JP2005230849A - Continuous casting method using twin-mold, electromagnetic braking apparatus for twin-mold and mold for continuous casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform the optimum control of an electromagnetic brake at the narrow width time and at the wide width time with one set of an electric source device. <P>SOLUTION: In the case of casting by using a twin-mold changeable to the width of both sub-molds 3a, 3b parted with a water-cooled copper plate 3c for parting, inserted into the width center part by individually moving both short wall sides 3d at the outside in the width direction of the mold, a method for continuous casting is performed by setting the total eight pieces of electromagnetic coils 3e for braking by acting the electromagnetic force to molten steel spouted flow from each spouting hole of an immersion nozzle 2 having two holes whose spouting direction is the width direction of the mold at the outer peripheral part of the copper plate of the mold. It is selected by using a changeover circuit at the electric source device 7 side, whether only two of the molten steel spouted flows directed to the interval between the immersion nozzle 2 and the water-cooled copper plate 3c are braked, or the whole four molten steel spouted flows are braked, according to the width of the above sub-molds 3a, 3b at both sides. The brake efficiency can be improved by performing the optimum electromagnetic brake control according to the casting width. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a molten steel flow control technology in a twin mold for the purpose of quality improvement and casting speed improvement (productivity improvement) in a slab continuous casting facility.

There is twin mold casting technology for improving productivity in slab casting. In this method, two cast pieces are pulled out simultaneously by the same pinch roll.
As shown in FIG. 7, the twin mold 21 used for casting is obtained by inserting a partitioning water-cooled copper plate 22 at the center of the width, and the width of the sub-molds 21 a and 21 b partitioned right and left by the water-cooled copper plate 22. The change, that is, the change of the casting width, is generally performed by synchronously moving both short sides 23 located outside the twin mold 21 in the mold width direction, so that the widths of the left and right sub molds 21a and 21b are the same. is there.

  By the way, the immersion nozzle 24 for injecting the molten steel in the tundish into the twin mold is positioned at the center of the width of the sub molds 21a and 21b when the casting width is the narrowest as shown in FIG. It is fixed to the bottom of the tundish and its position is unchanged.

  Therefore, as shown in FIG. 7B, when the casting width is wide, the relative position of the immersion nozzle 24 with respect to the sub molds 21a and 21b is located closer to the water-cooled copper plate 22 from the center of the width of the sub molds 21a and 21b. It will be.

  When the width is wide, the flow velocity energy of the molten steel discharged from the immersion nozzle 24 (usually a two-hole nozzle) is stronger toward the water-cooled copper plate 22 at the center than toward the outer short side 23, and the sub molds 21a and 21b. Drift and temperature deviation in the width direction of the steel plate, and stagnation may occur in the slab portion located on the central water-cooled copper plate 22 side. ) And outside (short sides on both sides).

  Increasing the casting speed improves the productivity of continuous casting. However, when the casting speed is increased, the amount of molten steel discharged from the immersion nozzle increases, the collision energy to the short side also increases, the reverse flow of the molten steel increases, and the molten metal surface fluctuation also increases. Therefore, in order to increase the casting speed, it is necessary to laminate and calm the molten steel flow. Application of electromagnetic braking is effective for laminating and calming the molten steel flow, and a technique for installing an electromagnetic braking device (hereinafter referred to as “electromagnetic brake”) on a mold is known.

  Usually, an immersion nozzle that discharges molten steel in a tundish into a mold has discharge holes on both sides in the mold width direction, and the number of discharge holes is generally two. If the distance from the immersion nozzle to the water-cooled copper plate located in the center and the short side located outside is the same as in the narrow width, the electromagnetic brake may be applied evenly over the entire mold width. In addition, if the distance is different, it is necessary to change the applied strength of the electromagnetic brake in the mold width direction.

  In continuous casting equipment, thermocouples are installed on the mold copper plate for analysis of molten steel flow in the mold during casting, molten steel temperature measurement and breakout prediction, etc., but electromagnetic brakes and electromagnetic stirrers are installed in the mold. In this case, since the coil portion is installed in contact with the backup frame that holds the mold copper plate, it interferes with the thermocouple, and the thermocouple cannot be installed at the coil installation portion. Therefore, a thermocouple should be installed avoiding the coil installation part, or the coil must be installed away from the backup frame.

However, in order to individually control the amount of deceleration of the discharge flow rate inside and outside each sub-mold of the twin mold, it is necessary to individually change the strength of the inner and outer electromagnetic brakes as shown in FIG. In this case, the power supply device is also required separately. For these reasons, in continuous casting using a twin mold, the same magnetic field strength is usually provided in the vicinity of each discharge hole regardless of whether the width is narrow or wide.
JP-T-2001-521444

  In addition, when the thermocouple is installed away from the coil installation part, the analysis accuracy, measurement accuracy, and prediction accuracy are deteriorated.On the other hand, when the coil is installed away from the backup frame, the electromagnetic brake or electromagnetic stirring is not performed. Inefficiency.

  The problem to be solved by the present invention is that the molten steel flow control technology in the twin mold cannot perform optimal control of the electromagnetic brake in a narrow width and a wide width with one set of power supply devices. The improvement in the efficiency of electromagnetic agitation and the improvement in accuracy of molten steel flow analysis, molten steel temperature measurement, breakout prediction and the like cannot be achieved at the same time.

  In a twin mold, in order to individually control the degree of deceleration of the molten steel discharge flow rate inside and outside the sub mold, it is common to install power supply devices that generate static magnetic fields individually (four in a twin mold). is there.

  On the other hand, the coil installed in the mold has a severe installation environment such as the heat effect of molten steel in the mold and steam from the mold cooling water, so the power supply cable to the coil is often an expensive cable with good environmental resistance, It is desirable to minimize the number as much as possible.

  Also, many thermocouples for breakout prediction (detection) are usually installed in the height direction and width direction on the long side and short side of the mold in order to accurately detect the behavior of the mold temperature. In that case, it is necessary to install without interfering with the electromagnetic brake or electromagnetic stirring coil.

  As a result of investigating and researching the configuration for selecting the electromagnetic force to be applied at the time of narrow width and wide width in continuous casting operation using such a twin mold, the present inventor has found that each of the sub molds constituting the twin mold. When electromagnetic brake iron cores are provided individually, air gaps are created between the iron cores, increasing the magnetic resistance as a whole, reducing brake efficiency, and reducing the generated electromagnetic force. I found out.

  In addition, in the twin molds in which the casting widths of the left and right sub-molds are the same, the strength of the electromagnetic brake to be applied to each sub-mold, that is, the applied strength to each sub-mold may be the same. Batch application is possible.

The present invention was made based on the above knowledge of the present inventor,
In the continuous casting method of the present invention, in continuous casting using a twin mold, an electromagnetic coil for braking a molten steel discharge flow from each discharge hole of an immersion nozzle having two holes whose discharge direction is the mold width direction is provided on the outer periphery of the mold copper plate. It is a method of arranging a total of 8 pieces in the part and continuously casting,
To enable optimal control of electromagnetic brakes at narrow and wide widths,
Depending on the width of the sub-mold, whether to brake only two molten steel discharge flows facing between the immersion nozzle and the partition water-cooled copper plate or whether to brake all four molten steel discharge flows is determined on the power supply side. Selection using a switching circuit is the main feature.

And the electromagnetic brake for the twin mold of the present invention used for carrying out the continuous casting method of the present invention is:
A water-cooled copper plate for partitioning is inserted in the center of the mold width, and the outer short sides are individually arranged in the outer periphery of the mold copper plate in a twin mold that can move in the mold width direction, and the molten steel from each discharge hole of the immersion nozzle An electromagnetic coil for braking by applying an electromagnetic force to the discharge flow of
A power supply device for supplying a direct current to the electromagnetic coil;
It is a twin mold electromagnetic brake that is arranged on the power supply side and has a circuit for switching current,
A total of eight electromagnetic coils are arranged on the outer periphery of the mold copper plate,
When the immersion nozzle has two holes whose molten steel discharge direction is the mold width direction,
Depending on the width of the sub-mold, the circuit selects whether to brake only two molten steel discharge flows between the immersion nozzle and the partition water-cooled copper plate or to brake all four molten steel discharge flows The most important feature is what is possible.

In the electromagnetic brake for the twin mold of the present invention,
The power supply device for supplying a direct current converted from an alternating current to the eight electromagnetic coils is one set, and six power supply cables from the power supply device to the eight electromagnetic coils are used. It is desirable that a total of eight magnetic poles for applying electromagnetic force to the discharge flow are arranged in the vicinity of each discharge hole of the immersion nozzle, and that the four magnetic poles on each long side are each of an integrated structure.

Further, the continuous casting mold of the present invention used for carrying out the continuous casting method of the present invention,
Mold copper plate,
A backup frame for supporting the mold copper plate;
A thermocouple for measuring the temperature of the mold copper plate;
A mold having an electromagnetic coil disposed on the outer periphery of the mold copper plate,
Place the thermocouple by providing a slit-shaped notch in the thermocouple installation site of the backup frame at a position that interferes with the electromagnetic coil,
The main feature is that the electromagnetic coil can be arranged in contact with the backup frame at the interference position.

  According to the present invention, in continuous casting using a twin mold, an electromagnetic coil to be braked is selected according to the casting width, so that the optimum electromagnetic brake control according to the casting width can be performed and the braking efficiency can be improved. is there.

  Further, in the continuous casting mold of the present invention, since a thermocouple can be installed in the vicinity of the electromagnetic coil installed in contact with the backup frame, the molten steel flow analysis in the mold, molten steel can be performed without deteriorating the electromagnetic brake and electromagnetic stirring efficiency. There is an advantage that accuracy can be improved such as temperature measurement and breakout prediction.

Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS.
FIG. 1 is a view for explaining continuous casting using the twin mold of the present invention. As shown in FIG. 1 (a), the molten steel in the tundish 1 has a length in the casting direction, for example, via an immersion nozzle 2. It is injected into both sub-molds 3a and 3b of the twin mold 3 of 900 mm. At this time, as indicated by the arrows, the molten steel flow is discharged from the immersion nozzle 2 downward, for example, at an angle of 25 ° toward the central water-cooled copper plate 3c and the outer short side 3d.

  3e is an electromagnetic coil 3e that applies an electromagnetic brake force to the molten steel flow discharged from the discharge hole of the immersion nozzle 2 to equalize the flow velocity energy of the molten steel. As shown in FIG. A total of eight are arranged, two each so that the center in the height direction comes to both sides of the discharge hole of the immersion nozzle 2 on the long side of 3a and 3b. In FIG. 1, reference numeral 4 denotes a vortex flow level meter for detecting the level of hot water in the mold, 5 denotes a sliding nozzle attached to the immersion nozzle 2, and 6 denotes a pinch roll.

  As described above, the electromagnetic coil 3e has a structure in which the magnetic poles of the electromagnetic coil 3e arranged on the long side of each of the sub-molds 3a and 3b are integrated as shown in FIG. Depending on the casting width, the electromagnetic coil 3e to be applied is selected from these electromagnetic coils 3e.

  FIG. 3 shows an example of a power supply device 7 for supplying a direct current converted from an alternating current to the electromagnetic coil 3e, and a circuit that is arranged on the power supply device 7 side and switches the current to be supplied to the electromagnetic coil 3e. Show. As shown in FIG. 3, the energized current is switched by the switch board 9 when only the inner electromagnetic coil 3e is applied (A) and when all the electromagnetic coils 3e are applied (B). Yes.

  The example shown in FIG. 3 shows that one power supply device 7 is connected to eight electromagnetic coils 3e by six power supply cables 8a to 8f, but the circuit is devised. Thus, the polarity of one of the four electromagnetic coils 3e located at the center (the right side in FIG. 3) in parentheses corresponds to the switching of the current to be supplied from the narrow to the wide. As shown, the S pole is changed to the N pole, and the N pole is changed to the S pole. In addition, 10 in FIG. 3 is a cable which connects between the electromagnetic coils 3e, and this cable 10 does not appear outside.

  In the continuous casting using the twin mold 3 having such a configuration, when both of the short sides 3d are brought closer to the center of the width and the casting width is narrow, the two immersion nozzles 2 are positioned at the center of the sub-molds 3a and 3b. The water-cooled copper plate 3c and the short side 3d located outside are located at the center.

  Therefore, as shown in FIG. 4A, the switch panel 9 is switched to B, and the same application is applied to the eight electromagnetic coils 3e as shown in FIG. A braking force as indicated by an arrow is applied to both discharge flows to the water-cooled copper plate 2c located at the center and the short side 3d located outside.

  On the other hand, when the casting width is wide when both short sides 3d are moved to the outside of the twin mold 3, the distance L1 between the two immersion nozzles 2 to the water-cooled copper plate 3c located at the center of the sub-molds 3a and 3b is small. It is shorter than the distance L2 to the short side 3d located outside (see FIG. 1B).

  Therefore, as shown in FIG. 4B, the switch panel 9 is switched to A and applied only to the four electromagnetic coils 3e located at the center as shown in FIG. A braking force as indicated by an arrow is applied only to the discharge flow to the water-cooled copper plate 2c located at the center.

  In the twin mold 3 used in the above-described continuous casting method of the present invention, or in the twin mold 3 in which the electromagnetic brake of the present invention is installed, the thermocouple 11 installed to predict breakout is the above-mentioned problem. In order to solve the problem, it is desirable to install without interfering with the electromagnetic coil 3e of the electromagnetic brake.

  Therefore, in the twin mold 3 of the present invention, as shown in FIG. 5, a slit-like shape having a width of 50 mm, a depth of 30 mm, and a length of 400 mm, for example, is provided at the thermocouple 11 installation site of the backup frame 3g that supports the mold copper plate 3f. By providing a notch 3ga and disposing the thermocouple 11 in the notch 3ga, the electromagnetic coil 3e disposed on the outer periphery of the mold copper plate 3f can be disposed in contact with the backup frame 3g. Needless to say, the thermocouple 11 attached to the notch 3ga is shorter than the thermocouple 11 attached to other parts as shown in FIG.

  The twin mold 3 of the present invention having such a configuration is not limited to the one provided with an electromagnetic brake, but can be applied to one provided with an electromagnetic stirring device.

Hereinafter, the results of experiments conducted to confirm the effects of the present invention will be described.
The twin mold used in the experiment has the configuration shown in FIG. 3 and FIG. 5, and the electromagnetic coil used was a coil of 100 turns per magnetic pole wound around an iron core that is a laminated structure of silicon steel plates. The magnetic flux generated by this electromagnetic coil has a maximum magnetic flux density of 0.35 Tesla, the normal applied magnetic flux density is 0.15 to 0.35 Tesla, and a power supply having a direct current of 440 volts, 750 amps and 330 kW is used.

  FIG. 6 shows the results when low carbon steel was cast at a width of 1250 mm by the method of the present invention using the twin mold of the present invention and the electromagnetic brake. As is clear from FIG. 6, when the electromagnetic brake control was not performed (no electromagnetic brake), the maximum casting speed at which no rash occurred was 1.4 m / min (solid line in FIG. 6).

  On the other hand, when the electromagnetic brake control according to the present invention is carried out (electromagnetic brake current 250A and 500A energization: broken line in FIG. 6), the maximum casting speed that does not cause rash is 1.6 m / min. I was able to improve.

  It goes without saying that the present invention is not limited to the above-described examples, and the embodiment may be appropriately changed within the scope of the technical idea described in each claim.

  The present invention described above is not limited to a twin mold, and can be applied to an ordinary mold as long as the electromagnetic force can be controlled symmetrically in the long side direction.

It is a front view for demonstrating the continuous casting using the twin mold of this invention, (a) is explanatory drawing of the discharge hole and eddy current level meter of an immersion nozzle, (b) is explanatory drawing of the arrangement position of an electromagnetic coil. . It is a figure for demonstrating the brake force applied at the time of the continuous casting operation using the twin mold of this invention, (a) is at the time of narrow width, (b) is at the time of wide. It is a figure explaining the connection state of the power supply device of the twin mold of this invention, and an electromagnetic coil. FIGS. 3A and 3B are diagrams similar to FIG. 3, in which FIG. 3A is a diagram when applying a narrow width, and FIG. 3B is a diagram when applying a wide width. It is a figure explaining the installation state of the thermocouple in the twin mold of this invention, (a) is the figure seen from the plane, (b) is BB sectional drawing of (a). It is the figure which showed the effect of this invention, and is the figure which showed the relationship between casting speed and molten steel superheat degree. It is explanatory drawing of a twin casting_mold | template, (a) shows the time of narrow width, (b) shows the time of wide width. It is a figure explaining the structure of the electromagnetic coil in the case of changing the electromagnetic brake force applied to a twin mold | type with a prior art.

Explanation of symbols

2 Submerged nozzle 3 Twin mold 3a, 3b Sub mold 3c Water-cooled copper plate 3d Short side 3e Electromagnetic coil 3f Molded copper plate 3g Backup frame 3ga Notch 7 Power supply device 8a-8f Power supply cable 9 Switch panel 11 Thermocouple

Claims (5)

When casting using twin molds that can change the width of both sub molds partitioned by the water-cooled copper plate for partition inserted in the center of the width by individually moving the outer short sides in the mold width direction ,
A total of eight electromagnetic coils that are braked by applying electromagnetic force to the molten steel discharge flow from each discharge hole of the immersion nozzle having two holes whose discharge direction is the mold width direction are continuously cast on the outer periphery of the mold copper plate. A method,
Depending on the width of the sub-mold, whether to brake only two molten steel discharge flows facing between the immersion nozzle and the partition water-cooled copper plate or whether to brake all four molten steel discharge flows is determined on the power supply side. A continuous casting method using a twin mold, wherein selection is performed using a switching circuit. A water-cooled copper plate for partitioning is inserted in the center of the mold width, and both outer short sides are individually arranged on the outer periphery of the mold copper plate in the twin mold that can move in the mold width direction, and the molten steel from each discharge hole of the immersion nozzle An electromagnetic coil for braking by applying an electromagnetic force to the discharge flow of
A power supply device for supplying a direct current to the electromagnetic coil;
A twin mold electromagnetic braking device that is arranged on the power supply device side and has a circuit for switching current,
A total of eight electromagnetic coils are arranged on the outer periphery of the mold copper plate,
When the immersion nozzle has two holes whose molten steel discharge direction is the mold width direction,
Depending on the width of the sub-mold, the circuit selects whether to brake only two molten steel discharge flows between the immersion nozzle and the partition water-cooled copper plate or to brake all four molten steel discharge flows An electromagnetic braking device for a twin mold characterized by being made possible.   The power supply device for supplying a direct current converted from an alternating current to the eight electromagnetic coils is one set, and six power supply cables from the power supply device to the eight electromagnetic coils are provided. Item 3. An electromagnetic braking device for a twin mold according to Item 2.   A total of eight magnetic poles for applying an electromagnetic force to the discharge flow of molten steel are arranged in the vicinity of each discharge hole of the immersion nozzle, and each of the four magnetic poles on the long side has an integrated structure. Item 4. The electromagnetic braking device for a twin mold according to Item 2 or 3. Mold copper plate,
A backup frame for supporting the mold copper plate;
A thermocouple for measuring the temperature of the mold copper plate;
A mold having an electromagnetic coil disposed on the outer periphery of the mold copper plate,
Place the thermocouple by providing a slit-like notch in the thermocouple installation site of the backup frame at a position that interferes with the electromagnetic coil,
A casting mold for continuous casting, characterized in that the electromagnetic coil can be disposed in contact with the backup frame at the interference position.

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