JP7031517B2 - Continuous casting method - Google Patents

Description

The present invention relates to a continuous casting method.

In continuous casting, molten metal (for example, molten steel) once stored in the tundish is injected into the mold from above via a dipping nozzle, where the outer peripheral surface is cooled and the solidified slab is pulled out from the lower end of the mold. Therefore, casting is continuously performed. The solidified portion of the outer peripheral surface of the slab is called a solidified shell.

Here, the molten metal contains gas bubbles of an inert gas (for example, Ar gas) supplied together with the molten metal to prevent clogging of the discharge hole of the immersion nozzle, non-metal inclusions, and the like. If these impurities remain in the slab after casting, it causes deterioration of the quality of the product. In general, since the specific gravity of these impurities is smaller than the specific gravity of the molten metal, they are often floated and removed in the molten metal during continuous casting. Therefore, when the casting speed is increased, the floating separation of the impurities is not sufficiently performed, and the quality of the slab tends to deteriorate. In this way, in continuous casting, there is a trade-off relationship between productivity and slab quality, that is, when productivity is pursued, slab quality deteriorates, and when slab quality is prioritized, production is performed. There is a relationship that reduces sex.

In recent years, the quality required for some products such as automobile exterior materials has become stricter year by year. Therefore, in continuous casting, there is a tendency that operations are carried out at the expense of productivity in order to ensure quality. In view of such circumstances, in continuous casting, a technique for further improving productivity while ensuring the quality of slabs has been required.

On the other hand, it is known that the quality of slabs is greatly affected by the flow of molten metal in the mold during continuous casting. Therefore, by appropriately controlling the flow of the molten metal in the mold, it may be possible to realize high-speed stable operation while maintaining the desired quality of the slab, that is, to improve the productivity.

In order to control the flow of the molten metal in the mold, a technique using an electromagnetic force generator that applies an electromagnetic force to the molten metal in the mold has been developed. In this specification, the group of members around the mold including the mold and the electromagnetic force generator is also referred to as a mold facility for convenience.

Specifically, as the electromagnetic force generator, an electromagnetic brake device and an electromagnetic agitation device are widely used. Here, the electromagnetic braking device is a device that suppresses the flow of the molten metal by applying a static magnetic field to the molten metal to generate a braking force in the molten metal. On the other hand, the electromagnetic agitator generates an electromagnetic force called Lorentz force in the molten metal by applying a dynamic magnetic field to the molten metal, and the molten metal is swirled in the horizontal plane of the mold. It is a device that gives a pattern.

The electromagnetic brake device is generally provided so as to generate a braking force in the molten metal that weakens the force of the discharge flow ejected from the immersion nozzle. Here, the discharge flow from the immersion nozzle collides with the inner wall of the mold, so that the upward flow (that is, the direction in which the molten metal surface is present) and the downward direction (that is, the slab is pulled out). Form a downward flow toward (direction). Therefore, by weakening the momentum of the discharge flow by the electromagnetic brake device, the momentum of the ascending flow can be weakened and the fluctuation of the molten metal level can be suppressed. Further, since the momentum of the discharge flow colliding with the solidified shell is weakened, the effect of suppressing the breakout due to the remelting of the solidified shell can be exhibited. As described above, the electromagnetic brake device is often used for the purpose of high-speed stable casting. Further, according to the electromagnetic brake device, since the flow velocity of the downward flow formed by the discharge flow is suppressed, the floating separation of impurities in the molten metal is promoted, and the internal quality of the slab (hereinafter, also referred to as internal quality) is promoted. It becomes possible to obtain the effect of improving.

On the other hand, the disadvantage of the electromagnetic braking device is that the flow velocity of the molten metal at the solidified shell interface becomes low, so that the surface quality of the slab may deteriorate. In addition, since it becomes difficult for the ascending flow formed by the discharge flow to reach the molten metal surface, there is a concern that the temperature of the molten metal decreases, causing skin tension and causing internal defects.

The electromagnetic agitator imparts a predetermined flow pattern to the molten metal as described above, that is, generates a swirling flow in the molten metal. As a result, the flow of the molten metal at the solidified shell interface is promoted, so that impurities such as the above-mentioned Ar gas bubbles and non-metal inclusions are suppressed from being trapped by the solidified shell, and the surface quality of the slab is improved. Can be improved. On the other hand, the disadvantage of the electromagnetic agitator is that when the swirling flow collides with the inner wall of the mold, ascending and descending flows are generated in the same manner as the discharge flow from the immersion nozzle described above, so that the ascending flow is on the molten metal surface. It may be mentioned that the internal quality of the slab may be deteriorated by entraining molten powder or the like and causing the downward flow to push impurities downward from the mold.

As described above, the electromagnetic brake device and the electromagnetic agitator have advantages and disadvantages from the viewpoint of ensuring the quality of the slab (meaning the surface quality and the internal quality in the present specification). Therefore, for the purpose of improving both the surface quality and the internal quality of the slab, a technique for performing continuous casting using a mold facility equipped with both an electromagnetic brake device and an electromagnetic agitation device for the mold has been developed. .. For example, Patent Document 1 discloses a mold facility having an electromagnetic agitator on the upper side and an electromagnetic brake device on the lower side of the long side mold plate of the mold.

Japanese Unexamined Patent Publication No. 2008-137031

Here, the electromagnetic brake device and the electromagnetic agitation device do not mean that the advantages of both devices can be easily obtained by simply installing both devices. For example, as can be seen from the effect on the flow velocity of the molten metal at the solidified shell interface described above, these devices also have an effect of canceling each other's effects. Therefore, in continuous casting using both an electromagnetic brake device and an electromagnetic agitation device, the quality of the slab is often deteriorated as compared with the case where each of these devices is used alone.

For example, as in Patent Document 1, consider a configuration in which an electromagnetic agitator is provided in the upper part and an electromagnetic brake device is provided in the lower part. In this configuration, the electromagnetic brake device can bounce the discharge flow upward to the mold. If the flow velocity of the discharge flow bounced up by the electromagnetic brake device is excessively large, the formation of a swirling flow due to electromagnetic agitation in the upper part of the mold may be hindered. Therefore, in this case, the effect of improving the surface quality of the slab by electromagnetic agitation cannot be suitably obtained. On the other hand, when the discharge flow descends without being flipped up by the electromagnetic brake device, it becomes difficult to obtain the effect of improving the internal quality of the slab by the electromagnetic brake.

In this way, when both the electromagnetic brake device and the electromagnetic agitation device are used, in order to further improve the quality of the slab, the configuration and driving method of both devices, etc., so that the advantages of both devices can be effectively exhibited. It is necessary to devise. Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved continuous casting method capable of further improving the quality of slabs. There is something in it.

In order to solve the above problems, according to a certain viewpoint of the present invention, an electromagnetic force is applied to the molten metal in the mold so as to generate a swirling current in the horizontal plane by the electromagnetic stirring device, and the electromagnetic stirring device is used. A continuous casting method in which continuous casting is performed while applying an electromagnetic force in a direction for braking the discharge flow to the discharge flow of the molten metal from the immersion nozzle in the mold by an electromagnetic braking device installed below. The immersion nozzle is provided with a pair of molten metal discharge holes on both sides of the mold in the long side direction of the mold, and the electromagnetic braking device is outside each of the pair of long side mold plates in the mold. An iron core provided on each side surface and provided with a pair of teeth portions facing the long side mold plate on both sides of the immersion nozzle in the mold long side direction, and wound around each of the teeth portions. A coil is provided, and by applying a DC current to the coil of the electromagnetic braking device to generate a magnetic field, an electromagnetic force in a direction for braking the discharge flow is applied to the discharge flow. On each side of the central axis of the immersion nozzle in the long side direction of the mold, the direction from the immersion nozzle to the short side mold plate of the mold along the long side direction of the mold is the positive direction of the first direction and is vertically upward. When the direction is the positive direction of the second direction, the positional relationship between the immersion nozzle and the tooth portion of the electromagnetic braking device can be determined by the continuous casting method given by the following formulas (1) and (2). Provided.

However,
x0: Coordinates in the first direction of the lower end of the opening formed on the inner peripheral surface of the immersion nozzle by the discharge hole y0: The lower end of the opening formed on the inner peripheral surface of the immersion nozzle by the discharge hole. Coordinates x1 in the second direction of the portion 1: Coordinates in the first direction of the central portion of the teeth portion y1: Coordinates x2 of the central portion of the teeth portion in the second direction: The dipping nozzle side end portion of the teeth portion Coordinates y2 of the upper end portion in the first direction: Coordinates α in the second direction of the upper end portion of the immersion nozzle side end portion of the teeth portion: Inclinement angle of the lower portion of the discharge hole with respect to the first direction.

The positional relationship between the immersion nozzle and the tooth portion of the electromagnetic brake device on each side of the central axis of the immersion nozzle in the long side direction of the mold is given by the following equations (3) and (4). May be good.

The positional relationship between the immersion nozzle and the tooth portion of the electromagnetic brake device on each side of the central axis of the immersion nozzle in the long side direction of the mold is given by the following equations (5) and (6). May be good.

As described above, according to the present invention, it is possible to further improve the quality of slabs in continuous casting.

It is a side sectional view schematically showing one configuration example of the continuous casting machine which concerns on this embodiment. It is sectional drawing in the YY plane of the mold equipment which concerns on the same embodiment. It is sectional drawing of the mold equipment in the cross section AA shown in FIG. It is sectional drawing of the mold equipment in the BB cross section shown in FIG. It is sectional drawing of the mold equipment in the CC cross section shown in FIG. It is a figure for demonstrating the direction of the electromagnetic force applied to the discharge flow of molten steel by an electromagnetic brake device. It is a figure which shows the state of the flip-up behavior of a discharge flow obtained by a numerical analysis simulation schematically. It is a figure for demonstrating the trajectory of the main flow at the time of discharge of the discharge flow of molten steel. It is a figure which shows the relationship between the casting speed (m / min) and the distance (mm) from the molten steel surface when the thickness of a solidified shell is 4 mm or 5 mm. It is a figure which shows the evaluation result of the quality of a slab for each combination of a throughput (ton / min) and a magnetic flux density (T) of an electromagnetic brake. It is a figure which shows the evaluation result of the quality of a slab for each combination of a value h1 and a value h2.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, and duplicate description will be omitted.

In each drawing shown in the present specification, the sizes of some constituent members may be exaggerated for the sake of explanation. The relative size of each member shown in each drawing does not necessarily accurately represent the magnitude relationship between the actual members.

Further, in the following, as an example, an embodiment in which the molten metal is molten steel will be described. However, the present invention is not limited to such an example, and the present invention may be applied to continuous casting on other metals.

<1. Configuration of continuous casting machine>
First, with reference to FIG. 1, the configuration of the continuous casting machine 1 and the continuous casting method according to the embodiment of the present invention will be described. FIG. 1 is a side sectional view schematically showing a configuration example of a continuous casting machine 1 according to the present embodiment.

As shown in FIG. 1, the continuous casting machine 1 according to the present embodiment is an apparatus for continuously casting molten steel 2 using a mold 110 for continuous casting to manufacture slabs and other slabs 3. The continuous casting machine 1 includes a mold 110, a ladle 4, a tundish 5, a dipping nozzle 6, a secondary cooling device 7, and a slab cutting machine 8.

The ladle 4 is a movable container for transporting the molten steel 2 from the outside to the tundish 5. The ladle 4 is arranged above the tundish 5, and the molten steel 2 in the ladle 4 is supplied to the tundish 5. The tundish 5 is arranged above the mold 110 to store the molten steel 2 and remove inclusions in the molten steel 2. The immersion nozzle 6 extends downward from the lower end of the tundish 5 toward the mold 110, and the tip thereof is immersed in the molten steel 2 in the mold 110. The immersion nozzle 6 continuously supplies the molten steel 2 from which inclusions have been removed by the tundish 5 into the mold 110.

The mold 110 has a square tubular shape according to the width and thickness of the slab 3, and is, for example, a pair of long-side mold plates (corresponding to the long-side mold plates 111 shown in FIG. 2 and the like described later) and a pair of short sides. It is assembled so as to sandwich the side mold plate (corresponding to the short side mold plate 112 shown in FIG. 4 described later) from both sides. The long-side mold plate and the short-side mold plate (hereinafter, may be collectively referred to as a mold plate) are, for example, water-cooled copper plates provided with a water channel through which cooling water flows. The mold 110 cools the molten steel 2 in contact with the mold plate to produce the slab 3. As the slab 3 moves downward to the mold 110, solidification of the internal unsolidified portion 3b progresses, and the thickness of the solidified shell 3a of the outer shell gradually increases. The slab 3 including the solidified shell 3a and the unsolidified portion 3b is pulled out from the lower end of the mold 110.

In the following description, the vertical direction (that is, the direction in which the slab 3 is pulled out from the mold 110) is also referred to as the Z-axis direction. The Z-axis direction is also referred to as a vertical direction. Further, the two directions orthogonal to each other in the plane (horizontal plane) perpendicular to the Z-axis direction are also referred to as the X-axis direction and the Y-axis direction, respectively. Further, the X-axis direction is defined as a direction parallel to the long side of the mold 110 in the horizontal plane (that is, the mold width direction or the mold long side direction), and the Y-axis direction is parallel to the short side of the mold 110 in the horizontal plane. (Ie, the mold thickness direction or the mold short side direction). The direction parallel to the XY plane is also called the horizontal direction. Further, in the following description, when expressing the size of each member, the length of the member in the Z-axis direction is also referred to as a height, and is the length of the member in the X-axis direction or the Y-axis direction. May also be called width.

Here, although the illustration is omitted in FIG. 1 in order to avoid complication of the drawing, in the present embodiment, the electromagnetic force generator is installed on the outer surface of the long side mold plate of the mold 110. Then, continuous casting is performed while driving the electromagnetic force generator. The electromagnetic force generating device includes an electromagnetic stirring device and an electromagnetic braking device. In the present embodiment, continuous casting is performed while driving the electromagnetic force generator, so that casting can be performed at a higher speed while ensuring the quality of the slab. The configuration of the electromagnetic force generator will be described later with reference to FIGS. 2 to 8.

The secondary cooling device 7 is provided in the secondary cooling zone 9 below the mold 110, and cools the slab 3 drawn from the lower end of the mold 110 while supporting and transporting it. The secondary cooling device 7 includes a plurality of pairs of support rolls (for example, support rolls 11, pinch rolls 12 and segment rolls 13) arranged on both sides of the slab 3 in the thickness direction, and cooling water for the slab 3. It has a plurality of spray nozzles (not shown) for injecting water.

The support rolls provided in the secondary cooling device 7 are arranged in pairs on both sides of the slab 3 in the thickness direction, and function as a support and transport means for transporting the slab 3 while supporting it. By supporting the slab 3 from both sides in the thickness direction by the support roll, it is possible to prevent breakout and bulging of the slab 3 during solidification in the secondary cooling zone 9.

The support roll 11, the pinch roll 12, and the segment roll 13, which are the support rolls, form a transport path (pass line) for the slab 3 in the secondary cooling zone 9. As shown in FIG. 1, this path line is vertical just below the mold 110, then curves in a curved line, and finally becomes horizontal. In the secondary cooling zone 9, the portion where the pass line is vertical is referred to as a vertical portion 9A, the curved portion is referred to as a curved portion 9B, and the horizontal portion is referred to as a horizontal portion 9C. The continuous casting machine 1 having such a pass line is referred to as a vertical bending type continuous casting machine 1. The present invention is not limited to the vertical bending type continuous casting machine 1 as shown in FIG. 1, and can be applied to various other continuous casting machines such as the curved type and the vertical type.

The support roll 11 is a non-driven roll provided in the vertical portion 9A directly below the mold 110, and supports the slab 3 immediately after being pulled out from the mold 110. Since the solidified shell 3a is in a thin state, the slab 3 immediately after being pulled out from the mold 110 needs to be supported at a relatively short interval (roll pitch) in order to prevent breakout and bulging. Therefore, as the support roll 11, it is desirable to use a roll having a small diameter capable of shortening the roll pitch. In the example shown in FIG. 1, three pairs of support rolls 11 made of small-diameter rolls are provided on both sides of the slab 3 in the vertical portion 9A at a relatively narrow roll pitch.

The pinch roll 12 is a drive type roll that is rotated by a drive means such as a motor, and has a function of pulling out the slab 3 from the mold 110. The pinch roll 12 is arranged at an appropriate position in the vertical portion 9A, the curved portion 9B, and the horizontal portion 9C, respectively. The slab 3 is pulled out from the mold 110 by the force transmitted from the pinch roll 12 and conveyed along the pass line. The arrangement of the pinch roll 12 is not limited to the example shown in FIG. 1, and the arrangement position may be arbitrarily set.

The segment roll 13 (also referred to as a guide roll) is a non-driving roll provided on the curved portion 9B and the horizontal portion 9C, and supports and guides the slab 3 along the pass line. Depending on the position on the pass line, the segment roll 13 may be on either the F surface (Fixed surface, the lower left surface in FIG. 1) or the L surface (Lose surface, the upper right surface in FIG. 1) of the slab 3. They may be arranged with different roll diameters and roll pitches depending on whether they are provided.

The slab cutting machine 8 is arranged at the end of the horizontal portion 9C of the pass line, and cuts the slab 3 conveyed along the pass line to a predetermined length. The cut plate-shaped slab 14 is conveyed to the equipment in the next process by the table roll 15.

As described above, with reference to FIG. 1, the overall configuration of the continuous casting machine 1 according to the present embodiment has been described. In this embodiment, an electromagnetic force generator having a configuration described later is installed on the mold 110, and continuous casting may be performed using the electromagnetic force generator, and the electromagnetic force is generated in the continuous casting machine 1. The configuration other than the apparatus may be the same as that of a general conventional continuous casting machine. Therefore, the configuration of the continuous casting machine 1 is not limited to the one shown in the figure, and any continuous casting machine 1 may be used.

<2. Configuration of electromagnetic force generator>
Subsequently, with reference to FIGS. 2 to 8, the configuration of the electromagnetic force generator installed on the mold 110 described above will be described in detail.

2 to 5 are views showing a configuration example of the mold equipment according to the present embodiment. FIG. 2 is a cross-sectional view of the mold equipment 10 according to the present embodiment in the YY plane. FIG. 3 is a cross-sectional view of the mold equipment 10 in the cross section taken along the line AA shown in FIG. FIG. 4 is a cross-sectional view of the mold equipment 10 in the BB cross section shown in FIG. FIG. 5 is a cross-sectional view of the mold equipment 10 in the CC cross section shown in FIG. Since the mold equipment 10 has a configuration symmetrical with respect to the center of the mold 110 in the Y-axis direction, only the portion corresponding to one of the long side mold plates 111 is shown in FIGS. 2, 4 and 5. Shows. Further, in FIGS. 2, 4 and 5, the molten steel 2 in the mold 110 is also shown for ease of understanding.

Referring to FIGS. 2 to 5, in the mold equipment 10 according to the present embodiment, two water boxes 130 and 140 and electromagnetic force are generated on the outer surface of the long side mold plate 111 of the mold 110 via the backup plate 121. The device 170 and the device 170 are installed and configured.

As described above, the mold 110 is assembled so that the pair of short-sided mold plates 112 are sandwiched between the pair of long-sided mold plates 111 from both sides. The mold plates 111 and 112 are made of a copper plate. However, this embodiment is not limited to such an example, and the mold plates 111 and 112 may be formed of various materials generally used as a mold for a continuous casting machine.

Here, in the present embodiment, continuous casting of steel slabs is targeted, and the slab size thereof is about 800 to 2300 mm in width (that is, length in the X-axis direction) and thickness (that is, length in the Y-axis direction). ) About 200 to 300 mm. That is, the mold plates 111 and 112 also have a size corresponding to the slab size. That is, the long-side mold plate 111 has a width in the X-axis direction that is at least longer than the width of the slab 3 of 800 to 2300 mm, and the short-side mold plate 112 has a Y that is substantially the same as the thickness of the slab 3 of 200 to 300 mm. Has an axial width.

Further, as will be described in detail later, in the present embodiment, in order to more effectively obtain the effect of improving the quality of the slab 3 by the electromagnetic force generator 170, the length in the Z-axis direction is set to be as long as possible. The mold 110 is configured. Generally, when solidification of the molten steel 2 progresses in the mold 110, the slab 3 may be separated from the inner wall of the mold 110 due to solidification shrinkage, and the slab 3 may be insufficiently cooled. Are known. Therefore, the length of the mold 110 is limited to about 1000 mm at the longest from the molten steel surface. In the present embodiment, in consideration of such circumstances, the mold plates 111 and 112 are formed so that the length from the molten steel surface to the lower ends of the mold plates 111 and 112 is about 1000 mm.

The backup plates 121 and 122 are made of stainless steel, for example, and are provided so as to cover the outer surfaces of the mold plates 111 and 112 in order to reinforce the mold plates 111 and 112 of the mold 110. Hereinafter, for the sake of distinction, the backup plate 121 provided on the outer surface of the long side mold plate 111 is also referred to as the long side backup plate 121, and the backup plate 122 provided on the outer surface of the short side mold plate 112 is short. It is also called a side backup plate 122.

Since the electromagnetic force generator 170 applies an electromagnetic force to the molten steel 2 in the mold 110 via the long side backup plate 121, at least the long side backup plate 121 is a non-magnetic material (for example, non-magnetic stainless steel). Etc.). However, the magnetic flux of the electromagnetic brake device 160 is located on the long side backup plate 121 at a portion facing the teeth portion 164 of the iron core (core) 162 (hereinafter, also referred to as the electromagnetic brake core 162) of the electromagnetic brake device 160 described later. In order to secure the density, the magnetic soft iron 124 is embedded.

The long-side backup plate 121 is further provided with a pair of backup plates 123 extending in a direction perpendicular to the long-side backup plate 121 (that is, in the Y-axis direction). As shown in FIGS. 3 to 5, an electromagnetic force generator 170 is installed between the pair of backup plates 123. In this way, the backup plate 123 can define the width (that is, the length in the X-axis direction) of the electromagnetic force generator 170 and the installation position in the X-axis direction. In other words, the mounting position of the backup plate 123 is determined so that the electromagnetic force generator 170 can apply the electromagnetic force to the desired range of the molten steel 2 in the mold 110. Hereinafter, for the sake of distinction, the backup plate 123 is also referred to as a backup plate 123 in the width direction. The widthwise backup plate 123, like the backup plates 121 and 122, is also made of, for example, stainless steel.

The water boxes 130 and 140 store cooling water for cooling the mold 110. In the present embodiment, as shown in the figure, one water box 130 is installed in a region of a predetermined distance from the upper end of the long side mold plate 111, and the other water box 140 is placed in a region of a predetermined distance from the lower end of the long side mold plate 111. Install in. By providing the water boxes 130 and 140 in the upper part and the lower part of the mold 110, respectively, it is possible to secure a space for installing the electromagnetic force generator 170 between the water boxes 130 and 140. Hereinafter, for the sake of distinction, the water box 130 provided at the upper part of the long side mold plate 111 is also referred to as an upper water box 130, and the water box 140 provided at the lower part of the long side mold plate 111 is also referred to as a lower water box 140.

A water channel (not shown) through which cooling water passes is formed inside the long side mold plate 111 or between the long side mold plate 111 and the long side backup plate 121. The waterway extends to water boxes 130 and 140. A pump (not shown) causes cooling water to flow from one water box 130, 140 toward the other water box 130, 140 (eg, from the lower water box 140 toward the upper water box 130) through the channel. As a result, the long side mold plate 111 is cooled, and the molten steel 2 inside the mold 110 is cooled via the long side mold plate 111. Although not shown, the short-side mold plate 112 is similarly provided with a water box and a water channel, and the short-side mold plate 112 is cooled by flowing cooling water.

The electromagnetic force generator 170 includes an electromagnetic stirring device 150 and an electromagnetic braking device 160. As shown in the figure, the electromagnetic agitator 150 and the electromagnetic brake device 160 are installed in the space between the water boxes 130 and 140. In the space, the electromagnetic stirring device 150 is installed above and the electromagnetic braking device 160 is installed below. The heights of the electromagnetic agitator 150 and the electromagnetic brake device 160, and the installation positions of the electromagnetic agitator 150 and the electromagnetic brake device 160 in the Z-axis direction are described in the following [2-2. Details of the installation position of the electromagnetic force generator] will be explained in detail.

The electromagnetic stirring device 150 applies an electromagnetic force to the molten steel 2 in the mold 110 by applying a dynamic magnetic field to the molten steel 2. The electromagnetic agitator 150 is driven so as to apply an electromagnetic force in the width direction (that is, the X-axis direction) of the long-side mold plate 111 on which it is installed to the molten steel 2. In FIG. 4, the direction of the electromagnetic force applied to the molten steel 2 by the electromagnetic agitator 150 is shown by a thick arrow in a simulated manner. Here, the electromagnetic stirring device 150 provided on the long-sided mold plate 111 (that is, the long-sided mold plate 111 facing the long-sided mold plate 111 shown) is a long-sided mold plate 111 on which it is installed. Along the width direction of the mold plate 111, it is driven so as to apply an electromagnetic force in the direction opposite to the direction shown in the drawing. In this way, the pair of electromagnetic agitators 150 are driven to generate a swirling flow in the horizontal plane. According to the electromagnetic agitator 150, by generating such a swirling flow, the molten steel 2 at the interface of the solidified shell is flowed, and a cleaning effect of suppressing the trapping of air bubbles and inclusions in the solidified shell 3a is obtained, and casting is performed. The surface quality of the piece 3 can be improved.

The detailed configuration of the electromagnetic agitator 150 will be described. The electromagnetic agitation device 150 is configured by winding a lead wire around a case 151, an iron core (core) 152 (hereinafter, also referred to as an electromagnetic agitation core 152) housed in the case 151, and the electromagnetic agitation core 152. It is composed of a plurality of coils 153.

The case 151 is a hollow member having a substantially rectangular parallelepiped shape. The size of the case 151 is such that the electromagnetic stirring device 150 can apply an electromagnetic force to a desired range of the molten steel 2, that is, the coil 153 provided inside is arranged at an appropriate position with respect to the molten steel 2. It can be determined as appropriate to obtain. For example, the width W4 in the X-axis direction of the case 151, that is, the width W4 in the X-axis direction of the electromagnetic agitator 150 applies an electromagnetic force to the molten steel 2 in the mold 110 at any position in the X-axis direction. To obtain, it is determined to be larger than the width of the slab 3. For example, W4 is about 1800 mm to 2500 mm. Further, in the electromagnetic stirring device 150, an electromagnetic force is applied to the molten steel 2 from the coil 153 through the side wall of the case 151, so that the material of the case 151 is, for example, non-magnetic stainless steel or FRP (Fiber Reinforced Plastics). ) And other non-magnetic members that can secure strength are used.

The electromagnetic stirring core 152 is a solid member having a substantially rectangular parallelepiped shape, and is installed in the case 151 so that the longitudinal direction thereof is substantially parallel to the width direction (that is, the X-axis direction) of the long side mold plate 111. Will be done. The electromagnetic stirring core 152 is formed, for example, by laminating electromagnetic steel sheets.

A coil 153 is formed by winding a conducting wire around the electromagnetic stirring core 152 with the X-axis direction as the winding axis direction (that is, the coil 153 so as to magnetize the electromagnetic stirring core 152 in the X-axis direction). Is formed). As the conducting wire, for example, a copper conductor having a cross section of 10 mm × 10 mm and an internal cooling water channel having a diameter of about 5 mm is used. When a current is applied, the conductor is cooled using the cooling water channel. The surface layer of the conductor is insulated with insulating paper or the like, and the conductor can be wound in a layered manner. For example, one coil 153 is formed by winding the conducting wire in about 2 to 4 layers. Coil 153 having a similar configuration is provided in parallel at a predetermined interval in the X-axis direction.

A power supply device (not shown) is connected to each of the plurality of coils 153. By the power supply device, an alternating current is applied to the plurality of coils 153 so that the phases of the currents are appropriately shifted in the order of arrangement of the plurality of coils 153, thereby causing a swirling flow in the molten steel 2. Electromagnetic force can be applied. The drive of the power supply device can be appropriately controlled by operating a control device (not shown) including a processor or the like according to a predetermined program. The control device appropriately controls the amount of current applied to each of the coils 153, the phase of the alternating current applied to each of the coils 153, and the like, and controls the strength of the electromagnetic force applied to the molten steel 2. obtain.

The width W1 of the electromagnetic agitation core 152 in the X-axis direction is such that the electromagnetic agitation device 150 can apply an electromagnetic force to a desired range of the molten steel 2, that is, the coil 153 is in an appropriate position with respect to the molten steel 2. It can be determined as appropriate so that it can be placed. For example, W1 is about 1800 mm.

The electromagnetic brake device 160 applies an electromagnetic force to the molten steel 2 by applying a static magnetic field to the molten steel 2 in the mold 110. Here, FIG. 6 is a diagram for explaining the direction of the electromagnetic force applied to the discharge flow of the molten steel 2 by the electromagnetic brake device 160. FIG. 6 schematically shows a cross section of the configuration near the mold 110 in the XX plane. Further, in FIG. 6, the positions of the electromagnetic stirring core 152 and the tooth portion 164 of the electromagnetic brake core 162, which will be described later, are shown by simulated broken lines.

As shown in FIG. 6, the immersion nozzle 6 is provided with a pair of discharge holes 61 of the molten steel 2 on both sides in the mold long side direction (that is, the X-axis direction). The discharge hole 61 faces the short side mold plate 112, and is provided so as to be inclined downward as it advances in this direction from the inner peripheral surface side to the outer peripheral surface side of the immersion nozzle 6. The electromagnetic brake device 160 is driven so as to apply an electromagnetic force in a direction for braking the flow (discharge flow) of the molten steel 2 from the discharge hole 61 of the immersion nozzle 6 to the discharge flow. In FIG. 6, the direction of the discharge flow is shown by a thin arrow in a simulated manner, and the direction of the electromagnetic force applied to the molten steel 2 by the electromagnetic brake device 160 is shown by a thick arrow in a simulated manner. According to the electromagnetic brake device 160, by generating an electromagnetic force in a direction for braking such a discharge flow, a downward flow is suppressed, an effect of promoting floating separation of bubbles and inclusions is obtained, and the slab 3 is obtained. It is possible to improve the internal quality of.

The detailed configuration of the electromagnetic brake device 160 will be described. The electromagnetic brake device 160 includes a case 161, an electromagnetic brake core 162 housed in the case 161 and a plurality of coils 163 configured by winding a conducting wire around the electromagnetic brake core 162.

The case 161 is a hollow member having a substantially rectangular parallelepiped shape. The size of the case 161 is such that the electromagnetic braking device 160 can apply an electromagnetic force to a desired range of the molten steel 2, that is, the coil 163 provided inside is arranged at an appropriate position with respect to the molten steel 2. It can be determined as appropriate to obtain. For example, the width W4 in the X-axis direction of the case 161, that is, the width W4 in the X-axis direction of the electromagnetic brake device 160 may apply an electromagnetic force to the molten steel 2 in the mold 110 at a desired position in the X-axis direction. As such, it is determined to be larger than the width of the slab 3. In the illustrated example, the width W4 of the case 161 is substantially the same as the width W4 of the case 151. However, this embodiment is not limited to such an example, and the width of the electromagnetic stirring device 150 and the width of the electromagnetic braking device 160 may be different.

Further, in the electromagnetic brake device 160, since the electromagnetic force is applied to the molten steel 2 from the coil 163 through the side wall of the case 161, the case 161 is, for example, non-magnetic stainless steel or FRP, as in the case 151. It is made of a non-magnetic material that can ensure strength.

The electromagnetic brake core 162 corresponds to an example of an iron core of the electromagnetic brake device according to the present invention. The electromagnetic brake core 162 is a solid member having a substantially rectangular parallelepiped shape and a pair of teeth portions 164 around which the coil 163 is wound, and a pair of solid members having a substantially rectangular parallelepiped shape. It is composed of a connecting portion 165 that connects the portions 164 and a connecting portion 165. The electromagnetic brake core 162 is configured by providing a pair of tooth portions 164 so as to project from the connecting portion 165 in the Y-axis direction toward the long side mold plate 111. The electromagnetic brake core 162 may be formed, for example, by using soft iron having high magnetic properties, or by laminating electromagnetic steel sheets.

Specifically, a pair of teeth portions 164 are provided on both sides of the immersion nozzle 6 in the long side direction of the mold so as to face the long side mold plates 111, and such an electromagnetic brake device 160 is provided with a pair of long sides of the mold 110. It is installed on each outer surface of the mold plate 111. The installation position of the teeth portion 164 is such that the position where the electromagnetic force is to be applied to the molten steel 2, that is, the discharge flow from the pair of discharge holes 61 of the immersion nozzle 6 passes through the region where the magnetic field is applied by the coil 163, respectively. Can be provided in position (see also FIG. 6). The relative installation position of the tooth portion 164 with respect to the immersion nozzle 6 is described in the following [2-1. Details of the positional relationship between the immersion nozzle and the tooth portion of the electromagnetic brake device] will be described in detail.

A coil 163 is formed (that is, the electromagnetic brake core 162 is magnetized in the Y-axis direction) by winding a conductor wire around the tooth portion 164 of the electromagnetic brake core 162 with the Y-axis direction as the winding axis direction. The coil 163 is formed so as to be formed). The structure of the coil 163 is the same as that of the coil 153 of the electromagnetic stirring device 150 described above.

A power supply device (not shown) is connected to each of the coils 163. By applying a direct current to each coil 163 by the power supply device, an electromagnetic force that weakens the momentum of the discharge flow can be applied to the molten steel 2. The drive of the power supply device can be appropriately controlled by operating a control device (not shown) including a processor or the like according to a predetermined program. The control device can appropriately control the amount of current applied to each coil 163 and control the strength of the electromagnetic force applied to the molten steel 2.

The width W0 in the X-axis direction of the electromagnetic brake core 162, the width W2 in the X-axis direction of the teeth portion 164, and the distance W3 between the teeth portions 164 in the X-axis direction are set with respect to the desired range of the molten steel 2 by the electromagnetic stirring device 150. It can be appropriately determined so that the electromagnetic force can be applied, that is, the coil 163 can be arranged at an appropriate position with respect to the molten steel 2. For example, W0 is about 1600 mm, W2 is about 500 mm, and W3 is about 350 mm.

Here, for example, as in the technique described in Patent Document 1, there is an electromagnetic brake device that has a single magnetic pole and generates a uniform magnetic field in the mold width direction. In an electromagnetic brake device having such a configuration, a uniform electromagnetic force is applied in the width direction, so that the range in which the electromagnetic force is applied cannot be controlled in detail, and appropriate casting conditions are limited. There is a drawback.

On the other hand, in the present embodiment, as described above, the electromagnetic brake device 160 is configured to have two teeth portions 164, that is, to have two magnetic poles. According to such a configuration, for example, when driving the electromagnetic brake device 160, these two magnetic poles function as N pole and S pole, respectively, and are near the substantially center in the width direction (that is, the X-axis direction) of the mold 110. The application of the current to the coil 163 can be controlled by the above control device so that the magnetic flux density becomes substantially zero in the region. The region where the magnetic flux density is substantially zero is a region where an electromagnetic force is hardly applied to the molten steel 2, and is a region where the escape of the molten steel flow can be ensured so to be released from the braking force by the electromagnetic braking device 160. By securing such a region, it becomes possible to correspond to a wider range of casting conditions.

As described above, in the present embodiment, the continuous casting method using the electromagnetic force generator 170 including the electromagnetic stirring device 150 and the electromagnetic braking device 160 described above can be carried out.

In the continuous casting method according to the present embodiment, the electromagnetic stirring device 150 applies an electromagnetic force that generates a swirling flow in the horizontal plane to the molten steel 2 in the mold 110, and is installed below the electromagnetic stirring device 150. Continuous casting is performed while applying an electromagnetic force in a direction for braking the discharge flow of the molten steel 2 from the immersion nozzle 6 into the mold 110 by the electromagnetic brake device 160. Specifically, the electromagnetic force in the direction of braking the discharge flow with respect to the discharge flow by generating a magnetic field by applying a direct current to the coil 163 wound around the teeth portion 164 of the electromagnetic brake device 160. Power is given.

Further, in the continuous casting method according to the present embodiment, continuous casting is performed after the positional relationship between the immersion nozzle 6 and the teeth portion 164 of the electromagnetic brake device 160 satisfies a predetermined relationship. In the present embodiment, the quality of the slab 3 can be further improved by satisfying the predetermined relationship between the immersion nozzle 6 and the teeth portion 164 of the electromagnetic brake device 160 in this way.

[2-1. Details of the positional relationship between the immersion nozzle and the teeth of the electromagnetic brake device]
Subsequently, the positional relationship between the immersion nozzle 6 and the teeth portion 164 of the electromagnetic brake device 160 will be described in detail.

As described above, in continuous casting using both the electromagnetic brake device 160 and the electromagnetic agitation device 150, how the discharge flow of the molten steel 2 is flipped up by the electromagnetic brake device 160 (in other words, the discharge flow jumping behavior). ) Has a great influence on the quality of the slab 3.

Therefore, the inventor of the present invention investigated in detail the flip-up behavior of the discharge flow by the electromagnetic brake device 160 by performing a numerical analysis simulation simulating the casting conditions in actual operation, and as a result, various findings described below. I found.

FIG. 7 is a diagram schematically showing the state of the flip-up behavior of the discharge flow obtained by the numerical analysis simulation. In FIG. 7, as the loci of the discharge flow showing each flip-up behavior, the trajectories T11, T12, and T13 followed by the discharge flow before and after the electromagnetic force is applied from the electromagnetic brake device 160 are shown, respectively.

In FIG. 7 and FIG. 8 described later, only one side of the central axis of the immersion nozzle 6 in the long side direction of the mold (that is, the X-axis direction) is shown for ease of understanding. The mold equipment 10 has a configuration symmetrical with respect to the central axis of the immersion nozzle 6 in the long side direction of the mold. Further, in FIG. 7 and FIG. 8 described later, an X'axis having a positive direction from the immersion nozzle 6 toward the short-side mold plate 112 along the long-side direction of the mold and a Y-axis having a vertical upward direction as a positive direction. An XY'coordinate system with an'axis'is defined. The origin of the X'Y'coordinate system is set at the intersection of the molten steel surface and the central axis of the immersion nozzle 6. The X'axis direction and the Y'axis direction correspond to examples of the first direction and the second direction according to the present invention, respectively. Further, the X'coordinate and the Y'coordinate correspond to an example of the coordinate in the first direction and the coordinate in the second direction according to the present invention, respectively.

In the locus T11 exemplified in FIG. 7, the discharge flow is incident at a position relatively distant from the immersion nozzle 6 side end portion on the upper side of the region where the tooth portion 164 of the electromagnetic brake device 160 is projected onto the X'-Y'plane. It corresponds to the flip-up behavior of the discharge flow in the case.

In this case, the discharge flow may be bounced up by the electromagnetic brake device 160, but does not rise to the molten steel surface and collides with the inner wall of the short side mold plate. At this time, since the discharge flow is relatively high temperature and high speed, breakout may occur due to remelting of the solidified shell 3a.

Further, the discharge flow collides with the inner wall of the short side mold plate to form an upward flow and a downward flow. Impurities such as gas bubbles and non-metal inclusions are pushed downward from the mold by such a downward flow, so that the internal quality of the slab 3 may be deteriorated. Further, since the flow velocity of the ascending flow formed in this case is relatively large, the formation of a swirling flow by electromagnetic agitation is hindered in the upper part of the mold, and the effect of improving the surface quality of the slab 3 by electromagnetic agitation can be suitably obtained. May not be possible.

The locus T12 exemplified in FIG. 7 is a bounce of the discharge flow when the discharge flow is incident on the side of the immersion nozzle 6 in the region where the tooth portion 164 of the electromagnetic brake device 160 is projected onto the X'-Y'plane. Corresponds to raising behavior.

In this case, the discharge flow is pushed back toward the immersion nozzle 6 by the electromagnetic brake device 160, and descends without being flipped upward. Therefore, although the discharge flow does not collide with the inner wall of the short-side mold plate, the internal quality of the slab 3 can be significantly deteriorated by the relatively large amount of impurities being swept downward from the mold. It becomes difficult to obtain the effect of improving the internal quality of piece 3.

The locus T13 exemplified in FIG. 7 is a bounce of the discharge flow when the position and direction in which the discharge flow is incident on the region where the teeth portion 164 of the electromagnetic brake device 160 is projected onto the X'-Y'plane are appropriate. Corresponds to the raising behavior.

In this case, the discharge flow is bounced up by the electromagnetic brake device 160 and rises to the molten steel surface without colliding with the inner wall of the short side mold plate. As a result, the advantages of both the electromagnetic stirring device 150 and the electromagnetic braking device 160 can be obtained while suppressing the occurrence of breakout, so that the quality of the slab 3 can be further improved.

As described above, according to the numerical analysis simulation, the flip-up behavior of the discharge flow by the electromagnetic brake device 160 is before being affected by the trajectory at the time of discharge of the discharge flow (in other words, the electromagnetic force applied by the electromagnetic brake device 160). It was found that it was particularly greatly affected by the trajectory of the discharge flow in. Therefore, it is considered that by appropriately setting the trajectory of the discharge flow at the time of discharge, the flip-up behavior of the discharge flow is optimized and the quality of the slab 3 can be further improved.

Here, the present inventor has found by numerical analysis simulation that the trajectory of the main flow at the time of discharging the discharge flow of the molten steel 2 depends on the position and shape of the discharge hole 61 of the immersion nozzle 6.

FIG. 8 is a diagram for explaining the trajectory of the main flow at the time of discharging the discharge flow of the molten steel 2. In FIG. 8, the trajectory of the main flow at the time of discharging the discharged flow is shown by a straight line L10.

Specifically, according to the numerical analysis simulation, the main flow of the discharge flow at the time of discharge passes through the lower end portion P0 of the opening formed on the inner peripheral surface of the immersion nozzle 6 by the discharge hole 61, and becomes the lower end portion P0. It was found that the discharge hole 61 extends in the direction along the portion between the lower end portion P0'of the opening formed on the outer peripheral surface of the immersion nozzle 6. It is considered that this is because the flow of the molten steel 2 in the immersion nozzle 6 forms a turbulent flow, but an inertial force is applied to the molten steel 2 vertically downward at the time of ejection. In the present specification, the lower end portion P0 of the opening formed on the inner peripheral surface of the immersion nozzle 6 by the discharge hole 61 and the lower end portion P0'of the opening formed on the outer peripheral surface of the immersion nozzle 6 by the discharge hole 61. The portion between and the lower portion of the discharge hole 61 is also referred to as a lower portion.

Therefore, the straight line L10 indicating the trajectory of the main flow at the time of discharging the discharged flow is represented by the following equation (7) in the X'Y'coordinate system.

In the equation (7), α is an inclination angle (0 ° <α <90 °) with respect to the X'axis direction of the lower part of the discharge hole 61. Further, b0 is a Y'intercept of the straight line L10 and is represented by the following formula (8).

In the formula (8), x0 is the X'coordinate of the lower end P0 of the opening formed on the inner peripheral surface of the immersion nozzle 6 by the discharge hole 61, and y0 is the inner circumference of the immersion nozzle 6 by the discharge hole 61. It is the Y'coordinate of the lower end P0 of the opening formed in the surface.

Furthermore, the present inventor has found by numerical analysis simulation the conditions that the trajectory at the time of discharging the discharge flow should be satisfied in order to optimize the flip-up behavior of the discharge flow by the electromagnetic brake device 160.

Specifically, according to the numerical analysis simulation, the trajectory of the main flow at the time of discharging the discharge flow passes above the upper end portion P2 of the immersion nozzle 6 side end portion of the tooth portion 164 of the electromagnetic brake device 160, and It has been found that the flip-up behavior of the discharge flow is optimized when passing below the central portion P1 of the teeth portion 164.

When the trajectory of the main flow at the time of discharging the discharge flow passes above the upper end portion P2 of the immersion nozzle 6 side end portion of the tooth portion 164 of the electromagnetic brake device 160, X'on the straight line L10 as shown in FIG. Assuming that the point whose coordinates match the X'coordinate x2 of the upper end portion P2 is the point P4, the value h2 obtained by subtracting the Y'coordinate y2 of the upper end portion P2 from the Y'coordinate y4 of the point P4 is the following equation (9). Corresponds to the case of satisfying.

Further, when the trajectory of the main flow at the time of discharging the discharged flow passes below the central portion P1 of the teeth portion 164, the X'coordinate is the X'coordinate x1 of the central portion P1 on the straight line L10 as shown in FIG. Assuming that the point corresponding to is the point P3, the value h1 obtained by subtracting the Y'coordinate y1 of the central portion P1 from the Y'coordinate y3 of the point P3 corresponds to the case where the following equation (10) is satisfied.

By substituting the equation (8) into the equations (9) and (10), the following equations (1) and (2) can be obtained. The left side of the following equation (1) and the following equation (2) corresponds to the value h1 and the value h2, respectively.

In the continuous casting method according to the present embodiment, the positional relationship between the immersion nozzle 6 and the tooth portion 164 of the electromagnetic brake device 160 on each side of the central axis of the immersion nozzle 6 in the long side direction of the mold is the equation (1) and the equation. It is given by (2). By performing continuous casting after the above positional relationship satisfies the relationship represented by the formulas (1) and (2), the occurrence of breakout is suppressed, and the electromagnetic stirring device 150 and the electromagnetic braking device 160 The flip-up behavior of the discharge flow can be optimized so that the advantages of both devices can be obtained. Therefore, the quality of the slab 3 can be further improved.

Preferably, in the continuous casting method according to the present embodiment, the positional relationship between the immersion nozzle 6 and the tooth portion 164 of the electromagnetic brake device 160 is as follows (3) on each side of the central axis of the immersion nozzle 6 in the long side direction of the mold. ) And the following formula (4). By performing continuous casting after the above positional relationship satisfies the relationship represented by the formulas (3) and (4), the effect of further improving the quality of the slab 3 is more effective, as will be described later. Can be played as a target.

More preferably, in the continuous casting method according to the present embodiment, the positional relationship between the immersion nozzle 6 and the tooth portion 164 of the electromagnetic brake device 160 is as follows on each side of the central axis of the immersion nozzle 6 in the long side direction of the mold. It is given by 5) and the following formula (6). By performing continuous casting after the above positional relationship satisfies the relationship represented by the formulas (5) and (6), the effect of further improving the quality of the slab 3 is further enhanced, as will be described later. It can be played effectively.

[2-2. Details of the installation position of the electromagnetic force generator]
In the electromagnetic force generator 170, the height of the electromagnetic agitator 150 and the electromagnetic brake device 160, and the installation positions of the electromagnetic agitator 150 and the electromagnetic brake device 160 in the Z-axis direction are appropriately set, so that the slab 3 is formed. The quality can be further improved. Here, an appropriate height of the electromagnetic agitator 150 and the electromagnetic brake device 160 in the electromagnetic force generator 170, and an appropriate installation position of the electromagnetic agitator 150 and the electromagnetic brake device 160 in the Z-axis direction will be described.

In the electromagnetic stirring device 150 and the electromagnetic braking device 160, it can be said that the larger the height of the electromagnetic stirring core 152 and the electromagnetic brake core 162, the higher the performance of applying the electromagnetic force. For example, the performance of the electromagnetic brake device 160 is the cross-sectional area (height in the Z-axis direction H2 × width W2 in the X-axis direction) of the teeth portion 164 of the electromagnetic brake core 162 in the XZ plane and the DC current to be applied. It depends on the value and the number of turns of the coil 163. Therefore, when both the electromagnetic agitation device 150 and the electromagnetic brake device 160 are installed on the mold 110, the installation positions of the electromagnetic agitation core 152 and the electromagnetic brake core 162, more specifically, the electromagnetic agitation, in a limited installation space. How to set the height ratio of the core 152 and the electromagnetic brake core 162 is very important from the viewpoint of more effectively exerting the performance of each device in order to improve the quality of the slab 3. ..

Here, as disclosed in Patent Document 1, conventionally, a method of using both an electromagnetic agitator and an electromagnetic brake device in continuous casting has been proposed. However, in reality, even if both the electromagnetic agitator and the electromagnetic brake device are combined, the quality of the slab is often deteriorated as compared with the case where the electromagnetic agitator or the electromagnetic brake device is used alone. This does not mean that the advantages of both devices can be easily obtained by simply installing both devices, and depending on the configuration and installation position of each device, the advantages of each may cancel each other out. Because you get. Also in the above-mentioned Patent Document 1, the specific device configuration thereof is not specified, and the heights of the cores of both devices are not specified. That is, in the conventional method, there is a possibility that the effect of improving the quality of the slab by providing both the electromagnetic agitator and the electromagnetic brake device cannot be sufficiently obtained.

On the other hand, in the present embodiment, as described below, the electromagnetic stirring core 152 and the electromagnetic brake core 162 are suitable so that the quality of the slab 3 can be further ensured even in high-speed casting. Specify the ratio of height. This makes it possible to more effectively obtain the effect of improving productivity while ensuring the quality of the slab 3, in addition to the configuration of the electromagnetic force generator 170 described above.

Here, the casting speed in continuous casting varies greatly depending on the slab size and type, but is generally about 0.6 to 2.0 m / min, and continuous casting exceeding 1.6 m / min is called high-speed casting. Will be. Conventionally, for automobile exterior materials that require high quality, it is difficult to ensure quality in high-speed casting where the casting speed exceeds 1.6 m / min, so about 1.4 m / min is used. This is a general casting speed. Therefore, here, as an example, even in high-speed casting in which the casting speed exceeds 1.6 m / min, the quality of the slab 3 equal to or higher than that in the case of continuous casting at a slower casting speed than the conventional one is ensured. Will be set as a specific target, and the ratio of the heights of the electromagnetic stirring core 152 and the electromagnetic brake core 162 so as to satisfy the target will be described in detail.

As described above, in the present embodiment, in order to secure a space for installing the electromagnetic stirring device 150 and the electromagnetic braking device 160 in the central portion of the mold 110 in the Z-axis direction, the water boxes 130 are placed at the upper and lower portions of the mold 110, respectively. , 140 are placed. Here, even if the electromagnetic stirring core 152 is located above the molten steel surface, the effect cannot be obtained. Therefore, the electromagnetic agitation core 152 should be installed below the molten steel surface. Further, in order to effectively apply a magnetic field to the discharge flow, the electromagnetic brake core 162 is preferably located near the discharge hole of the immersion nozzle 6. When the water boxes 130 and 140 are arranged as described above, in a general arrangement, the discharge hole of the immersion nozzle 6 is located above the lower water box 140, so that the electromagnetic brake core 162 is also located above the lower water box 140. Should be installed above. Therefore, the height H0 of the space where the effect can be obtained by installing the electromagnetic stirring core 152 and the electromagnetic brake core 162 (hereinafter, also referred to as an effective space) is the height from the molten steel surface to the upper end of the lower water box 140 (hereinafter, also referred to as an effective space). See Figure 2).

In the present embodiment, in order to make the most effective use of the effective space, the electromagnetic stirring core 152 is installed so that the upper end of the electromagnetic stirring core 152 is substantially the same height as the molten steel surface. At this time, the height of the electromagnetic stirring core 152 of the electromagnetic stirring device 150 is H1, the height of the case 151 is H3, the height of the electromagnetic brake core 162 of the electromagnetic braking device 160 is H2, and the height of the case 161 is H4. Then, the following mathematical formula (11) is established.

In other words, while satisfying the above formula (11), the ratio H1 / H2 (hereinafter, also referred to as core height ratio H1 / H2) between the height H1 of the electromagnetic stirring core 152 and the height H2 of the electromagnetic brake core 162 is obtained. Need to be specified. Hereinafter, the heights H0 to H4 will be described respectively.

(About the height H0 of the effective space)
As described above, in the electromagnetic stirring device 150 and the electromagnetic braking device 160, it can be said that the larger the height of the electromagnetic stirring core 152 and the electromagnetic brake core 162, the higher the performance of applying the electromagnetic force. Therefore, in the present embodiment, the mold equipment 10 is configured so that the height H0 of the effective space is as large as possible so that both devices can more exert their performance. Specifically, in order to increase the height H0 of the effective space, the length of the mold 110 in the Z-axis direction may be increased. On the other hand, as described above, in consideration of the cooling property of the slab 3, it is desirable that the length from the molten steel surface to the lower end of the mold 110 is about 1000 mm or less. Therefore, in the present embodiment, in order to make the height H0 of the effective space as large as possible while ensuring the cooling property of the slab 3, the mold 110 is set so that the distance from the molten steel surface to the lower end of the mold 110 is about 1000 mm. Form.

Here, if the lower water box 140 is to be configured so as to store enough water to obtain a sufficient cooling capacity, the height of the lower water box 140 needs to be at least about 200 mm based on past operation results and the like. Will be. Therefore, the height H0 of the effective space is about 800 mm or less.

(About the heights H3 and H4 of the case of the electromagnetic agitator and the electromagnetic brake device)
As described above, the coil 153 of the electromagnetic stirring device 150 is formed by winding 2 to 4 layers of a conducting wire having a cross-sectional size of about 10 mm × 10 mm around the electromagnetic stirring core 152. Therefore, the height of the electromagnetic stirring core 152 including the coil 153 is about H1 + 80 mm or more. Considering the space between the inner wall of the case 151 and the electromagnetic stirring core 152 and the coil 153, the height H3 of the case 151 is about H1 + 200 mm or more.

Similarly, for the electromagnetic brake device 160, the height of the electromagnetic brake core 162 including the coil 163 is about H2 + 80 mm or more. Considering the space between the inner wall of the case 161 and the electromagnetic brake core 162 and the coil 163, the height H4 of the case 161 is about H2 + 200 mm or more.

(Range that H1 + H2 can take)
By substituting the above-mentioned values of H0, H3, and H4 into the above formula (11), the following formula (12) is obtained.

That is, the electromagnetic stirring core 152 and the electromagnetic brake core 162 need to be configured so that the sum H1 + H2 of their heights is about 500 mm or less. Hereinafter, an appropriate core height ratio H1 / H2 will be examined so that the effect of improving the quality of the slab 3 can be sufficiently obtained while satisfying the above formula (12).

(About core height ratio H1 / H2)
In the present embodiment, an appropriate range of the core height ratio H1 / H2 is set by defining the range of the height H1 of the electromagnetic stirring core 152 so that the effect of the electromagnetic stirring can be obtained more reliably.

As described above, in electromagnetic agitation, by flowing the molten steel 2 at the interface of the solidified shell, a cleaning effect of suppressing the trapping of impurities in the solidified shell 3a can be obtained, and the surface quality of the slab 3 can be improved. can. On the other hand, the thickness of the solidified shell 3a in the mold 110 increases toward the lower side of the mold 110. Since the effect of the electromagnetic agitation is exerted on the unsolidified portion 3b inside the solidification shell 3a, the height H1 of the electromagnetic agitation core 152 ensures the surface quality of the slab 3 to what thickness. It can be determined by what is needed.

Here, in varieties with strict surface quality, a step of grinding the surface layer of the slab 3 after casting by several millimeters is often performed. This grinding depth is about 2 mm to 5 mm. Therefore, in the varieties that require such strict surface quality, even if electromagnetic stirring is performed in the mold 110 in a range where the thickness of the solidified shell 3a is smaller than 2 mm to 5 mm, impurities are reduced by the electromagnetic stirring. The surface layer of the slab 3 will be removed by the subsequent grinding process. In other words, unless electromagnetic stirring is performed in the range where the thickness of the solidified shell 3a is 2 mm to 5 mm or more in the mold 110, the effect of improving the surface quality of the slab 3 cannot be obtained.

It is known that the solidified shell 3a gradually grows from the molten steel surface, and its thickness is expressed by the following mathematical formula (13). Here, δ is the thickness (m) of the solidified shell 3a, k is a constant depending on the cooling capacity, x is the distance from the molten steel surface (m), and Vc is the casting speed (m / min).

From the above formula (13), the relationship between the casting speed (m / min) and the distance (mm) from the molten steel surface was obtained when the thickness of the solidified shell 3a was 4 mm or 5 mm. The result is shown in FIG. FIG. 9 is a diagram showing the relationship between the casting speed (m / min) and the distance (mm) from the molten steel surface when the thickness of the solidified shell 3a is 4 mm or 5 mm. In FIG. 9, the horizontal axis is the casting speed, the vertical axis is the distance from the molten steel surface, and the thickness of the solidified shell 3a is 4 mm, and the thickness of the solidified shell 3a is 5 mm. The relationship is plotted. In the calculation for obtaining the result shown in FIG. 9, k = 17 was set as the value corresponding to the general template.

For example, from the results shown in FIG. 9, if the thickness to be ground is smaller than 4 mm and the molten steel 2 can be electromagnetically agitated within the range where the thickness of the solidified shell 3a is up to 4 mm, the height of the electromagnetic agitation core 152 is high. It can be seen that if H1 is 200 mm, the effect of electromagnetic stirring can be obtained in continuous casting at a casting speed of 3.5 m / min or less. If the thickness to be ground is smaller than 5 mm and the molten steel 2 should be electromagnetically agitated within the range where the thickness of the solidified shell 3a is up to 5 mm, if the height H1 of the electromagnetic agitation core 152 is set to 300 mm, the casting speed It can be seen that the effect of electromagnetic stirring can be obtained in continuous casting at 3.5 m / min or less. The value of "3.5 m / min" of this casting speed corresponds to the maximum casting speed possible in terms of operation and equipment in a general continuous casting machine.

Here, as described above, as an example, even in high-speed casting in which the casting speed exceeds 1.6 m / min, the quality of the slab 3 equivalent to that in the case of continuous casting at a slower casting speed than the conventional one is ensured. Consider the case where the goal is to do. In order to obtain the effect of electromagnetic agitation even if the thickness of the solidified shell 3a becomes 5 mm when the casting speed exceeds 1.6 m / min, from FIG. 9, the height H1 of the electromagnetic agitation core 152 is at least about 150 mm. It turns out that we have to do the above.

From the results of the above examination, in the present embodiment, for example, in continuous casting at a relatively high speed of more than 1.6 m / min, the effect of electromagnetic stirring can be obtained even if the thickness of the solidified shell 3a is 5 mm. In addition, the electromagnetic stirring core 152 is configured so that the height H1 of the electromagnetic stirring core 152 is about 150 mm or more.

As for the height H2 of the electromagnetic brake core 162, as described above, the larger the height H2, the higher the performance of the electromagnetic brake device 160. Therefore, from the above mathematical formula (12), when H1 + H2 = 500 mm, the range of H2 corresponding to the range of the height H1 of the electromagnetic stirring core 152 may be obtained. That is, the height H2 of the electromagnetic brake core 162 is about 350 mm.

From the values of the height H1 of the electromagnetic stirring core 152 and the height H2 of the electromagnetic brake core 162, the core height ratio H1 / H2 in the present embodiment is, for example, the following mathematical formula (14).

In summary, in the present embodiment, for example, even when the casting speed exceeds 1.6 m / min, the quality of the slab 3 equal to or higher than that in the case of continuous casting at a lower casting speed than the conventional one is ensured. When the target is to be achieved, the electromagnetic stirring core 152 and the electromagnetic brake core 162 are arranged so that the height H1 of the electromagnetic stirring core 152 and the height H2 of the electromagnetic brake core 162 satisfy the above equation (14). It is composed.

The preferable upper limit value of the core height ratio H1 / H2 can be defined by the minimum value that the height H2 of the electromagnetic brake core 162 can take. The smaller the height H2 of the electromagnetic brake core 162, the larger the core height ratio H1 / H2. However, if the height H2 of the electromagnetic brake core 162 is too small, the electromagnetic brake does not function effectively and the slab by the electromagnetic brake is used. This is because it becomes difficult to obtain the effect of improving the internal quality of 3. The minimum value of the height H2 of the electromagnetic brake core 162 in which the effect of the electromagnetic brake can be fully exerted differs depending on the casting conditions such as the slab size, the type, and the casting speed. Therefore, the minimum value of the height H2 of the electromagnetic brake core 162, that is, the upper limit of the core height ratio H1 / H2 is defined based on, for example, an actual machine test or a numerical analysis simulation simulating casting conditions in actual operation. Can be done.

The appropriate heights of the electromagnetic agitator 150 and the electromagnetic brake device 160 in the electromagnetic force generator 170, and the appropriate installation positions of the electromagnetic agitator 150 and the electromagnetic brake device 160 in the Z-axis direction have been described above. In the above description, when the relationship shown in the above formula (14) is obtained, these relationships are obtained by setting H1 + H2 = 500 mm from the above formula (12). However, this embodiment is not limited to such an example. As described above, in order to further exhibit the performance of the device, it is preferable that H1 + H2 is as large as possible. Therefore, in the above example, H1 + H2 = 500 mm. On the other hand, for example, in consideration of workability when installing the water boxes 130 and 140, the electromagnetic agitator 150 and the electromagnetic brake device 160, it may be preferable that there is a gap between these members in the Z-axis direction. .. When other factors such as workability are more important, the core height ratio H1 / H2 does not necessarily have to be H1 + H2 = 500 mm, and H1 + H2 is set to a value smaller than 500 mm, for example, H1 + H2 = 450 mm. May be set.

Further, in the above description, when the casting speed exceeds 1.6 m / min, the electromagnetic agitation core 152 is shown in FIG. 9 as a condition for obtaining the effect of the electromagnetic agitation even if the thickness of the solidified shell 3a becomes 5 mm. The minimum value of the height H1 of about 150 mm was obtained, and 0.43, which is the value of the core height ratio H1 / H2 at this time, was set as the lower limit value of the core height ratio H1 / H2. However, this embodiment is not limited to such an example. If the target casting speed is set faster, the lower limit of the core height ratio H1 / H2 may also change. That is, in the electromagnetic stirring core 152, the effect of electromagnetic stirring can be obtained even if the thickness of the solidified shell 3a becomes a predetermined thickness corresponding to the thickness removed in the grinding process at the casting speed targeted in the actual operation. The minimum value of the height H1 may be obtained from FIG. 9, and the core height ratio H1 / H2 corresponding to the value of H1 may be set as the lower limit value of the core height ratio H1 / H2.

As an example, in consideration of workability and the like, H1 + H2 = 450 mm, and even at a faster casting speed of 2.0 m / min, the quality of the slab 3 equal to or higher than that in the case of continuous casting at a lower casting speed than the conventional one is achieved. Let's find the condition of the core height ratio H1 / H2 when the goal is to secure it. First, from FIG. 9, when the casting speed is 2.0 m / min or more, the conditions for obtaining the effect of electromagnetic stirring even if the thickness of the solidified shell 3a becomes 5 mm are obtained. Referring to FIG. 9, when the casting speed is 2.0 m / min, the thickness of the solidified shell is 5 mm at a position of about 175 mm from the molten steel surface. Therefore, considering the margin, the minimum value of the height H1 of the electromagnetic agitation core 152 so that the effect of the electromagnetic agitation can be obtained even when the thickness of the solidified shell 3a is 5 mm is required to be about 200 mm. At this time, since H1 + H2 = 450 mm and H2 = 250 mm, the conditions required for the core height ratio H1 / H2 are expressed by the following mathematical formula (15).

That is, in the present embodiment, for example, when the goal is to ensure the quality of the slab 3 equal to or higher than that in the case of continuous casting at a lower casting speed than the conventional one even at a casting speed of 2.0 m / min. The electromagnetic stirring core 152 and the electromagnetic brake core 162 may be configured so as to satisfy at least the above equation (15). As described above, the upper limit of the core height ratio H1 / H2 may be specified based on an actual machine test, a numerical analysis simulation simulating casting conditions in an actual operation, or the like.

As described above, in the present embodiment, even when the casting speed is increased, it is possible to secure the quality (surface quality and internal quality) of the slab equal to or higher than that of the conventional continuous casting at a lower speed. The range of the core height ratio H1 / H2 can vary depending on the specific value of the target casting speed and the specific value of H1 + H2. Therefore, when setting an appropriate range of the core height ratio H1 / H2, the target casting speed and H1 + H2 are set in consideration of the casting conditions at the time of actual operation, the configuration of the continuous casting machine 1, and the like. The value may be appropriately set, and an appropriate range of the core height ratio H1 / H2 at that time may be appropriately obtained by the method described above.

The results of the actual machine test 1 and the actual machine test 2 conducted to confirm the quality improvement effect of the slab 3 by the continuous casting method according to the present embodiment described above will be described. In each actual machine test, a continuous casting machine (similar to the continuous casting machine 1 shown in FIG. 1) in which an electromagnetic force generator having the same configuration as the electromagnetic force generator 170 according to the above-described embodiment is actually used for operation. It was installed in a structure), and continuous casting was performed while changing various casting conditions. Then, the surface quality and the internal quality of the slab 3 obtained after casting were inspected visually and by ultrasonic flaw detection, respectively.

[Actual machine test 1]
First, in the actual machine test 1, in order to investigate an appropriate range of the magnitude of the magnetic flux density of the magnetic field generated by the electromagnetic brake device 160 (magnetic flux density of the electromagnetic brake), among the casting conditions, the mold width, the casting speed, and the electromagnetic wave are used. The magnetic flux density of the brake, the depth of the bottom surface of the immersion nozzle 6 with respect to the molten steel surface, and the throughput (specifically, the total value of the flow rates of the molten steel 2 discharged from the pair of discharge holes 61 of the immersion nozzle 6) are various. Continuous casting was performed while changing. The main casting conditions are as follows. The depth of the upper end of the teeth portion 164 with respect to the molten steel surface and the depth of the bottom surface of the immersion nozzle 6 with respect to the molten steel surface correspond to the Y'coordinates of the upper end of the teeth portion 164 and the bottom surface of the immersion nozzle 6, respectively.

(Cast)
Cast size (mold size): width 1050 mm to 1630 mm, thickness 250 mm
Casting speed: 0.8m / min to 2.6m / min
(Electromagnetic agitator)
Electromagnetic stirring core size: width (W1) 1928 mm, height (H1) 250 mm
Alternating current applied to the coil: 680A, 1.5Hz
(Electromagnetic brake device)
Depth of the upper end of the tooth part with respect to the molten steel surface: -516 mm
Size of teeth: width (W2) 550 mm, height (H2) 200 mm
Distance between teeth (W3): 370 mm
Magnetic flux density of electromagnetic brake: 0T to 0.48T
(Immersion nozzle)
Immersion nozzle size: outer diameter φ152 mm, inner diameter φ87 mm
Depth of the bottom surface of the dipping nozzle with respect to the molten steel surface (bottom depth): -390 mm to -320 mm
Tilt angle (α) with respect to the X'axis direction at the bottom of the discharge hole: 45 °
Throughput: 1.81 ton / min to 6.60 ton / min

In the actual machine test 1, the value h1 (= y3-y1) represented by the equation (10) is obtained by variously changing the depth (bottom depth) of the bottom surface of the immersion nozzle 6 with respect to the molten steel surface. It was changed in the range of -158 mm to -88 mm, and the value h2 (= y4-y2) represented by the formula (9) was changed in the range of 17 mm to 87 mm.

The result of the actual machine test 1 is shown in FIG. FIG. 10 is a diagram showing the evaluation results of the quality of the slab 3 for each combination of the throughput P (ton / min) and the magnetic flux density Q (T) of the electromagnetic brake. In FIG. 10, the surface quality of the slab is at a level where almost no defects are found or defects are found but maintenance is not required, and the internal quality of the slab is a large inclusion by ultrasonic flaw detection inspection. If the number of detections per slab (diameter of about 0.4 mm) is less than 20, "○" is displayed. If a defect is found in the surface quality of the slab and maintenance is required, maintenance is required. Alternatively, the internal quality of the slab is expressed by adding an "x" when the number of detected pieces per slab of a large inclusion is 20 or more.

Referring to FIG. 10, when the relationship between the throughput P and the magnetic flux density Q satisfies the relationship expressed by the following formula (16), the evaluation result of the quality of the slab 3 becomes “◯”, which is shown by the following formula (16). It was confirmed that the quality evaluation result of the slab 3 was "x" when the relationship was not satisfied.

It is considered that this is because the relative magnitude of the magnetic flux density Q with respect to the throughput P affects the jumping behavior of the discharge flow of the molten steel 2 as follows. When the relative magnitude of the magnetic flux density Q with respect to the throughput P is excessively large (specifically, when Q ≧ 0.06P + 0.12), the flow velocity of the discharge flow bounced up by the electromagnetic braking device 160 is excessive. Further, the discharge flow tends to increase toward the vicinity of the immersion nozzle 6 which is difficult to be agitated by electromagnetic stirring. As a result, the formation of a swirling flow by electromagnetic agitation is hindered in the upper part of the mold 110, and it becomes difficult to suitably obtain the effect of improving the surface quality of the slab 3 by electromagnetic agitation. On the other hand, when the relative magnitude of the magnetic flux density Q with respect to the throughput P is excessively small (specifically, when Q≤0.06P-0.07), the discharge flow is bounced up by the electromagnetic brake device 160. It becomes easy to descend without. As a result, it becomes difficult to suitably obtain the effect of improving the internal quality of the slab by the electromagnetic brake.

As described above, according to the actual machine test 1, it was confirmed that it is preferable to perform continuous casting after satisfying the relationship expressed by the equation (16) between the throughput P and the magnetic flux density Q.

[Actual machine test 2]
Next, in the actual machine test 2, in order to investigate the influence of the positional relationship between the immersion nozzle 6 and the tooth portion 164 of the electromagnetic brake device 160 on the quality of the slab 3, among the casting conditions, the mold width and the casting speed are used. Continuous casting was performed while variously changing the magnetic flux density of the electromagnetic brake, the depth from the molten steel surface to the bottom surface of the immersion nozzle 6, the inclination angle α of the lower part of the discharge hole 61 in the X'axis direction, and the throughput. The main casting conditions are as follows. The depth of the upper end of the teeth portion 164 with respect to the molten steel surface and the depth of the bottom surface of the immersion nozzle 6 with respect to the molten steel surface correspond to the Y'coordinates of the upper end of the teeth portion 164 and the bottom surface of the immersion nozzle 6, respectively.

(Cast)
Shard size (mold size): width 1290 mm or 1650 mm, thickness 250 mm
Casting speed: 1.0 m / min to 2.6 m / min
(Electromagnetic agitator)
Electromagnetic stirring core size: width (W1) 1928 mm, height (H1) 250 mm
Alternating current applied to the coil: 680A, 1.5Hz
(Electromagnetic brake device)
Depth of the upper end of the tooth part with respect to the molten steel surface: -516 mm
Size of teeth: width (W2) 550 mm, height (H2) 200 mm
Distance between teeth (W3): 370 mm
Magnetic flux density of electromagnetic brake: 0.15T to 0.45T
(Immersion nozzle)
Immersion nozzle size: outer diameter φ152 mm, inner diameter φ87 mm
Depth of the bottom surface of the dipping nozzle with respect to the molten steel surface (bottom depth): -420 mm to -320 mm
Tilt angle (α) of the lower part of the discharge hole with respect to the X'axis direction: 35 ° to 45 °
Throughput: 2.26 ton / min to 6.93 ton / min

In the actual machine test 2, the casting conditions were set so that the relationship between the throughput P and the magnetic flux density Q satisfied the relationship expressed by the equation (16). Further, in the actual machine test 2, the depth (bottom depth) of the bottom surface of the immersion nozzle 6 with respect to the molten steel surface is variously changed, so that the opening formed on the inner peripheral surface of the immersion nozzle 6 by the discharge hole 61. The X'coordinate x0 and Y'coordinate y0 of the lower end P0 of the above have been changed in various ways. In addition, the value h1 (= y3-y1) represented by the formula (10) and the value h2 (= y4-y2) represented by the formula (9) have been variously changed accordingly. Since the mold equipment 10 has a configuration symmetrical with respect to the central axis of the immersion nozzle 6 in the mold long side direction (that is, the X-axis direction), each side of the central axis of the immersion nozzle 6 in the mold long side direction. In, the values of x0, y0, α, h1 and h2 for each casting condition are common.

The results of the actual machine test 2 are shown in Table 1, Table 2 and FIG. Table 1 shows the evaluation results of the quality of the slab 3 for each of the casting conditions in which the mold width is 1290 mm. Table 2 shows the evaluation results of the quality of the slab 3 for each of the casting conditions in which the mold width is 1650 mm. In Tables 1 and 2, regarding the surface quality of the slab, "○" is given when almost no defects are found by visual inspection, and "△" is given when defects are found but maintenance is not required. Is expressed by adding an "x" when a defect is found and maintenance is required. Further, in Tables 1 and 2, when no large inclusions (diameter of about 0.4 mm) are detected by ultrasonic flaw detection inspection on the internal quality of the slab, "○" is added to one slab. On the other hand, when the number of detections is less than 20, "Δ" is added, and when the number of detections is 20 or more for one slab, "x" is added.

FIG. 11 is a diagram showing the evaluation results of the quality of the slab 3 for each of the combinations of the values h1 and the value h2. Specifically, FIG. 11 focuses on the combination of the values h1 and h2 for the various casting conditions shown in Tables 1 and 2, and corresponds to the evaluation result of the quality of the slab 3 on the h1-h2 plane. It is a plot of the marks to be used. In FIG. 11, when the evaluation result of the surface quality of the slab 3 is “○” and the evaluation result of the internal quality is “○”, “○” is displayed, and the evaluation result of the surface quality of the slab 3 is “Δ”. When the evaluation result of the internal quality is "○", "△" is displayed, and when the evaluation result of the surface quality of the slab 3 is "○" and the evaluation result of the internal quality is "△". "□", "×" when the evaluation result of the surface quality of the slab 3 is "x", and "*" when the evaluation result of the internal quality of the slab 3 is "x". It is expressed by adding.

Referring to Table 1, Table 2 and FIG. 11, the positional relationship between the immersion nozzle 6 and the tooth portion 164 of the electromagnetic brake device 160 is set in the equation (1) and on each side of the central axis of the immersion nozzle 6 in the long side direction of the mold. It was confirmed that both the evaluation results of the surface quality and the internal quality of the slab 3 were at least "Δ" when the relationship represented by the formula (2) was satisfied. On the other hand, when the positional relationship between the immersion nozzle 6 and the tooth portion 164 of the electromagnetic brake device 160 does not satisfy the above relationship, at least one of the evaluation results of the surface quality and the internal quality of the slab 3 may be "x". confirmed. Therefore, the positional relationship between the immersion nozzle 6 and the tooth portion 164 of the electromagnetic brake device 160 on each side of the central axis of the immersion nozzle 6 in the long side direction of the mold is expressed by the equations (1) and (2). It was confirmed that the quality of the slab 3 can be further improved by performing continuous casting after filling.

Further, referring to Table 1, Table 2 and FIG. 11, the positional relationship between the immersion nozzle 6 and the tooth portion 164 of the electromagnetic brake device 160 is set in the equation (3) on each side of the central axis of the immersion nozzle 6 in the long side direction of the mold. ) And the relationship expressed by the formula (4), it was confirmed that the evaluation result of the surface quality of the slab 3 was at least "Δ", but the evaluation result of the internal quality was "◯". Therefore, on each side of the central axis of the immersion nozzle 6 in the long side direction of the mold, the positional relationship between the immersion nozzle 6 and the tooth portion 164 of the electromagnetic brake device 160 is expressed by the equations (3) and (4). It was confirmed that the effect of further improving the quality of the slab 3 can be more effectively achieved by performing continuous casting after filling.

Further, referring to Table 1, Table 2 and FIG. 11, the positional relationship of the teeth portion 164 between the immersion nozzle 6 and the electromagnetic brake device 160 on each side of the central axis of the immersion nozzle 6 in the long side direction of the mold is the equation (5). ) And the relationship expressed by the formula (6), it was confirmed that both the evaluation results of the surface quality and the internal quality of the slab 3 were “◯”. Therefore, the positional relationship between the immersion nozzle 6 and the tooth portion 164 of the electromagnetic brake device 160 on each side of the central axis of the immersion nozzle 6 in the long side direction of the mold is expressed by the equations (5) and (6). It was confirmed that the effect of further improving the quality of the slab 3 can be more effectively achieved by performing continuous casting after filling.

<3. Summary>
As described above, in the continuous casting method according to the present embodiment, the electromagnetic stirring device 150 applies an electromagnetic force such as to generate a swirling flow in the horizontal plane to the molten steel 2 in the mold 110, and the electromagnetic stirring device. Continuous casting is performed while applying an electromagnetic force in a direction for braking the discharge flow of the molten steel 2 from the immersion nozzle 6 into the mold 110 by an electromagnetic brake device 160 installed below the 150. Specifically, the electromagnetic force in the direction of braking the discharge flow with respect to the discharge flow by generating a magnetic field by applying a direct current to the coil 163 wound around the teeth portion 164 of the electromagnetic brake device 160. Give power. Further, the positional relationship between the immersion nozzle 6 and the tooth portion 164 of the electromagnetic brake device 160 is given by the equations (1) and (2) on each side of the central axis of the immersion nozzle 6 in the long side direction of the mold. As a result, it is possible to optimize the flip-up behavior of the discharge flow so that the advantages of both the electromagnetic stirring device 150 and the electromagnetic braking device 160 can be obtained while suppressing the occurrence of breakout. Therefore, the quality of the slab 3 can be further improved.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or applications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

1 Continuous casting machine 2 Molten steel 3 Shards 3a Solidification shell 3b Unsolidified part 4 Ladle 5 Tandish 6 Immersion nozzle 10 Mold equipment 61 Discharge hole 110 Mold 111 Long side mold plate 112 Short side mold plate 121, 122, 123 Backup plate 130 Upper water box 140 Lower water box 150 Electromagnetic stirring device 151 Case 152 Electromagnetic stirring core 153 Coil 160 Electromagnetic brake device 161 Case 162 Electromagnetic brake core 163 Coil 164 Teeth part 165 Connection part 170 Electromagnetic force generator

Claims (3)

The electromagnetic agitator applies an electromagnetic force to the molten metal in the mold to generate a swirling flow in the horizontal plane, and the electromagnetic brake device installed below the electromagnetic agitator applies the electromagnetic force to the molten metal in the mold. A continuous casting method in which continuous casting is performed while applying an electromagnetic force in a direction for braking the discharged metal to the discharged flow of the molten metal from the nozzle.
The immersion nozzle is provided with a pair of molten metal discharge holes on both sides of the mold in the long side direction of the mold.
The electromagnetic brake device is installed on each outer surface of each pair of long-side mold plates in the mold, and is provided on both sides of the dipping nozzle in the mold long-side direction so as to face the long-side mold plate. An iron core having a tooth portion to be formed and a coil wound around each of the teeth portions are provided.
By generating a magnetic field by applying a direct current to the coil of the electromagnetic braking device, an electromagnetic force in a direction for braking the discharge flow is applied to the discharge flow.
On each side of the central axis of the immersion nozzle in the long side direction of the mold, the direction from the immersion nozzle to the short side mold plate of the mold along the long side direction of the mold is the positive direction of the first direction and is vertically upward. When the direction is the positive direction of the second direction, the positional relationship between the immersion nozzle and the tooth portion of the electromagnetic braking device is given by the following equations (1) and (2).
Continuous casting method.

However,
x0: Coordinates in the first direction of the lower end of the opening formed on the inner peripheral surface of the immersion nozzle by the discharge hole y0: The lower end of the opening formed on the inner peripheral surface of the immersion nozzle by the discharge hole. Coordinates x1 in the second direction of the portion 1: Coordinates in the first direction of the central portion of the teeth portion y1: Coordinates x2 of the central portion of the teeth portion in the second direction: The dipping nozzle side end portion of the teeth portion Coordinates y2 of the upper end portion in the first direction: Coordinates α in the second direction of the upper end portion of the immersion nozzle side end portion of the teeth portion: Inclinement angle of the lower portion of the discharge hole with respect to the first direction. The positional relationship between the immersion nozzle and the tooth portion of the electromagnetic brake device on each side of the central axis of the immersion nozzle in the long side direction of the mold is given by the following equations (3) and (4).
The continuous casting method according to claim 1.

The positional relationship between the immersion nozzle and the tooth portion of the electromagnetic brake device on each side of the central axis of the immersion nozzle in the long side direction of the mold is given by the following equations (5) and (6).
The continuous casting method according to claim 2.

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