Thin-walled casting method

Abstract

To provide a twin drum type continuous casting device capable of suppressing the winding of a thin slab around cooling drums and stably executing casting.SOLUTION: In a twin drum type continuous casting device 10, a molten metal 3 is fed to a molten metal pool part 16 formed by a pair of rotating cooling drums 11, 11 and a pair of side weirs 15 to form and grow solidified shells 5, 5 on the circumferential faces of the cooling drums 11, and the solidified shells 5, 5 respectively formed on the circumferential faces of the cooling drums 11 are joined at a drum kiss point so as to be pressure-reduced to produce a thin slab 1. On the lower part of the drum kiss point at the end pars of the cooling drums 11, disk members 20 having circumferential faces directed to the side of the thin slab 1 and projected from the circumferential faces of the cooling drums 11 are disposed at positions in which angles sandwiched by a line connecting central points of the two cooling drums 11, 11 and lines connecting central points of the cooling drums 11 and central points of the disk members 20 reaches 45° or less viewed from a direction parallel to the rotary shaft of the cooling drums 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention provides a method for producing a thin-walled cast slab by supplying molten metal to a molten metal pool formed by a pair of rotating cooling drums and a pair of side weirs, forming and growing solidified shells on the circumferential surfaces of the cooling drums, and joining and rolling down the solidified shells formed on the circumferential surfaces of the cooling drums at drum kiss points. Ruthless This invention relates to a method for manufacturing a cast piece. [Background technology]

[0002] As a method for producing thin metal billets, for example, as disclosed in Patent Documents 1 and 2, a twin-drum continuous casting machine is provided, which is equipped with cooling drums having an internal water-cooling structure, and which supplies molten metal to a molten metal reservoir formed between a pair of rotating cooling drums, causing solidified shells to form and grow on the circumferential surfaces of the cooling drums, and joining the solidified shells formed on the circumferential surfaces of the pair of cooling drums at drum kiss points, which are then pressed down to produce thin billets of a predetermined thickness. Such production methods using twin-drum continuous casting machines are applied to various metals.

[0003] In the twin-drum casting machine described above, side weirs are pressed against both end faces of the cooling drum to form a molten metal pool. The portions of the side weirs that contact the end faces of the cooling drum are made of a heat-resistant material that is softer than the cooling drum in order to withstand high temperatures and maintain a seal with the end faces of the cooling drum through wear. When producing thin steel billets, boron nitride-based refractories are usually used.

[0004] If a large gap were to form between the end face of the cooling drum and the contact surface of the side weir, molten metal would enter the gap, solidify, and form flash, which could cause the thin-walled cast strip to wrap around the cooling drum instead of being peeled off, resulting in a casting interruption and a loss of quality.

[0005] Therefore, as a technology for ensuring sealing between the cooling drum and the side dam, for example, Patent Document 3 proposes a technology that includes an elastic member that biases the side dam and a restraining member that limits the movement of the side dam. Patent Document 4 proposes a technology for detecting one-sided wear of the refractory material of a side weir and suppressing the tilt of the side weir. Patent Document 5 proposes a technique for suppressing molten metal leakage at the end of a cooling drum by measuring the amount of axial movement of the cooling drum and correcting this. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 01-166863 [Patent Document 2] Japanese Patent Application Publication No. 05-228586 [Patent Document 3] Japanese Patent Application Publication No. 01-083337 [Patent Document 4] Japanese Patent Application Publication No. 05-269553 [Patent Document 5] Japanese Patent Application Laid-Open No. 2002-219558 Summary of the Invention [Problem to be solved by the invention]

[0007] However, even if the contact condition between the end face of the cooling drum and the abutment surface of the side dam is adjusted at room temperature, the side dam becomes hot during casting, and there is a risk that the side dam will deform due to thermal expansion, resulting in a gap between the end face of the cooling drum and the abutment surface of the side dam. Furthermore, since the side dam is in contact with the rotating cooling drum, the friction between the end surface of the cooling drum and the contact surface of the side dam can cause the side dam to shift position, which can also increase the gap. Therefore, it is practically very difficult to completely prevent the molten metal from getting between the cooling drum and the side weir.

[0008] If molten metal gets between the cooling drum and the side gate and forms a burr, the burr may get caught on the end face of the cooling drum edge, causing the end of the thin billet to wrap around the cooling drum. If the burr is very slight, the thin billet will be torn off from the cooling drum by its own weight immediately after being discharged from the cooling drum, and will not affect stable casting. However, if the burr becomes large, the thin billet may not be torn off from the cooling drum and may wrap around it, causing casting to be interrupted. In particular, when the thickness is 1.5 mm or less, this tendency becomes more pronounced because the weight of the thin-walled cast piece is light and the peripheral speed of the cooling drum is fast, which becomes a major factor in preventing stable casting.

[0009] The present invention has been made in view of the above-mentioned circumstances, and is capable of preventing thin-walled cast pieces from wrapping around a cooling drum, thereby enabling stable casting. Thin The object of the present invention is to provide a method for producing a cast piece. [Means for solving the problem]

[0013] The method for producing a thin slab according to the present invention comprises supplying molten metal to a molten metal pool formed by a pair of rotating cooling drums and a pair of side weirs, forming and growing solidified shells on the circumferential surfaces of the cooling drums, and joining and rolling down the solidified shells formed on the circumferential surfaces of the cooling drums at drum kiss points, wherein a disk member having a peripheral surface facing the thin slab and protruding from the circumferential surface of the cooling drum is disposed at an end of the cooling drum below the drum kiss point in a position such that, when viewed from a direction parallel to the rotation axis of the cooling drums, an angle formed by a line connecting the center points of the two cooling drums and a line connecting the center point of the cooling drum and the center point of the disk member is 45° or less; a ratio V1 / V0 of a peripheral speed V1 of the disk member to a peripheral speed V0 of the cooling drum is set within a range of 0.3 to 0.6 or 1.4 to 2.0, The thin-walled cast strip wound in the cooling drum is separated from the cooling drum by the disk member. Furthermore, the present invention provides a method for producing a thin slab, which comprises supplying molten metal to a molten metal pool formed by a pair of rotating cooling drums and a pair of side weirs, forming and growing solidified shells on the circumferential surfaces of the cooling drums, and joining and rolling down the solidified shells formed on the circumferential surfaces of the cooling drums at drum kiss points. The method comprises disposing a disk member, whose circumferential surface faces the thin slab and whose circumferential surface protrudes from the circumferential surface of the cooling drum, at an end of the cooling drum below the drum kiss point, in a position such that, when viewed from a direction parallel to the rotation axis of the cooling drums, an angle formed by a line connecting the center points of the two cooling drums and a line connecting the center point of the cooling drum and the disk member is 45° or less, and rotating the disk member in a direction opposite to the rotation direction of the cooling drums, so that the thin slab, which is caught in the cooling drum, is separated from the cooling drum by the disk member.

[0014] According to the method for manufacturing thin cast slabs having the above-described configuration, a disk member with its peripheral surface facing the thin cast slab and whose peripheral surface protrudes from the peripheral surface of the cooling drum is disposed at a position below the drum kiss point at the end of the cooling drum such that, when viewed from a direction parallel to the rotation axis of the cooling drum, the angle formed by a line connecting the center points of the two cooling drums and a line connecting the center point of the cooling drum and the center point of the disk member is 45° or less.The thin cast slab that is wound around the cooling drum at the end of the cooling drum is separated from the cooling drum by the disk member, thereby preventing the thin cast slab from wrapping around the cooling drum. Furthermore, since the peripheral surface of the disk member is configured to come into contact with the thin-walled cast strip, damage to the thin-walled cast strip can be suppressed. [Effects of the Invention]

[0017] As described above, according to the present invention, it is possible to prevent the thin-walled cast piece from wrapping around the cooling drum, and to carry out stable casting. Thin It is possible to provide a method for producing a cast piece. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is an explanatory diagram of a twin-drum continuous casting apparatus according to an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is an enlarged explanatory view of a molten steel pool portion of the twin-drum continuous casting machine shown in FIG. [Figure 3] FIG. 2 is an enlarged explanatory view of a disk member of the twin-drum continuous casting machine shown in FIG. [Figure 4] FIG. 2 is an explanatory diagram showing a state in which wrapping of a thin cast strip around a cooling drum is suppressed in a thin cast strip manufacturing method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a twin-drum continuous casting apparatus and a method for producing a thin-walled cast strip according to an embodiment of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiment. In this embodiment, molten steel is used as the molten metal, and a thin cast 1 made of steel is produced. In this embodiment, the width of the produced thin cast 1 is within a range of 200 mm to 1800 mm, and the thickness is within a range of 0.8 mm to 5 mm.

[0020] As shown in FIG. 1 , the twin-drum continuous casting apparatus 10 of this embodiment includes a pair of cooling drums 11, 11, pinch rolls 12, 12 and 13, 13 that support a thin-walled cast strip 1, side weirs 15 arranged at the widthwise ends of the pair of cooling drums 11, 11, a tundish 18 that holds molten steel 3 to be supplied to a molten steel pool 16 defined by the pair of cooling drums 11, 11 and the side weir 15, and an immersion nozzle 19 that supplies molten steel 3 from the tundish 18 to the molten steel pool 16.

[0021] In this twin-drum continuous casting apparatus 10, the molten steel 3 comes into contact with the rotating cooling drums 11, 11 and is cooled, causing solidified shells 5, 5 to grow on the peripheral surfaces of the cooling drums 11, 11, and the solidified shells 5, 5 formed on the pair of cooling drums 11, 11 are pressed together at the drum kiss points, thereby casting a thin-walled cast 1 of a predetermined thickness.

[0022] As shown in FIG. 2, a side weir 15 is provided on the end face of the cooling drum 11 to define a molten steel pool portion 16 . As shown in FIG. 2, the molten steel surface in the molten steel pool 16 is rectangular, surrounded on all four sides by the peripheral surfaces of the pair of cooling drums 11 and a pair of side weirs 15, and an immersion nozzle 19 is disposed in the center of this rectangular molten steel surface.

[0023] As described above, the side weir 15 slides against the end face of the cooling drum 11 and has a sealing effect of preventing the molten steel 3 from leaking from the end of the cooling drum 11 . It is important that the side weir 15 stably holds the molten steel 3 and does not adversely affect the formation of the solidified shell 5 on the circumferential surface of the cooling drum 11. For this reason, the side weir 15 is made of a heat-resistant material that is poorly reactive with the molten steel 3, such as graphite, boron nitride, aluminum nitride, silicon nitride, alumina, silica, or a composite material of these. In this embodiment, the side weir 15 is made of boron nitride.

[0024] In the twin-drum continuous casting apparatus 10 of this embodiment, as shown in Figures 1 and 2, below the drum kiss point at the end of the cooling drum 11, a disk member 20 is disposed with its peripheral surface facing the thin-walled cast slab 1 and its peripheral surface protruding from the peripheral surface of the cooling drum 11 in a position such that, when viewed from a direction parallel to the rotation axis of the cooling drum 11, the angle (hereinafter referred to as α) formed by the line connecting the center points of the two cooling drums 11, 11 and the line connecting the center point of the cooling drum 11 and the center point of the disk member 20 is 45° or less. If the angle α exceeds 45°, the shape of the loop below the cooling drum 11 changes significantly, causing a change in the loop detection position and causing a significant disturbance to the conveying speed control after the pinch rolls 12, 12, which is undesirable. Note that the angle α does not include 0°. The lower limit of the angle α may be determined so as not to interfere with the side weir 15. The preferred range of the angle α is 30° or less.

[0025] In this embodiment, the disk member 20 is configured to be rotatable about an axis parallel to the rotation axis of the cooling drum 11 . In this embodiment, a rotation drive device (not shown) is provided on the disk member 20, and the disk member 20 can be driven to rotate. Here, as shown in FIG. 3, it is preferable that the maximum protrusion amount P of the peripheral surface of the disk member 20 from the peripheral surface of the cooling drum 11 is within the range of 1 mm to 5 mm.

[0026] Next, a method for producing the thin-walled cast strip 1 using the above-described twin-drum continuous casting apparatus 10 will be described.

[0027] As shown in Figure 1, molten steel 3 is supplied from a tundish 18 via an immersion nozzle 19 to a molten steel pool 16 formed by a pair of cooling drums 11, 11 and a side weir 15, and the pair of cooling drums 11, 11 are rotated in a rotation direction R, i.e., so that the area where the pair of cooling drums 11, 11 are adjacent to each other faces the withdrawal direction of the thin-walled cast 1 (downward in Figure 1).

[0028] As a result, the molten steel 3 comes into contact with the rotating cooling drums 11 and is cooled, causing solidified shells 5 and 5 to grow on the peripheral surfaces of the cooling drums 11 and 11, and the solidified shells 5 and 5 formed on the pair of cooling drums 11 and 11 are pressed together at the drum kiss points, thereby casting a thin-walled cast 1 of a predetermined thickness.

[0029] In this embodiment, as shown in FIG. 3, the disk member 20 is rotated in the same direction as the rotation direction R of the cooling drum 11 by a rotation drive device (not shown). Furthermore, the ratio V1 / V0 of the peripheral speed V1 of the disk member 20 to the peripheral speed V0 of the cooling drum 11 is set within the range of 0.3 to 2.0.

[0030] In the twin-drum continuous casting apparatus 10 of this embodiment, a thin-walled cast strip 1 is normally produced vertically downward from the drum kiss point of the cooling drums 11, 11 as shown in FIG. 4(a). Here, molten steel 3 may get into the gap between the end face of the cooling drum 11 and the side weir 15, causing burrs to form, and these burrs may get caught in the cooling drum 11, causing the widthwise end of the thin-walled cast slab 1 to wrap around the cooling drum 11.

[0031] In this embodiment, a disk member 20, whose peripheral surface faces the thin billet 1 and whose peripheral surface protrudes from the peripheral surface of the cooling drum 11, is disposed below the drum kiss point at the end of the cooling drum 11 at a position where the angle α is 45° or less. As a result, as shown in Fig. 4(b), the wrapped thin billet 1 comes into contact with the peripheral surface of the disk member 20 and is separated from the cooling drum 11. As a result, the thin billet 1 is produced vertically downward as shown in Fig. 4(a).

[0032] According to the twin-drum continuous casting apparatus 10 and the manufacturing method of the thin-walled cast 1 of this embodiment configured as described above, as described above, the disk member 20, whose peripheral surface faces the thin-walled cast 1 and whose peripheral surface protrudes from the peripheral surface of the cooling drum, is arranged at a position where the above-mentioned angle α is 45° or less, below the drum kiss point at the end of the cooling drum 11.Therefore, when the thin-walled cast 1 wraps around the cooling drum 11, the peripheral surface of the disk member 20 comes into contact with the thin-walled cast 1, separating the thin-walled cast 1 from the cooling drum 11 and preventing the thin-walled cast 1 from wrapping around the cooling drum 11. Furthermore, since the peripheral surface of the disk member 20 is configured to come into contact with the thin-walled cast 1, damage to the widthwise ends of the thin-walled cast 1 can be prevented, and breakage of the thin-walled cast 1 can be prevented. Therefore, it becomes possible to stably carry out continuous casting of the thin-walled cast strip 1.

[0033] In this embodiment, when the disk member 20 is configured to be rotatable around an axis parallel to the rotation axis of the cooling drum 11, damage to the thin-walled cast 1 can be further prevented when the thin-walled cast 1 comes into contact with the peripheral surface of the disk member 20. Furthermore, in this embodiment, if the disk member 20 is configured to rotate in the same direction as the rotation direction of the cooling drum 11, damage to the thin-walled cast 1 can be further suppressed when the thin-walled cast 1 comes into contact with the peripheral surface of the disk member 20.

[0034] Furthermore, in this embodiment, when the ratio V1 / V0 of the peripheral speed V1 of the disk member 20 to the peripheral speed V0 of the cooling drum 11 is set within the range of 0.3 or more and 2.0 or less, damage to the thin-walled cast piece when it comes into contact with the peripheral surface of the disk member can be further suppressed. It is more preferable that the ratio V1 / V0 of the peripheral speed V1 of the disk member 20 to the peripheral speed V0 of the cooling drum 11 is within the range of 0.6 to 1.7.

[0035] The twin-drum continuous casting apparatus 10 and the method for manufacturing the thin-walled cast strip 1, which are embodiments of the present invention, have been specifically described above. However, the present invention is not limited to this and can be modified as appropriate within the scope of the technical concept of the invention. In this embodiment, the twin-drum continuous casting apparatus shown in FIG. 1 has been described as an example, but the present invention is not limited to this. In addition, in this embodiment, the disk member is described as being rotated by a rotary drive device, but the disk member may be fixed, or may be passively rotated by the frictional force generated when the disk member comes into contact with the thin-walled cast piece. [Example]

[0036] The following describes the results of experiments conducted to confirm the effects of the present invention. Using the twin-drum continuous casting apparatus shown in Figures 1 to 4, thin-walled cast strips were produced under the following casting conditions. The disk members were rotated under the conditions shown in Table 1. The casting results are shown in Table 1. Steel type: Low carbon steel (carbon concentration: 0.04% by mass) Drum size: width 400mm, diameter 600mm Drum peripheral speed: 130 mpm Drum reaction force: 2 tonf Cast size: Target thickness 1.0 mm x width 400 mm x length 170 m Molten steel amount: 500kg Disc size: 200mm diameter x 20mm thickness Disk protrusion from the cooling drum surface: 3 mm Angle α: 30°

[0037] [Table 1]

[0038] In the comparative example in which no disk member was provided, the thin-walled cast strips wrapped around the cooling drum in 3 out of 10 casts, and casting was discontinued. In contrast, in Inventive Example 1-11 in which the disk member was provided, it was possible to suppress the thin-walled cast strip from wrapping around the cooling drum. In particular, in Example 1-7 of the present invention, in which the rotation direction of the disk member was the same as that of the cooling drum and the ratio V1 / V0 of the peripheral speed V1 of the disk member to the peripheral speed V0 of the cooling drum was within the range of 0.3 to 2.0, the occurrence of end cracks in the slab was reduced to one cast or less. In Example 1-5 of the present invention, in which V1 / V0 was within the range of 0.6 to 1.7, no cracks occurred at the ends of the thin-walled slabs, and the entire amount was cast in every cast.

[0039] From the above experimental results, it has been confirmed that the present invention can provide a twin-drum continuous casting apparatus and a method for manufacturing thin-walled slabs that can prevent the thin-walled slabs from wrapping around the cooling drum and enable stable casting. [Explanation of symbols]

[0040] 1 Thin-walled cast billets 3 Molten steel (molten metal) 5 Solidified shell 10. Twin drum continuous casting equipment 11 Cooling drum 15 Side Weir 16 Molten steel pool section (molten metal pool section) 20 Disk member

Claims

1. A method for producing a thin cast slab, comprising: supplying molten metal to a molten metal pool formed by a pair of rotating cooling drums and a pair of side weirs; forming and growing solidified shells on the circumferential surfaces of the cooling drums; and joining and reducing the solidified shells formed on the circumferential surfaces of the cooling drums at drum kiss points, the method comprising: a disk member having a peripheral surface facing the thin-walled cast strip and protruding from the peripheral surface of the cooling drum is disposed at a position below the drum kiss point at the end of the cooling drum such that, when viewed in a direction parallel to the rotation axis of the cooling drum, an angle formed by a line connecting the center points of the two cooling drums and a line connecting the center point of the cooling drum and the center point of the disk member is 45° or less; a ratio V1 / V0 of a peripheral speed V1 of the disk member to a peripheral speed V0 of the cooling drum is set within a range of 0.3 to 0.6 or 1.4 to 2.0, A method for producing a thin-walled cast strip, comprising: separating the thin-walled cast strip wound in the cooling drum from the cooling drum by the disk member.

2. A method for producing a thin cast slab, comprising: supplying molten metal to a molten metal pool formed by a pair of rotating cooling drums and a pair of side weirs; forming and growing solidified shells on the circumferential surfaces of the cooling drums; and joining and reducing the solidified shells formed on the circumferential surfaces of the cooling drums at drum kiss points, the method comprising: a disk member having a peripheral surface facing the thin-walled cast strip and protruding from the peripheral surface of the cooling drum is disposed at a position below the drum kiss point at the end of the cooling drum such that, when viewed in a direction parallel to the rotation axis of the cooling drum, an angle formed by a line connecting the center points of the two cooling drums and a line connecting the center point of the cooling drum and the center point of the disk member is 45° or less; rotating the disk member in a direction opposite to the rotation direction of the cooling drum; A method for producing a thin-walled cast strip, comprising: separating the thin-walled cast strip wound in the cooling drum from the cooling drum by the disk member.

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