JP7295380B2 - tundish - Google Patents

Description

The present invention relates to a tundish.

In continuous casting, in order to stably pour molten steel into the mold, a device called a tundish is used to temporarily receive the molten steel transported to the mold by a ladle before being poured into the mold. The tundish has the function of receiving and stabilizing the molten steel in the ladle and removing inclusions in the molten steel to improve the cleanliness of the molten steel. Specifically, since the specific gravity of inclusions in molten steel is generally smaller than the specific gravity of molten steel, once the molten steel is stored in the tundish, the inclusions rise to the surface in the molten steel and are removed. becomes.

Here, if the residence time of the molten steel in the tundish increases due to continuous casting over a long period of time or a low casting speed, the temperature of the molten steel in the tundish becomes excessive. It is likely to decline. If the temperature of the molten steel drops excessively, the quality of the slab may deteriorate and the molten steel may solidify in the tundish. Therefore, in order to prevent the temperature of the molten steel in the tundish from dropping excessively, the tundish is often provided with a heating device for heating the molten steel.

As a heating device provided in a tundish, there is an induction heating device that heats molten steel using the principle of electromagnetic induction, as disclosed in Patent Document 1, for example. Here, by using an induction heating device to heat the molten steel in the tundish, the ability to remove inclusions can be improved by the electromagnetic force generated in the molten steel. Therefore, the induction heating device is superior to other heating devices such as a plasma heating device from the viewpoint of improving the ability to remove inclusions. Therefore, in the continuous casting of blooms and billets used as spring materials and bearing steels, which require particularly high cleanliness, an induction heating apparatus is often used to heat the molten steel in the tundish.

Japanese Utility Model Laid-Open No. 6-86849

By the way, in order to improve casting production capacity, molten steel may be distributed and supplied from the tundish to a plurality of molds by providing the tundish with a plurality of submerged nozzles for supplying molten steel into the molds. Here, in order to further improve casting production capacity, it is conceivable to increase the number of submerged nozzles provided in the tundish so that molten steel can be supplied from the tundish to more molds. be done. In this case, as the volume of molten steel stored in the tundish increases, it is necessary to install two induction heating devices in order to appropriately heat the molten steel in the tundish. This is because the heating capacity of one induction heating device has an upper limit.

A tundish that uses an induction heating device to heat molten steel consists of a receiving chamber into which molten steel is poured from a ladle, a tapping chamber provided with an immersion nozzle for supplying molten steel into a mold, and a receiving chamber. and a hot water path connecting the hot water chamber. And the induction heating device is provided in the hot water passage. Here, when an induction heating device is used to heat molten steel, it is necessary to provide two hot water passages for one induction heating device in order to appropriately generate an eddy current in the molten steel in the tundish. Therefore, when two induction heating devices are installed in the tundish as described above, it is necessary to provide four hot water passages.

However, when the tundish is provided with four hot water passages, the length of the route to reach the tapping chamber differs depending on which hot water passage the molten steel poured into the receiving chamber passes. Moreover, a difference also arises in the flow rate of molten steel between the hot water passages. As a result, a temperature difference is likely to occur between the molten steel flowing into the tapping chamber from each runner, so the temperature difference between the molten steel passing through each submerged nozzle of the tapping chamber (that is, the molten steel supplied to each mold) It may become large. Such an increase in the temperature difference of the molten steel between the submerged nozzles causes an increase in the quality difference of the slab between the molds.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide continuous casting using a tundish having four hot water passages connecting a receiving hot water chamber and a hot water discharging chamber. Another object of the present invention is to provide a new and improved tundish capable of suppressing an increase in the quality difference of slabs between molds.

In order to solve the above problems, according to one aspect of the present invention, a receiving chamber into which molten steel is poured from a ladle, a tapping chamber provided with a plurality of submerged nozzles for supplying the molten steel into a mold, and and four hot water passages that connect the hot water receiving chamber and the hot water discharge chamber and are provided horizontally between the hot water receiving chamber and the hot water discharge chamber. An induction heating device is provided in each of the two hot water paths and the two hot water paths on the other side in the side-by-side direction. The distance between the center axes of the two hot water paths is 1200 to 1400 mm, and of the two hot water paths on one side, the hot water path arranged inside in the side-by-side direction and the two hot water paths on the other side. Among them, the distance between the central axes of the hot water passages arranged inside in the parallel installation direction is 4200 to 5200 mm, the diameter of the hot water passage is 120 to 140 mm, The injection nozzle of the ladle is arranged in the center of the installation direction and the direction vertical and horizontal to the side-by-side direction, and the side-by-side nozzles are arranged on both sides of the molten steel injection position in the receiving chamber in the side-by-side direction. A weir is provided that extends across the installation direction, has openings at both ends of the lower portion, and has an upper end positioned above the surface of the molten steel, or the weir is not provided, and the The distance in the arranging direction between the end side wall portion of the tapping chamber in the arranging direction and the submerged nozzle closest to the wall portion is 120 mm or more and 300 mm or less, and the arranging of the hot water receiving chamber is The distance in the side-by-side installation direction between the wall on the end side of the direction and the hot tub closest to the wall is 80 mm or more and 260 mm or less, and when the weir is provided, the injection position and the weir The distance in the side-by-side direction is 655 mm or more and 1140 mm or less between the The tapping chamber has a length of 10000 to 12000 mm in the direction parallel to the long side of the mold, and the short side of the mold The induction heating device has a cylindrical shape with a length of 900 to 1100 mm in a direction parallel to the , and the induction heating device includes an annular iron core arranged so as to surround the hot water passage, and a coil wound around the iron core. The iron core provided in the two hot water passages on one side surrounds the hot water passages arranged outside in the side-by-side direction of the two hot water passages on one side, and the two hot water passages on the other side The iron core provided in the hot water passage surrounds the hot water passage arranged outside in the side-by-side direction of the two hot water passages on the other side, and the submerged nozzle extends downward from the bottom of the tapping chamber. An extending tundish is provided.

A first distance is defined as a distance in the side-by-side installation direction between the end side wall portion of the hot water discharge chamber in the side-by-side installation direction and the submerged nozzle closest to the wall portion, and When the distance in the side-by-side installation direction between the wall on the end side and the hot tub closest to the wall is the second distance, the first distance is 170 mm or more and 260 mm or less, and the second distance is 80 mm. The first distance may be 120 mm or more and 300 mm or less and the second distance may be 190 mm or more and 230 mm or less.

As described above, according to the present invention, in continuous casting using a tundish having four hot water passages connecting a receiving chamber and a tapping chamber, it is possible to suppress an increase in the difference in quality of slabs between molds. becomes possible.

It is a side sectional view showing roughly a continuous casting machine concerning this embodiment. It is the schematic by the top view of the tundish which concerns on the same embodiment. FIG. 2 is a cross-sectional view of the tundish according to the same embodiment taken along line AA. 4 is a diagram showing a distance D1 in the parallel installation direction X between the end side wall portion of the tapping chambers in the parallel installation direction X and the submerged nozzle closest to the wall portion in the tundish according to the same embodiment. FIG. 4 is a diagram showing the relationship between the distance D1 in the side-by-side direction X between the end side wall portion of the tapping chamber in the side-by-side direction X and the immersion nozzle closest to the wall portion and the temperature difference of the molten steel between the immersion nozzles; FIG. . FIG. 10 is a diagram showing a relationship between a distance D1 in the parallel installation direction X between an end side wall portion of the tapping chamber in the parallel installation direction X and the immersion nozzle closest to the wall portion and the concentration difference of inclusions between the immersion nozzles; . FIG. 10 is a diagram showing the relationship between the average inclusion concentration and the distance D1 in the juxtaposed direction X between the end side wall of the tapping chamber in the juxtaposed direction X and the submerged nozzle closest to the wall. Fig. 10 is a view showing a distance D2 in the juxtaposition direction X between the end side wall in the juxtaposition direction X of the hot water receiving chamber and the hot tub closest to the wall in the tundish according to the same embodiment. A diagram showing the relationship between the distance D2 in the side-by-side installation direction X between the end side wall in the side-by-side installation direction X of the receiving chamber and the hot water path closest to the wall and the temperature difference of the molten steel between the submerged nozzles. be. A diagram showing the relationship between the distance D2 in the side-by-side installation direction X between the end side wall portion in the side-by-side installation direction X of the hot water receiving chamber and the hot water passage closest to the wall portion and the concentration difference of inclusions between the submerged nozzles. be. 4 is a diagram showing the relationship between the average concentration of inclusions and the distance D2 in the juxtaposition direction X between the end side wall portion of the receiving chamber in the juxtaposition direction X and the hot tub closest to the wall portion; FIG. FIG. 2 is a cross-sectional view of the tundish according to the same embodiment taken along the line BB. It is a figure which shows the model of several weirs produced in the numerical simulation. FIG. 4 is a diagram showing the relationship between the shape of a weir and the temperature difference of molten steel between submerged nozzles. FIG. 5 is a diagram showing the relationship between the shape of the weir and the concentration difference of inclusions between submerged nozzles. FIG. 5 is a diagram showing the relationship between the shape of a weir and the average inclusion concentration; FIG. 4 is a diagram showing the relationship between the distance D3 in the side-by-side installation direction X between the injection position of molten steel and the weir and the temperature difference of the molten steel between the submerged nozzles. FIG. 10 is a diagram showing the relationship between the distance D3 in the side-by-side installation direction X between the injection position of molten steel and the weir and the concentration difference of inclusions between the submerged nozzles.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

<1. Continuous casting machine>
First, a continuous casting machine 1 according to an embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a side sectional view schematically showing a continuous casting machine 1. FIG.

In each drawing referred to below, the vertical direction (that is, the direction in which the slab 3 is pulled out from the mold 6) is defined as the Z direction, and two mutually orthogonal directions in a horizontal plane perpendicular to the Z direction are defined as the X direction and the X direction, respectively. It is shown as the Y direction. As will be described later, the X direction corresponds to the direction in which the hot tubs provided in the tundish 100 are arranged side by side.

As shown in FIG. 1, a continuous casting machine 1 is an apparatus for continuously casting molten steel 2 using a mold 6 for continuous casting to produce a bloom 3 such as a bloom or a billet. A continuous casting machine 1 includes a ladle 4 , a tundish 100 , a mold 6 , a secondary cooling device 7 and a cast strip cutter 8 .

The ladle 4 is a movable container for conveying the molten steel 2 to the tundish 100 from the outside. A ladle 4 is placed above a tundish 100 , and molten steel 2 in the ladle 4 is supplied to the tundish 100 from a pouring nozzle 5 extending downward from the bottom of the ladle 4 .

The tundish 100 is arranged above the mold 6 to store the molten steel 2 and remove inclusions in the molten steel 2 . An immersion nozzle 125 extending downward toward the mold 6 is provided at the bottom of the tundish 100 , and the tip of the immersion nozzle 125 is immersed in the molten steel 2 in the mold 6 . The molten steel 2 from which inclusions have been removed in the tundish 100 is continuously supplied from the immersion nozzle 125 into the mold 6 .

Although the details of the tundish 100 will be described later, the tundish 100 is provided with a plurality of immersion nozzles 125 , and the molten steel 2 is supplied from each immersion nozzle 125 to molds 6 different from each other. In FIG. 1, only one mold 6 out of a plurality of molds 6 to which the molten steel 2 is distributed and supplied from the tundish 100 is shown for easy understanding. As will be described later, the tundish 100 uses two induction heating devices to heat the molten steel 2, and has four hot water passages connecting the receiving chamber and the dispensing chamber.

The mold 6 has a rectangular tubular shape corresponding to the width and thickness of the slab 3, and is assembled, for example, by sandwiching a pair of short side mold plates between a pair of long side mold plates. The long-side mold plate and the short-side mold plate are, for example, water-cooled copper plates provided with channels through which cooling water flows. In FIG. 1, the direction parallel to the long sides of the mold 6 is the X direction, and the direction parallel to the short sides of the mold 6 is the Y direction. The mold 6 cools the molten steel 2 in contact with the long side mold plate and the short side mold plate to produce the slab 3 . As the slab 3 moves downward from the mold 6, solidification of the unsolidified portion 3b inside 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 6. As shown in FIG.

The secondary cooling device 7 is provided in a secondary cooling zone 9 below the mold 6 and cools the cast slab 3 pulled out from the lower end of the mold 6 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. and a plurality of spray nozzles (not shown) that spray the

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 supporting and conveying means for supporting and conveying the slab 3 . By supporting the slab 3 from both sides in the thickness direction with the support rolls, it is possible to prevent breakout and bulging of the slab 3 during solidification in the secondary cooling zone 9 .

Support rolls 11 , pinch rolls 12 , and segment rolls 13 that are support rolls form a conveying path (pass line) for the slab 3 in the secondary cooling zone 9 . This pass line is vertical immediately below the mold 6, then curves into a curve, and finally becomes horizontal, as shown in FIG. In the secondary cooling zone 9, a portion where the pass line is vertical is called a vertical portion 9A, a curved portion is called a curved portion 9B, and a horizontal portion is called a horizontal portion 9C. A continuous casting machine 1 having such a pass line is called a vertical bending type continuous casting machine. The present invention is not limited to the vertical bending type continuous casting machine 1 as shown in FIG. 1, but can also be applied to other various types of continuous casting machines such as curved type or vertical type.

The support rolls 11 are non-driven rolls provided in the vertical portion 9A directly below the mold 6 and support the cast slab 3 immediately after being pulled out from the mold 6 . Since the slab 3 immediately after being pulled out from the mold 6 has a thin solidified shell 3a, it needs to be supported at relatively short intervals (roll pitch) to prevent breakout and bulging. Therefore, as the support roll 11, it is desirable to use a small-diameter roll 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 at a relatively narrow roll pitch on both sides of the cast slab 3 in the vertical portion 9A.

The pinch rolls 12 are drive rolls that are rotated by drive means such as a motor, and have a function of pulling out the cast slab 3 from the mold 6 . The pinch rolls 12 are arranged at appropriate positions in the vertical section 9A, the curved section 9B and the horizontal section 9C. The cast slab 3 is pulled out from the mold 6 by the force transmitted from the pinch rolls 12 and conveyed along the pass line. The arrangement of the pinch rolls 12 is not limited to the example shown in FIG. 1, and the arrangement position may be set arbitrarily.

The segment rolls 13 (also referred to as guide rolls) are non-driven rolls provided on the curved portion 9B and the horizontal portion 9C, and support and guide the slab 3 along the pass line. The segment roll 13 is positioned on the pass line and on either the F surface (fixed surface, lower left surface in FIG. 1) or the L surface (loose surface, upper right surface in FIG. 1) of the slab 3. Depending on whether they are provided, they may be arranged with different roll diameters and roll pitches.

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

The continuous casting machine 1 has been described above with reference to FIG. Note that the continuous casting machine 1 is merely an example of a continuous casting machine including the tundish 100 according to the present embodiment. may be used as appropriate.

<2. Tundish>
Next, details of the tundish 100 according to the embodiment of the present invention will be described with reference to FIGS. 2 to 18. FIG.

[2-1. overall structure]
First, the overall configuration of the tundish 100 will be described with reference to FIGS. 2 and 3. FIG.

FIG. 2 is a schematic top view of the tundish 100. As shown in FIG. FIG. 3 is a cross-sectional view of the tundish 100 taken along line AA. Specifically, the AA cross section is a cross section parallel to the XZ plane passing through hot water paths 130c and 130d and induction heating devices 20 provided in the hot water paths 130c and 130d, which will be described later.

As shown in FIG. 2, the tundish 100 includes a hot water receiving chamber 110, a hot water discharging chamber 120, and four hot water passages 130a, 130b, 130c, and 130d connecting the hot water receiving chamber 110 and the hot water discharging chamber 120. As shown in FIG. The tundish 100 is also provided with two induction heating devices 20 for heating the molten steel 2 . Additionally, the tundish 100 includes a weir 140 . In the following description, when the runners 130a, 130b, 130c, and 130d are not particularly distinguished, they are simply referred to as runners 130. FIG.

The hot water receiving chamber 110 is a portion into which the molten steel 2 is poured from the ladle 4 . Specifically, the hot water receiving chamber 110 has a cylindrical shape with an opening at the top and a bottom at the bottom. More specifically, the hot water receiving chamber 110 has a substantially prismatic shape extending in the X direction. Note that the shape of the hot water receiving chamber 110 is not particularly limited. The length L11 in the X direction of the hot water receiving chamber 110 is longer than the length L12 in the Y direction. For example, the length L11 is about 7200-8800 mm and the length L12 is about 900-1100 mm.

The injection nozzle 5 of the ladle 4 is arranged above the hot water receiving chamber 110 , and the tip of the injection nozzle 5 is immersed in the molten steel 2 stored in the hot water receiving chamber 110 . Thereby, the molten steel 2 in the ladle 4 is injected from the injection nozzle 5 into the hot water receiving chamber 110 . Specifically, the injection nozzle 5 is positioned at the center of the hot water receiving chamber 110 in the X direction and the Y direction when viewed from above. Therefore, the pouring position P of the molten steel 2 in the receiving hot water chamber 110 is located at the center of the receiving hot water chamber 110 in the X direction and the Y direction when viewed from above.

Note that if the angle θ between the wall 112 on the positive side in the Y direction of the hot water receiving chamber 110 and the walls 111, 111 on both end sides in the X direction is excessively small, the wall 112 and the wall in the hot water receiving chamber 110 The molten steel 2 may stay in the vicinity of the connection with the part 111, and the temperature of the molten steel 2 may become excessively low at that position, causing skinning on the molten steel surface. Therefore, the angle .theta. formed by the wall portion 112 and the wall portion 111 is set to a large angle, such as about 90.degree.

The hot water discharge chamber 120 is a portion through which the molten steel 2 stored in the hot water receiving chamber 110 is sent via the hot water passage 130 . Specifically, the tapping chamber 120 has a cylindrical shape with an opening at the top and a bottom at the bottom. More specifically, the hot water discharge chamber 120 is provided facing the hot water receiving chamber 110 in the Y direction and has a substantially prismatic shape extending in the X direction. Note that the shape of the tapping chamber 120 is not particularly limited. The length L21 in the X direction of the tapping chamber 120 is longer than the length L22 in the Y direction.

The tapping chamber 120 is provided with a plurality of submerged nozzles 125 for supplying the molten steel 2 into the mold 6 . Specifically, the submerged nozzle 125 is provided extending downward from the bottom of the tapping chamber 120 . 2 shows an example in which six submerged nozzles 125a, 125b, 125c, 125d, 125e, and 125f are provided in the tapping chamber 120 as the submerged nozzles 125, but the submerged nozzles provided in the tapping chamber 120 are shown in FIG. The number of nozzles 125 is not particularly limited. Specifically, the six submerged nozzles 125 are positioned in the center of the hot water discharge chamber 120 in the Y direction when viewed from above, and are arranged side by side at intervals in the X direction.

The hot water passage 130 connects the hot water receiving chamber 110 and the hot water dispensing chamber 120, and is a portion through which the molten steel 2 sent from the hot water receiving chamber 110 to the hot water dispensing chamber 120 passes. The four hot water passages 130 are arranged horizontally between the receiving hot water chamber 110 and the hot water discharging chamber 120 . Specifically, a hollow cylindrical member extending in the Y direction between the wall portion 112 of the hot water receiving chamber 110 on the positive Y direction side and the wall portion 122 of the hot water discharge chamber 120 on the negative Y direction side. A sleeve is provided, and the inner space of the sleeve corresponds to the hot tub 130 . The hot tubs 130a, 130b, 130c, and 130d are arranged side by side along the X direction in this order from the positive direction side of the X direction. Thus, the X direction corresponds to the direction in which the hot tubs 130 are arranged side by side.

Although the positional relationship between the hot water passage 130 and the submerged nozzle 125 is not particularly limited, for example, in the example shown in FIG. is located between the hot water paths 130a and 130b, the submerged nozzles 125c and 125d are located between the hot water paths 130b and 130c, the submerged nozzle 125e is located between the hot water paths 130c and 130d, The immersion nozzle 125f is located on the negative direction side of the hot water passage 130d.

The hot water passages 130a and 130b are located on one side of the tundish 100 in the side-by-side direction X (specifically, on the positive side of the X direction from the pouring position P of the molten steel 2 in the receiving chamber 110). On the other hand, the hot water passages 130c and 130d are located on the other side of the parallel installation direction X in the tundish 100 (specifically, on the negative side of the X direction from the injection position P of the molten steel 2 in the receiving chamber 110). . For example, the diameter of the hot water passage 130 is about 120 to 140 mm, and the distance L31 between the central axes of the hot water passages 130a and 130b and between the central axes of the hot water passages 130c and 130d is about 1200 to 1400 mm. , the distance L32 between the central axes of the hot water passages 130b and 130c is about 4200 to 5200 mm.

Here, the hot water paths 130a and 130b on one side in the juxtaposed direction X and the hot water paths 130c and 130d on the other side in the juxtaposed direction X are provided with induction heating devices 20, respectively. Specifically, the induction heating device 20 includes an annular iron core 21 and a coil 22, as shown in FIGS. The iron core 21 is arranged so as to surround the hot water passage 130 , and the coil 22 is wound around the iron core 21 . For example, the iron core 21 of the induction heating device 20 on one side in the parallel installation direction X is arranged so as to surround the hot water passage 130a, and the iron core 21 of the induction heating device 20 on the other side in the parallel installation direction X is arranged so as to surround the hot water passage 130a. 130d.

When an alternating current is applied to the coil 22 of the induction heating device 20 , a magnetic circuit is generated in the iron core 21 so as to surround the hot water passage 130 . For example, in FIG. 3, a magnetic circuit generated in the iron core 21 when an alternating current is applied to the coil 22 of the induction heating device 20 on the other side of the side-by-side arrangement direction X is indicated by a dashed-dotted line arrow. Eddy currents are generated in the molten steel 2 in the tundish 100 by the magnetic circuit generated in the iron core 21 . For example, in FIG. 2, an eddy current generated so as to form a closed loop passing through the runners 130a and 130b on one side in the juxtaposed direction X and a closed loop passing through the runners 130c and 130d on the other side in the juxtaposed direction X are formed. The eddy currents that occur are indicated by dashed arrows. Thus, the molten steel 2 is heated by the eddy current generated in the molten steel 2 in the tundish 100 .

Weirs 140 are provided to regulate the flow of molten steel 2 in tundish 100 for the purpose of reducing temperature differences in molten steel 2 between submerged nozzles 125 . The weirs 140 are provided on both sides of the pouring position P of the molten steel 2 in the receiving chamber 110 in the side-by-side direction X, and extend across the side-by-side direction X (specifically, parallel to the YZ plane). do. Although the details of the shape of the weir 140 will be described later, an opening is formed in the weir 140, and the molten steel 2 injected from the injection nozzle 5 to the injection position P in the hot water receiving chamber 110 flows through the opening. Pass through weir 140 .

As described above, the molten steel 2 in the ladle 4 is injected from the injection nozzle 5 into the hot water receiving chamber 110 . Then, the molten steel 2 injected into the hot water receiving chamber 110 is sent to the hot water tapping chamber 120 through one of the four hot water passages 130 . In FIG. 2, solid arrows indicate how the molten steel 2 injected into the hot water receiving chamber 110 is sent from the injection position P through the hot water passages 130 to the hot water tapping chamber 120 . Here, as described above, the length of the route to reach the hot water discharge chamber 120 differs depending on which hot water passage 130 the molten steel 2 poured into the hot water receiving chamber 110 passes. Moreover, a difference also arises in the flow rate of the molten steel 2 between the hot water passages 130 . As a result, a temperature difference is likely to occur between the molten steel 2 flowing into the tapping chamber 120 from each hot water passage 130 .

Specifically, when the molten steel 2 passes through the hot water paths 130a and 130d far from the pouring position P, it takes longer to reach the tapping chamber 120 than when it passes through the hot water paths 130b and 130c near the pouring position P. As the length of the path increases, the time required to reach the tapping chamber 120 increases, and the flow rate of the molten steel 2 decreases. Therefore, the temperature of the molten steel 2 flowing into the tapping chamber 120 through the hot water paths 130a and 130d farther from the injection position P is the temperature of the molten steel 2 flowing into the tapping chamber 120 through the hot water paths 130b and 130c closer to the injection position P. tends to be low compared to Therefore, for example, the molten steel 2 flowing into the tapping chamber 120 from the hot water passages 130a, 130d is mainly sent to the immersion nozzles 125a, 125f, and the molten steel 2 flowing into the tapping chamber 120 from the hot water passages 130b, 130c is mainly sent. The temperature difference between the molten steel 2 and the immersion nozzles 125c and 125d tends to increase.

Therefore, the present inventor conducted a numerical simulation of the thermal flow of the molten steel 2 in the tundish 100, and determined that the temperature difference of the molten steel 2 between the immersion nozzles 125 can be reduced by appropriately setting various dimensions of the tundish 100. It was discovered that it is possible to suppress the growth. Therefore, by appropriately setting various dimensions and the like in the tundish 100, in continuous casting using the tundish 100 having the four hot water passages 130 connecting the hot water receiving chamber 110 and the hot water discharge chamber 120, the mold It is possible to suppress an increase in the quality difference of the slabs 3 between 6. The setting of various dimensions of the tundish 100 for suppressing the temperature difference of the molten steel 2 between the immersion nozzles 125 from increasing will be described in detail later.

[2-2. Various dimensions of the tundish]
Next, details such as various dimensions of the tundish 100 will be described with reference to FIGS. 4 to 18. FIG.

As described above, the present inventor investigated the setting of various dimensions of the tundish 100 for suppressing an increase in the temperature difference of the molten steel 2 between the immersion nozzles 125. 2 was numerically simulated for heat flow. As a result, various dimensions of the tundish 100 for suppressing an increase in the temperature difference of the molten steel 2 between the submerged nozzles 125 include the position of the submerged nozzle 125, the position of the hot water passage 130, the shape of the weir 140, and the We obtained new knowledge about the position and

Moreover, the difference in quality of the slab 3 between the molds 6 is affected not only by the difference in temperature of the molten steel 2 between the immersion nozzles 125 but also by the difference in concentration of inclusions in the molten steel 2 between the immersion nozzles 125 . Specifically, an increase in the concentration difference of inclusions in the molten steel 2 between the molten steel 2 passing through each submerged nozzle 125 of the tapping chamber 120 (that is, the molten steel supplied to each mold 6) is a factor that increases the quality difference of the slab 3. Therefore, using the results of this numerical simulation, the relationship between the various dimensions of the tundish 100 and the difference in concentration of inclusions in the molten steel 2 between the submerged nozzles 125 was also investigated.

As this numerical simulation, for example, non-patent documents "Tetsu to Hagane, Vol.83 (1997), No.1, P.30-35" and "K. Takatani: ISIJ International, Vol.43, 2003, No. 6, P. 915-922” was used. In detail, this simulation was carried out by solving the governing equation regarding the heat flow of fluid in a time-evolving manner using the finite volume method.

In this numerical simulation, it is assumed that the fluid is incompressible and that the solid and liquid phases have the same density and specific heat. In addition, it was assumed that the flow resistance of the solid-liquid coexisting phase was calculated from Darcy's law. Further, a region where the solid fraction fs>0.8 or more is defined as a solid phase, and it is assumed that the solid phase is stationary within the tundish 100 as a rigid body. It is also assumed that the motion of bubbles and inclusions follows the equation of motion of spheres in the liquid phase. We also assumed that the bubbles were incompressible and spheres of constant size. Also, the volume of inclusions was assumed to be negligible. A LES model was applied as a turbulence model.

As the analysis result, a value obtained by averaging the results of unsteady calculation over 100 seconds was used. The molten steel 2 had a specific gravity of 7000 kg/m ³ and a viscosity coefficient of 0.005 Pa·s. The amount of heat generated by the induction heating device 20 and the electromagnetic force (Lorentz force density) were calculated using values obtained from electromagnetic field analysis by the finite element method. The frequency of the induction heating device 20 was set to 60 Hz, and the power consumption was set to 800 kW per induction heating device 20 for calculation. The iron core 21 of the induction heating device 20 is assumed to be a plurality of laminated electromagnetic steel plates. Moreover, the electric conductivity of the molten steel 2 was set to 7.14×10 ⁵ S/m.

As the characteristics of the number density of inclusions contained in the molten steel 2 poured from the ladle 4 into the tundish 100 with respect to the diameter, characteristics obtained based on past knowledge were used. In addition, the initial value of the weight ratio of inclusions in the molten steel 2 was set to 12.64 ppm, and the calculation was performed in consideration of the adhesion of inclusions to the wall surface due to electromagnetic force and the floatation separation from the molten steel surface. The diameter of inclusions was calculated by classifying them into 34 levels, with a minimum of 2 μm and a maximum of 100 μm. Alumina was assumed as inclusions, and its specific gravity was set to 3900 kg/m ³ . Also, the calculation was performed assuming that the temperature of the molten steel 2 when it is poured from the ladle 4 into the tundish 100 is 1600°C.

In the explanation of the simulation results below, the temperature difference of the molten steel 2 between the submerged nozzles 125, the inclusion concentration difference between the submerged nozzles 125, and the average inclusion concentration will be described. means the difference between the maximum and minimum temperatures of the molten steel 2 passing through each immersion nozzle 125, and the inclusion concentration difference between the immersion nozzles 125 is the concentration of inclusions in the molten steel 2 passing through each immersion nozzle 125 means the difference between the maximum value and the minimum value of , and the average inclusion concentration means the average value of the concentration of inclusions in the molten steel 2 passing through each submerged nozzle 125 .

(Position of immersion nozzle)
First, the position of the submerged nozzle 125 will be described with reference to FIGS. 4 to 7. FIG.

From the results of numerical simulations, the inventors of the present invention have found that the direction X between the wall portion 121 on the end side of the tundish 100 in the direction X in which the tapping chambers 120 are arranged side by side and the submerged nozzle 125 closest to the wall portion 121 is It was found that by appropriately setting the distance D1, it is possible to suppress the temperature difference of the molten steel 2 between the submerged nozzles 125 from increasing.

FIG. 4 is a view showing the distance D1 in the juxtaposition direction X between the wall portion 121 on the end side in the juxtaposition direction X of the tapping chamber 120 in the tundish 100 and the submerged nozzle 125 closest to the wall portion 121 . . Specifically, FIG. 4 shows the wall portion 121 on the end side of the hot water discharge chamber 120 on the positive direction side in the side-by-side installation direction X and the immersion nozzle 125a closest to the wall portion 121 .

Specifically, the wall portion 121 on the end side of the hot water discharge chamber 120 in the tundish 100 in the parallel direction X and the submerged nozzle 125 closest to the wall portion 121 (that is, the submerged nozzle 125 on the end side in the parallel direction X) As shown in FIG. 4, the distance D1 in the side-by-side installation direction X between It means the shortest distance in the juxtaposition direction X between the inner surfaces.

Numerical simulation results for the distance D1 will be described below with reference to FIGS. Numerical simulation for the distance D1 assumes that the casting speed is 0.6 m/min and that the weir 140 is not provided. Under the condition that the distance D2 in the side-by-side installation direction X between 111 and the nearest hot tub 130 was set to 220 mm, it was performed with and without induction heating.

FIG. 5 is a diagram showing the relationship between the distance D1 and the temperature difference of the molten steel 2 between the submerged nozzles 125. As shown in FIG.

From the results shown in FIG. 5, it was found that the temperature difference of the molten steel 2 between the submerged nozzles 125 tends to decrease and then increase as the distance D1 increases. Therefore, it can be seen that the temperature difference of the molten steel 2 between the submerged nozzles 125 increases both when the distance D1 is too short and when it is too long.

The reason why the temperature difference of the molten steel 2 between the submerged nozzles 125 increases when the distance D1 is excessively short is that the shorter the distance D1, the more molten steel 2 sent to the submerged nozzles 125 on the end side in the side-by-side installation direction X. It is conceivable that the degree of cooling by the wall portion 121 on the end side of the side-by-side arrangement direction X of 120 increases. The reason why the temperature difference of the molten steel 2 between the submerged nozzles 125 increases when the distance D1 is excessively long is that the longer the distance D1, the more molten steel 2 sent to the submerged nozzles 125 on the end side in the parallel installation direction X. When detouring to the side of the wall 121 on the end side of the parallel installation direction X of the tapping chamber 120, it takes longer to reach the submerged nozzle 125, and the temperature of the molten steel 2 is likely to decrease.

Here, generally, when the temperature difference of the molten steel 2 between the submerged nozzles 125 exceeds 5° C., the temperature of the slab 3 between the molds 6 increases to the extent that it becomes necessary to take measures such as adjusting the casting speed between the molds 6 . Quality difference increases. Therefore, in this embodiment, the distance D1 is set to 120 mm or more and 300 mm or less, which is a range in which the temperature difference of the molten steel 2 between the submerged nozzles 125 is 5° C. or less as shown in FIG. 5 when induction heating is performed. be. As a result, in continuous casting using the tundish 100 having the four hot water passages 130 connecting the hot water receiving chamber 110 and the hot water tapping chamber 120, an increase in the temperature difference of the molten steel 2 between the submerged nozzles 125 can be appropriately suppressed. Therefore, it is possible to suppress an increase in the difference in quality of the slab 3 between the molds 6 .

Furthermore, when induction heating is performed, the distance D1 is more preferably set to 170 mm or more and 260 mm or less, which is a range in which the temperature difference of the molten steel 2 between the submerged nozzles 125 is 3° C. or less as shown in FIG. . As a result, in continuous casting using the tundish 100 having the four hot water passages 130 connecting the hot water receiving chamber 110 and the hot water tapping chamber 120, an increase in the temperature difference of the molten steel 2 between the submerged nozzles 125 is further appropriately suppressed. Therefore, an increase in the quality difference of the slabs 3 between the molds 6 can be suppressed more appropriately.

From the results shown in FIG. 5, it can be seen that the temperature difference of the molten steel 2 between the submerged nozzles 125 tends to increase when induction heating is performed, as compared to when induction heating is not performed. This is because induction heating not only heats the molten steel 2 in the tundish 100, but also makes the flow of the molten steel 2 more likely to be disturbed, thereby increasing the wall thickness of the tapping chamber 120 on the end side in the direction X in which it is arranged side by side. This is also considered to be caused by the fact that the molten steel 2 cooled by the portion 121 is easily sent to the submerged nozzle 125 on the end side in the side-by-side arrangement direction X. The reason why the flow of the molten steel 2 is easily disturbed by induction heating is that the electromagnetic force is generated in the hot water passage 130 by the induction heating toward the inside of the hot water passage 130 (that is, in the direction toward the central axis). , the cross-sectional area of the molten steel 2 in the hot water passage 130 substantially decreases, and the flow velocity of the molten steel 2 increases.

FIG. 6 is a diagram showing the relationship between the distance D1 and the concentration difference of inclusions between the submerged nozzles 125. As shown in FIG.

From the results shown in FIG. 6, it was found that the inclusion concentration difference in the molten steel 2 between the submerged nozzles 125 tends to decrease as the distance D1 increases. In particular, when performing induction heating, when the distance D1 is 200 mm or more, it can be seen that the inclusion concentration difference in the molten steel 2 between the submerged nozzles 125 is significantly reduced.

The reason why the difference in concentration of inclusions decreases as the distance D1 increases is that the flow of the molten steel 2 sent to the submerged nozzle 125 on the end side in the side-by-side direction X increases as the distance D1 becomes shorter. Non-metallic inclusions (for example, oxides of aluminum and magnesium) floating on the surface of the hot water are likely to be involved due to interference with the wall 121 on the end side of the Conceivable.

In addition, it can be seen from the results shown in FIG. 6 that the difference in concentration of inclusions in the molten steel 2 between the submerged nozzles 125 is reduced when induction heating is performed, compared to when induction heating is not performed. This is thought to be due to the fact that induction heating improves the ability to remove inclusions due to the electromagnetic force generated in the molten steel 2 . Specifically, by performing induction heating, as described above, an electromagnetic force is generated in the hot water passage 130 toward the inside of the hot water passage 130 (that is, in the direction toward the central axis). Therefore, in the hot water passage 130, as the molten steel 2 is drawn toward the inner side of the hot water passage 130 (that is, in the direction toward the central axis), the inclusions move to the outside of the hot water passage 130 (that is, in the direction away from the central axis). ) and adheres to the inner wall of the sleeve that defines the runner 130 . Thereby, inclusions in the molten steel 2 are removed.

FIG. 7 is a diagram showing the relationship between the distance D1 and the average inclusion concentration.

From the results shown in FIG. 7, it can be seen that the average inclusion concentration decreases when induction heating is performed compared to when induction heating is not performed. This is thought to be due to the fact that induction heating improves the ability to remove inclusions due to the electromagnetic force generated in the molten steel 2 . From the results shown in FIG. 7, it can be seen that the influence of the distance D1 on the average inclusion concentration is relatively small.

(Position of hot tub)
Next, the position of the runner 130 will be described with reference to FIGS. 8 to 11. FIG.

From the results of numerical simulations, the inventors of the present invention found that the wall portion 111 on the end side of the tundish 100 in the direction X in which the hot water receiving chambers 110 are arranged side by side and the hot water passage 130 closest to the wall portion 111 are arranged in the direction X It was found that by appropriately setting the distance D2 of , it is possible to suppress the temperature difference of the molten steel 2 between the submerged nozzles 125 from increasing.

FIG. 8 is a diagram showing a distance D2 in the juxtaposition direction X between the wall portion 111 on the end side in the juxtaposition direction X of the hot water receiving chamber 110 in the tundish 100 and the hot tub 130 closest to the wall portion 111. FIG. be. Specifically, FIG. 8 shows the wall portion 111 on the end side of the receiving hot water chamber 110 on the positive direction side in the parallel direction X and the hot tub 130a closest to the wall portion 111 .

Specifically, the wall portion 111 of the tundish 100 on the end side in the parallel installation direction X of the hot water receiving chamber 110 and the hot water passage 130 closest to the wall portion 111 (that is, the hot water passage 130 on the end side in the parallel installation direction X) As shown in FIG. 8, the distance D2 in the side-by-side installation direction X between and the It means the shortest distance in the side-by-side installation direction X between the wall portion 111 and the inner surface of the nearest hot tub 130 (for example, hot tub 130a).

Numerical simulation results for the distance D2 will be described below with reference to FIGS. 9 to 11. FIG. Numerical simulation for the distance D2 assumes that the casting speed is 0.6 m/min and the weir 140 is not provided, and the wall portion 121 on the end side of the tapping chamber 120 and the wall portion 121 Under the condition that the distance D1 in the side-by-side arrangement direction X between the submerged nozzle 125 closest to the nozzle 125 is 230 mm, induction heating is performed and not performed.

FIG. 9 is a diagram showing the relationship between the distance D2 and the temperature difference of the molten steel 2 between the submerged nozzles 125. As shown in FIG.

From the results shown in FIG. 9, it was found that the temperature difference of the molten steel 2 between the submerged nozzles 125 tends to decrease and then increase as the distance D2 increases. Therefore, it can be seen that the temperature difference of the molten steel 2 between the submerged nozzles 125 increases both when the distance D2 is too short and when it is too long.

The reason why the temperature difference of the molten steel 2 between the submerged nozzles 125 increases when the distance D2 is excessively short is that the shorter the distance D2, the more molten steel 2 sent to the hot water passage 130 on the end side in the side-by-side installation direction X. It is conceivable that the degree of cooling by the wall portions 111 on the end side of the parallel arrangement direction X of the chambers 110 is increased. Further, the reason why the temperature difference of the molten steel 2 between the submerged nozzles 125 increases when the distance D2 is excessively long is that the longer the distance D2, the more the molten steel 2 sent to the hot water passage 130 on the end side in the side-by-side installation direction X. When detouring to the side of the wall 111 on the end side of the side-by-side arrangement direction X of the hot water receiving chamber 110, it takes longer to reach the hot water passage 130, and the temperature of the molten steel 2 is likely to decrease.

As described above, generally, from the viewpoint of suppressing an increase in the quality difference of the slabs 3 between the molds 6, it is preferable to set the temperature difference of the molten steel 2 between the submerged nozzles 125 to 5°C or less. Therefore, when performing induction heating, the distance D2 is preferably set to 80 mm or more and 260 mm or less, which is a range in which the temperature difference of the molten steel 2 between the submerged nozzles 125 is 5° C. or less as shown in FIG. Thereby, in continuous casting using the tundish 100 having the four hot water passages 130 connecting the hot water receiving chamber 110 and the hot water tapping chamber 120, an increase in the temperature difference of the molten steel 2 between the submerged nozzles 125 is suppressed more appropriately. Therefore, an increase in quality difference of the slabs 3 between the molds 6 can be suppressed more appropriately.

Furthermore, when induction heating is performed, the distance D2 is more preferably set to 190 mm or more and 230 mm or less, which is a range in which the temperature difference of the molten steel 2 between the submerged nozzles 125 is 3° C. or less as shown in FIG. . As a result, in continuous casting using the tundish 100 having the four hot water passages 130 connecting the hot water receiving chamber 110 and the hot water tapping chamber 120, an increase in the temperature difference of the molten steel 2 between the submerged nozzles 125 is further appropriately suppressed. Therefore, an increase in the quality difference of the slabs 3 between the molds 6 can be suppressed more appropriately.

From the results shown in FIG. 9, similarly to the results shown in FIG. is likely to become large.

FIG. 10 is a diagram showing the relationship between the distance D2 and the concentration difference of inclusions between the submerged nozzles 125. As shown in FIG.

From the results shown in FIG. 10, it was found that the inclusion concentration difference in the molten steel 2 between the submerged nozzles 125 tends to decrease as the distance D2 increases.

The reason why the inclusion concentration difference decreases as the distance D2 increases is that the flow of the molten steel 2 sent to the hot water passage 130 on the end side in the side-by-side installation direction X moves toward the side-by-side installation direction of the receiving chamber 110 as the distance D2 becomes shorter. Non-metallic inclusions (for example, oxides of aluminum and magnesium) floating on the surface of the melt are likely to be involved due to interference with the wall portion 111 on the end side of X, which is likely to be disturbed. can be considered.

From the results shown in FIG. 10, similarly to the results shown in FIG. It can be seen that the density difference is reduced.

FIG. 11 is a diagram showing the relationship between the distance D2 and the average inclusion concentration.

From the results shown in FIG. 11, it can be seen that the average inclusion concentration decreases when induction heating is performed compared to when induction heating is not performed. This is thought to be due to the fact that induction heating improves the ability to remove inclusions due to the electromagnetic force generated in the molten steel 2 . From the results shown in FIG. 11, it can be seen that the influence of the distance D2 on the average inclusion concentration is relatively small.

(Shape and position of weir)
Next, the shape and position of the weir 140 will be described with reference to FIGS. 12 to 18. FIG.

FIG. 12 is a cross-sectional view of the tundish 100 taken along line BB. Specifically, FIG. 12 is a cross-sectional view parallel to the YZ plane passing through a portion on the positive side in the side-by-side direction X of the weir 140 on the positive side in the side-by-side direction X in the hot water receiving chamber 110. be.

As described above with reference to FIG. 2, the weirs 140 extend across the side-by-side direction X (specifically, parallel to the YZ plane). Specifically, the weir 140 provided on the tundish 100 has openings 141, 141 at both ends of its lower portion, as shown in FIG. Here, the upper end of the weir 140 is located above the surface of the molten steel 2 in the receiving hot water chamber 110 (that is, the height of the weir 140 is longer than the depth of the molten steel 2 in the receiving hot water chamber 110). is). In addition, in FIG. 12, the position of the molten metal surface is indicated by the one-dot chain line F1. Therefore, the molten steel 2 poured into the pouring position P in the hot water receiving chamber 110 passes through the openings 141 , 141 and is sent to each hot water passage 130 .

From the viewpoint of suppressing an increase in the temperature difference of the molten steel between the submerged nozzles 125, the inventors of the present invention conducted numerical simulations to determine the shape of the weirs provided on the tundish 100 at both ends of the lower portion as described above. It has been found that a shape with openings is preferable. Specifically, in the numerical simulation of the shape of the weir 140, weir models having shapes 1 to 6 shown in FIG. 13 were created, and numerical simulations were performed for each model. In FIG. 13, the shape of each model is indicated by solid lines.

The weir of Shape 1 has an opening only at the end on the negative Y direction side of the lower portion, and the upper end is positioned below the molten metal surface. Further, the weir of shape 2 is obtained by adding a weir having an opening in the lower part and having an upper end located above the surface of the hot water, to the outer side of the weir of shape 1 in the X direction. Further, the weir of shape 3 is obtained by adding a weir which has an opening in the lower part and whose upper end is located above the surface of the hot water, with a space above the weir of shape 1. Also, the shape 4 weir has the same shape as the above-described weir 140 provided on the tundish 100 . Further, the weir of shape 5 has an opening only at the end on the positive side in the Y direction of the lower part, and the upper end is located above the molten metal surface. Moreover, the weir of shape 6 has an opening only at the end on the negative side in the Y direction of the lower part, and the upper end is located above the molten metal surface.

Numerical simulation results regarding the shape of the weir 140 will be described below with reference to FIGS. 14 to 16. FIG. In the numerical simulation of the shape of the weir 140, the casting speed was set to 0.6 m/min and induction heating was not performed. The distance D1 in the side-by-side arrangement direction X between the submerged nozzle 125 closest to 121 is set to 230 mm, and the wall 111 on the end side in the side-by-side arrangement direction X of the above-described hot water receiving chamber 110 and the hot water passage closest to the wall 111 130 in the parallel arrangement direction X was set to 220 mm.

FIG. 14 is a diagram showing the relationship between the shape of the weir and the temperature difference of the molten steel 2 between the submerged nozzles 125. As shown in FIG.

From the results shown in FIG. 14, it was found that the shape 4 weir has a smaller temperature difference of the molten steel 2 between the submerged nozzles 125 than the other shape weirs. In particular, in the weir of Shape 4, unlike the weirs of other shapes, the difference in temperature of the molten steel 2 between the submerged nozzles 125 is lower than in the case where no weir is provided. Therefore, from the viewpoint of suppressing an increase in the temperature difference of the molten steel between the submerged nozzles 125, it is preferable that the weir provided in the tundish 100 has a shape in which openings are formed at both ends of the lower portion. Recognize.

FIG. 15 is a diagram showing the relationship between the weir shape and the concentration difference of inclusions between the submerged nozzles 125 .

From the results shown in FIG. 15, it was found that the difference in concentration of inclusions in the molten steel 2 between the submerged nozzles 125 was smaller in the weir of shape 4 than in the weirs of other shapes.

FIG. 16 is a diagram showing the relationship between the shape of the weir and the average concentration of inclusions.

From the results shown in FIG. 16, it was found that any of the weirs of Shapes 1 to 6 reduced the average inclusion concentration as compared to the case where no weir was provided. In particular, the weirs of Shapes 2 to 6, whose upper end is located above the molten steel surface and can dam the flow of the molten steel 2 near the molten steel surface, are relatively effective in reducing the average inclusion concentration. I understand.

Further, from the results of numerical simulations, the inventors of the present invention found that by appropriately setting the distance D3 (see FIG. It was found that it is possible to suppress an increase in the temperature difference of the molten steel 2 between.

Results of numerical simulations for the distance D3 will be described below with reference to FIGS. 17 and 18. FIG. Numerical simulation for the distance D3 was performed with a casting speed of 0.6 m/min, and the distance between the wall 121 on the end side of the tapping chamber 120 in the side-by-side direction X and the submerged nozzle 125 closest to the wall 121 was measured. The distance D1 in the parallel installation direction X is 230 mm, and the distance in the parallel installation direction X between the wall 111 on the end side in the parallel installation direction X of the above-described hot water receiving chamber 110 and the hot tub 130 closest to the wall 111 Under the condition that the distance D2 was set to 220 mm, the measurement was performed with and without induction heating.

FIG. 17 is a diagram showing the relationship between the distance D3 and the temperature difference of the molten steel 2 between the submerged nozzles 125. As shown in FIG.

From the results shown in FIG. 17, it was found that the temperature difference of the molten steel 2 between the submerged nozzles 125 tends to decrease and then increase as the distance D3 increases. Therefore, it can be seen that the temperature difference of the molten steel 2 between the submerged nozzles 125 increases both when the distance D3 is too short and when it is too long.

The reason why the temperature difference of the molten steel 2 between the submerged nozzles 125 increases when the distance D3 is excessively short is that the shorter the distance D3, the more molten steel 2 is placed in the space defined by the two weirs 140 in the receiving hot water chamber 110. It is conceivable that the effect of soaking the temperature of the molten steel 2 in the space is reduced due to the shortened storage time. The reason why the temperature difference of the molten steel 2 between the submerged nozzles 125 increases when the distance D3 is excessively long is that the longer the distance D3, the larger the space defined by the two weirs 140 in the receiving hot water chamber 110. Due to this, it is conceivable that the temperature difference of the molten steel 2 tends to occur depending on the position in the space.

As described above, generally, from the viewpoint of suppressing an increase in the quality difference of the slabs 3 between the molds 6, it is preferable to set the temperature difference of the molten steel 2 between the submerged nozzles 125 to 5°C or less. Therefore, when induction heating is performed, the distance D3 is preferably set to 655 mm or more and 1140 mm or less, which is the range in which the temperature difference of the molten steel 2 between the submerged nozzles 125 is 5° C. or less as shown in FIG. As a result, in continuous casting using the tundish 100 having the four hot water passages 130 connecting the hot water receiving chamber 110 and the hot water tapping chamber 120, an increase in the temperature difference of the molten steel 2 between the submerged nozzles 125 is further appropriately suppressed. Therefore, an increase in the quality difference of the slabs 3 between the molds 6 can be suppressed more appropriately.

From the results shown in FIG. 17, similarly to the results shown in FIGS. 5 and 9, when induction heating is performed, the molten steel 2 between the submerged nozzles 125 It can be seen that the temperature difference between

FIG. 18 is a diagram showing the relationship between the distance D3 and the concentration difference of inclusions between the submerged nozzles 125. As shown in FIG.

From the results shown in FIG. 18, similarly to the results shown in FIGS. It can be seen that the density difference is reduced. From the results shown in FIG. 18, it can be seen that the inclusion concentration difference in the molten steel 2 between the submerged nozzles 125 is relatively low regardless of the distance D3.

Results of an actual machine test conducted to confirm the relationship between the various dimensions of a tundish with four hot water passages connecting the receiving chamber and the hot water discharge chamber, the temperature difference of the molten steel between the submerged nozzles, and the inclusion concentration difference. will be explained.

In the actual machine test, a continuous casting machine (having the same configuration as the continuous casting machine 1 shown in FIG. 1) actually using a tundish having the same configuration as the tundish 100 according to the present embodiment described above is used. It was installed in the , and continuous casting was performed. The temperature difference of the molten steel between the submerged nozzles was calculated by measuring the temperature of the molten steel in the tundish directly above each submerged nozzle. In addition, regarding the inclusion concentration difference in the molten steel between the immersion nozzles, a sample of 50 mm × 50 mm × 20 mm was cut from the slab obtained after casting with each mold, melted, and the inclusion concentration in each sample was measured. Calculated by asking. In this actual machine test, the frequency of the induction heating device was set to 60 Hz, and the power consumption was set to 800 kW per one induction heating device.

Table 1 shows the results of this actual machine test. Table 1 shows the results of the difference in molten steel temperature and inclusion concentration between submerged nozzles for each test condition. Specifically, the casting speed, throughput, distance D3, presence/absence of induction heating, distance D2, and distance D1 were variously changed as test conditions. In addition, the condition that the distance D3 is "none" is the condition that the weir is not provided. The conditions for which a numerical value is entered in the column of the distance D3 are conditions in which a weir having the same configuration as the above-described weir 140 is provided so that the value of the distance D3 is the numerical value entered.

As shown in Table 1, in this actual machine test, the distance D1 that defines the position of the immersion nozzle with respect to the tapping chamber is set to 120 mm or more and 300 mm or less, and the distance D2 that defines the position of the hot water passage with respect to the receiving chamber is 80 mm. It is set to 260 mm or less. Here, according to Table 1, regardless of the presence or absence of induction heating, the temperature difference of the molten steel between the submerged nozzles is 5°C or less under each test condition. Therefore, in continuous casting using a tundish having four hot water passages connecting the receiving chamber and the tapping chamber, when at least the distance D1 and the distance D2 are set as described above, the molten steel between the submerged nozzles It was confirmed that the increase in the temperature difference was appropriately suppressed, and the increase in the quality difference of the slab between the molds was suppressed.

As described above, the range of the distance D1 that more easily suppresses an increase in the temperature difference of the molten steel between the submerged nozzles is 170 mm or more and 260 mm or less. Moreover, the range of the distance D2 that more easily suppresses the increase in the temperature difference of the molten steel between the submerged nozzles is the range of 190 mm or more and 230 mm or less. Therefore, from the viewpoint of more appropriately suppressing an increase in temperature difference of molten steel between the submerged nozzles, the distance D1 is 170 mm or more and 260 mm or less and the distance D2 is 80 mm or more and 260 mm or less, or the distance D1 is 120 mm or more and 300 mm or less. The dovetail distance D2 is preferably 190 mm or more and 230 mm or less.

Further, according to Table 1, for example, by comparing conditions 4 and 5 in which weirs are provided with conditions 1 and 2 in which weirs are not provided, weirs having openings at both ends of the lower portion are found to be tanks. It was confirmed that the increase in the temperature difference of the molten steel between the submerged nozzles was further suppressed by providing them in the dish.

Further, according to Table 1, for example, by comparing conditions 4 and 8 in which the distance D3 is 800 mm and 1000 mm, respectively, and conditions 20 and 22 in which the distance D3 is 600 mm and 1200 mm, It was confirmed that an increase in the temperature difference of molten steel between the submerged nozzles can be further suppressed by setting the distance D3 that defines the position of the weir with respect to the position to 655 mm or more and 1140 mm or less.

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 such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modifications or applications within the scope of the technical idea described in the claims. It is understood that these also naturally belong to the technical scope of the present invention.

1 Continuous Caster 2 Molten Steel 3 Slab 3a Solidified Shell 3b Unsolidified Portion 4 Ladle 5 Injection Nozzle 6 Mold 7 Secondary Cooling Device 8 Slab Cutting Machine 20 Induction Heating Device 21 Iron Core 22 Coil 100 Tundish 110 Receiving Chamber 120 tapping chambers 125, 125a, 125b, 125c, 125d, 125e, 125f immersion nozzles 130, 130a, 130b, 130c, 130d hot water path 140 weir 141 opening

Claims (2)

a receiving chamber into which molten steel is poured from a ladle;
a pouring chamber provided with a plurality of submerged nozzles for supplying the molten steel into the mold;
four hot water passages connecting the hot water receiving chamber and the hot water discharge chamber and provided horizontally between the hot water receiving chamber and the hot water discharge chamber;
with
An induction heating device is provided in each of the two hot water passages on one side in the parallel installation direction of the hot water passages and the two hot water passages on the other side in the parallel installation direction,
The distance between the center axes of the two runners on one side and the distance between the centers of the two runners on the other side are 1200 to 1400 mm. The center-to-center distance between the hot water passage arranged inside in the installation direction and the hot water passage arranged inside in the side-by-side arrangement direction of the two hot water passages on the other side is 4200 to 5200 mm,
The diameter of the runner is 120 to 140 mm,
An injection nozzle of the ladle is arranged above the receiving chamber in the center of the side-by-side direction and the direction vertical and horizontal to the side-by-side direction,
On both sides of the pouring position of the molten steel in the receiving chamber in the side-by-side direction, the lower part extends crosswise in the side-by-side direction, has openings at both ends, and has an upper end above the surface of the molten steel. or there is no weir located above the
The distance in the side-by-side direction between the end side wall portion of the tapping chamber in the side-by-side direction and the submerged nozzle closest to the wall portion is 120 mm or more and 300 mm or less,
The distance in the side-by-side installation direction between the end side wall of the hot water receiving chamber in the side-by-side installation direction and the hot water passage closest to the wall is 80 mm or more and 260 mm or less,
When the weir is provided, the distance in the side-by-side installation direction between the injection position and the weir is 655 mm or more and 1140 mm or less,
The hot water receiving chamber has a cylindrical shape with a length of 7200 to 8800 mm in a direction parallel to the long side of the mold and a length of 900 to 1100 mm in a direction parallel to the short side of the mold. ,
The tapping chamber has a cylindrical shape with a length of 10000 to 12000 mm in a direction parallel to the long side of the mold and a length of 900 to 1100 mm in a direction parallel to the short side of the mold,
The induction heating device includes an annular iron core arranged to surround the hot water passage, and a coil wound around the iron core,
The iron core provided in the two hot water passages on one side surrounds the hot water passages arranged outside in the side-by-side direction of the two hot water passages on one side, and the two hot water passages on the other side. The iron core provided in the second side surrounds the hot water passage arranged outside in the side-by-side direction of the two hot water passages on the other side,
The submerged nozzle is provided extending downward from the bottom of the tapping chamber,
tundish. A first distance is defined as a distance in the side-by-side installation direction between the end side wall portion of the hot water discharge chamber in the side-by-side installation direction and the submerged nozzle closest to the wall portion, and When the distance in the side-by-side installation direction between the wall portion on the end side and the hot tub closest to the wall portion is the second distance,
The first distance is 170 mm or more and 260 mm or less and the second distance is 80 mm or more and 260 mm or less, or the first distance is 120 mm or more and 300 mm or less and the second distance is 190 mm or more and 230 mm or less.
A tundish according to claim 1 .

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