JPH11226705A - Device for controlling fluidity of molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of large vibration of molten metal surface and to stabilize the molten metal level by arranging an electric coil energizing means for energizing AC current for giving an electromagnetic force having specific frequency to the electric coil at the outside of a mold. SOLUTION: Molten steel MM is poured into the mold MD through a pouring nozzle 30 and a meniscus of the molten steel MM is covered with powder PW and an electromagnetic brake 4 is arranged at the upper part of the mold MD and electromagnetic control force is applied to the molten steel descending flow, and linear motors 3F, 3L are arranged along the outside of the long sides 11F of the mold at the lower part of the electromagnetic brake 4. In this electromagnetic brake 4, the electric coil energizing means with which the AC current having phase difference for producing the electromagnetic force of the frequency having >=F expressed by F=1/[2π(λ/2)/g]<1/2> . (λ is the width of the mold MD and (g) is the gravitational acceleration) is applied to the molten steel MM along the mold MD, is provided. In this way, the electromagnetic thrust is applied to the molten steel MM so as to become swirling flow circulated on the parallel surface to the horizontal surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten metal having a function of agitating and driving a molten metal by an electric coil disposed on a side of a mold surrounding the molten metal and further applying a braking magnetic field to a downward flow of the molten metal by a braking means. To a flow control device.

[0002]

2. Description of the Related Art In continuous casting, for example, molten steel is poured into a mold from a tundish, and the molten steel is drawn from the mold wall while being gradually cooled. 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, a proposal has been made to use a linear motor to drive molten steel in a mold in parallel with the upper surface thereof along the mold wall surface and to perform electromagnetic stirring (for example, Japanese Patent Application Laid-Open No. 1-228645). Or pouring nozzle 3
There is a proposal (for example, JP-A-5-177317) for reducing inclusions contained in molten steel by applying braking to the molten steel descending flow flowing into the mold from zero.

FIG. 10 (a) is a vertical sectional view of a mold, and FIG. 10 (b) is a plan view of the upper surface (meniscus) of 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. 9, linear motors 3F and 3L facing the outer surface of the mold are provided along the long side of the mold with respect to the surface flow caused by the surface flow. An electromagnetic driving force in the direction indicated by the dotted arrow is applied to the molten steel in (b), and a circulating flow along the inner wall of the mold as shown by the two-dot chain arrow in FIG. . 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. -Way,
In the method proposed in Japanese Patent Application Laid-Open No. 5-177317, an electromagnetic stirrer is disposed near the meniscus along the long side of the mold, and the width of the long side of the mold near the bottom of the mold along the long side of the mold. A pair of electromagnets of equal width are installed facing each other, and a direct current is passed through the 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. .

[0005]

When an electromagnetic stirrer (linear motor) is arranged above one mold, that is, near the meniscus, and an electromagnetic brake (electromagnetic brake) is arranged below the mold. In some cases, the two electromagnetic forces interact with the molten steel, causing the molten metal surface to vibrate unstable. For example, FIG. 8A shows an enlarged vertical cross section of a mold in which a linear motor is arranged at the upper part and an electromagnetic brake is arranged at the lower part. The magnetic flux density KM applied by the linear motor of the mold to the molten steel in the mold and the magnetic flux density BM applied by the electromagnetic brake to the molten steel in the mold indicate a region where the magnetic flux density KM and the magnetic flux density BM cause mutual interference with the electromagnetic fluid. FIG. 8A shows a two-dot chain line circle. As shown in FIG. 8 (b), this electromagnetic fluid mutual interference is as follows: When the linear motor is operated only, no unstable vibration of the molten metal surface is generated. When the electromagnetic brake is operated only. Unstable vibration of the molten metal surface does not occur.-Unstable vibration of the molten metal surface occurs only when the linear motor and the electromagnetic brake are operated and the operating frequency of the linear motor is set to a certain value. understood.

(1) Electromagnetic force Fd generated by linear motor
Is: Fd = F0 + Fac · sin (2ωt + φd) (1) where F0 is a DC component, and Fac is an AC component at twice the frequency of the current flowing through the linear motor, and usually only the F0 component Consider,
Fac ignores it.

(2) Electromagnetic force Fb generated by electromagnetic brake
Fb = Fp (BDC, u) (2) where Fp (BDC, u): DC component, BDC: DC magnetic flux density, and u: flow velocity. The electromagnetic force Fb is a function of the DC magnetic flux density BDC and the flow velocity u, and was derived from the Poisson equation.

(3) When the electromagnetic force generated by the linear motor and the electromagnetic brake is in the same space, the following electromagnetic force F is generated.

F = F 0 + Fac · sin (2ωt + φd) + Fp (BDC, u) + Fm · sin (ωt + φm) (3) where Fm is newly generated by the interaction between the linear motor and the electromagnetic brake. Electromagnetic force.

The frequency of Fm is ωt as shown in equation (3), which is the same as the frequency of the current flowing through the linear motor. Fm becomes zero when a time average value of one cycle is taken, and is usually ignored.

(4) Fm is given by: Fm = JK * Bb = JK0 · sin (ωt + φm) * Bb (4), and when the magnetic field of the linear motor and the electromagnetic brake is present in the same space, It can be seen that an electromagnetic force having a frequency component of the current supplied to the linear motor is generated.

The distance a (inter-surface distance) between opposing long sides of the mold is determined by the vibration of the molten metal in a direction perpendicular to the long sides at a specific frequency (typically, waves on the surface of molten steel). On the other hand, there is a correlation. For example, the period of vibration T = 1 / F
Is equal to twice the time a / v during which the vibration propagates during the interval a (that is, T = 2a / v), the vibration reflected on the long side overlaps the original vibration, and the amplification of the vibration is performed. Resonance occurs. v is the propagation speed of the vibration along the molten metal surface. The frequency F at this time is called a resonance frequency.

FIG. 4 schematically shows a mold and its resonance waveform. The curve shown in FIG. 4 shows the level of the molten metal surface in the mold. When vibration is applied to the mold in a state where the mold is filled with molten steel, for example, paying attention to the ripples in the short side direction of the molten steel mold,
When the wavelength WL of the vibration is twice the interval a, the amplitude of the wave is maximized due to resonance, and the wave shown in FIG.
After T / 4, the state shown in FIG.
Later, the state shown in (c) is reached, and after T / 4, (d)
, And after T / 4, the state shown in FIG. That is, the surface of the molten metal is largely wavy.
T is the period of the vibration, and if the frequency of the vibration is F, T
= 1 / F.

That is, in a mold in which the linear motor and the electromagnetic brake are simultaneously operated, if the frequency f of the exciting AC current of the linear motor matches the resonance frequency, the mold in the mold due to the above-described effect of Fm. Vibration of the molten metal causes resonance in the short side direction (the direction orthogonal to the long piece), causing large ripples (fluctuations in the molten metal level) in the molten steel (FIG. 4).

The resonance frequency also exists in the direction of the long side of the mold, but since the resonance frequency is lower than the length of the long side, the excitation frequency is substantially outside the range of the excitation frequency used in the linear motor. Actually, the ripple in the short side direction also affects the long side direction.

FIGS. 14 and 15 show an example of a change in the molten metal surface shape when a mold having both a linear motor and an electromagnetic brake is operated simultaneously. The vertical axis indicates the swelling height of the molten steel on the inner wall of the long side of the mold, and the horizontal axis indicates the position of the long side of the mold. Lines indicated by white triangles are x-axis positions 0, +2, and +17 120 seconds after both electromagnetic forces are applied.
cm, and the line indicated by a black triangle indicates the state at x-axis positions 0, +2, and +17 cm 14 seconds after the application of both electromagnetic forces. The position of the x-axis 0 is the center position of the short side,
The nozzle 30 is located at a position of x = 0 and a long side direction position = 0.5.

The fluctuation of the molten metal level in the meniscus due to such Fm hinders the circulating flow of molten steel along the inner wall of the mold, and inclusions penetrate into the molten steel from the meniscus and are trapped inside the slab, resulting in poor quality. It becomes a problem.

Although the above description has been made with reference to a mold having a long side and a short side and having a rectangular shape as viewed from above, the above-described "operating the linear motor and the electromagnetic brake and controlling the operating frequency of the linear motor Only when a certain value is set, unstable vibration of the molten metal surface occurs '' phenomenon does not occur only in a rectangular mold, for example, even in a square mold,
Alternatively, it can occur in a round mold.

An object of the present invention is to reduce the fluctuation of the molten metal level due to the interaction between the electromagnetic force for stirring the molten metal and the magnetic field for braking the weld metal.

[0020]

Means for Solving the Problems (1) The present invention relates to a mold (M
D), a nozzle for injecting the molten metal into this, an electric coil (CF1 to 36, CL1 to 36 / CS1 to 24) outside the mold, and a braking magnetic field applied to the molten metal in the mold near the electric coil In a molten metal flow control device provided with a braking means (4, 20 VD), F = 1 / √ [2π (λ / 2) / g], λ: width of the mold, g: acceleration of gravity, Frequency f, an alternating current having a phase difference for applying an electromagnetic force to the molten metal in the mold along the mold, electric coil energizing means (20F1, 20F2) for energizing each of the electric coils. It is characterized by having.

For easier understanding, the symbols of the corresponding elements of the embodiment shown in the drawings and described later are added for reference in parentheses.

Since the frequency f above F = 1 / √ [2π (λ / 2) / g] is higher than the resonance frequency when the interval is λ / 2, the resonance frequency Fλ = 1 when the interval is λ. / √ [2π
(2λ) / g], and does not resonate at the interval λ. Therefore, no large level vibration is caused.
That is, the level of the molten metal is stabilized.

(2) The mold (MD) surrounds the molten metal 1
A quadrilateral mold having a pair of long sides (11F, 11L) and a pair of short sides 14R, 14L), wherein λ is the distance a between the pair of long sides. Therefore, the linear motor energizing means (20F1, 20F2)
Is: F = 1 / √ [2π (a / 2) / g] (5) a: interval between the pair of long sides, g: acceleration of gravity, frequency f above F An alternating current having a phase difference for applying a thrust along the longitudinal direction to the molten metal in the mold is supplied to each of the electric coils.

(3) The nozzle includes a short nozzle in which a molten metal outlet into the mold is at a shallow level and a long nozzle at a deep level (FIG. 17). When the molten metal is injected by a single nozzle, the flow velocity of the molten metal around the molten metal outlet of the nozzle is high, and a large amount of energy is required for stirring and braking the molten metal in order to suppress or adjust the flow velocity as desired. By dispersing and injecting molten metal at different depths in the mold, the flow velocity around the nozzle outlet is low,
The flow is easily suppressed or adjusted, and the fluctuation of the meniscus level is reduced.

(4) The electric coils (CF1 to 36, CL1 to 36 / C
S1-24) were placed below the braking means (4,20VD). According to this, braking is applied to the molten metal at a level close to the meniscus, so that the fluctuation of the meniscus level is small.

(5) The electric coils (CF1 to 36, CL1 to 36 / C
S1 to S24) constitute a plurality of linear motors (3F, 3L / 3S), and the electric coil energizing means (20F1, 20F2) generates an alternating current which generates a traveling magnetic field as a whole in each of the electric coils. The molten metal flow control device according to claim 1, wherein electricity is supplied.

(6) The molten metal flow control device according to claim 5, wherein the electric coil energizing means applies a single-phase alternating current to each electric coil.

(7) The linear motor is a two-pole linear motor. When the frequency of the current supplied to the linear motor is increased, the thrust applied to the molten metal decreases accordingly. FIG. 16 shows the relationship between frequency and thrust. Therefore, in the embodiment of the present invention, the thrust reduction caused by increasing the frequency is compensated by decreasing the number of poles of the linear motor. That is, conventionally, a four-pole linear motor has f = 1.8.
Hz current was passed, but this was converted to a 2-pole linear motor.
The current was changed to a current of f = 3.4 Hz.
Thus, when the frequency of the current is changed from 1.8 Hz to 3.4 Hz while the linear motor is kept at 4 poles, the thrust of the linear motor decreases as shown in FIG. By changing the pole from 4 poles to 2 poles, the reduction in thrust is only slightly reduced, shown as DFi in FIG.

To explain the reason, a slot of a linear motor (winding (insertion) of an electric coil) along one mold side.
The pitch at which the grooves are arranged is τs, the number of slots is n, the length of the linear motor along the mold side is L, the number of alternating currents flowing through the coil is M (usually M = 3), and the pole pitch is τ.
Assuming that p and the number of poles are N, L = τs × n (6) = τp × N (7) τp = m × τs (8) m = n / M (9) The relationship is In order to increase the electromagnetic force, it is preferable to reduce the leakage inductance component. Therefore, the pole pitch τp is increased. That is, according to equation (8), the arrangement pitch τ
Increase s. Since L is a fixed length, (6),
From Equation (7), n and N are small. In the present invention, the number of poles N = 2
And When the pole pitch τp is increased in this manner, the electromagnetic force is large, and the thrust of the linear motor can reach the molten steel up to the molten steel.

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

[0031]

FIG. 1 shows a linear motor 3F (first embodiment) according to a first embodiment of the present invention.
3 shows a longitudinal section of a continuous casting mold provided with an electromagnet), a linear motor 3L (second electromagnet) and an electromagnetic brake 4 (third electromagnet). Molten steel is injected into the mold through the pouring nozzle 30 from the top downward (in the vertical direction z), and the meniscus (surface) of the molten steel MM is covered with powder PW. The mold MD 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 MD, and the slab SB is continuously drawn out. Since MM is poured,
There is always molten steel MM in the mold. An electromagnetic brake 4 is provided on the upper part of the mold, and applies an electromagnetic braking force to the downward flow of molten steel. Below the electromagnetic brake 4, the mold long side 11
F, two linear motors 3 along the outer surface of 11L
F, 3L are provided, these are the molten steel in the mold,
An electromagnetic thrust is applied so as to form a swirling flow swirling on a plane parallel to the horizontal plane.

FIG. 2 shows a cross section taken along the line II-II of the mold MD shown in FIG. In FIG. 2, 11F and 11L are first and second long pieces of the continuous casting mold, and 14R and 14L are first and second short pieces having a length a. That is, the length a of the first and second short pieces is equal to the width λ of the mold. The short side length a of the mold MD used in this embodiment is 286 mm. Therefore, as shown in FIG. 4, the relationship between the short side length a of the mold and the short side direction specific resonance wavelength WL is a = WL / 2, so that the short side direction natural resonance wavelength WL of the template is WL = 2a = 2 × 286 = 572 mm (10)

Molten steel is injected into the space surrounded by the long side and the short side through the pouring nozzle 30 from the front surface to the rear surface of FIG. 2 (from above in the vertical direction z to below). Each piece (11F, 11L, 14R, 14L) is a copper plate (13
F, 13L, 15R, 15L) and a non-magnetic stainless steel plate (12F, 12L, 16R, 16L). In this embodiment, the molten steel in the mold is moved from left to right along the long piece 11F by the three-phase linear motor 3F (from -y to +
In order to drive from right to left (in the direction from + y to -y) along the long piece 11L by the three-phase linear motor 3L (in the direction of y), facing the upper surface of the molten steel in the mold (MD). An electric coil of the linear motor 3F and an electric coil of the linear motor 3L are arranged to face each other with the pouring nozzle 30 as a center.

The electromagnet core 17F has 36 slots. Each of the slots has an electric coil CF1 to CF3.
6 has been inserted. The electromagnet core 17F and the electric coils CF1 to CF36 are cooled and heat-resistant.
However, the cooling structure and the cover are not shown. The electromagnet core 17F has a comb shape with slots on the inner surface. An electric coil is inserted into each slot, the magnetic poles are located between the slots, and the inner end faces the molten steel in the continuous casting mold (MD).

The electric coil is wound around the core 17F. The linear motor 3L has the same structure as the linear motor 3F. The electromagnet core 17L has 36 slots, each of which has an electric coil CL1 to CL36.
Is inserted, but the direction of the generated thrust is opposite to that of the linear motor 3F. The linear motors 3F and 3L are to apply a thrust indicated by a dotted arrow in FIG. 9B to the molten steel MM.

FIG. 3 shows an enlarged cross section taken along the line III-III of FIG. 1, that is, a cross section of the electromagnetic brake 4 cut horizontally. The electromagnetic brake 4 applies an electromagnetic force to the molten steel passing from above to below the upper part of the mold, and applies a braking force to the molten steel downward projecting flow. The electromagnetic brake 4 is disposed so as to sandwich the mold horizontally, and the electromagnet of the electromagnetic brake 4 is
F, the width of the magnetic pole 4A
F, 4AL are provided facing each other with the mold long pieces 11F, 11L interposed therebetween, and coils 4CF, 4CL are wound around the outer circumference of the magnetic poles. The left and right yokes 4BL and 4BR connect the left and right magnetic poles to form a closed magnetic circuit. Accordingly, the electromagnetic brake 4 applies a magnetic field between the magnetic poles 4AF and 4AL in the horizontal direction (x-axis direction in FIG. 3), and the molten steel MM descends (z-axis direction) in this horizontal magnetic field. Since the molten steel as a conductor crosses the horizontal magnetic field, an electromagnetic braking force is applied to the molten steel to stop the movement.

FIG. 5 shows the connection of the electric coils CF1 to CF36 of the first group and the electric coils CL1 to CL36 of the linear motor 3L of the linear motor 3F shown in FIG. Show.

The connection between the linear motors 3F and 3L shown in FIG. 5 is of two poles (N = 2), and a three-phase alternating current (M = 3) is supplied to the electric coil. For example, in FIG. 5, the electric coils CF1 to CF36 of the first group of the linear motor 3F are arranged in this order as u, u, u, u, u, u, V, V, V,
V, V, V, w, w, w, w, w, w, U, U, U,
U, U, U, v, v, v, v, v, v, W, W, W,
W, W, and W are represented. “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
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. The terminals U11, V11 and W11 shown in FIG. 5 are connected to the electric coil CF1 of the first linear motor 3F.
To the power supply connection terminals of CF36, terminals U12, V12
And W12 are the electric coils C of the second linear motor 3L.
L1 to CL36 power connection terminals.

FIG. 7 shows a power supply circuit 20F for supplying a three-phase alternating current to the electric coils CF1 to CF36 of the first linear motor 3F.
1 is shown. A thyristor bridge 22A1 for DC rectification is connected to the three-phase AC power supply (three-phase power line) 21, and its output (pulsating flow) is smoothed by the inductor 25A1 and the capacitor 26A1. The smoothed DC voltage is applied to a power transistor bridge 27 for forming a three-phase AC.
The U-phase of the three-phase alternating current applied to A1 and output from the power supply terminals U11 and U12, the V-phase to the power supply terminals V11 and V12, and the W-phase to the power supply terminals W11 and W12 shown in FIG. Applied.

The electric coil CF1 of the first linear motor 3F
, A coil voltage command value VdcA1 for generating a thrust indicated by a dotted arrow in FIG. 5 is given to the phase angle α calculator 24A1 by an operator, and the phase angle α calculator 24A1
The conduction phase angle α (thyristor trigger-phase angle) corresponding to the command value VdcA1 is calculated, and a signal representing this is given to the gate driver 23A1. The gate driver 23A1
The thyristor of each phase starts phase counting from the zero crossing point of each phase and triggers conduction at the phase angle α. As a result, the command value VdcA is applied to the transistor bridge 27A1.
1 is applied.

On the other hand, the three-phase signal generator 31A1 outputs the frequency specified by the frequency command value Fdc (3.4 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.

Thus, the power supply connection terminals U11 and U1
2, a U-phase voltage of a three-phase AC, that is, a single-phase AC is output, and a similar V-phase voltage, that is, a single-phase AC having a phase difference of 120 ° is output to the power supply connection terminals V11 and V12. A similar W-phase voltage, that is, a single-phase AC having a phase difference of 240 °, is output to terminals W11 and W12, and the level between the upper and lower peaks of these voltages is determined by the coil voltage command value VdcA1.

Here, the frequency command value Fdc will be described. The natural resonance period T and the natural resonance frequency F corresponding to the interval a of the mold are represented by the following equations.

T = √ (4πa / g) (11) F = 1 / T (12) As shown in the above equation (1), the short side length a of the mold used in this embodiment is: 286 mm, and the natural resonance wavelength WL in the short side direction of the mold is 572 mm. This natural resonance wavelength WL = 57
The cycle T of 2 mm is as follows: T = {[(2 × 3.14 × 0.572) /9.8] ≒ 0.6 [sec] (13) Therefore, the natural resonance frequency F is: F = 1 / 0.6 ≒ 1. 7 [Hz] (14) Therefore, if the frequency command value Fdc is a value equivalent to the power supply output frequency of 1.7 Hz, when the linear motor excited by this output is used together with the electromagnetic brake, hot water is generated due to electromagnetic fluid mutual interference. The surface is rippling. Conventionally, the frequency was set to 1.8 Hz.

Therefore, in this embodiment, F = 1 / √ [2π
(A / 2) / g], the frequency f of the current supplied to the linear motor was set to 3.4 Hz. Actual long side interval a is 0.2
Since the resonance frequency is 86 m and the resonance frequency is 1.7 Hz, no vibration (wave) resonating at the interval a = 0.286 m is generated. That is, even if the electromagnets for electromagnetic braking are operated at the same time, no rippling of the molten metal surface occurs due to mutual interference of the electromagnetic fluids.

In this embodiment, a three-phase voltage having a frequency of 3.4 Hz is output according to the frequency command value Fdc. That is, the 3.4-Hz three-phase AC voltage of the peak voltage value (thrust) specified by the coil voltage command value VdcA1 is applied to the electric coils CF1 to CF1 of the first linear motor 3F shown in FIGS.
CF36 and electric coil CL of second linear motor 3L
A three-phase alternating current flows through 1 to CL36. 2nd linear motor 3L
Connection of the electric coils CL1 to CL36 of the first linear motor
Since it is different from that of the motor 3F, a thrust having the same magnitude and the opposite direction to that of the first linear motor 3F is applied to the molten steel.

FIG. 7 shows an electric coil connection of the electromagnetic brake 4,
And a power supply circuit 20VD. Electromagnetic blur
A DC power supply 20 is connected to the electric coils 4CF and 4CL of the key 4.
Direct current is supplied from VD, and a certain direction is
That is, a uniform horizontal magnetic field is applied in a direction orthogonal to the long side of the mold.

A thyristor bridge 22D1 for DC rectification is connected to a three-phase AC power supply (three-phase power line) 21, which is a power input of a DC power supply 20VD, and its output (pulsating flow) is smoothed by an inductor 25D1 and a capacitor 26D1. Is done. The smoothed DC voltage is applied to the terminals 4P and 4M of the electromagnetic brake shown in FIG.

Electric coils 4CF, 4C of electromagnetic brake 4
L is a coil voltage command value VdcD3 for generating a braking force for suppressing the downflow of molten steel is given to the phase angle α calculator 24D1 by an operator, and the phase angle α calculator 24D1
The conduction phase angle α (thyristor trigger-phase angle) corresponding to the command value VdcD3 is calculated, and a signal representing this is given to the gate driver 23D1. The gate driver 23D1 is
The thyristor of each phase starts phase counting from the zero crossing point of each phase and triggers conduction at the phase angle α. Thereby, the command value VdcD3 is applied to the terminal VD of the power supply circuit 20VD.
Is output.

FIG. 11 shows a third linear motor 3 according to a second embodiment of the present invention.
1 shows a cross section of a continuous casting mold with S and electromagnetic brake 4 (not shown). Molten steel is injected into the square mold MD from an upper side to a lower side (vertical direction z) through an injection nozzle 30 (not shown). An electromagnetic brake 4 (not shown) is provided on the upper part of the mold, and applies an electromagnetic braking force to the downward flow of molten steel. Below the electromagnetic brake 4, a third linear motor 3S is arranged in a shape surrounding each side of the mold MD, and applies an electromagnetic force to the molten steel MM. The linear motor 3S, which is substantially the same as that used in the first embodiment, is mounted so as to surround a square mold MD. The linear motor 3S has a continuous start and end. . Each of the slots of the electromagnet core 17S having a shape surrounding the mold MD is provided with a mold MD.
A total of 24 coils CS1 to CF24 are wound around each side, and the coil CS1 to CF24 operate as a two-pole linear motor as a whole.

FIG. 12 shows the connection between the coils and the power supply circuit 20F.
1 shows a connection mode. The protrusion between the slots serves as a magnetic pole and protrudes toward the inside of the mold MD, applies a moving magnetic field to the molten steel MM in the mold MD, and gives a stirring drive thrust to the molten steel.

Since the mold width (length of one side) of the square mold MD is λ, the natural resonance period T and the natural resonance frequency F of the mold corresponding to the mold width λ are represented by the following equations.

T = √ (4πλ / g) (15) F = 1 / T = 1 / √ (4πλ / g) (16) Therefore, if the third linear motor 3S is connected to the F To excite,
In addition, when used together with the electromagnetic brake 4, the molten metal surface is likely to undulate due to electromagnetic fluid mutual interference.

Therefore, in the second embodiment, F = 1 / √ [2
π (λ / 2) / g], the excitation frequency f of the linear motor was set to be twice as high as the frequency F shown by the equation (16).
Therefore, no vibration (wave) resonating with the square mold MD having the mold width λ occurs. That is, even if the electromagnets 4 for electromagnetic braking are simultaneously operated, no waving of the molten metal surface occurs due to mutual interference of the electromagnetic fluids. The other parts are the same as those of the first embodiment, and the description is omitted.

Third Embodiment FIG. 13 shows a third linear motor 3 according to a third embodiment of the present invention.
1 shows a cross section of a continuous casting mold with S and electromagnetic brake 4 (not shown). Molten steel is injected into the cylindrical mold MD from above through downward (in the vertical direction z) through an injection nozzle 30 (not shown). Below the electromagnetic brake 4 (not shown) mounted on the upper part of the mold MD, a third linear motor 3S having a square shape is arranged so as to surround the cylindrical mold MD. Gives electromagnetic thrust. The third linear motor 3S is the same as that used in the second embodiment. The electromagnetic brake 4 mounted on the upper part of the mold MD provides an electromagnetic braking force against the downward flow of molten steel.

Mold width (diameter of mold) of cylindrical mold MD
Is λ, so that the natural resonance period T and the natural resonance frequency F of the mold MD corresponding to the mold width λ are represented by the following equations.

T = √ (4πλ / g) (17) F = 1 / T = 1 / √ (4πλ / g) (18) Therefore, if the third linear motor 3S is connected to the F To excite,
In addition, when used together with the electromagnetic brake 4, the molten metal surface is likely to undulate due to electromagnetic fluid mutual interference.

Therefore, in the third embodiment, F = 1 / √ [2
π (λ / 2) / g], the excitation frequency f of the linear motor was set to be twice as high as the frequency F shown by the equation (18).
Therefore, no vibration (wave) resonating with the circular mold having the mold width λ is generated. That is, even if the electromagnets 4 for electromagnetic braking are simultaneously operated, no waving of the molten metal surface occurs due to mutual interference of the electromagnetic fluids. The other parts are the same as those of the first and second embodiments, and the description is omitted.

Although FIG. 1 shows an embodiment in which molten steel is injected into the mold MD with one pouring nozzle 30, as shown in FIG. 17, two pouring nozzles 30a and 30b or Injecting molten steel at different depths with more pouring nozzles is effective in reducing the fluctuation of the meniscus level, increasing the braking effect of the molten steel descending flow, and the effect of stirring the molten steel by the linear motor. It is preferable in increasing the value.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a continuous casting rectangular mold, a linear motor, a pouring nozzle 30 and an electromagnetic brake of a controlled object according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1 and is an enlarged cross-sectional view of a mold and a linear motor.

FIG. 3 is an enlarged cross-sectional view showing a cross section taken along line III-III of FIG.

FIG. 4 is a schematic diagram showing a resonance wavelength with respect to a long side interval a of a mold, and shows an exaggerated level of a molten metal level in a vertical cross section of the mold.

5 is an electric circuit diagram showing connection of electric coils of the linear motor shown in FIG.

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

7 is an electric circuit diagram showing connection of electric coils of the electromagnet for electromagnetic braking shown in FIG. 2 and a second power supply circuit for applying a DC voltage to the electric coils.

8A is a graph showing a magnetic flux density distribution generated in a mold when an electromagnetic stirrer and an electromagnetic brake are operated, and an electromagnetic fluid mutual interference region, and FIG. 8B is a graph showing the operation of the mold. It is a table showing a situation.

FIG. 9 (a) is a plan view showing a surface layer flow caused by injection of molten steel from a pouring nozzle in a meniscus of molten steel in a mold, and FIG. 9 (b) is a dotted arrow showing thrust applied to molten steel by linear motors 3F and 3L. (C) is a plan view showing the sum of the surface flow generated by the injection of molten steel from the pouring nozzle and the surface flow generated by the thrust of the linear motor, as indicated by a two-dot chain line arrow.

10A is a cross-sectional view of molten steel in a mold, showing a flow of molten steel injected from a nozzle, and FIG. 10B is a plan view showing a surface layer flow (by molten steel injection) in a meniscus of the molten steel in the mold.

FIG. 11 is a cross-sectional view showing a square mold for continuous casting and a third linear motor 3S to be controlled according to a second embodiment of the present invention.

12 is an electric circuit diagram showing connection of electric coils of the third linear motor 3S shown in FIG.

FIG. 13 is a cross-sectional view showing a cylindrical mold for continuous casting and a third linear motor 3S to be controlled according to a third embodiment of the present invention.

FIG. 14 is a graph showing a change in the shape of the molten metal on the inner wall of the mold when the mold is equipped with an electromagnetic stirrer and an electromagnetic brake, and when both are operated simultaneously.

FIG. 15 is a graph showing a change in the shape of the molten metal on the inner wall of the mold when the mold is equipped with an electromagnetic stirrer and an electromagnetic brake when both are simultaneously operated.

FIG. 16 is a graph showing the relationship between the number of poles of the linear motor and the current flow frequency, and the thrust applied to molten steel by the linear motor.

FIG. 17 shows a rectangular casting mold and a pouring nozzle 30 for another continuous controlled object of the first embodiment of the present invention.
It is a longitudinal section showing a, 30b, a linear motor, and an electromagnetic brake.

[Explanation of symbols]

1: inner wall 2: outer wall 4: electromagnetic brake 17F: first linear motor core 17L: second linear motor core 17S: third linear motor core 19: outlet 30, 30a, 30
b: Pouring nozzle CF1 to CF36: Electric coil of first linear motor CL1 to CL36: Electric coil of second linear motor CS1 to CS24: Electric coil of third linear motor 13F, 13L, 15L, 15R: Copper plate 12F, 12L, 16L, 146: Non-magnetic stainless steel plate 4AF, 4AL: Electromagnetic brake core 4BF, 4BL: Electromagnetic brake yoke 4CF, 4CL: Electromagnetic brake coil 11F, 11L: Long piece 14R, 14L: short piece 20F1, 20VD: power supply circuit 3F, 3L, 3S: linear motor a: short side length C: casing G: void MD: mold MM: molten steel (molten metal) PW: powder SB: casting Piece U11, V11, W11 / U12, V12, W12, 4P, 4M: Power supply connection terminal λ: Mold width

Claims (6)

[Claims] 1. A mold, a nozzle for injecting molten metal into the mold,
A molten metal flow control device comprising: an electric coil outside the mold; and a braking means for applying a braking magnetic field to the molten metal in the mold near the electric coil, wherein F = 1 / √ [2π (λ / 2) / g], λ: width of the mold, g: acceleration of gravity, an alternating current of a frequency f equal to or higher than F for applying an electromagnetic force to the molten metal in the mold along the mold is applied to the electric coil. A flow control device for molten metal, comprising: an electric coil energizing means for energizing. 2. The mold according to claim 1, wherein said mold is a quadrilateral mold having a pair of long sides and a pair of short sides surrounding said molten metal, and said λ is a distance a between said pair of long sides. Item 1. A flow controller for molten metal according to Item 1. 3. The molten metal flow control device according to claim 1, wherein the nozzle includes a short nozzle having a shallow level and a long nozzle having a deep level at a molten metal outlet into the mold. 4. The molten metal flow control device according to claim 1, wherein the electric coil is placed below the braking means. 5. The electric coil according to claim 1, wherein said electric coil comprises a plurality of linear motors, and said electric coil energizing means applies an alternating current for generating a traveling magnetic field to each of said electric coils as a whole. Claim 2, Claim 3 or Claim 4
The molten metal flow control device according to the above. 6. The molten metal flow control device according to claim 1, wherein said electric coil energizing means applies a single-phase alternating current to said electric coil. .