JP3138611B2 - Flow control device for molten metal in continuous casting mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control device for controlling a flow speed of a molten metal, and more particularly, but not exclusively, to a flow control device for a molten metal in a plurality of juxtaposed molds. Related to the device.

[0002]

2. Description of the Related Art For example, in continuous casting of a billet, 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 slab temperature is not uniform on the wall surface of the mold at the same height, surface cracks and shell fractures are likely to occur. That is, the molten metal is partitioned by the mold, and the molten steel is injected into the mold through a nozzle inserted at a substantially central position of the mold, so that the flow velocity distribution of the molten steel is not uniform, and the temperature distribution is not uniform. Longitudinal cracks (surface flaws having a longitudinal component in the slab drawing direction z), lateral cracks (surface flaws having a longitudinal component in the horizontal direction y)
Is one of the causes. In order to improve this, conventionally, a linear motor placed outside the long side of the mold or a linear motor facing the upper surface of the molten steel applies an electromagnetic driving force (thrust) in a certain direction to the molten steel in the mold to remove the molten steel. It is actively flowing. The thrust applied to the molten steel in the mold can be adjusted by the linear motor current.

[0003]

However, in addition to the non-uniform flow velocity distribution of the molten steel in the mold, the electromagnetic thrust applied by the linear motor to the molten steel in the mold is not uniform. However, it was difficult to sufficiently rectify the molten steel temperature distribution in the same horizontal section. Furthermore, in continuous casting using a mold having a relatively small cross section, for example, in billet casting, a plurality of molds are arranged side by side and casting is performed in each mold simultaneously and in parallel, but since the mold shape is small, Even if an attempt is made to equip each mold independently with a linear motor, it is difficult to install the linear motors individually in each of the molds because the linear motors of the adjacent molds mechanically interfere with each other. If the size is reduced, sufficient thrust may not be obtained. Furthermore, the linear motors of the adjacent molds cause electromagnetic interference, and there is a problem that the designed thrust (direction, strength, distribution) is not applied to the molten steel in the mold.

A first object of the present invention is to finely adjust the distribution of thrust applied to a molten metal, and to finely adjust the distribution of thrust applied to a molten metal by using as few linear motors as possible. This is the purpose of 2. A third object is to adjust the flow of the molten metal in each of the plurality of molds arranged in parallel, and a fourth object is to perform this operation with as few linear motors as possible.

[0005]

According to the present invention, there is provided an apparatus for controlling the flow of molten metal in a continuous casting mold, comprising: an electromagnet core (Ea, Eb) having a plurality of slots distributed in the y direction; A first linear motor having a plurality of sets n (3) of electric coil groups (E1 to E12) distributed in the direction; an electromagnet core (La, Lb) having a plurality of slots distributed in the y direction; A plurality of sets n distributed in the y direction
The first linear motor has an electric coil group (L1 to L12), and a mold (M1 to M3) and a molten metal (MM) therein.
A second linear motor opposed to (1E); a set of opposed electric coil groups (E1 to E4, L1 to L4) (E5) of the first and second linear motors (1E, 1L), respectively; ~ E8, L5 ~ L8) (E9 ~ E1
2, L8 to L12), there is a phase difference that gives a thrust to the molten metal along the slot arrangement direction y, and the voltage level signals (VdcA1, VdcB
2, VdcC3) a plurality of sets of energizing means (20A1, 20B2, 20C3) for applying an AC voltage having a voltage level specified by the mold (M1 to M3)
In the slab to be cast in, the surface flaw having a longitudinal component in the drawing direction (z), the set division of the electric coil (E1 ~ E4, L1 ~ L4)
(E5 to E8, L5 to L8) Surface flaw detection means (t1, tma), (t2, tm) detected at each surface section (M1 to M3) corresponding to (E9 to E12, L8 to L12)
b), (t3, tmc); and the surface flaw detection means (t1, tma), (t2,
(tmb), (t3, tmc) is the surface classification that detected the increase of the surface flaw
Set (E1-E4, L1-L4) corresponding to (M1-M3) (E5-E8, L5-L8)
The power supply means (20A1, 20B2, 20C3) of (E9 to E12, L8 to L12) includes a level control means (P2) for supplying a voltage level signal designating application of a high voltage level.

[0006] In the parentheses, for easy understanding, symbols attached to corresponding elements or matters of the embodiment shown in the drawings and described later are added for reference.

[0007]

When the first and second linear motors (1E, 1L) are opposed to each other with a molten metal interposed therebetween, the stronger the magnetic field generated by each linear motor, the stronger the mutual interference. Since the linear motor extending in the y direction has a different magnetic field distribution at the end and the middle, the mutual interference also differs between the end and the middle. Linear motor
When the correspondence (phase arrangement of two opposed linear motors) between each of the electric coils of the motor and each phase AC voltage output by the energizing means is fixed, the molten metal has a thrust having a distribution in the y direction. Is added. For example, a strong thrust distribution at the middle portion is weak at the end portion, and conversely, a weak thrust distribution at the middle portion is strong at the end portion.

Here, for example, when n = 3, according to the present invention, the first linear motor (1E) and the first linear motor (1L) mounted opposite to each other with the molten steel (MM) interposed therebetween. Electric coil group
By switching the voltage level (0, VL, Vh) of the AC voltage (U, V, W) applied by the first energizing means (E1 to E4, L1 to L4) to the first electric coil group The electromagnetic thrust generated by (E1 to E4, L1 to L4) changes. Also, a second electric coil group (E5) mounted on the first linear motor (1E) and the second linear motor (1L).
To E8, L5 to L8), by switching the voltage level (0, VL, Vh) of the AC voltage (U, V, W) applied by the second energizing means (20B2), the first electric coil group (E1 To E4, L1 to L4) change. Further, a third electric coil group (E9) mounted on the first linear motor (1E) and the second linear motor (1L).
To E12, L9 to L12), by switching the voltage level (0, VL, Vh) of the AC voltage (U, V, W) applied by the third energizing means (20C3), the third electric coil group (E9 To E12, L9 to L12) change.

As a result, the y-direction distribution of the electromagnetic thrust applied to the molten steel from the first and second linear motors (1E, 1L) becomes
Installed coil group (E5 to E8, L5 to L8, E5 to E8, L5 to L
8, changes according to E9-E12, L9-L12). Therefore, the electromagnetic thrust distribution can be adjusted by the voltage level instruction signals (VdcA1, VdcB2, VdcC3), and this adjustment is performed by the level control means (P2).

[0010] In the case of continuous casting, the temperature distribution of the molten metal in the horizontal section of the mold, particularly the temperature distribution in the horizontal direction along the inner wall surface of the mold (the y direction orthogonal to the slab drawing direction z) is uniform. Preferably, the vertical cracks or the horizontal cracks generated in the formed slab are more remarkable due to the uneven temperature. In the present invention, surface flaw detection means (t1 to t3, tma to tmc)
Detects vertical cracks in the slab and selects the voltage level (0, VL, Vh) that provides a thrust distribution suitable for reducing the vertical cracks according to the size of the vertical cracks by the level control means (P2). Then, voltage level instruction signals (VdcA1, VdcB2, VdcC3) are set. This reduces longitudinal cracks.

As described above, when a plurality of molds having relatively small cross sections are arranged side by side in the y direction and casting is performed in each mold simultaneously and in parallel, since the mold shape is small, each mold is independent. It is difficult to equip with a linear motor. Therefore, in such applications, the present invention provides a common linear motor (1E, 1L) for a plurality of molds (M1 to M3),
~ M3), the magnitude of the electromagnetic thrust applied to the molten metal in each mold is adjusted for each mold by associating the electric coil group and the conducting means with each other. According to this, the linear motor
It is easy to arrange the molds and multiple molds (M1-M3)
However, the flow rate of the molten metal (MM) can be adjusted for each mold (M1 to M3), for example, by increasing the electromagnetic force of one molten metal (MM) and lowering the other.

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

[0013]

FIG. 1 shows an arrangement of a linear motor according to an embodiment of the present invention. In the figure, M1, M2, and M3 are small continuous casting molds for producing billets, and are a first mold, a second mold, and a third mold. Molten steel MM is injected from the front side to the rear side (vertical direction z from above to below) of FIG. 1 through an injection nozzle (not shown). Each mold M
Each side forming a square mold of 1, M2, M3 is a copper plate M
12, M22, M32, non-magnetic stainless steel plate M11,
M21 and M31 are backed.

In this embodiment, each of the templates M1, M2, M3
In order to rotationally drive the molten steel inside the mold in a clockwise direction on the plane of FIG. 1 along each side of the mold with a three-phase linear motor,
The first and second electromagnet cores 1E and 1L face the outer surfaces of the continuous casting molds M1, M2, and M3 in the x direction, and each of the first and second electromagnet cores y
Molds M1, M2, M3 arranged in a row at equal intervals in the direction
Are arranged in parallel and symmetrically with respect to the mold rows M1 to M3. FIG. 2 shows an enlarged cross section (an enlarged cross section taken along line 2A-2A in FIG. 1) of the second mold M2, the linear motor 1E, and the linear motor 1L. In these drawings, small numbers between dimension lead lines (dashed lines) indicate dimension values (m
m). Note that the first linear motor 1E and the second linear motor 1L have the same dimensions and the same electrical rating.

Referring to FIGS. 1 and 2, in this embodiment, the electromagnet core 1E is long in the y direction,
Is formed by laminating comb-shaped thin steel plates with a flat plate surface in which twelve notches for slots are formed at an equal pitch, and there are twelve slots, and each of the slots has an electric coil E1.
E12 is inserted. The electromagnet core 1E and the electric coils E1 to E12 are cooled and covered with a heat-resistant cover, but the cooling structure and the cover are not shown. The electromagnet core 1E is a comb shape having slots extending in the x direction on the lateral side surface, an electric coil is inserted into each slot, the teeth between the slots are magnetic poles, and the lower end faces of the continuous casting molds M1, M2, M3. It faces the side surface in the x direction. The electric coils E1 to E12 are “wrapped around” the electromagnet core 1E.

In this embodiment, the electric coils E1 to E12
After passing an electromagnet core Ea having a width (x) of 345 mm into the inner space of the electric coil, one side of the electric coils E1 to E12 is pushed into each slot. In the embodiment, since the slot is 360 mm and the depth (x) of the slot is 95 mm, after the electric coil is pushed into the slot, the upper side of the electric coil and the core 1 are pressed.
A gap of 110 mm is formed between the back side (lateral side) of E. An auxiliary core E in which rectangular thin steel sheets are laminated in this gap
b is inserted. Electromagnetic core Ea and auxiliary core E
Both of them have a cooling fluid flow path to which a refrigerant pipe is connected, but these are not shown.

Below the mold M2 shown in FIG. 2 (z direction), pinch rolls R are arranged facing down the mold so as to sandwich the molten steel MM flowing out from the lower part of the mold M2 from both sides in the x direction. The molten steel MM is rotating in a direction to be drawn from the mold M2. The pinch roll R is always cooled by a large amount of cooling water injected, and the molten steel MM drawn from the mold M2 is cooled from the side as it is conveyed by the pinch roll R, so that the solidified layer of the surface layer gradually becomes internal. Grow up.

An infrared camera t2 is arranged between the pinch rolls R near the mold M2 to aim at the slab surface, and photographs the slab surface. The configurations and functions of the molds M1 and M3 are the same. An infrared camera t1 is arranged between the pinch rolls R near the mold M1 to aim at the slab surface. An infrared camera t3 is arranged between the cast slab surfaces. The infrared cameras t1, t2 and t3 are of the same type and standard.

FIG. 16 shows an enlarged cross section of a hood indicating the infrared camera t2. The substantially funnel-shaped hood t2e having a rectangular opening faces the slab with a small gap from the slab, with the opening facing the side of the slab. Food t
2e Waterproof infrared camera t2c at the center of the rear wall
However, it is mounted with the center of its visual field facing the center of the opening of the hood. Cooling water is injected into the hood from an injection port provided on the hood-side peripheral surface, and the hood is always filled with cooling water.
Ejects from a small gap between e and the slab surface. The infrared camera t2c photographs the surface of the slab through water filled in the hood.

FIG. 3 shows the overall system configuration and the connection of all electric coils according to the embodiment of the present invention shown in FIG. The electric coils E1 to E4 of the first linear motor 1E and the electric coils L1 to L4 of the second linear motor 1L are connected to the three-phase power connection terminals Ua and Wa of the power circuit 20A1 for generating a three-phase AC voltage.
It is connected to the. The electric coils E5 to E8 of the first linear motor 1E are connected to a power supply circuit 2 for generating a three-phase AC voltage.
0B2 is connected to the three-phase power connection terminals Vb and Wb,
The electric coils L5 to L8 of the linear motor 1L are also connected to the three-phase power connection terminals Vb and Ub of the power circuit 20B2. Further, the electric coil E of the first linear motor 1E
9 to E12 are power supply circuits 20C3 for generating a three-phase AC voltage.
And the electric coils L9 to L12 of the second linear motor 1L are also connected to the three-phase power connection terminals Wc and Vc of the power supply circuit 20C3.

The connection shown in FIG. 3 has two poles, and a three-phase alternating current is supplied to the electric coil. For example, the first linear model
In FIG. 3, the electric coils E1 to E12 of the heater 1E are arranged in this order in the order of W, W, u, u, V, V, w, w, U, U, v, v.
It is expressed as “U” indicates U-phase normal-phase energization of three-phase alternating current (as is), and “u” indicates U-phase reverse-phase energization (U
180 degrees from the current phase), and the U phase is applied to the electric coil "U" at the winding start end,
It means that the U-phase is applied to the electric coil "u" at the winding end. Similarly, “V” indicates V-phase normal-phase energization of three-phase AC, “v” indicates V-phase reverse-phase energization, “W” indicates W-phase positive-phase energization of three-phase AC, and “w” Represents reverse phase energization of the W phase.

The power supply circuits 20A1, 20B2 and 20C3 are connected to a control circuit P2 and a three-phase signal generator 31, respectively. The control circuit P2 includes a signal indicating the casting speed Vc and the vertical crack information Sa to Sc and the horizontal crack information La to L detected based on the images captured by the infrared cameras t1 to t3.
c is given. The image processing devices tma to tmc process the image signals (video signals) of the slab surface photographed by the infrared cameras t1 to t3 and binarize them into the presence or absence of flaws to generate binarized image data. The image data between the flaw points whose relative distance is a predetermined short distance on the flaw image represented by the data is expressed as flawed data.
Data (continuation of adjacent points), and detection of a series of flaw points on the flaw image (assuming one series as one flaw)
The length (vertical length) Sa to S in the z direction of each detected flaw
The lengths (horizontal lengths) La to Lc in the c and y directions are calculated, and the flaw data (Sa to Sc and La to Lc for one flaw; when a plurality of flaws are detected, a plurality of flaws are detected) is controlled. The image processing and the flaw determination are repeated at a predetermined cycle.

The control circuit P2 performs the following processing every cycle, with a period Ts inversely proportional to the slab drawing speed Vc (the lowest of the drawing speeds of the molds M1 to M3). First, the flaw data given by the image processing devices tma to tmc are read for a predetermined length of the slab drawing. Next, read the flaw data
The maximum length of the length (vertical length) Sa in the z direction is defined as the vertical crack length, the maximum length of the length (horizontal length) La in the y direction is defined as the horizontal crack length, and the length of the vertical crack is two. Threshold (S
m, Sh), it is determined whether the level of longitudinal cracks in the molten steel in the mold is high, medium, or low. Where Sm
Is an intermediate level threshold value, and the control circuit P2 determines that the vertical crack length is a low level if the length is smaller than the threshold value Sm, and determines a middle level if the vertical crack length is equal to or more than the threshold value Sm and less than Sh. , Sh or higher, it is determined that the level is high. Similarly, it is determined whether the side crack length is low level, middle level, or high level. This determination is made in the same manner for the data Sb, Sc, Lb, and Lc for the other molds. Based on the result of this determination, the control circuit P2 makes the following Table 1 stored in the internal memory in advance.
According to each of the molds M1, M2, M3 (M
1: E1 to E4 & L1 to L4, M2: E5 to E8 & L5
To L8, M3: E9 to E12 & L9 to L12) are selected from high, medium and low, and the coil voltage command values VdcA1, VdcB2 and V corresponding to the selected voltage level.
By calculating dcC3, the power supply circuits 20A1, 20B2, 20
Output to C3. Also, the frequency command value F of the three-phase AC voltage
dc is calculated and output to the three-phase signal generator 31.

[0024]

[Table 1]

In the cycle Ts, the slab at the position of the electric coil group moves at the drawing speed Vc and the cameras t1 to t1 move.
This is the time required to reach the position of t3, or a slightly longer time.

FIG. 4 shows a circuit configuration of the three-phase signal generator 31 shown in FIG. The frequency command value Fdc input to the three-phase signal generator 31 is provided to a VCO (voltage controlled oscillator: voltage / frequency converter) A2. In this embodiment, the VCO A2 oscillates an analog sine wave whose oscillation frequency changes in accordance with the voltage level of the frequency command value Fdc, binarizes the analog sine wave, converts the sine wave into a pulse, and converts the sine wave into a designated frequency Fdc × 36.
0, and generates a high-frequency pulse PL of
A5 is given as a count pulse. When the frequency indication value Fdc of the three-phase AC is 50 Hz, the frequency of the pulse PL is 18000 Hz.

The counters A3, A4 and A5 count up the incoming pulse PL. Counters A3, A4
The count data of A5 are stored in ROMs A12 and A1, respectively.
3, the read address of A14 is designated.

In the ROMs A12, A13, and A14, level data of one cycle of a sine wave is stored in 1 ° sections (addresses).
For example, these ROM addresses 0
, The data (0) of the sine wave phase of 0 °, the upper peak value data at the address 90, and the data at the address 180.
Data (0), the lower peak value data at address 270,
The address 359 stores 359 ° data.

Count data (DL) of the counter A3
And data representing 360 generated by a code generator A9 composed of a dip switch are compared by a coincidence determiner A6, and when they match, the coincidence determiner A6 provides a clear signal to the counter A3. Thus, the count data (DL) of the counter A3 is 0, 1, 2,.
9, 360 (0 by clearing), 1, 2, ..., 35
9, 360 (0 by clearing), 1, 2,... Sequentially change from 0 to 359 in synchronization with the arrival of the pulse PL, and this is repeated. Thereby, the pulse PL
Sine wave level data with one cycle of 1 ° is stored in ROM
The signal is read out from A12, converted into an analog signal (sine wave: AC waveform) by the D / A converter A15, and compared with the comparator 29A1 of the power supply circuit 20A1, the comparison circuit 29B2 of the power supply circuit 20B2, and the comparison circuit 29C3 of the power supply circuit 20C3.
Are provided as U-phase alternating current.

When the count data (DL) of the counter A3 reaches 120, the coincidence determination circuit A7 sets the counter A
4 is cleared, the counter A4 counts up the pulse PL, and uses the count data as address data as RO.
Give to MA13. The sine wave level data is read from the ROMA 13 and converted into an analog signal (sine wave: AC waveform) by the D / A converter A16.
0A1 of the comparator 29A1, the comparison circuit 29B2 of the power supply circuit 20B2, and the comparison circuit 29C3 of the power supply circuit 20C3 have V.
Given as a phase exchange. Count data of counter A3
When the data is 120, the count data of the counter A4 is 0.
Therefore, the output sine wave (V phase) of the D / A converter A16 is delayed by 120 ° from the output sine wave (U phase) of the D / A converter A15.

When the count data (DL) of the counter A3 becomes 240, the coincidence determination circuit A8
5 is cleared, the counter A5 counts up the pulse PL, and uses the count data as address data as RO.
Give to MA14. The sine wave level data is read from the ROMA 14 and converted into an analog signal (sine wave: AC waveform) by the D / A converter A17.
The comparator 29A0A1, the comparison circuit 29B2 of the power supply circuit 20B2, and the comparison circuit 29C3 of the power supply circuit 20C3 receive W.
Given as a phase exchange. Count data of counter A3
When the data is 240, the count data of the counter A5 is 0.
Therefore, the output sine wave (W phase) of the D / A converter A17 is delayed by 240 ° from the output sine wave (U phase) of the D / A converter A15.

Power supply circuits 20A1, 20L2 and 20C
3 is a three-phase signal (U) output from the three-phase signal generator 31.
Phase, V phase, W phase) corresponding three-phase AC voltage (U, V,
The voltage level W) is determined by the coil voltage command values VdcA1, VdcB2 and VdcC3 output from the control circuit P2.

FIG. 5 shows electric coils E1 to E4 and L1 to L4.
The configuration of a power supply circuit 20A1 for flowing three-phase alternating current through L4 is shown.
A thyristor bridge 22A1 for DC rectification is connected to the three-phase AC power supply (three-phase power line) 21, and the output (pulsating flow) of the thyristor bridge 22A1 is the inductor 25A1 and the capacitor 26A.
It is smoothed by one. The smoothed DC voltage is applied to a 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 connected to the power connection terminal Ua shown in FIG. , And the W phase is applied to the power supply connection terminal Wa.

A coil voltage command value VdcA1 for generating a thrust for rotating the molten steel MM in the continuous casting mold (M1) by the electric coils E1 to E4 and L1 to L4 is given to the phase angle α calculator 24A1. α calculator 24A1 calculates conduction phase angle α (thyristor trigger-phase angle) corresponding to command value VdcA1, and provides a signal representing this to 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. This allows
The DC voltage indicated by the command value VdcA1 is applied to the transistor bridge 27A1.

On the other hand, the comparator 29A1 is supplied from the three-phase signal generator 31 with constant-voltage three-phase AC signals U, V, W having a frequency designated by the frequency command value Fdc.

The comparator 29A1 also includes a triangular wave generator 3
0A1 gives a constant voltage triangular wave of 3 KHz. Comparator 2
9A1 is a high-level H (transistor on) signal when the U-phase signal is at a positive level or higher when the triangular wave generated by the triangular wave generator 30A1 is higher than the triangular wave level, and a low-level L (transistor off) signal when the U-phase signal is lower than the triangular wave level. To the U-phase positive section (to the U-phase positive voltage output transistor). When the U-phase signal is at a negative level, it is lower than the level of the triangular wave provided by the triangular wave generator 30A1. When the signal is at the high level H, and when the level exceeds the triangular wave level, the signal at the low level L is sent to the negative section of the U phase (U
Gate driver 2 to the phase negative voltage output transistor)
Output to 8A1. The same applies to the V-phase signal and the W-phase signal. The gate driver 28A1 is connected to each of these phases,
Each transistor of the transistor bridge 27A1 is turned on and off in response to signals addressed to the positive and negative sections.

As a result, a three-phase AC U-phase voltage is output to the power supply connection terminal Ua, a similar V-phase voltage is output to the power supply connection terminal Va, and a similar W-phase voltage is output to the power supply connection terminal Wa.
Phase voltages are output, and the level between the upper and lower peaks of these voltages is determined by the coil voltage command value VdcA1. This 3
In this embodiment, the frequency of the phase voltage is determined by the frequency command value Fdc. That is, the three-phase AC voltage having a frequency of Fdc (for example, 50 Hz) of the peak voltage value (thrust) specified by the coil voltage command value VdcA1 is equivalent to the electric coils E1 to E4 and L1 to L4 shown in FIGS. Applied to L4.

FIG. 6 shows electric coils E5 to E8 and L5 to L
8 shows the configuration of a power supply circuit 20B2 for passing a three-phase alternating current. 3
A thyristor bridge 22B2 for DC rectification is connected to the three-phase AC power supply (three-phase power line) 21, and its output (pulsating current) is supplied to an inductor 25B2 and a capacitor 26B.
It is smoothed by 2. The smoothed DC voltage is applied to a power transistor bridge 27B2 for forming a three-phase AC, and the U-phase of the three-phase AC output from the power transistor bridge 27B2 is connected to the power connection terminal Ub shown in FIG. , And the W phase is applied to the power supply connection terminal Wb.

The electric coils E5 to 8 and L5 to L8 generate a thrust for rotatingly driving the molten steel MM inside the continuous casting mold (M2). The coil voltage command value VdcB2 is calculated by the phase angle α calculator 2
4B2, and the phase angle α calculator 24B2 calculates the conduction phase angle α (thyristor trigger) corresponding to the command value VdcB2.
Phase angle) is calculated, and a signal representing this is supplied to the gate driver 23B2. The gate driver 23B2 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 VdcB2 is applied to the transistor bridge 27B2.

On the other hand, the comparator 29B2 is supplied from the three-phase signal generator 31 with the constant-voltage three-phase AC signals U, V, and W having the frequency specified by the frequency command value Fdc.

The comparator 29B2 also has a triangular wave generator 3
0B2 gives a constant voltage triangular wave of 3 KHz. Comparator 2
9B2 is a high-level signal H (transistor on) when the U-phase signal is higher than the level of the triangular wave provided by the triangular wave generator 30B2, and a low-level signal L (transistor off) when the U-phase signal is lower than the triangular wave level. To the U-phase positive section (to the U-phase positive voltage output transistor), and when the U-phase signal is at a negative level, it is lower than the level of the triangular wave provided by the triangular wave generator 30B2. When the signal is at the high level H, and when the level exceeds the triangular wave level, the signal at the low level L is sent to the negative section of the U phase (U
Gate driver 2 to the phase negative voltage output transistor)
8B2. The same applies to the V-phase signal and the W-phase signal. Gate driver 28B2 is provided for each of these phases,
The respective transistors of the transistor bridge 27B2 are turned on and off in response to signals addressed to the positive and negative sections.

Thus, a three-phase AC U-phase voltage is output to the power supply connection terminal Ub, a similar V-phase voltage is output to the power supply connection terminal Vb, and a similar W-phase voltage is output to the power supply connection terminal Wb.
Phase voltages are output, and the level between the upper and lower peaks of these voltages is determined by the coil voltage command value VdcB2. This 3
In this embodiment, the frequency of the phase voltage is determined by the frequency command value Fdc. That is, the three-phase AC voltage having a frequency of Fdc (for example, 50 Hz) of the peak voltage value (thrust) specified by the coil voltage command value VdcB2 corresponds to the electric coils E5-8, L5 shown in FIGS. Applied to L8.

FIG. 7 shows electric coils E9 to E12 and L9.
The configuration of a power supply circuit 20C3 for flowing three-phase alternating current through L12 is shown. A thyristor bridge 22C3 for DC rectification is connected to the three-phase AC power supply (three-phase power line) 21, and its output (pulsating current) is supplied to the inductor 25C3 and the capacitor 2C.
6C3 smoothing. The smoothed DC voltage is applied to a power transistor bridge 27C3 for forming a three-phase AC, and the U-phase of the three-phase AC output from the power transistor bridge 27C3 is connected to the power supply connection terminal Uc shown in FIG. , And the W phase is applied to the power supply connection terminal Wc.

Electric coils E9 to E12, L9 to L12
However, the coil voltage command value VdcC3 that generates a thrust for rotatingly driving the molten steel MM inside the continuous casting mold (M3) has a phase angle α.
The phase angle α calculator 24C3
Calculates a conduction phase angle α (thyristor trigger-phase angle) corresponding to the command value VdcC3, and gates a signal representing this.
To the driver 23C3. Gate driver 23C3
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 command value V is supplied to the transistor bridge 27C3.
A DC voltage indicated by dcC3 is applied.

On the other hand, the comparator 29C3 is supplied from the three-phase signal generator 31 with the constant-voltage three-phase AC signals U, V, W having the frequency designated by the frequency command value Fdc.

The comparator 29C3 also includes a triangular wave generator 3
0C3 gives a constant voltage triangular wave of 3 KHz. Comparator 2
9C3 is a high-level H (transistor on) signal when the U-phase signal is at a positive level or higher than the triangular wave level provided by the triangular wave generator 30C3, and a low-level L (transistor off) signal when the U-phase signal is lower than the triangular wave level. To the U-phase positive section (to the U-phase positive voltage output transistor). When the U-phase signal is at a negative level, it is lower than the level of the triangular wave provided by the triangular wave generator 30C3. When the signal is at the high level H, and when the level exceeds the triangular wave level, the signal at the low level L is sent to the negative section of the U phase (U
Gate driver 2 to the phase negative voltage output transistor)
Output to 8C3. The same applies to the V-phase signal and the W-phase signal. The gate driver 28C3 is provided for each of these phases,
Each transistor of the transistor bridge 27C3 is turned on and off in response to signals addressed to the positive and negative sections.

Thus, a three-phase AC U-phase voltage is output to the power supply connection terminal Uc, a similar V-phase voltage is output to the power supply connection terminal Vc, and a similar W-phase voltage is output to the power supply connection terminal Wc.
The phase voltages are output, and the level between the upper and lower peaks of these voltages is determined by the coil voltage command value VdcC3. This 3
In this embodiment, the frequency of the phase voltage is determined by the frequency command value Fdc. That is, the three-phase AC voltage having a frequency of Fdc (for example, 50 Hz) of the peak voltage value (thrust) specified by the coil voltage command value VdcC3 corresponds to the electric coils E9 to E12, L9 to L9 shown in FIGS. L12 is applied.

Power supply circuits 20A1, 20B2 and 20C
3 supplies the three-phase AC voltages (U, V, W) whose voltage levels and frequencies have been determined in this way to the respective power supply terminals Ua, W
a, Ub, Vb, Wb, Uc, Vc, Wc are applied to the electric coils E1 to E12, L1 to L12.

FIGS. 8 to 15 show the control circuit P2 shown in FIG.
2 shows the electric coil voltage control operation of the first embodiment. When the power is turned on, the control circuit P2 performs initialization, that is, clears a register (one area of a memory) (step 1). In the following, the word “step” is omitted in parentheses, and step No. Fill in the numbers.

When the initialization is completed, the control circuit P2 determines, based on the lowest casting speed among the given casting speeds (three types of molds M1 to M3), the drawing speed of the lowest casting speed, The time required for the slab, which was located at the position (z direction) of the electric coil group, to reach the positions of the cameras t1 to t3 is calculated, and a time Ts obtained by adding a predetermined value to the calculated time is calculated.
s (Ts timed program timer) is started (3), and z-direction lengths Sa-Sc and y-direction lengths La-Lc of the detected flaw are read by the image processing circuits tma, tmb, and tmc at a predetermined cycle. Put in. When the number of readings reaches a predetermined length in the slab pull-out direction, the maximum value of the length Sa in the z direction among the read values is stored in the register RSa, the maximum value of Sb is stored in the register RSb, and the maximum value of Sc is stored in the register RSb. RSc, and similarly, the maximum value of the length La in the y direction among the read values is stored in the register RLa, and the maximum value of the length Lb is stored in the register R.
The maximum value of Lc is written to Lb in register RLc (4).

Next, the read vertical crack length (RSa-RS
c) and whether the lateral crack length (RLa to RLc) is in a high, medium or low level region,
Voltage command value Vdc output to 0A1, 20B2, 20C3
A1, VdcB2, VdcC3 are determined, and a register RVdcA is determined.
1, RVdcB2 and RVdcC3. The process will be described below.

First, the control circuit P2 determines the level regions of the vertical crack length RSa and the horizontal crack length RLa. RSa
If (vertical crack length) and RLa (horizontal crack length) are less than the respective intermediate level thresholds Sm and Lm, both are determined to be "small" and the voltage level value giving a low level according to Table 1. Write data VL to register RVdcA1 (5,
6, 7A), RSa is less than threshold value Sm, and RLa
Is greater than or equal to the threshold value Lm, the voltage level value data 0 for giving the 0 level (power off) is written into the register RVdcA1 (5, 6, 7B).

On the other hand, if RSa (vertical crack length) is not less than the intermediate level threshold value Sm and less than the high level threshold value Sh, the routine proceeds to step 15 (14). And RLa
If the (lateral crack length) is less than the intermediate level threshold value Lm, the voltage level value data Vh giving a high level is written into the register RVdcA1 (15, 19), and RLa is not less than the threshold value Lm and the high level threshold value is set. If the value is less than the value Lh, the voltage level value data VL giving a low level is written into the register RVdcA1 (15, 16, 17).
Is written into the register RVdcA1 (15, 16, 18).

However, if RSa (vertical crack length) is equal to or greater than the high level threshold value Sh, the process proceeds to step 20 (1).
4). If RLa (length of lateral crack) is less than the intermediate level threshold Lm, the voltage level value data Vh giving a high level is written to the register RVdcA1 (20, 2).
4) If RLa is equal to or larger than threshold value Lm and smaller than high level threshold value Lh, voltage level value data VL giving a low level is written to register RVdcA1 (20, 2).
1, 22), if RLa is equal to or greater than threshold value Lh, voltage level value data 0 for giving 0 level (power off) is written to register RVdcA1 (20, 21, 23).

According to the size of the vertical crack length Sa and the horizontal crack length of the slab drawn from the mold M1 by the above process, a voltage for applying an electromagnetic force to the molten steel MM in the mold M1 in a direction to reduce both of them. Command value VdcA1 is determined.

Similarly, the control circuit P2 executes steps 8 to 10.
B and a voltage command for applying an electromagnetic force to the molten steel MM in the mold M2 in a direction in which both are reduced according to the length of the vertical crack length Sb and the length of the horizontal crack length Lb of the slab extracted from the mold M2 in 25 to 35. The value VdcB2 is determined, and at 11-13B and 36-45, the inside of the mold M3 is reduced in a direction to reduce both according to the size of the vertical crack length Sc and the horizontal crack length Lc of the slab extracted from the mold M3. A voltage command value VdcC3 for applying an electromagnetic force to molten steel MM is determined.

These processes are summarized in Tables 2, 3 and 4
And step Nos. Shown in FIGS. Is additionally shown.

[0058]

[Table 2]

[0059]

[Table 3]

[0060]

[Table 4]

Registers RVdcA1, RVdcB2, RVdc
Voltage command values VdcA1 and VdcB respectively stored in C3
2 and VdcC3 (0, VL or Vh) are output to the power supply circuits 20A1, 20B2 and 20C3, respectively (4
7). When the timer Ts has timed out, a process for controlling the coil voltage is performed in the same manner from step 3 described above.

FIGS. 17 and 18 show the second linear motor 1.
L phase arrangement of each of the L electric coils L1 to L12 (U, u, and U for easy understanding of the polarity relationship with the first linear motor 1E).
V, v, W, w), and each voltage command value Vdc
A1, VdcB2, VdcC3 compatible continuous casting mold M1,
The electromagnetic force (arrow; vector) acting on the molten steel MM in M2 and M3 is shown. Note that in FIGS. 17 and 18,
(A) and (d) also show the phase arrangement (fixed) of the first linear motor 1E, while the other figures (b) and (c) show the phase arrangement of the first linear motor 1E. Was omitted.

As shown in FIGS. 17 and 18, when the voltage applied to the electric coil is increased to increase the coil current, the swirling flow thrust of the molten steel in the mold is large. This thrust agitates the molten steel and suppresses the occurrence of vertical cracks. On the other hand, this agitation may promote lateral cracking, and it is better to suppress the swirling flow thrust for suppressing lateral cracking.
Therefore, in this embodiment, as shown in Table 1, the coil current (applied voltage that causes it) is increased as the vertical crack is large and the lateral crack is small, and the coil current is decreased as the vertical crack is small and the horizontal crack is large. I have to.

In the embodiment described above, each of the molds M1 and M1 has a period Ts substantially inversely proportional to the slab drawing speed.
2, voltage command values VdcA1, VdcB2, VdcC3 applied to power supply circuits 20A1, 20B2, 20C3 for driving molten steel MM inside molds M1, M2, M3 in response to vertical and horizontal cracks on the slab surface drawn from M3. Is a voltage level value (0, VL or V
h), a high-quality product can be stably produced for each mold.

Further, the molten steel MM inside each of the molds M1, M2, M3 is provided with the molds M1, M2 of the set of linear motors 1E, 1L.
The electric coil group (E1 to E4, L1 to L1 corresponding to M1) divided into three corresponding to the ranges facing M2 and M3, respectively.
4. E5 to E8, L5 to L8 for M2, E for M3
9 to E12, L9 to L12).
0A1, 20B2, 20C3, the three-phase AC voltage command values VdcA1, VdcB2, VdcC3 (0,
VL or Vh). There is no need to provide a linear motor for each mold, and the working space can be used effectively.

[Brief description of the drawings]

FIG. 1 is a horizontal sectional view showing an arrangement of a linear motor with respect to a mold according to one embodiment of the present invention.

FIG. 2 shows a second mold M2 and a linear motor 1E shown in FIG.
FIG. 2 is a longitudinal sectional view (a sectional view taken along line 2A-2A in FIG. 1) of the linear motor 1L.

FIG. 3 is a block diagram showing the overall configuration of the embodiment shown in FIG.

FIG. 4 is a block diagram illustrating a configuration of a three-phase signal generator 31 illustrated in FIG.

FIG. 5 is an electric circuit diagram showing a configuration of a power supply circuit 20A1 shown in FIG.

6 is an electric circuit diagram illustrating a configuration of a power supply circuit 20B2 illustrated in FIG.

7 is an electric circuit diagram illustrating a configuration of a power supply circuit 20C3 illustrated in FIG.

FIG. 8 is a flowchart showing a part of the control operation of the control circuit P2.

FIG. 9 is a flowchart showing a part of the control operation of the control circuit P2.

FIG. 10 is a flowchart showing a part of the control operation of the control circuit P2.

FIG. 11 is a flowchart showing a part of the control operation of the control circuit P2.

FIG. 12 is a flowchart showing a part of the control operation of the control circuit P2.

FIG. 13 is a flowchart showing a part of the control operation of the control circuit P2.

FIG. 14 is a flowchart showing a part of the control operation of the control circuit P2.

FIG. 15 is a flowchart showing the rest of the control operation of the control circuit P2.

FIG. 16 is a longitudinal sectional view of the pickup camera t2 shown in FIG.

FIG. 17A shows power supply circuits 20A1, 20b2,
20C3, voltage command value VdcA1 = VdcB2 = VdcC3
= Vh (Vh = 3.5 + e6 [A / m ² ]), phase arrangement of linear motor 1L and continuous casting mold M1,
FIG. 4B is a block diagram showing the electromagnetic force (thrust) applied to the molten steel MM in M2 and M3, and FIG. 4B shows a voltage command value VdcA1 = 0, Vdc.
Linear motor 1 when B2 = VdcC3 = Vh is specified
FIG. 3C is a block diagram showing the phase arrangement and electromagnetic force of the linear motor 1L when the voltage command values VdcB2 = 0 and VdcA1 = VdcC3 = Vh are indicated. .

FIG. 18D shows the power supply circuits 20A1, 20b2,
20C3, voltage command value VdcC3 = 0, VdcA1 = Vdc
It is a block diagram which shows the phase arrangement of 1 L of linear motors when B2 = Vh was instructed, and the electromagnetic force applied to the molten steel MM in the continuous casting molds M1, M2, M3.

[Explanation of symbols]

1E, 1L: Linear motor 20A1, 20B
2,20C3: Power supply circuit Ea, La: Electromagnet core Eb, Lb: Auxiliary core E1 to E12, L1 to L12: Electric coil MM: Molten metal M11, M21, M31: Non-magnetic stainless steel plate M12, M22, M
32: Copper plate M1, M2, M3: Continuous casting mold P2: Control circuit t1, t2, t3: Pickup camera U, V, W: AC voltage Ua, Va, Wa, Ub, Vb, Wb, Uc, Vc, Wc: Power supply connection terminal VCO: Voltage controlled oscillator

Continuation of front page (56) References JP-A-6-182511 (JP, A) JP-A-5-146854 (JP, A) JP-A-6-182518 (JP, A) JP-A-4-200849 (JP) JP-A-8-290249 (JP, A) JP-A-8-224648 (JP, A) JP-A-8-243698 (JP, A) JP-A-8-206800 (JP, A) JP-A-8-108264 (JP, A) JP-A-8-108257 (JP, A) JP-A-8-90169 (JP, A) JP-A-7-256412 (JP, A) JP-A-7-246444 (JP, A) A) JP-A-6-182517 (JP, A) JP-A-5-38559 (JP, A) JP-A-63-188461 (JP, A) JP-A-7-24559 (JP, A) JP-A-63 -183761 (JP, A) JP-A-62-279060 (JP, A) JP-A-2-16251 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/115 B22D 11/00 B22D 11/04 311 B22D 11/16 104

Claims (4)

(57) [Claims] An electromagnet core having a plurality of slots distributed in a y-direction and a first linear motor mounted in the slots and having a plurality of sets of electric coils n distributed in the y-direction.
An electromagnet core having a plurality of slots distributed in the y direction and a plurality of sets of n electric coils distributed in the y direction mounted on the slots, with the mold and the molten metal in the mold interposed therebetween; A second linear motor facing the first linear motor; each of which applies a thrust along a slot arrangement direction y to a molten metal to a pair of electric coils facing the first and second linear motors; A plurality of sets of energizing means for applying an AC voltage having a given phase difference and a voltage level specified by the voltage level signal;
A surface flaw detecting means for detecting a surface flaw having a longitudinal component in the drawing direction at each surface section corresponding to the set section of the electric coil; and a surface flaw at which the surface flaw detection means has detected an increase in the surface flaw. A level control means for providing a voltage level signal designating application of a high voltage level to a corresponding set of energizing means; and a flow control device for molten metal in a continuous casting mold. 2. A surface flaw detecting means detects a surface flaw having a longitudinal component in a drawing direction, and a level control means applies a current to a set of energizing means corresponding to a surface section which has detected an increase in the surface flaw.
The apparatus for controlling the flow of molten metal in a continuous casting mold according to claim 1, wherein a voltage level signal specifying the application of a low voltage level is provided. 3. An electromagnet core having a plurality of slots distributed in the direction of arrangement of a plurality of n molds arranged in the y direction and having a plurality of slots facing the molds, and a plurality of n sets of electric coil groups mounted in the slots. 1 linear motor; an electromagnet core having a plurality of slots distributed in the arrangement direction of the mold and facing the mold, and a plurality of n sets of electric coils mounted in the slots, wherein the plurality of n molds are interposed. A second linear motor opposite to the first linear motor;
And a pair of opposing electric coil groups of the second linear motor having a phase difference for applying a thrust to the molten metal along a slot arrangement direction to the molten metal, and applying an AC voltage having a voltage level designated by a voltage level signal. Set n conducting means; surface flaw detecting means for detecting surface flaws having a longitudinal component in a drawing direction of each cast piece cast by the plurality n of molds; and A level control means for supplying a voltage level signal designating the application of a high voltage level to an energizing means connected to a group of electric coils immediately adjacent to the mold in which the increase has been detected; . 4. The surface flaw detecting means detects a surface flaw having a longitudinal component in the drawing direction, and the level control means is connected to an electric coil group of the nearest set of the mold which has detected the increase of the surface flaw. 4. The flow control device for molten metal in a continuous casting mold according to claim 3, wherein a voltage level signal designating application of a low voltage level is supplied to the energizing means.