficiently reduced.

Therefore, when swirling and agitating the molten steel in the mold of the slab slab, a method of disposing a pair of linear motors facing each other along the facing long sides and generating moving magnetic fields that travel in opposite directions is known. Widely used.

In this conventional method, a plurality of vortices of stirring force are generated in the long side direction of the mold, and the molten steel in the mold is swirled and stirred by the effect of these vortices overlapping.

[0007]

By the way, in the above-mentioned conventional method, under the condition that the phase difference between the pair of linear motors is constant, the vortex of the stirring force is always substantially constant regardless of the length of the slab in the long side direction. Position, and the interval is the pole pitch of the linear motor (the pitch between poles with a 180 ° phase difference)
Is almost the same as. Therefore, depending on the long side length of the slab, when the molten steel in the mold is swirled and stirred almost entirely from the long side end to the end, and the long side end, etc. Occurs when there is a region where swirling and stirring cannot be performed smoothly.

That is, when the positions of both ends of the slab in the long side direction substantially coincide with the positions of the ends of the vortex of the stirring force, the entire long side direction is swirled and stirred almost smoothly. On the other hand, when both end positions of the slab in the long side direction substantially coincide with the center position of the vortex of the stirring force, it is difficult to smoothly swirl and stir the whole slab. In particular, when the long side length of the slab is as short as about 2.5 times the pole pitch or less, the center position of the vortex of the stirring force has a great effect on the smoothness of the swirling stirring, and the position of the pair of linear motors If the phase difference is inappropriate, it is difficult to smoothly swirl the molten steel in the mold.

The present invention has been made in view of such a situation, and the phase relationship between the pair of linear motors is changed in accordance with the length of the rectangular slab in the long side direction so that the stirring force is vortexed. By controlling the center position of the, the entire molten metal in the mold is smoothly swirled, the surface layer defects of the slab can be reduced and stabilized, and a method for producing a continuously cast slab and an electromagnetic stirring device in the continuous casting mold. The purpose is to provide.

As a technique for changing the phase relationship of the linear motor as in the present invention, mainly the surface temperature distribution in the long side direction of the slab is detected, and the phase difference between the pair of linear motors is detected according to this temperature distribution. There is a proposed technique (Japanese Patent Laid-Open No. 11-170016). However, this proposed technique does not determine the phase difference between the pair of linear motors according to the long side length of the rectangular shaped slab, and in the case of continuously casting a slab of any long side length. However, it does not provide smooth swirling agitation.

[0011]

The method for producing a continuously cast slab according to the present invention is a method for producing a continuously cast slab, wherein the continuous casting mold having a rectangular cross section is provided with a back surface of a long side mold wall facing each other or above, or a molten metal melt in the mold. A pair of linear motors are arranged facing each other above the surface, and a moving magnetic field that advances in mutually opposite directions is generated to swirl and agitate the molten metal in the mold to produce a continuously cast slab. At 18
Depending on the relationship between the pitch between poles with 0 ° phase difference and the long side length of the cast piece to be cast, the center position of the vortex of the stirring force should be approximately the same as the position of both ends in the long side direction of the cast piece. In order to prevent the above, the phase of the pair of linear motors is switched to either the same phase or the opposite phase to change the stirring force distribution.

Further, the electromagnetic stirrer in the continuous casting mold of the present invention is provided on the back surface of the long side mold walls facing each other of the continuous casting mold having a rectangular cross section or above, or above the molten metal surface in the mold. , A pair of linear motors having a core and a plurality of energizing coils are opposed to each other, and generate a moving magnetic field that travels in the opposite directions to swirl and agitate the molten metal in the casting mold electromagnetic stirring device in a continuous casting mold In a pair of linear motors, there is a power source or a changeover switch capable of simultaneously changing the phase of the electric current flowing through each coil of at least one of the linear motors by 180 °, and the 180 ° phase difference in the linear motor is Depending on the relationship between the pitch between different poles and the long side length of the cast piece to be cast, the center position of the vortex of the stirring force is To prevent substantially in accordance with the location, characterized in that a pair of linear motor phase is configured to switch in phase or antiphase.

According to the method of the present invention and the apparatus of the present invention, the phases of the pair of linear motors are switched to the same phase or opposite phases according to the long side length of the cast piece to be cast, so that the molten metal in the mold is swirled. The position of the magnetic field generated by the pair of linear motors for applying the stirring force can be changed, which prevents the center position of the vortex of the stirring force from substantially matching the positions of the ends of the slab in the long side direction. Yes, more preferably, the position of the end of the vortex of the stirring force can be made to substantially coincide with the positions of both ends in the long side direction of the slab, and the entire long side direction of the molten metal in the mold is swirled and stirred almost smoothly. Will be done. Therefore, the occurrence rate of surface layer defects of the cast slab can be reduced and stabilized.

In the electromagnetic stirrer in the continuous casting mold of the present invention, the long side length (W) of the cast piece to be cast,
When the relationship with the pole pitch (P) of the linear motor satisfies the following expression (1), the pair of linear motors have opposite phases, and when the following expression (2) is satisfied, the pair of linear motors have the same phase. It is characterized by switching the phase to.

[0015]     (2n-1.5) P ≤ W <(2n-0.5) P (1)     (2n-0.5) P ≤ W <(2n + 0.5) P (2) However, n is a natural number (n = 1, 2, 3, ...).

According to the present invention, a pair of linear motors are installed in accordance with the relationship between the pitch between poles having different 180 ° phase difference in the linear motor installed in the continuous casting mold and the long side length of the cast slab to be cast. It will be possible to easily judge whether to make the phase the opposite phase or the same phase.

For example, when W≈2 · P shown in FIG. 9A and when W≈4 · P shown in FIG. 9C, the same phase (0
9), and when W≈3 · P shown in FIG. 9B, the opposite phase (180 °) is set. The pole pitch (P) of the linear motor is the dimension indicated by P in FIG. 9, and the long side length (W) of the slab is the long side length of the mold indicated by W in FIG. It is almost equal to the size.

The rectangular frame in FIG. 9 indicates the size of the mold,
The solid and dashed arrows indicate the direction and position of the magnetic field at a given moment. The direction of the magnetic field that penetrates the molten metal is (1) the direction of the solid line → (2) the direction of the broken line → (3) the direction opposite to the solid line → (4)
When the direction is changed in the opposite direction of the broken line, an electromagnetic force that acts to agitate leftward acts in the molten metal in accordance with the rotation of the magnetic field. Since this electromagnetic force acts in the circumferential direction to the left around the intersection of the solid line and the broken line, a plurality of vortices of stirring force are generated in the mold. By changing the phase of the linear motor according to the size of the mold and appropriately controlling the generation position of the vortex of the stirring force, the stagnation portion of the molten metal is less likely to occur at both ends of the mold. In addition, by changing the direction of the magnetic field in the order of (4) → (3) → (2) → (1) to generate the vortex of the rightward stirring force in the molten metal, the leftward stirring force It is possible to obtain the same effect as in the case of generating a vortex and electromagnetically stirring the molten metal.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. (1st Embodiment) FIG. 1: is a figure which shows the electromagnetic stirring apparatus in the continuous casting mold which concerns on 1st Embodiment of this invention, and is the front view seen from the short side of a mold, FIG.2 (a) (c). FIG. 2 is a diagram showing a configuration of a power supply circuit that applies a current to a pair of linear motors provided in the electromagnetic stirring device, and FIG. 2B is a diagram showing a phase difference of four-phase currents output from the power supply circuit. 3 (a) and 4 (a) are plan views showing the direction of the magnetic field and the position of the magnetic field at a certain moment in the electromagnetic stirring device.
FIG. 4A shows a state where a pair of linear motors have the same phase, FIG.
(A) shows a state in which the pair of linear motors have opposite phases.

Electromagnetic stirring device 10 in this embodiment
Is a cylindrical continuous casting mold 1 having a rectangular cross section provided on the upper part of the continuous casting machine, as shown in FIG. Linear motors 11A and 11B are arranged. Continuous casting mold 1
Has a structure in which two long side portions 1A of the copper plate 2 and two short side portions 1B of the copper plate 2 are assembled in a cross beam shape, and the copper plate 2 on each side is held by the back frame 3. ing.
Further, in the continuous casting mold 1, the position of the short side portion 1B in the long side direction of the copper plate 2 can be adjusted so that the long side length of the cross section of the cast piece 4 can be changed, and the cast piece thickness can be changed. Short side 1B
It is possible to replace the copper plate 2 with a different width dimension (dimension corresponding to the thickness of the slab 4) and to adjust one position of the copper plate 2 of the long side portion 1A in the thickness direction of the slab 4. There is. The copper plate 2 of the long side 1A whose position can be adjusted is called the variable side, and the copper plate 2 of the other long side 1A is called the fixed side. Further, in the continuous casting mold 1, each copper plate 2 is cooled by the cooling water flowing inside.

Molten metal, such as molten steel, is injected into the inside of the continuous casting mold 1 through the immersion nozzle 7, and the molten metal 6 is adjusted so that the height of the molten metal surface becomes substantially constant. The molten metal 6 in the mold 1 is solidified from the outer surface by the copper plate 2 cooled by the cooling water, and after the solidified layer 5 is formed to have a certain thickness or more, a large number of counter rolls provided below the mold 1. Flock (the top pair 8 is shown in Figure 1)
Will be pulled out by. Further, the cast slab 4 to be pulled out is cooled by cooling water ejected from a large number of nozzles (not shown).

The linear motor 11A arranged on the rear side of the long side of the fixed side of the mold 1 has an iron core (core) 12 and a coil 13, as shown in FIG.
It is wound around the salient pole part. The linear motor 11B has a core 14 and a coil 15 on the rear surface of the long side on the variable side of the mold 1, as shown in FIG.
It is wound around the salient pole part.

As shown in FIG.
As shown in (a), U-phase, V-phase, U′-phase, and V′-phase currents are directly applied from the power supply 16 through the power supply cable 17, and the variable-side linear motor 11B is supplied with the power supply cable 17. U-phase, V-phase, U'phase, V'from the power source 16 via the branch power supply cable 18 and the changeover switch 19
The phase current is applied. The U-phase, V-phase, U′-phase, and V′-phase currents have the phase difference shown in FIG. 2B, and the U-phase and U′-phase and the V-phase and V′-phase have a phase difference of 180 °, respectively. At °
The phase difference between the U phase and the V phase is 90 °. The power source 16 is
It is composed of two single-phase circuits, and is designed to output the above-mentioned four-phase currents.

The changeover switch 19 is used for the linear motor 1
Pole pitch (P) in 1A and 11B (see FIG. 9)
And the long side length of the cast slab 4 to be cast,
The state of (a) and the state of FIG. 2 (c) are switched.
That is, when the state of FIG. 2A is switched to the state of FIG. 2C, the U phase and the U ′ phase are switched, and the V phase and the V ′ phase are switched to change the linear motor on the variable side. Current is supplied to 11B. On the contrary, from the state of FIG.
When the state is switched to the state of (a), the U phase and the U ′ phase are switched, and the V phase and the V ′ phase are switched, and the current is supplied to the variable side linear motor 11B. This switching is performed all at once.

The contents of supply of the current having such a phase difference to the coil of the linear motor will be specifically described.

FIG. 3 (a) shows the power feeding state in the case of FIG. 2 (a). That is, at a certain moment, when the U-phase, V-phase, U′-phase, and V′-phase currents are sequentially applied to the coil 13 of the fixed side (upper side of the figure) linear motor 11A from the left side of the figure, the variable side Linear motor 11 (bottom of figure)
In the coil 15 in B, the U phase and V
Phase, U'phase and V'phase currents are applied.

FIG. 4A shows a power supply state in the case of FIG. 2C in which the changeover switch 19 is switched. That is, at a certain moment, in the coil 13 of the fixed side (upper side of the figure) linear motor 11A, the U-phase, V-phase, U′-phase, and V′-phase currents are sequentially output from the left side of the figure, as in FIG. 3A. Is given to the coil 15 of the linear motor 11B on the variable side (the lower side of the figure), in order from the right side of the figure, the U'phase, V'phase, and U phase of the opposite phase (180 °) to the fixed side. , V
The phase current is applied.

Next, the relationship between the pole pitch (P) in the linear motor for switching the changeover switch 19 and the long side length of the cast slab 4 to be cast will be described.

In FIG. 3, (b) shows the size of the mold or slab when W≈3 · P, and (c) shows the size of the mold or slab. In the figure, A is a portion where the solid line magnetic field and the broken line magnetic field intersect, and the distance between AA corresponds to P. B
Is a portion P / 2 away from A.

In the case of the length of the slab 4 in FIG. 3 (B) (W≈3 · P), the center of the vortex of the stirring force generated in A is located at the end of the mold 1, and the mold 1 It is difficult to smoothly swirl and agitate the entire area of the molten metal mainly in the horizontal direction. This also applies to the following case (1).

[0031]     (2n-1.5) P ≤ W <(2n-0.5) P (1) However, n is a natural number (n = 1, 2, 3, ...).

On the other hand, in the case of the length of the slab 4 in FIG. 3C, the end of the vortex of the stirring force generated in B is located at the end of the mold 1, and the molten metal in the mold 1 Mainly, the whole area in the horizontal direction is swirled and stirred smoothly. This also applies to the following case (2).

(2n−0.5) P ≦ W <(2n + 0.5) P (2) Therefore, in the case of (2) above, electromagnetic stirring is performed with the phases of the pair of linear motors being the same phase. Is preferred.

In FIG. 4, (b) shows the size of the mold or slab when W≈3 · P, and (c) shows the size of the mold or slab.

In the case of the length of the slab 4 in FIG. 4B (W≈3 · P), the end of the vortex of the stirring force generated in B is located at the end of the mold 1, and the mold 1 The whole area of the molten metal in the inside, mainly in the horizontal direction, is swirled and stirred smoothly. This also applies to the above case (1).

On the other hand, in the case of the length of the slab 4 in FIG. 4C (W≈2 · P), the center of the vortex of the stirring force generated in A is located at the end of the mold 1, It is difficult to smoothly swirl and stir the molten metal in the mold 1 mainly in the horizontal direction. This also applies to the above case (2).

Therefore, in the case of the above (1), it is preferable to carry out electromagnetic stirring with the phases of the pair of linear motors 11A and 11B as opposite phases.

Therefore, in the case of the above (2), electromagnetic stirring is performed with the phase of the pair of linear motors 11A and 11B being the same phase, and in the case of the above (1), the phase of the pair of linear motors 11A and 11B. It is preferable to carry out the magnetic stirring with the phase in the opposite phase. When electromagnetic stirring is performed in this manner, the entire molten metal in the mold 1 can be swirled and stirred smoothly regardless of the length of the slab 4 in the long side direction, and surface defects of the slab 4 are generated. It is possible to lower the rate and stabilize it. (Second Embodiment) In the first embodiment, the power supply is a single-phase, two-circuit power supply, and the coil is a salient pole winding. However, in the present embodiment, a three-phase AC power supply is used.
The coil is wound between poles. Further, also in the second embodiment, as in the first embodiment, as shown in FIG. 1, a pair of linear motors are arranged on the back surface on the long side of the continuous casting mold.

FIGS. 5 (a) and 5 (c) are views showing the configuration of a power supply circuit for applying a current to a pair of linear motors provided in the electromagnetic stirrer of the second embodiment, and FIG. 5 (b) is an output from the power supply circuit. It is a figure which shows the phase difference of the electric current of the six phases made. 6 (a) and 7 (a) are plan views showing the direction and position of the magnetic field at a certain moment in the electromagnetic stirrer, and FIG. 6 (a) shows a pair of linear motors. Shows the same phase, and FIG. 7A shows the state where the pair of linear motors have opposite phases.

The electromagnetic stirrer 20 of this embodiment has a pair of linear motors 21A and 21B, and the fixed linear motor 21A has an iron core 22 and a coil 23 as shown in FIG. However, the coil 23 is wound around the inter-electrode portion of the iron core 22. The variable side linear motor 21B has an iron core (core) 24 and a coil 25, and the coil 25 is wound around an interelectrode portion of the iron core 24.

As shown in FIG.
As shown in (a), the S phase, the R phase, the T phase, the -S phase, the -R phase, and the -T directly from power source 26 via power feeding cable 27.
A phase feeding current 2 is applied to the variable side linear motor 21B, and the feeding cable 27 is branched from the feeding cable 27.
8 from the power source 26 through the changeover switch 29, S phase, R
Phase, T phase, -S phase, -R phase, and -T phase currents are applied. As shown in FIG. 5B, the S phase and −S phase, the R phase and −R phase, and the T phase and −T phase each have a phase difference of 180 °.
The phase difference between S phase and R phase, and R phase and T phase is 12 degrees.
It is 0 °.

The changeover switch 29 is used for the linear motor 2
Pole pitch in 1A and 21B and cast slab 4
The state of FIG. 5A and the state of FIG.
The state is switched to the state of (c). That is, FIG. 5 (a)
When the state of FIG. 5C is switched to the state of FIG. 5C, the S phase and the -S phase are switched, and the R phase and the -R phase and the T phase and the -T phase are switched, and the variable side linear motor is switched. Current is supplied to 21B. Conversely, from the state of FIG.
When the state is switched to the state of (a), the S phase and the -S phase are switched, and the R phase and the -R phase and the T phase and the -T phase are switched to supply a current to variable linear motor 21B. To be done. This switching is performed all at once.

The contents of supply of the current having such a phase difference to the coil of the linear motor will be specifically described.

FIG. 6A shows the power supply state in the case of FIG. 5A. That is, at a certain moment, the coils 23 in the fixed side (upper side of the figure) linear motor 21A are supplied with R-phase, -S-phase, T-phase, -R-phase, S-phase, and -T-phase currents in order from the left side of the figure. At this time, the coils 25 in the variable-side (lower side of the figure) linear motor 21B are supplied with R-phase, -S-phase, T-phase, -R-phase, S-phase, and -T-phase currents in order from the right side of the figure. .

FIG. 7A shows a power supply state in the case of FIG. 5C in which the changeover switch 29 is switched. That is, at a certain moment, in the coil 23 of the fixed side (upper side of the figure) linear motor 21A, the R phase, the -S phase, the T phase, the -R phase, and the S phase are sequentially arranged from the left side of the figure as in the case of FIG. 6A. phase,
When a -T phase current is applied, the coil 25 in the linear motor 21B on the variable side (the lower side of the figure) has the -R phase, the S phase, which are in the opposite phase (180 °) to the fixed side in order from the right side of the figure.
-T phase, R phase, -S phase, and T phase currents are applied.

Next, the relationship between the pole pitch in the linear motors 21A and 21B for switching the changeover switch 29 and the long side length of the cast slab 4 to be cast will be described.

In FIG. 6, (b) shows the size of the mold or slab when W≈3 · P, and (c) shows the size of the mold or slab.

In the case of the length of the slab 4 in FIG. 6B (W≈3 · P), the center of the vortex of the stirring force generated in A is located at the end of the mold 1 and the mold 1 It is difficult to smoothly swirl and agitate the entire area of the molten metal mainly in the horizontal direction. This also applies to the above case (1).

On the other hand, in the case of the length of the cast slab 4 in FIG. 6 (c), the end of the vortex of the stirring force generated in B is located at the end of the mold 1, and the molten metal in the mold 1 Mainly, the whole area in the horizontal direction is swirled and stirred smoothly. This also applies to the above case (2).

Therefore, in the case of the above (2), it is preferable to perform electromagnetic stirring with the phases of the pair of linear motors being the same.

In FIG. 7, (b) shows the size of the mold or slab when W≈3 · P and (c) shows the size when W≈2 · P.

In the case of the length of the slab 4 in FIG. 7B (W≈3 · P), the end of the vortex of the stirring force generated in B is located at the end of the mold 1 and the mold 1 The whole area of the molten metal in the inside, mainly in the horizontal direction, is swirled and stirred smoothly. This also applies to the above case (1).

On the other hand, in the case of the length of the slab 4 in FIG. 4 (c) (W≈2 · P), the center of the vortex of the stirring force generated in A is located at the end of the mold 1, It is difficult to smoothly swirl and stir the molten metal in the mold 1 mainly in the horizontal direction. This also applies to the above case (2).

Therefore, in the case of the above (1), it is preferable to carry out the electromagnetic stirring with the phases of the pair of linear motors 21A and 21B as opposite phases.

Therefore, in the case of the above (2), electromagnetic stirring is performed with the phase of the pair of linear motors 21A and 21B being the same phase, and in the case of the above (1), the phase of the pair of linear motors 21A and 21B. It is preferable to carry out the magnetic stirring with the phase in the opposite phase. When electromagnetic stirring is performed in this manner, the entire molten metal in the mold 1 can be swirled and stirred smoothly regardless of the length of the slab 4 in the long side direction, and surface defects of the slab 4 are generated. It is possible to lower the rate and stabilize it.

[0056]

EXAMPLE The number of surface defects of a cast piece was examined in the case of the configuration of the first embodiment. Table 1 (a) shows the electromagnetic stirring conditions at that time, and (b) shows the investigation result.

[0057]

[Table 1]

As shown in Table 1 (a), the electromagnetic stirring condition is that in Comparative Example 1 without electromagnetic stirring, in Comparative Example 2, electromagnetic stirring was always performed in the same phase regardless of the length of the slab in the long side direction. In Comparative Example 3, electromagnetic stirring is always performed in the opposite phase regardless of the length of the slab in the long side direction.

On the other hand, in the case of the present invention, the electromagnetic stirring is performed by setting the phases of the pair of linear motors to be the same phase or opposite phases according to the length of the slab in the long side direction. Specifically, the pole pitch (P) is 450 mm, and the length of the slab in the long side direction is 800 mm to 1009 mm, 160
At 0 mm to 1800 mm, the pair of linear motors have the same phase, and the length of the slab in the long side direction is 1100 mm to
At 1599 mm, the phase of the pair of linear motors is opposite.

As shown in Table 1 (b), the result of the investigation is that the surface defect index (vertical axis) of the slab in the case of Comparative Example 1 without electromagnetic stirring was 1, and Comparative Examples 2 and 3 and the present invention were evaluated. It represents the surface defect index of the cast slab according to the example. In the case of Comparative Example 1, the surface defect index of the slab is the highest regardless of the length of the slab in the long side direction. The length of the slab in the long side direction is 800 mm to 1009 mm and 1600 mm to 1800
In mm, the surface defect index of the slab is lower in Comparative Example 2 and the present invention than in Comparative Example 3, and when the length of the slab in the long side direction is 1100 mm to 1599 mm, it is the same as Comparative Example 3. In the case of the invention, the surface defect index of the slab is lower than that of Comparative Example 2.

As can be understood from this, in the case of the present invention, the phase of the pair of linear motors is switched to the same phase or the opposite phase according to the long side length of the cast piece to be cast, so that It is possible to swirl and agitate the entire long-side direction of the molten metal almost smoothly, and thus it is possible to stabilize the occurrence rate of surface layer defects of the cast slab.

In the first and second embodiments described above,
As shown in FIG. 1, a pair of linear motors are provided on the back side of the mold 1 and below the molten metal 5 molten metal surface 5a. However, the present invention is not limited to this, and the mold 1 A pair of linear motors may be provided on the rear side above the molten metal 5 molten metal 5a, or as shown in FIG. 8, a pair of linear motors may be disposed above the molten metal 5 molten metal 5 inside the mold 1. Motor 31A, 3
1B may be provided.

In FIG. 8, 32 and 34 are both iron cores, 33 and
Reference numeral 35 denotes a coil, and hanging portions 32a and 34a for positioning a magnetic field in the mold 1 are formed to extend from the tip ends of the iron cores 32 and 34.

In this way, the pair of linear motors 31A, 3
Even if an electromagnetic stirrer consisting of 1B is provided, the mold 1
The entire long-side direction of the molten metal 5 inside can be swirled and stirred almost smoothly, and the occurrence rate of surface layer defects of the cast slab 4 can be reduced and stabilized.

In the first and second embodiments described above,
The phase of one linear motor in the pair of linear motors is simultaneously switched to either the same phase or the opposite phase, but the present invention is not limited to this, and the phase in both of the pair of linear motors is not limited to this. May be switched. However, even in that case, the relationship between the long side length of the slab and the pole pitch of the linear motor in claim 3 is satisfied so as to satisfy the relationships of the expressions (1) and (2).

In the first and second embodiments described above,
A changeover switch 1 is provided as means for simultaneously changing the phase of the pair of linear motors to either the same phase or the opposite phase.
9 and 29 are used, the present invention is not limited to this, and it is also possible to use a power supply having a configuration in which the phase of the current output by the power supply itself can be switched to either the same phase or the opposite phase all at once. Good. In this case, there is no need for the changeover switch, and it can be omitted.

[0067]

As described above in detail, in the case of the present invention, the phase of the pair of linear motors is switched to the same phase or the opposite phase according to the long side length of the cast piece to be cast, so that The position of the magnetic field generated by the pair of linear motors for applying the swirling stirring force to the molten metal can be changed, so that the center position of the vortex of the stirring force substantially matches the positions of both ends in the long side direction of the slab. Can be prevented, more preferably,
The position of the end of the vortex of the stirring force can be made to almost coincide with the position of both ends in the long side direction of the cast piece, and it becomes possible to swirl and stir the entire long side direction of the molten metal in the mold. Thus, the occurrence rate of surface layer defects of the cast slab can be reduced and stabilized.

[Brief description of drawings]

FIG. 1 is a view showing an electromagnetic stirring device in a continuous casting mold according to a first embodiment of the present invention, and is a front view seen from the short side of the mold.

2 (a) and 2 (c) are views showing a configuration of a power supply circuit for applying a current to a pair of linear motors provided in the electromagnetic stirring device in the continuous casting mold according to the first embodiment of the present invention; 4] is a diagram showing a phase difference of four-phase currents output from the power supply circuit.

FIG. 3A is a plan view showing a magnetic field direction and a magnetic field position at a certain moment in the electromagnetic stirring device in the continuous casting mold according to the first embodiment of the present invention (the pair of linear motors are the same). Phase), (b) shows a template of W≈3 · P,
(C) shows a template of W≈2 · P.

FIG. 4A is a plan view showing a magnetic field orientation and a magnetic field position at a certain moment in the electromagnetic stirrer in the continuous casting mold according to the first embodiment of the present invention (a pair of linear motors are opposite to each other; Phase), (b) shows a template of W≈3 · P,
(C) shows a template of W≈2 · P.

5 (a) and 5 (c) are views showing a configuration of a power supply circuit for applying a current to a pair of linear motors provided in an electromagnetic stirrer in a continuous casting mold according to a second embodiment of the present invention; 6] is a diagram showing a phase difference of six-phase currents output from the power supply circuit.

FIG. 6A is a plan view showing a magnetic field direction and a magnetic field position at a certain moment in the electromagnetic stirrer in the continuous casting mold according to the second embodiment of the present invention (the pair of linear motors are the same). Phase), (b) shows a template of W≈3 · P,
(C) shows a template of W≈2 · P.

FIG. 7A is a plan view showing a magnetic field direction and a magnetic field position at a certain moment in the electromagnetic stirrer in the continuous casting mold according to the second embodiment of the present invention (a pair of linear motors are opposite to each other; Phase), (b) shows a template of W≈3 · P,
(C) shows a template of W≈2 · P.

FIG. 8 is a front view showing another arrangement position of the electromagnetic stirring device for the continuous casting mold applicable in the present invention.

FIG. 9 is a diagram for explaining the principle of the present invention, and is a diagram showing the direction of the magnetic field and the position of the magnetic field at a certain moment in the electromagnetic stirrer when the size of the continuous casting mold is variously changed.

[Explanation of symbols]

1 Continuous casting mold 4 Cast slab 5 Molten metal 10, 20 Electromagnetic stirrer 11A, 11B, 21A, 21B, 31A, 31B Linear motor 12, 14, 22, 24 Iron core (core) 13, 15, 23, 25 Coil 16 , 26 Power supply 19, 29 Changeover switch

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-290249 (JP, A) JP-A-8-206800 (JP, A) JP-A-9-136147 (JP, A) JP-A-7- 24559 (JP, A) Actual Kaihei 2-16251 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22D 11/115 B22D 27/02

Claims (3)

(57) [Claims] 1. A pair of linear motors are arranged opposite to each other on the back surface of a long side mold wall facing each other of a continuous casting mold having a rectangular cross section or above, or above the molten metal molten metal surface in the mold, and they are opposite to each other. In a method of manufacturing a continuously cast slab by swirling and stirring molten metal in a mold by generating a moving magnetic field that travels in a direction, between linear poles with different 180 ° phase differences in a linear motor.
Depending on the relationship between the pitch of the slab and the long side length of the cast slab to be cast, the center position of the vortex of the stirring force is at the end of the slab in the long side direction.
In order to prevent the phase of a pair of linear motors from being changed to either one of the same phase and the opposite phase to change the stirring force distribution, a method for producing a continuously cast slab . 2. A pair having a core and a plurality of current-carrying coils on the back side or above the facing long side mold walls of a continuous casting mold having a rectangular cross section, or above the molten metal level inside the mold. In the electromagnetic stirrer in the continuous casting mold, in which the linear motors of the pair are opposed to each other, and the moving magnetic fields that move in opposite directions are generated, the molten metal in the mold is swirl-stirred. a power supply or change-over switch capable of simultaneously changing 180 degrees the phase of the current supplied to each coil of the linear motor, PAU 180 ° phase difference in the linear motor is different
The center position of the vortex of the stirring force depends on the relationship between the pitch between the ruler and the long side length of the cast piece
An electromagnetic stirrer in a continuous casting mold, characterized in that the phases of a pair of linear motors are configured to be switched to the same phase or opposite phases in order to prevent the positions from substantially matching . 3. The relationship between the long side length (W) of the cast slab and the pole pitch (P) of the linear motor is expressed by the following (1).
The continuous casting according to claim 2, wherein when the expression is satisfied, the pair of linear motors are set to have opposite phases, and when the expression (2) below is satisfied, the pair of linear motors are switched to have the same phase. Electromagnetic stirrer in the mold. (2n-1.5) P ≤ W <(2n-0.5) P (1) (2n-0.5) P ≤ W <(2n + 0.5) P (2) where n is a natural number ( n = 1, 2, 3 ...).