JPH09155515A - Flow controller for molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the seizure of a slab to a casting mold and to prevent the intrusion of inclusions into the slab by stirring and driving the surface on the molten metal in the casting mold by an electromagnet and applying the brake by another electromagnet on the descending flow of the molten metal. SOLUTION: The meniscus of the molten steel MM is covered with powder PW when the molten steel MM is poured via a pouring nozzle into the casting mold from above. The casting mold is cooled by the cooling water flowing in the flow passage therein and the molten steel MM solidifies gradually from the surface in contact with the inside wall 1 of the casting mold to the inside. The slab SB is continuously withdrawn. At this time, electromagnet force is applied on the part right below the meniscus from two pieces of linear motors LMF, LML disposed to face the meniscus of the molten steel MM, by which the molten steel MM is stirred and driven. On the other hand, the part near the lower part of the casting mold is provided with another electromagnet brake 4 with the molten steel MM in-between to apply electromagnet force (braking force) on the descending flow of the molten steel. As a result, the molten steel MM is effectively driven near the meniscus and its descending flow is suppressed and is made uniform.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to stirring and driving a molten metal by an electromagnet arranged facing the upper surface of the molten metal,
Further, the present invention relates to an electromagnetic stirrer having a function of applying a braking force to the downward flow of molten metal by another electromagnet that is disposed below the meniscus with the molten metal interposed therebetween.

[0002]

2. Description of the Related Art In continuous casting, for example, molten steel is poured into a mold from a tundish, and in the mold, the molten steel is drawn out while being gradually cooled from the mold wall surface. If the temperatures on the mold wall surfaces at the same height are not uniform, surface cracks and shell ruptures are likely to occur. In order to improve this, conventionally, molten steel was placed in a mold parallel to its upper surface using a linear motor.
Proposal to drive flow along the mold wall surface (for example, JP-A-1-
No. 228645), or by applying a brake to the molten steel flow flowing into the mold from the pouring nozzle 30, a proposal is made to reduce inclusions contained in the molten steel (for example, Japanese Patent Laid-Open No. Hei 3).
-258442).

Although the flow driving of molten steel disclosed in Japanese Patent Application Laid-Open No. 1-228645 has a certain effect, the circulating flow along the mold wall surface is disturbed by the flow of molten steel flowing into the tundish through the injection nozzle. . For this type of flow driving, a linear motor type electromagnet in which an electric coil is wound around each of a plurality of magnetic poles arranged along the long side of the mold is used. Bundled into
The phase and the phase of the three-phase power supply are connected in units bundled into each phase of the three-phase power supply having a phase shift of 120 °, and the voltage and / or frequency of the three-phase power supply is adjusted by an inverter or a cycloconverter. Speed is obtained.

FIG. 10 (a) shows a vertical sectional view of the mold, and FIG. 10 (b) shows a plane looking down on the upper surface (meniscus) of the molten steel in the mold from above the mold. As shown by a solid arrow in FIG.
The molten steel flows into the mold through 9 and generates a molten steel flow,..., In the direction of the short side of the mold and slightly downward, and this flows on the short side of the mold, partly upward and others downward. The molten steel flow flowing upward generates a surface flow toward the nozzle 30 at the meniscus as shown by a solid line arrow in FIG. This surface flow tends to entrain the powder on the meniscus. On the other hand, when the molten steel changes to a solid, a gas (bubbles) such as CO is generated. In addition, if the molten steel stays in a part of the inner surface of the mold, the powder is likely to remain in the molten steel, and furthermore, it tends to cause seizure which causes breakout. In order to prevent these, it is preferable to form a stable rectification on the surface layer.

Therefore, conventionally, as shown in FIG. 13 (b), the linear motors 3RF and 3RL facing the outer surface of the mold along the long side of the mold are used for the surface flow caused by the surface flow. An electromagnetic driving force in a direction indicated by a dotted arrow in FIG. 10B is applied to the molten steel, and a circulating flow along the mold inner wall 1 as indicated by a two-dot chain line arrow in FIG. Trying to happen. Due to this circulation flow, the floating of bubbles is promoted, powder is not entrained in the molten steel, the inner surface of the mold near the surface layer is wiped cleanly, and the stagnation of the molten steel is eliminated.

On the other hand, in the "electromagnetic brake device" proposed in Japanese Patent Laid-Open No. 3-258442, a pair of electromagnets having a width substantially equal to the width of the long side face each other along the long side of the mold. It is installed and a direct current is applied to its electric coil.
The molten steel flowing in the constant magnetic field (DC magnetic field) generated by the electromagnet generates an electromotive force according to Fleming's right-hand rule, and a current circulating in the magnetic flux flows. The braking force acts to stop the flow, which brakes the downward molten steel flow shown in FIG. 10 (a), and suppresses the sinking of the inclusions accompanying the molten steel flow downward. .

[0007]

By the way, for example, FIG.
As shown in FIG. 3 (a), when one of the molten steel flows flowing out of the two outlets 19 of the pouring nozzle 30 into the space inside the mold becomes strong and the other weakens, that is, when the symmetry collapses, As for the superficial flow, as shown in FIG. 13B, the superficial flow located on the outlet where the molten steel flow is weak (the molten steel flow side) becomes weak.

Such turbulence (uneven flow) of the molten steel flow causes a high temperature portion and a low temperature portion in the molten steel MM in the mold. That is, the temperature is high at a location where the molten steel flow is strong and low at a location where it is weak. If the temperatures on the mold wall surfaces at the same height are not uniform, surface cracks and shell ruptures are likely to occur.

Although the non-uniformity of the temperature can be avoided to some extent by driving the molten steel by the linear motor, the pouring nozzle 3
The outflow characteristic of the outflow port 0 of 0 changes due to the adhesion of steel to the outflow port 19 during pouring, and when this change, especially the difference in the outflow property of the two outflow ports becomes large, a considerable temperature deviation occurs. Further, a part of the molten steel flowing into the mold from the pouring nozzle 30 is directed downward as described above, but inclusions enter the molten steel flow, which flows downward, penetrate deep into the mold, and are trapped inside the slab. It becomes a quality problem.

When the electromagnetic brake device is used alone, the symmetry flowing from the pouring nozzle 30 into the mold,
Alternatively, even if the effect of uniformizing the velocity on the asymmetric molten steel flow is recognized, when the molten steel flow in the mold using a linear motor or the like is used together, the molten steel flow (circulation flow) by the drive device is also braked. I will end up. That is, the electromagnetic blur
G is a force that applies a braking force to the molten steel moving in the applied constant magnetic field.
Not only that, the braking force also acts on the surface flow.

A first object of the present invention is to prevent seizure of a cast piece on a mold and to prevent inclusion of inclusions in the cast piece. The inner surface of the cast piece near the meniscus of molten steel in the cast piece. The second purpose is to effectively drive molten steel along and to suppress and make the downflow uniform, and the third purpose is to rectify and uniformize the surface flow to strongly suppress the downward protruding flow. To do.

[0012]

A molten metal flow control device according to the present invention comprises a plurality of four mold pieces surrounding each of the four sides of a quadrilateral, which are arranged along a first long piece (5F). Slots are distributed, the first set of electromagnet cores (10) facing each other on the upper surface of the molten metal near the first long piece (5F) and the first short piece (6R) and each slot for exciting this. The first set of electromagnets (LM) consisting of a combination of multiple electric coils (1Aa to 2Ca) inserted in the
F); a plurality of slots are distributed along the second long piece (5L) of the mold piece, and are arranged to face the molten metal upper surface near the second long piece (5L) and the second short piece (6L). The second set of electromagnets (L) consisting of a combination of the second set of electromagnet cores (20) and a plurality of electric coils (4Ab to 5Cb) inserted in each slot to excite the same.
ML); The first set of electromagnets (LMF) applies thrust in the direction along the first long piece (5F) to the molten metal upper surface, and the second set of electromagnets (LML) follows the second long piece (5L). Applying AC voltage with a phase difference to give directional thrust to the molten metal upper surface to each of the electric coils (1Aa to 2Ca, 4Ab to 5Cb) of the first and second electromagnets (LMF, LML) To energize at least one pair of magnetic poles (4AF, 4AL) facing each other with a molten metal in between, below the meniscus of the first set of energizing means (20F1, 20L2); Third electromagnet (4), which is a combination of the electric coils (4CF, 4CL), and a third energizing means (20V) for energizing the electric coil with a current for applying a braking force to the molten metal.
D); In addition, in order to facilitate understanding, in parentheses, the symbols of the corresponding elements of the embodiments shown in the drawings and described later,
Added for reference.

According to this, when looking down from above the mold,
There is a pair of electromagnets (LMF, LML) in at least one of two diagonal directions of the square space surrounded by the mold pieces (5F, 6L, 5L, 6R). These pair of electromagnets (LMF, LML) are connected to the injection nozzle (3
Since the thrust (indicated by the dotted arrow in FIG. 2) in the direction opposite to the surface flow of the molten metal that is generated by the protruding flow of (0) is given to the molten metal,
A relatively regular surface layer flow is formed as shown by the solid arrow in FIG. 2, and as a result, a stable circulating flow at a relatively constant speed is obtained as shown by the two-dot chain line arrow in FIG. .
As a result, the floating of the bubbles is promoted, the powder is not caught in the molten metal, the inner surface of the mold near the surface layer is wiped cleanly, the molten metal does not stay, and seizure of the slab on the mold is suppressed. As shown in FIG. 10 (a), the molten metal (MM) is continuously supplied to the mold from the injection nozzle (30), and a part of the molten metal (MM) forms a downward protruding flow. A braking force is applied to the downward protruding flow by the pair of electromagnets (4), and the protruding flow is suppressed. Therefore, entrapment (intrusion) of foreign matter (inclusions) into the inside of the cast piece due to the protruding flow of the molten metal (MM) is suppressed, and the internal quality of the cast piece is improved.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of the present invention is a means for detecting the temperature distribution of a mold short piece (S31 to S3n, S41 to S4n);
The control means (43) further provides an energization command for imparting a high thrust to the molten metal near a location having a high temperature, to the first and second energization means (20F1, 20L2) of the first set. As a result, a high thrust acts on the molten steel having a high temperature, a uniform surface circulation flow is generated, and the stirring effect is high. Therefore, the temperature uniformizing effect is high.

Further, the relative relationship between the downward projecting flow component of the molten steel flow injected into the mold and the mold piece temperature, that is, when the molten steel flow rate from the nozzle is high, a flow that causes a surface layer flow,
An increase in the mold short piece temperature means an increase in the descending downflow component, since the and the downflow are strong, resulting in a high mold short piece temperature and a strong downflow. The temperature distribution detecting means (S31 to S3n, S41 to S4n) detects the short piece of the mold, and the control means (43) issues an energization command for giving a high braking force when the temperature of the short side of the mold is high to the second energizing means ( 20 VD), which causes the third set of electromagnets (4) to exert a high braking force on the downward protruding molten steel flow.

This increase in the braking force strongly damps the descending protruding molten steel flow, suppresses the inclusion (intrusion) of foreign matter (inclusions) inside the slab, and improves the internal quality of the slab.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0018]

FIG. 1 shows a linear motor L according to an embodiment of the present invention.
1 shows a longitudinal section of a continuous casting mold equipped with MF (first set of electromagnets), LML (second set of electromagnets) and electromagnetic brake 4 (third set of electromagnets). Molten steel is injected into the mold from an injection nozzle 30 (not shown) from the upper side to the lower side (vertical direction z), and the meniscus (surface) of the molten steel MM is covered with the powder PW. The mold is cooled by a water box (not shown) and cooling water flowing through a water flow path in the mold, and the molten steel MM gradually solidifies from the surface in contact with the mold, and the slab SB is continuously drawn out. As it is poured, there is always molten steel MM in the mold. Two linear motors LM facing the meniscus above the molten steel MM.
F and LML are provided, and these apply electromagnetic force to the portion (surface layer area) immediately below the meniscus of the molten steel MM. An electromagnetic brake 4 is provided near the lower part of the mold to apply an electromagnetic force (braking force) to the molten steel descending flow. In the mold, the magnetic flux given to the molten steel by the linear motors LMF and LML does not substantially reach the molten steel at the level of the electromagnetic brake 4,
On the contrary, the magnetic flux given to the molten steel by the electromagnetic brake 4 does not substantially reach the surface region of the molten steel.

FIG. 2 shows the plane (upper surface) of the mold shown in FIG. The illustration of the electromagnetic brake 4 is omitted. In FIG. 2, 5F and 5L are the first and second long pieces of the continuous casting mold, 6R and 6L are the first and second short pieces, and the molten steel is passed through the injection nozzle 30 into the space surrounded by them.
Injection is performed from the front side to the back side of the paper (from the upper side to the lower side in the vertical direction z). Each piece (5F, 5L, 6R, 6L)
Is a copper plate (1F, 1L, 3R, 3L) backed with a non-magnetic stainless steel plate (2F, 2L, 4R, 4L). In this embodiment, in order to drive the molten steel in the portion immediately below the meniscus (surface layer area) in the mold from right to left (in the + y to -y direction) along the long piece 5L with the three-phase linear motor type electromagnet. In addition, the first and second electromagnets LMF and LML are arranged on the opposite line with the injection nozzle 30 as the center so as to face the upper surface of the molten steel in the molds (5F, 5L, 6R, 6L).

FIG. 4 shows an enlarged cross section taken along line II-II of FIG. 1, that is, a cross section in which the electromagnetic brake 4 is horizontally broken. The electromagnetic brake 4 applies an electromagnetic force to the molten steel passing below the mold, and applies a braking force to the molten steel downward projecting flow. The electromagnetic brake 4 is arranged in the lower part of the mold so as to horizontally sandwich the mold. Referring to FIG. 4, the electromagnet of the electromagnetic brake 4 has a width substantially equal to the width of the long mold pieces 5F and 5L. The magnetic poles 4AF, 4AL are provided so as to face each other with the mold long pieces 5F, 5L interposed therebetween, and the coils 4CF, 4 are provided on the outer circumference of the magnetic poles.
CL is wound. In addition, left and right yokes 4BL, 4BR
The left and right magnetic poles are connected to form a closed magnetic path. Therefore, the electromagnetic brake 4 applies a magnetic field in the horizontal direction (x-axis direction in FIG. 4) between the magnetic poles 4AF and 4AL, and the molten steel MM descends in this horizontal magnetic field (z-axis direction). Since the molten steel, which is a conductor, crosses the horizontal magnetic field, a braking force for stopping the movement is applied to the molten steel.

FIG. 3A shows a first set of electromagnets LMF.
2 shows an enlarged vertical section (enlarged section 2A-2A in FIG. 2).
In this embodiment, the electromagnet core 10 has six slots, and each of the slots has an electric coil 1Aa to 2Ca.
Is inserted. Although the electromagnet core 10 and the electric coils 1Aa to 2Ca are cooled and covered with a heat-resistant cover, the cooling structure and the cover are not shown. The electromagnet core 10 has a comb shape having slots on the lower surface, an electric coil is inserted into each slot, and a magnetic pole is provided between the slots, and a lower end surface of the electromagnet core 10 has a continuous casting mold (5F, 5L,
6R, 6L) facing the upper surface of the molten steel. The electric coil is wound around the core 10. FIG. 3 (b)
And an enlarged vertical section of the second electromagnet LML (2B-2B in FIG. 2).
A line enlarged cross section) is shown. The second electromagnet LMF is also the first electromagnet L
It has the same structure as the ML, and its electric coil is also a body winding.

The linear motors LMF and LML are for applying a thrust indicated by dotted arrows in FIG. 2 to the molten steel MM. In this embodiment, the first linear motor LMF and the second linear motor LML To generate different thrusts,
A different level of current is applied to each linear motor. This content will be described later.

FIG. 5A shows electric coils 1Aa to 2Ca and 4Ab of the linear motors LMF and LML shown in FIG.
5 to 5 Cb are shown for connection and connection with the power supply circuit, and FIG. 5B shows connection for electric coil connection of the electromagnetic brake 4 and connection with the power supply circuit. The wiring of the linear motors LMF and LML shown in FIG. 5 (a) has two poles (N = 2), and three-phase alternating current (M = 3) is applied to the electric coil.
For example, the electric coils 1Aa to 2Ca are u, u, V, V, w, w, U, U, v, in this order in FIG.
It is represented as v, W, W. “U” represents the U-phase normal-phase energization of three-phase alternating current (current energization as it is), “u” represents the U-phase reverse-phase energization (energization 180 degrees out of phase with the U-phase), and the electric coil “U” ] Is applied with a U phase at the beginning of the winding, whereas the electric coil "u" is applied with a U phase at the end of the winding.
It means that a phase is applied. Similarly, “V” indicates V-phase positive-phase energization of three-phase AC, “v” indicates V-phase negative-phase energization,
“W” indicates the W-phase positive-phase energization of the three-phase AC, and “w” indicates the W-phase reverse-phase energization. Terminals U11 and V shown in FIG.
11 and W11 are power supply connection terminals of the electric coils 1Aa to 2Ca of the first linear motor LMF, and are terminals U1.
2, V12 and W12 are power supply connection terminals of the electric coils 4Ab to 5Cb of the second linear motor LML.

FIG. 5B shows the electric coil connection of the electromagnetic brake 4 and the magnetic poles formed thereby. Direct current is supplied to the electric coils 4CF and 4CL from a direct current power source 20VD, and a magnetic field in a certain direction is applied to the molten steel in the mold, but as can be seen from the arrangement structure of the electromagnetic brake 4, a direction orthogonal to the long side of the mold. A uniform horizontal magnetic field is applied to (x).

FIG. 6 shows the configuration of the first power supply circuit 20F1 of the first set in which the three-phase alternating current is passed through the electric coils 1Aa to 2Ca of the first linear motor LMF. The three-phase AC power supply (three-phase power line) 21 has a thyristor bridge 22A1 for DC rectification.
Is connected, and its output (pulsating flow) is
It is smoothed by A1 and the capacitor 26A1. The smoothed DC voltage is applied to the power transistor bridge 27A1 for forming a three-phase AC, and the U-phase of the three-phase AC output from the power-transistor bridge 27A1 is supplied to the power supply connection terminal U11 shown in FIG.
Phase is power supply connection terminal V11 and W phase is power supply connection terminal W
11 is applied.

The electric coil 1A of the first linear motor LMF
a to 2Ca, a coil voltage command value VdcA1 for generating a thrust indicated by a dotted arrow in FIG. 2 is given to a phase angle α calculator 24A1, and the phase angle α calculator 24A1 outputs a conduction phase angle α corresponding to the command value VdcA1. (Thyristor trigger-phase angle) is calculated, and a signal representing this is supplied to the gate driver 23A1. The gate driver 23A1 starts the phase count of the thyristor of each phase from the zero cross point of each phase and triggers conduction at the phase angle α. As a result, the DC voltage indicated by the command value VdcA1 is applied to the transistor bridge 27A1. On the other hand, the three-phase signal generator 31A1 outputs the frequency specified by the frequency command value Fdc (50 in this embodiment).
Hz), and generates a constant-voltage three-phase AC signal,
Give to A1. A triangular wave generator 30A1 supplies a constant voltage triangular wave of 3 KHz to the comparator 29A1. When the U-phase signal is at a positive level, the comparator 29A1 is at a high level H (transistor on) when the level is equal to or higher than the level of the triangular wave provided by the triangular wave generator 30A1, and at a low level L (transistor off) when the level is lower than the level of the triangular wave. Signal of U
To the positive section of the phase (to the U-phase positive voltage output transistor)
When the U-phase signal is at a negative level, a high-level signal is output when the U-phase signal is below the level of the triangular wave provided by the triangular-wave generator 30A1, and when the U-phase signal exceeds the level of the triangular wave, a low-level signal is output. , To the U-phase negative section (to the U-phase negative voltage output transistor). The same applies to the V-phase signal and the W-phase signal. The gate driver 28A1 energizes each transistor of the transistor bridge 27A1 in response to the signals addressed to each phase, positive and negative sections.

As a result, the power supply connection terminal U11 has three terminals.
A U-phase voltage of phase alternating current is output, a similar V-phase voltage is output to the power supply connection terminal V11, and a similar W-phase voltage is output to the power supply connection terminal W11. The inter-curve level is determined by the coil voltage command value VdcA1.
The frequency of the three-phase voltage is the frequency command value F in this embodiment.
It is 50 Hz by dc. That is, the peak voltage value (thrust) specified by the coil voltage command value VdcA1 is 50 Hz.
The three-phase AC voltage of the first is shown in (a) of FIG. 3 and FIG.
It is applied to the electric coils 1Aa to 2Ca of the linear motor LMF.

FIG. 7 shows the electric coil 4 of the second linear motor.
The structure of the 1st set 1st power supply circuit 20L2 which flows three-phase alternating current to Ab-5Cb is shown. The configuration of the power supply circuit 20L2 is the same as that of the above-described 20F1, but the coil voltage command value (VdcB2) is different.

That is, the coil voltage command value VdcB2 at which the electric coils 4Ab to 5Cb of the second linear motor LML generate the thrust indicated by the dotted arrow in FIG.
4B2. These coil voltage command values Vdc
As for A1 (FIG. 6) and the coil voltage command value VdcB2 (FIG. 7), the computer 43 shown in FIG.
Feed on 0F1 and 20L2.

FIG. 8 shows an electric coil 4C of the electromagnetic brake 4.
The structure of the 2nd set power supply circuit 20VD which sends a direct current to F and 4CL is shown. A thyristor bridge 22D1 for DC rectification is connected to the three-phase AC power supply (three-phase power line) 21,
The output (pulsating flow) is smoothed by the inductor 25D1 and the capacitor 26D1. The smoothed DC voltage is applied to the terminals 4P and 4M of the electromagnetic brake shown in FIG.

Electric coils 4CF, 4C of the electromagnetic brake 4
A coil voltage command value VdcD3 for generating a braking force that suppresses the molten steel descending flow is given to the phase angle α calculator 24D1, and the phase angle α calculator 24D1 determines the conduction phase angle corresponding to the command value VdcD3. α (thyristor trigger-phase angle) is calculated, and a signal representing this is given to the gate driver 23D1. The gate driver 23D1 starts phase counting of the thyristor of each phase from the zero-cross point of each phase and triggers conduction at the phase angle α. As a result, the power supply circuit 20
The DC voltage indicated by the command value VdcD3 is output to the terminal VD of VD. This coil voltage command value VdcD3 is given from the computer 43 shown in FIG. FIG. 9 shows the back part of the mold short pieces 6L and 6R shown in FIG. These short pieces 6L and 6R have thermocouples S31 to S3n and S41.
S4n are arranged at equal intervals in each row in the slab drawing direction (height direction; vertical direction), and each thermocouple penetrates the backing stainless steel plate and is slightly inside (surface in contact with molten steel). Temperature). That is, the signal processing circuits 41A and 41B generate an analog signal (detection signal) representing the temperature detected by the thermocouple and apply it to the analog gate 42.

The computer 43 is an analog gate 42.
Of the thermocouples S31 to S3n and S41 by controlling the output of
~ S4n detection signals are sequentially A / D converted and read, the high temperature value extraction processing 44 extracts the maximum temperature value Tm1L1 and the next highest temperature value Tm2L1 among the detection temperatures of the thermocouples S31 to S3n, and , The maximum temperature value Tm1R1 and the next highest temperature value Tm2R1 among the detected temperatures of the thermocouples S41 to S4n are extracted. Then, the representative temperature (Tm1L1-Tm2L1) * 0.7 + Tm2L1 of the short piece 6L is calculated, and the representative temperature (Tm1R1-Tm2R1) * 0.7 + Tm2R1 of the short piece 6R is calculated.

For controlling the flow velocity of the molten steel surface flow, the difference between the two, that is, the representative temperature difference between the short pieces 6R and 6L (Tm1R1-Tm2R1) × 0.7 + Tm2R1 -− (Tm1L1-Tm2L1) × 0.7-Tm2
L1 is calculated to calculate VdcA1 = (representative temperature difference × A) + B (A and B are coefficients), and VdcB2 = − (representative temperature difference × A) + B. When the representative temperature difference is a negative value (the temperature of the short piece 6L is higher), VdcA1 =
− (Absolute value of representative temperature difference × A) + B is calculated, and Vdc
B2 = (absolute value of representative temperature difference × A) + B.

VdcA1 is the electric coil 1A on the short piece 6R side.
a to 2Ca (first linear motor LMF; FIG. 2) are current level (thrust) command values, and VdcB2 is a short piece 6L.
Side electric coils 4Ab to 5Cb (second linear motor LM
L; a current level (thrust) command value for FIG. 2).
These command values have a positive representative temperature difference ((a) in FIG. 13).
When the temperature of the short piece 6R is higher due to the unbalanced flow as shown in (1), the electric coil 1 of the first linear motor LMF
The three-phase AC current level to be applied to the electric coils 4Ab to 5Cb of the second linear motor LML is increased by increasing the three-phase AC current level to be applied to Aa to 2Ca and applying a strong thrust (dotted arrow in (b) of FIG. 11). If the representative temperature difference is a negative value (the temperature of the short piece 6L is higher), the thrust is weakened to reduce the thrust, and conversely, the three-phase AC current level flowing through the electric coils 4Ab to 5Cb of the second linear motor LML is increased. It means that a strong thrust (a dotted arrow in (c) of FIG. 11) is applied to reduce the three-phase AC current level flowing in the electric coils 1Aa to 2Ca of the first linear motor LMF to weaken the thrust.

In order to control the flow velocity of the molten steel downward flow, the sum of the two, that is, the representative temperature sum of the short sides 6L and 6R (Tm1L1-Tm2L1) × 0.7 + Tm2L1 + (Tm1R1-Tm2R1) × 0.7 + Tm2
R1 is calculated to calculate VdcD3 = sum of representative temperatures × C (C
Is a coefficient). If VdcD3 is large, that is, if either or both of the short piece temperatures are high, it means that the flow rate of the molten steel descending flow (protruding flow) is high, and the time required for floating inclusions becomes insufficient. Therefore, the level of the direct current flowing through the electric coils 4CF and 4CR of the electromagnetic brake 4 is increased to strengthen the braking force applied to the downflow, and the downflow speed of the downflow is limited (the downflow is made uniform). Promote surfacing. Note that the braking force applied to the molten steel becomes higher as the molten steel flow velocity becomes higher.Therefore, the higher the downward flow of the molten steel, the stronger the braking force is exerted, and the speed decrease is large, and the downward flow velocity becomes uniform, and the DC current level is increased. By doing so, the homogenization and the suppression of the flow velocity act strongly.

From the above, for example, when the protruding flow shown in FIG. 10A is substantially symmetrical with respect to the nozzle 30, the temperatures of the short pieces 6R and 6L become substantially the same, and the superficial flow is shown in FIG. 10B. 2 and the solid line arrow in FIG. 2, the nozzles 30 are symmetrical with respect to each other, and in this case, VdcA1 = VdcB2, and the electric coils 1Aa to 2Ca on the short piece 6R side and the electric coil 4Ab on the short piece 6L side.
The energization levels of up to 5 Cb are substantially equal, and the first linear mode
The motor LMF and the second linear motor LML are shown in FIGS.
As indicated by the dotted arrow in (b) of Fig. 3, the thrust is applied to the molten steel with substantially the same strength and in the opposite directions. As a result, the actual superficial flow of molten steel becomes the difference indicated by the two-dot chain line in FIG.
A circulating flow having a uniform flow velocity distribution indicated by a chain double-dashed line in FIG. Thereby, the floating of bubbles is promoted, the powder is not entrained in the molten steel, the inner surface of the mold near the surface layer is wiped clean, and the stagnation of the molten steel is eliminated.
That is, the temperature distribution of the molten steel is made uniform, and seizure of the molten steel is suppressed.

As shown in FIG. 13 (a), when the protruding flow toward the short piece 6R is strong and the protruding flow toward the short piece 6L is weak, the temperature of the short piece 6R rises and the temperature of the short piece 6L decreases, and the surface layer flow 13B, the superficial flow between the nozzle 30 and the short piece 6R is strong and the superficial flow between the nozzle 30 and the short piece 6L is weak, as indicated by the solid arrow in FIG. 13B. In this case, VdcA1> VdcB2 Then, the energization level of the electric coils 1Aa to 2Ca on the short piece 6R side is high, the energization level of the electric coils 4Ab to 5Cb on the short piece 6L side is low, and the first linear motor LMF outputs a strong thrust to the second linear motor. LML gives a weak thrust to molten steel. As a result, FIG.
As indicated by a dotted arrow in (b) of FIG.
The MF gives a strong thrust to the molten steel and the second linear motor LML gives a weak thrust to the molten steel.

As a result, the circulating flow shown by the chain double-dashed line in FIG. In this case, the circulation flow is high speed on the high temperature short piece 6R side and low on the low temperature short piece 6L side, but does not generate a vortex because it is a circulation flow that draws a loop. The high temperature molten steel on the short piece 6R side is conveyed to the low temperature short piece 6L side to reduce the temperature difference. Due to this circulation flow, the floating of bubbles is promoted, powder is not entrained in the molten steel, the inner surface of the mold near the surface layer is wiped cleanly, and the stagnation of the molten steel is eliminated.
That is, the temperature distribution of the molten steel is made uniform, and seizure of the molten steel is suppressed.

On the contrary, when the projecting flow toward the short piece 6R is weak and the projecting flow toward the short piece 6L is strong, the temperature of the short piece 6R decreases and the temperature of the short piece 6L rises, and the surface layer flow between the nozzle 30 and the short piece 6R. The surface flow is weak and the surface flow between the nozzle 30 and the short piece 6L is strong, and in this case, VdcA1 <Vdc
It becomes B2, and the electric coils 1Aa to 2Ca on the short piece 6R side
The energization level is low, and the electric coil 4Ab on the short piece 6L side
The energization level of 5 Cb becomes high, and the first linear motor LM
F gives a weak thrust to the molten steel, and the second linear motor LML gives a strong thrust to the molten steel. As a result, the first linear motor LMF exerts a weak thrust, as indicated by a dotted arrow in (c) of FIG.
The second linear motor LML gives a strong thrust to the molten steel.

As a result, the circulating flow shown by the chain double-dashed line in FIG. In this case, the circulating flow is low speed on the low temperature short piece 6R side and high speed on the high temperature short piece 6L side, but it does not generate a vortex because it is a circulating flow drawing a loop. The high temperature molten steel on the short piece 6L side is conveyed to the low temperature short piece 6R side to reduce the temperature difference. Due to this circulation flow, the floating of bubbles is promoted, powder is not entrained in the molten steel, the inner surface of the mold near the surface layer is wiped cleanly, and the stagnation of the molten steel is eliminated.
That is, the temperature distribution of the molten steel is made uniform, and seizure of the molten steel is suppressed.

Further, when the molten steel flows downward from the outlet 19 shown in FIG. 10 (a) are both strong, the temperature of both short pieces of the mold becomes higher, and the sum of the representative temperatures detected by both short pieces rises. Therefore, the voltage command value VdcD3 to the power supply circuit 20VD increases, and the DC voltage applied to the electromagnetic brake 4 increases. As a result, the braking force of the electromagnetic brake 4 with respect to the molten steel descending flow in the mold increases, and the molten steel descending speed decreases. When the molten steel flow directed downward from the outlet 19 shown in (a) of FIG. 13 is stronger than the molten steel flow, the temperature of the mold short piece 6R becomes higher and the sum of the representative temperatures detected by both short pieces rises. The voltage command value VdcD3 to the circuit 20VD increases, and the DC voltage applied to the electromagnetic brake 4 increases. As a result, the braking force of the electromagnetic brake 4 with respect to the molten steel descending flow in the mold increases, and the molten steel descending speed decreases. When the molten steel flow is stronger than the molten steel flow, the temperature of the mold short piece 6L becomes higher, and the sum of the representative temperatures detected by both short pieces rises, so that the voltage command value VdcD3 to the power supply circuit 20VD rises, and the electromagnetic blur. The DC voltage applied to key 4 becomes high. As a result, the braking force of the electromagnetic brake 4 with respect to the molten steel descending flow in the mold increases, and the molten steel descending speed decreases. That is, it is possible to prevent a downward flow that protrudes, secure the time required for the inclusions to float on the meniscus, and manufacture a product with improved internal quality.

In the above-described embodiment, the temperatures of the short pieces 6R and 6L are detected by the thermocouple, and the strengths (flow velocities) of the superficial flow and the downward flow are determined according to the strength of the protruding flow from the injection nozzle 30 into the mold. The first linear motor LMF, the second linear motor LML, and the electromagnetic brake 4 are applied to the molten steel to detect and apply an electromagnetic thrust to generate a stable circulating flow or downward flow. However, for example, with the flow velocity sensor,
Surface flow Vsa at the position of spa and surface flow Vs at the position of Vspb
b, or the descending speed Vva of the Vvsa position in FIG.
Alternatively, the descending speed Vvb of the Vvsb position may be detected to control the current level indication values VdcA1, VdcB2 and VdcD3, respectively.

In the above-described embodiment, a pair of linear motors LMF and LML are used, but in the second embodiment of the present invention, two pairs are used, as shown in FIG. You may arrange. In this case, the first pair of linear motors LMF
1 and LML1 control the energization level similarly to the LMF and LML of the above-mentioned embodiment, but the second pair of linear motors LM.
As indicated by the dotted arrow in FIG. 12B, F2 and LML2 have thrust directions opposite to those of the first pair, and the increase and decrease of the energization level with respect to the detected temperature are the same as those of the first pair. However, since the thrust direction is the same as the direction of the surface layer flow generated by the nozzle injection flow, the thrust value (energization level) is set smaller than that of the first pair. According to the second embodiment, the surface circulation flow (see FIG. 1) is generated by the thrust of the linear motor.
The flow velocity of 0 (b) of the two-dot chain line) can be made stronger than in the case of the first embodiment.

Therefore, it is possible to realize further uniformization of the molten steel temperature in the surface layer region. As the flow velocity in the surface layer region is increased, the descending flow is partially strengthened, so that the energization level of the electromagnetic brake 4 is also increased.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view showing a cross section of a continuous casting mold to be controlled according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of a mold and a linear motor portion of FIG.

FIG. 3 (a) shows a linear motor LMF 2 shown in FIG.
FIG. 3 is an enlarged cross-sectional view taken along line A-2A, and FIG. 2 (b) is an enlarged cross-sectional view taken along line 2B-2B of the linear motor LML shown in FIG.

FIG. 4 is an enlarged cross-sectional view of the electromagnetic brake 4 shown in FIG. 1 which is horizontally broken.

FIG. 5 is an electric circuit diagram showing connection of the electric coils shown in FIGS. 2 and 3.

6 is an electric circuit diagram showing a first power supply circuit of a first set for applying a three-phase AC voltage to an electric coil of the linear motor LMF of the first set shown in FIG.

7 is an electric circuit diagram showing a first set of second power supply circuits for applying a three-phase alternating current to the electric coils of the second set of linear motors LML shown in FIG.

8 is an electric circuit diagram showing a second set of power supply circuits for applying a DC voltage to the electric coil of the electromagnetic brake 4 shown in FIG.

9 is a block diagram showing the backs of the short pieces 6L and 6R of the casting mold shown in FIG. 2, the electric circuits connected to the thermocouples provided therein, and the output of the computer 43. FIG.

10A is a cross-sectional view of molten steel in a mold, and FIG. 10B is a plan view showing a superficial flow in a meniscus of molten steel in a mold.

FIG. 11A is a plan view showing the upper surface of the molten steel in the mold;
(B) And (c) is a plan view showing a surface layer flow (dotted line arrow) induced in the molten steel in the mold by the linear motors LMF and LML.

FIG. 12 (a) is a plan view showing a superficial flow generated by pouring molten steel from a pouring nozzle in a meniscus of molten steel in a mold, and FIG. 12 (b) is a superficial flow to be generated in a second embodiment of the present invention. Is a plan view showing with a dotted arrow, (c) is a plan view showing with a solid arrow the Bertre sum of the surface flow generated by the molten steel injection from the pouring nozzle and the surface flow generated by the thrust of the linear motor of the second embodiment. is there.

13A is a cross-sectional view of molten steel in a mold, and FIG. 13B is a plan view showing a superficial flow (by molten steel injection) in a meniscus of molten steel in a mold and an arrangement of a conventional linear motor.

[Explanation of symbols]

1: Inner wall of mold 4: Electromagnetic brake 10: First linear motor core 20: Second linear motor core 19: Outflow port 30: Injection nozzle 43: Computer 1Aa to 2Ca: First linear motor Electric coil 4Ab-5Cb: second linear motor electric coil 1F, 1L, 3L, 3R: copper plate 2F, 2L, 4L, 4R: non-magnetic stainless steel plate 4AF, 4AL: electromagnetic brake core 4BF, 4BL : Electromagnetic brake yoke 4CF, 4CL: Electromagnetic brake coil 5F, 5L: Long piece 6R, 6L: Short piece 20F1, 20L2, 20VD: Power supply circuit 3RF, 3RL, LMF, LML: Linear motor MM : Molten steel PW: Powder SB: Slab S31 to S3n, S41 to S4n:
Thermocouple U11, V11, W11 / U12, V12, W12,4P, 4M: Power supply connection terminal

Claims (5)

[Claims] 1. A plurality of slots, each of which has four sides of a quadrangle and surrounds a molten metal, has a plurality of slots distributed along a first long piece and is provided near a first long piece and a first short piece. A first set of electromagnets, which is a combination of a first set of electromagnet cores arranged opposite to the upper surface of the molten metal and a plurality of electric coils inserted in each slot to excite the same; a second length of the mold piece. A plurality of slots are distributed along the strip, and a second set of electromagnet cores are disposed opposite to the upper surface of the molten metal near the second long piece and the second short piece, and inserted into each slot to excite the same. A second set of electromagnets composed of a combination of a plurality of electric coils; the first set of electromagnets applies thrust to the molten metal upper surface in a direction along the first long piece, and the second set of electromagnets follows the second long piece. AC voltage with a phase difference for giving a thrust in the direction to the molten metal upper surface A first set of energizing means for applying to each of the electric coils of the electromagnet; and at least one pair of magnetic poles facing each other with a molten metal in between and under the meniscus of the mold piece, and electricity for exciting this. A molten metal flow control device comprising: a third set of electromagnets, which is a combination of coils; and a second set of energizing means for passing a current to apply a braking force to the molten metal to the electric coils. 2. A plurality of slots, each of which is a four-sided quadrilateral that surrounds the molten metal and has a plurality of slots distributed along the first long piece, near the first long piece and the first short piece. A first electromagnet consisting of a combination of a first electromagnet core arranged facing the upper surface of the molten metal and a plurality of electric coils inserted in each slot to excite the same; a direction in which the first electromagnet core extends along the first long piece For applying an AC voltage having a phase difference for applying the thrust of the above to the upper surface of the molten metal to each of the electric coils of the first electromagnet
Energizing means: A second electromagnet core in which a plurality of slots are distributed along the second long piece of the mold piece, and the second electromagnet core is arranged to face the upper surface of the molten metal near the second long piece and the second short piece, and this is excited. A second electromagnet composed of a combination of a plurality of electric coils inserted in each slot in order to achieve the following; AC having a phase difference for giving a thrust in the direction along the second elongated piece to the upper surface of the molten metal by the second electromagnet core A second energizing means for applying a voltage to each of the electric coils of the second electromagnet; and at least a pair of magnetic poles facing each other with a molten metal in between and under the meniscus of the mold piece, A flow control device for molten metal, comprising: a third electromagnet, which is a combination of electric coils for use in the above, and a third energizing means for supplying a current for applying a braking force to the molten metal to the electric coil. 3. A molten metal flow immediately below the first and second electromagnet cores of the molten metal surrounded by the mold pieces, caused by the injection of new molten metal from the injection nozzle into the molten metal surrounded by the mold pieces. A means for measuring strength; and a current level of the electric coil of the first electromagnet via the first and second energizing means when the molten metal flow directly below the first electromagnet core is stronger than that directly below the second electromagnet core. Raising the current level of the electric coil of the second electromagnet, and vice versa, lowering the current level of the electric coil of the first electromagnet, raising the current level of the electric coil of the second electromagnet, and the first and / or second electromagnet core The molten metal flow control device according to claim 2, further comprising thrust control means for increasing the current level of the electric coil of the third electromagnet via the third energizing means when the molten metal flow immediately below is strong. 4. The measuring means is a temperature sensor for detecting the temperature of the first and second short pieces; the thrust control means is for the electric coil of the first electromagnet when the first short piece is hotter than the second short piece. Increasing the current level and decreasing the current level of the electric coil of the second electromagnet, and vice versa, decreasing the current level of the electric coil of the first electromagnet and increasing the current level of the electric coil of the second electromagnet, and the first and / or The molten metal flow control device according to claim 3, wherein the current level of the electric coil of the third electromagnet is increased when the two short pieces are at a high temperature, and the current level of the electric coil of the third electromagnet is decreased when the two short pieces are at a high temperature; 5. The temperature sensor for each short piece includes a plurality of temperature detecting elements distributed in the casting strip drawing direction; the thrust control means extracts the one having a high temperature detected by the thrust control means, and extracts it from each of the short pieces. The molten metal flow control device according to claim 4, which has a representative temperature.