JP6943159B2 - Double drum type continuous casting equipment, manufacturing method of thin-walled slabs - Google Patents

Description

The present invention, in the molten metal pool portion formed by a pair of cooling drums and a pair of side weirs, twin drum type continuous casting apparatus for producing thin cast strip by supplying molten metal, the manufacture how thin cast strip It is related.

As a method for producing a thin-walled metal slab, a cooling drum having a water-cooled structure is provided inside, and molten metal is supplied to a molten metal pool portion formed between a pair of rotating cooling drums, and the peripheral surface of the cooling drum is supplied. A solidified shell is formed and grown on the surface, and the solidified shells formed on the outer peripheral surfaces of the pair of cooling drums are joined at a drum kiss point and reduced to produce a thin-walled slab of a predetermined thickness. Equipment is provided.

Here, when starting casting, for example, as shown in Patent Document 1-5, a dummy sheet is inserted between the cooling drums, and a molten metal pool formed by a pair of cooling drums and a pair of side dams. A structure in which molten metal is supplied to a portion, a thin-walled slab is formed so as to be connected to a dummy sheet, and then a cooling drum is rotated to pull out the dummy sheet and the thin-walled slab connected to the dummy sheet from between the cooling drums. It is said that.

The thin-walled slabs produced downward from between the cooling drums are curved at the curved portion, and are conveyed in a substantially horizontal direction by a transport portion having a pinch roll that holds the thin-walled slabs in the vertical direction, and if necessary, an in-line mill. Rolled by and wound by a coiler.
At the start of casting, in order to convey the thin-walled slab connected to the dummy sheet to the coiler, the dummy sheet is sandwiched by pinch rolls, one end of which is inserted between the cooling drums, and the other end of which is the coiler. It is combined.

At the start of casting, first, with the rotation of the cooling drum stopped, molten metal is supplied to the molten metal pool where the dummy sheet is inserted, and one end of the dummy sheet is cast and wrapped to form a thin-walled slab and a dummy sheet. Is connected, and the rotation of the cooling drum is started with the dummy sheet and the thin-walled slab connected. In addition, the coiler is also started at the same time as the rotation of the cooling drum is started or at regular intervals.
In this way, the thin-walled slab is pulled by a dummy sheet, sandwiched by a pinch roll via a curved portion directly under the cooling drum, transported in the horizontal direction, and wound up by a coiler.

In the curved portion of the above-mentioned twin drum type continuous casting apparatus, when the dummy sheet or thin-walled slab moves along the support, when there is no support and the dummy sheet or thin-walled slab moves freely, or There is a form in which the support base is used only at the initial stage of casting, and the support base is moved after a predetermined time has passed so that the support base is no longer used.
For the shape from the curved part to the conveying part, when the lowest end of the curved part is connected to the conveying part (curved type), or after being lowered once to a position lower than the conveying part, it is lifted to become the curved part. There are cases such as when connecting (lifting type). In the lift type, when there is a speed difference between the cooling drum and the coiler winding speed, the slab length adjustment allowance can be increased.

At the start of casting, the casting conditions such as the amount of molten metal supplied to the molten metal pool and the temperature of the cooling drum are not stable, so the strength of the thin-walled slab formed so as to be connected to the dummy sheet. In some cases, casting could not be started due to problems such as the thin-walled slab breaking when the dummy sheet was pulled out. Therefore, conventionally, a means for reliably connecting the thin-walled slab and the dummy sheet has been proposed.

For example, Patent Document 1 discloses a dummy sheet in which a wire rod or a strip made of a refractory material is attached to the tip end portion of a dummy sheet inserted in a gap of a cooling drum. The wire or strip of the refractory material floats in the molten metal pool at the start of casting, the metal to be cast wraps the wire or strip, and in this state, the solidified shell is pressure-welded and integrated at the drum kiss point of the cooling drum. By doing so, the joint strength between the dummy sheet and the thin-walled slab is improved.

Further, in Patent Document 2, a metal plate along each peripheral surface of the cooling drum is attached to the tip of a dummy sheet inserted in the gap of the cooling drum, and a large number of holes are provided on the entire surface of the metal plate. Things are disclosed. By promoting solidification and adhesion of molten steel to the dummy sheet, the joint strength between the dummy sheet and the thin-walled slab is improved.

Further, in Patent Document 3, a double drum type continuous is provided with a pair of crimping rolls for sandwiching a dummy sheet and two crimping dummy sheets for sandwiching a thin-walled slab directly under the cooling drum directly under the pair of cooling drums. The casting equipment is disclosed. The fragile thin-walled slab discharged from the cooling drum is sandwiched between the crimping dummy sheets using a crimping roll, and the fragile thin-walled slab discharged from the cooling drum is welded to the crimping dummy sheet to cool the cooling drum. It reinforces the fragile part of the thin-walled slab discharged from.

Further, in Patent Document 4, in order to prevent the connecting portion between the thin-walled slab and the dummy sheet from breaking and breaking, the length is adjusted in the vicinity of the end portion on the side where the thin-walled slab is connected so that the thin-walled slab can be easily bent and deformed. A dummy sheet provided with a region is disclosed, and as a specific length adjustment region, a dummy sheet provided with a partial opening is disclosed. Since the purpose is to prevent the connecting portion from breaking, the length adjustment range is provided in the vicinity of the connecting portion between the thin-walled slab and the dummy sheet.

Further, when not only the connecting portion but also the thin-walled slab itself is fragile, a method in which the fragile thin-walled slab is placed on a sheet material and conveyed in order to wind up the thin-walled slab without breaking it. Is disclosed.
For example, in Patent Document 5, a dummy sheet and an auxiliary sheet are welded and joined, and one sheet material formed of the dummy sheet and the auxiliary sheet, or one formed only of a subsequent auxiliary sheet. A method is disclosed in which a thin-walled slab is placed on the sheet material, transported to a coiler, and the thin-walled slab is wound together with the sheet material.

Japanese Unexamined Patent Publication No. 63-224847 Japanese Unexamined Patent Publication No. 07-232243 Japanese Unexamined Patent Publication No. 2004-283870 Japanese Unexamined Patent Publication No. 05-138304 Japanese Unexamined Patent Publication No. 05-293605

By the way, at the start of casting of the above-mentioned twin drum type continuous casting apparatus, it is widespread that a predetermined time elapses in a state where the rotation of the cooling drum is stopped so that the dummy sheet is surely connected to the thin-walled slab. It is done. Therefore, the bottommost portion of the thin-walled slab, which is the connecting portion with the dummy sheet, is formed thicker than the thin-walled slab in the steady operation portion. Therefore, when the bottommost portion passes through the drum kiss point, the drum gap widens, and hot water leakage or splash (hereinafter referred to as splash or the like) may occur.

This splash or the like may fall and accumulate on a dummy sheet located directly under the cooling drum, and the large size reaches several mm. The splash that has fallen on the dummy sheet slides down and accumulates at the lowest part (lowest part) of the curved part.
In this way, the splash deposited on the upper surface of the dummy sheet is transported while being loaded on the dummy sheet, but may adhere to the upper pinch roll or the upper transport roll on the way. Then, the pinch roll or the transport roll has a shape in which a local convex portion is formed, and it is not possible to uniformly press down in the slab width direction, so that the thin-walled slab meanders and the operation becomes unstable. In some cases, it may cause the casting to be interrupted. Therefore, prevention of splash adhesion to pinch rolls and transport rolls is important for stabilizing operations and winding up the entire slab.

The present invention has been made in view of the above-mentioned situation, and it is possible to suppress the occurrence of meandering of thin-walled slabs due to the splash deposited on the dummy sheet, and it is possible to perform stable casting. drum type continuous casting apparatus, and an object thereof is to provide a manufacturing how thin cast strip.

In order to solve the above problems, the twin drum type continuous casting apparatus according to the present invention supplies molten metal to a molten metal pool portion formed by a pair of rotating cooling drums and a pair of side dams, and supplies the molten metal to the cooling drum. A double-drum type continuous casting device that manufactures thin-walled slabs by forming and growing a solidified shell on the peripheral surface, and transports the thin-walled slabs by a transport unit equipped with pinch rolls that sandwich the thin-walled slabs in the vertical direction. The double-drum type continuous casting dummy sheet used at the start is a dummy sheet main body sandwiched between the pinch rolls and inserted between the cooling drums, and an auxiliary sheet laminated on one surface side of the dummy sheet main body. And, in a state where one end of the dummy sheet main body sandwiched between the pinch rolls is inserted between the cooling drums, the dummy sheet is located upstream of the transport portion in the transport direction of the thin-walled slab. When the lowermost portion of the main body is set as the lowest portion, the area from the lowest portion to the pinch roll entry side on the downstream side in the transport direction of the thin-walled slab is the above-mentioned dummy sheet main body. An auxiliary sheet supply unit is provided on which the auxiliary sheet is laminated on the surface of the pinch roll facing the upper roll, and the auxiliary sheet has a length that covers at least the lowest portion of the dummy sheet main body. The pinch roll is characterized in that the laminated dummy sheet main body and the auxiliary sheet are sandwiched and conveyed in the vertical direction.

According to the twin-drum type continuous casting apparatus having this configuration, the dummy sheet main body is the most on the upstream side of the transport portion in a state where one end of the dummy sheet main body sandwiched between the pinch rolls is inserted between the cooling drums. When the lower portion is defined as the lowest portion, the region downstream from the lowest portion to the pinch roll entry side, with respect to the surface of the dummy sheet body facing the upper roll of the pinch roll. An auxiliary sheet supply unit for laminating the auxiliary sheets is provided, and the auxiliary sheet has a length that covers at least the lowest portion of the dummy sheet main body, so that the bottom portion of the wall thickness is the bottom portion. Even if the splash generated when passing through the drum kiss point is accumulated on the dummy sheet body, this splash will be covered with the auxiliary sheet, and the adhesion of the splash to the upper pinch roll and the upper transport roll will be suppressed. be able to. As a result, it is possible to suppress the occurrence of meandering of the thin-walled slab due to the splash, and the casting can be stably performed.

Here, in the twin drum type continuous casting apparatus of the present invention, the width of the auxiliary sheet is preferably 75% or more of the width of the dummy sheet main body.
Splashes that accumulate on the dummy sheet tend to accumulate in the center of the width of the dummy sheet body. Therefore, by setting the width of the auxiliary sheet to 75% or more of the width of the dummy sheet body, the dummy sheet body can be formed. The accumulated splash can be accurately covered with the auxiliary sheet, and it is possible to further suppress the splash from adhering to the upper pinch roll and the upper transport roll.

Further, in the method for producing a thin-walled slab according to the present invention, molten metal is supplied to a molten metal pool portion formed by a pair of rotating cooling drums and a pair of side dams, and a solidified shell is formed on the peripheral surface of the cooling drum. A method for producing a thin-walled slab that is formed and grown to produce a thin-walled slab, and the thin-walled slab is conveyed by a transport unit equipped with a pinch roll that sandwiches the thin-walled slab in the vertical direction. The drum type continuous casting dummy sheet includes a dummy sheet main body sandwiched between the pinch rolls and inserted between the cooling drums, and an auxiliary sheet laminated on one surface side of the dummy sheet main body. With one end of the dummy sheet main body sandwiched between the pinch rolls inserted between the cooling drums, the dummy sheet main body is located at the lowermost position on the upstream side in the conveying direction of the thin-walled slab from the conveying portion. When the portion to be formed is the lowest portion, in the region from the lowest portion to the downstream side in the transport direction of the thin-walled slab to the pinch roll entry side, the upper roll of the pinch roll in the dummy sheet main body Auxiliary sheets covering at least the lowest portion of the dummy sheet main body are laminated and arranged on the facing surfaces, and the laminated dummy sheet main body and the auxiliary sheet are sandwiched in the vertical direction by the pinch roll. It is characterized by being transported.

According to the method for manufacturing a thin-walled slab having this configuration, the dummy sheet main body is the most on the upstream side of the transport portion in a state where one end of the dummy sheet main body sandwiched between the pinch rolls is inserted between the cooling drums. When the lower portion is the lowest portion, in the region downstream from the lowest portion to the pinch roll entry side, the surface of the dummy sheet body facing the upper roll of the pinch roll Since the auxiliary sheet covering at least the lowest portion of the dummy sheet main body is laminated, the splash generated when the bottommost portion of the wall thickness passes the drum kiss point is generated on the dummy sheet main body. Even if it is deposited, this splash can be covered with an auxiliary sheet, and it is possible to prevent the splash from adhering to the upper pinch roll and the upper transport roll. As a result, it is possible to suppress the occurrence of meandering of the thin-walled slab due to the splash, and the casting can be stably performed.

Here, in the method for producing a thin-walled slab in the present invention, the width of the auxiliary sheet is preferably 75% or more of the width of the dummy sheet main body.
In this case, since the width of the auxiliary sheet is 75% or more of the width of the dummy sheet main body, the splash accumulated on the dummy sheet main body can be accurately covered with the auxiliary sheet.

As described above, according to the present invention, a twin-drum type continuous casting apparatus capable of suppressing the occurrence of meandering of thin-walled slabs due to splash deposited on a dummy sheet and stably casting. it is possible to provide a manufacturing how thin cast strip.

It is explanatory drawing which shows an example of the twin drum type continuous casting apparatus in 1st Embodiment of this invention. It is an enlarged explanatory view of the casting part of the twin drum type continuous casting apparatus shown in FIG. It is explanatory drawing which shows the state at the time of the start of casting in the twin drum type continuous casting apparatus shown in FIG. It is explanatory drawing of the dummy sheet for twin drum type continuous casting in 1st Embodiment of this invention. (A) is a top view, and (b) is a cross-sectional view taken along the line XX. It is explanatory drawing which shows the shape of the bottommost part. It is explanatory drawing which shows the state at the time of the start of casting in the twin drum type continuous casting apparatus in another embodiment of this invention. It is explanatory drawing which shows the state at the time of the start of casting in the twin drum type continuous casting apparatus in another embodiment of this invention. It is explanatory drawing which shows the state at the time of the start of casting in the twin drum type continuous casting apparatus in another embodiment of this invention. It is explanatory drawing which shows the state at the time of the start of casting in the twin drum type continuous casting apparatus in another embodiment of this invention. It is explanatory drawing which shows the state at the time of the start of casting in the twin drum type continuous casting apparatus in another embodiment of this invention.

Hereinafter, a twin-drum type continuous casting apparatus, a method for manufacturing a thin-walled slab, and a dummy sheet for double-drum type continuous casting, which are embodiments of the present invention, will be described with reference to the attached drawings. The present invention is not limited to the following embodiments.
Here, the thin-walled slab 1 produced in the present embodiment is made of steel having various compositions, and the width thereof is within the range of 500 mm or more and 2000 mm or less, and the thickness is within the range of 1 mm or more and 5 mm or less.

In the twin drum type continuous casting apparatus 10 of the present embodiment, as shown in FIG. 1, a pair of cooling drums 11 (11a, 11b) and a thin-walled slab 1 produced on the lower side of the cooling drum 11 progress. It includes a curved portion 18 that curves in a substantially horizontal direction, and a transport portion 20 that conveys the thin-walled slab 1 in a substantially horizontal direction.
In the present embodiment, the curved portion 18 has a "curved shape" in which the thin-walled slab 1 produced on the lower side of the cooling drum 11 is curved as it is and connected to the transport portion 20.

The transport unit 20 is a coiler that winds up a pinch roll 21 (21a, 21b), a transport roll 22 (22a, 22b), a looper 23, and a thin-walled slab 1 that sandwich and transport the thin-walled slab 1 in the vertical direction. 24 and.
Here, the pinch roll 21 is a drive roll that is rotationally driven, and the transport roll 22 is a driven roll that rotates with the movement of the thin-walled slab 1 and the double-drum type continuous casting dummy sheet 30. ..

Then, in the twin drum type continuous casting apparatus 10 of the present embodiment, as shown in FIG. 2, side weirs (not shown) are arranged at the widthwise end portions of the pair of cooling drums 11 (11a, 11b). The molten steel pool portion 13 is formed by a pair of cooling drums 11 (11a, 11b) and a side weir.
Further, above the pair of cooling drums 11 (11a, 11b), a tundish 14 holding the molten steel 5 supplied to the molten steel pool portion 13 and the molten steel 5 being supplied from the tundish 14 to the molten steel pool portion 13. The immersion nozzle 15 and the immersion nozzle 15 to be used are arranged.

In this twin-drum type continuous casting apparatus 10, the molten steel 5 comes into contact with the rotating cooling drums 11 (11a, 11b) and is cooled, so that the solidified shell is formed on the peripheral surface of the cooling drums 11 (11a, 11b). 7 and 7 grow, and the solidified shells 7 and 7 formed on the pair of cooling drums 11 (11a and 11b) are pressure-bonded to each other at the drum kiss point to cast a thin-walled slab 1 having a predetermined thickness.

Here, in the twin-drum type continuous casting apparatus 10 of the present embodiment, at the start of casting, as shown in FIG. 3, a double-drum type continuous casting dummy is provided between the pair of cooling drums 11 (11a, 11b). The sheet 30 is arranged.
As shown in FIG. 3, the dual drum type continuous casting dummy sheet 30 of the present embodiment includes a dummy sheet main body 31 inserted into the drum kiss point from below the pair of cooling drums 11 (11a, 11b) and a dummy sheet. It is provided with an auxiliary sheet 32 that is laminated and arranged on the upper surface side of the main body 31.

In the twin drum type continuous casting apparatus 10 of the present embodiment, as shown in FIG. 3, a support base 26 that supports the dummy sheet main body 31 and bends it in the horizontal direction is arranged below the cooling drum 11. ing. The support base 26 is configured to retract so as not to come into contact with the thin-walled slab 1 after the start of casting.

Then, in the twin-drum type continuous casting apparatus 10 of the present embodiment, one end of the dummy sheet main body 31 sandwiched between the pinch rolls 21 is inserted into the drum kiss point of the cooling drum 11, and the upstream side of the transport unit 20. In the case where the portion where the dummy sheet main body 31 is located at the lowermost position is the lowest portion A, the above-mentioned auxiliary sheet 32 is laminated in the region downstream from the lowest portion A to the entrance side of the pinch roll 21. Auxiliary sheet supply unit 27 is provided.
In the present embodiment, since the pinch roll 21 is arranged on the most upstream side of the transport portion 20, the dummy sheet main body 31 is the lowest on the upstream side of the pinch roll 21 in the above-mentioned lowest position portion A. It will be the part where it is located. Specifically, as shown in FIG. 3, the lowest portion A in which the dummy sheet main body 31 is located at the lowermost position on the upstream side of the transport portion 20 is the entry side of the pinch roll 21, and the pinch roll 21 It is located upstream from the roll kiss point by the distance of the roll radius r. The auxiliary sheet supply unit 27 is arranged so as to supply the auxiliary sheet 32 to the roll kiss point of the pinch roll 21.

One end of the dummy sheet main body 31 is inserted into the drum kiss point, is supported by the support base 26 and is curved in the horizontal direction, and the other end becomes the coiler 24 via the pinch roll 21, the transport roll 22, and the looper 23. It is combined.
Then, the auxiliary sheet 32 is laminated from the auxiliary sheet supply unit 27 with respect to the upper surface of the dummy sheet main body 31.
Here, it is preferable that the downstream end portion of the auxiliary sheet 32 is joined to the dummy sheet main body 31 by welding or the like. Since a step is generated in this welded portion, it is preferable to arrange the welded portion on the downstream side of the roll kiss point of the pinch roll 21 at the start of casting.

Here, the length of the auxiliary sheet 32 is set to cover at least the lowest portion A of the dummy sheet main body 31, and in the present embodiment, as shown in FIG. 3, up to the entrance side of the pinch roll 21. The minimum length of the pinch roll 21 that can be covered and is equal to or larger than the radius r is required. However, in FIG. 3, in order to supply the auxiliary sheet 32 from the auxiliary sheet supply unit 27, the length 0.5πr that wraps around 1/4 circumference of the pinch roll 21a and the center of the pinch roll 21a and the auxiliary sheet supply unit 27. An auxiliary sheet 32 having a total length of the point distance (where> r) is described. The lower limit of the length of the auxiliary sheet 32 is preferably up to 100 mm on the upstream side of the lowest portion A, and more preferably up to 500 mm on the upstream side. This is because the splash accumulation range may reach 100 mm on the upstream side or 500 mm on the upstream side from the lowest portion A.
The upper limit of the length of the auxiliary sheet 32 is not particularly specified, and the length reaches the connecting portion between the thin-walled slab 1 and the dummy sheet main body 31 (the bottommost portion 3 of the thin-walled slab 1) or longer. It may be the length.

Further, as shown in FIG. 4, the width W2 of the auxiliary sheet 32 is preferably 75% or more of the width W1 of the dummy sheet main body 31. This is because the splash easily accumulates in the center of the upper surface of the dummy sheet main body 31, and if the auxiliary sheet 32 can cover 75% of the width including the center of the width of the dummy sheet main body 31, the splash adheres to the pinch roll 21 or the like. This is because it is possible to suppress. Since the splash may remain at the width end of the dummy sheet main body 31, it is more preferable that the width W2 of the auxiliary sheet 32 is the same as the width W1 of the dummy sheet main body 31. Further, the width W2 of the auxiliary sheet 32 may be set wider than the width W1 of the dummy sheet main body 31 in consideration of the deviation in the width direction at the time of stacking, but in order to perform stable transportation, the auxiliary sheet may be set. The upper limit of the width W2 of 32 is preferably +10 mm (+5 mm on one side) with respect to the width W1 of the dummy sheet main body 31.

Further, the thickness t1 of the dummy sheet main body 31 is preferably in the range of 0.3 mm or more and 1.0 mm or less, and the thickness t2 of the auxiliary sheet 32 is in the range of 0.1 mm or more and 1.0 mm or less. It is preferably inside. This is because if it is 0.3 mm or more and 0.1 mm or more, respectively, it is sufficient to exhibit the desired function, and if it exceeds 1.0 mm, the material cost is wasted and it becomes difficult to handle. .. The thickness t2 of the auxiliary sheet 32 is preferably thinner than the thickness t1 of the dummy sheet main body 31.

In the double-drum type continuous casting apparatus 10 according to the present embodiment having the above-described configuration, the double-drum type continuous casting dummy sheet 30 is inserted into the drum kiss point of the cooling drum 11 from the tundish 14 to the immersion nozzle 15. The molten steel 5 is injected toward the molten steel pool portion 13 via the above. When the molten metal surface of the molten steel 5 in the molten steel pool portion 13 reaches a predetermined position, the cooling drums 11 (11a, 11b) are rotated.

At this time, in order to reliably connect the bottommost portion 3 of the thin-walled slab 1 and the dummy sheet main body 31, a predetermined time elapses without rotating the cooling drum 11. As a result, as shown in FIG. 5, the bottommost portion 3 of the thin-walled slab 1 is formed thicker than the thin-walled slab 1 in the steady operation portion.
When the bottommost portion 3 passes through the drum kiss point, the drum gap widens, and hot water leakage or splash may occur.

When this splash falls on the upper surface side of the dummy sheet main body 31, it will be accumulated in the lowest portion A of the dummy sheet main body 31.
Here, in the present embodiment, the auxiliary sheet 32 has a length that covers at least the lowest portion A of the dummy sheet main body 31, and is laminated on the upper surface of the dummy sheet main body 31 to form the dummy sheet main body. It is possible to cover the splash deposited on the 31.

Then, the double-drum type continuous casting dummy sheet 30 in which the dummy sheet main body 31 and the auxiliary sheet 32 are laminated and arranged is sandwiched between the pinch rolls 21 and conveyed toward the coiler 24.
Then, the thin-walled slab 1 is pulled out following the double-drum type continuous casting dummy sheet 30, and the thin-walled slab 1 is wound up by the coiler 24. In this way, the thin-walled slab 1 is cast.

According to the twin-drum type continuous casting apparatus 10, the method for manufacturing a thin-walled slab, and the double-drum type continuous casting dummy sheet 30 according to the present embodiment having the above-described configuration, the dummy sheet sandwiched between the pinch rolls 21. When one end of the main body 31 is inserted into the drum kiss point of the cooling drum 11, and the portion where the dummy sheet main body 31 is located at the lowest position on the upstream side of the transport portion 20 is set as the lowest portion A, this lowest portion An auxiliary sheet supply unit 27 for laminating and arranging the above-mentioned auxiliary sheets 32 is provided in a region downstream from A to the entrance side of the pinch roll 21, and specifically, a dummy sheet is provided on the upstream side of the transport unit 20. The lowest position A where the main body 31 is located at the lowermost position is the entry side of the pinch roll 21, and the auxiliary sheet supply unit 27 is arranged so as to supply the auxiliary sheet 32 to the roll kiss point of the pinch roll 21. Therefore, even if the splash generated when the thickest bottom portion 3 passes through the drum kiss point is accumulated on the dummy sheet main body 31, this splash can be covered with the auxiliary sheet 32, and the upper pinch. It is possible to prevent the splash from adhering to the roll 21a and the upper transport roll 22a. As a result, it is possible to suppress the occurrence of meandering of the thin-walled slab 1 due to the splash, and the casting can be stably performed.

Further, as a preferred embodiment of the present embodiment, if the width W2 of the auxiliary sheet 32 is 75% or more of the width W1 of the dummy sheet main body 31, most of the splash accumulated on the dummy sheet main body 31 is generated by the auxiliary sheet 32. It is preferable because it can be covered, the occurrence of meandering of the thin-walled slab 1 due to the splash can be suppressed, and the casting can be stably performed.
In addition, if the upper limit of the width W2 of the auxiliary sheet 32 is +10 mm (+5 mm on one side) with respect to the width W1 of the dummy sheet main body 31, the double drum type continuous casting dummy sheet 30 is stabilized by the pinch roll 21. It is preferable because it can be transported.

Further, as a preferred embodiment of the present embodiment, the thickness t2 of the auxiliary sheet 32 is preferably in the range of 0.1 mm or more and 1.0 mm or less, and is thinner than the thickness t1 of the dummy sheet main body 31. This is preferable because the desired function can be sufficiently exhibited, the step at the position where the auxiliary sheets 32 are laminated and arranged becomes small, and the pinch roll 21 can stably convey the auxiliary sheet 32.

Although the twin drum type continuous casting apparatus, the method for producing thin-walled slabs, and the dummy sheet for twin drum type continuous casting, which are the embodiments of the present invention, have been specifically described above, the present invention is not limited thereto. , It can be changed as appropriate without departing from the technical idea of the invention.

For example, as shown in FIG. 6, the double-drum type continuous casting dummy sheet 30 and the thin-walled slab may be of a lift type that is loosened to a position lower than the lower pinch roll 21b. In this case, the lowest portion A of the dummy sheet main body 31 becomes the lowest point (bottom of the free loop) of the loosened portion, and the auxiliary sheet 32 is supplied with the auxiliary sheet 32 as the length of the auxiliary sheet 32. The length is set to l or more to reach the lowest position A of the dummy sheet main body 31 from the position (roll kiss point of the pinch roll 21).

Further, as shown in FIGS. 7 and 8, in the curved twin drum type continuous casting apparatus, the guide roll 28 may be arranged on the upstream side of the pinch roll 21. The guide roll 28 is a driven roll. In this case, the guide roll 28 is arranged on the most upstream side of the transport portion 20, and the lowest portion A is a portion where the dummy sheet main body 31 is located at the lowermost position on the upstream side of the guide roll 28. Will be. Specifically, the lowest portion A of the dummy sheet main body 31 is the entry side of the guide roll 28, and is located upstream from the roll kiss point of the guide roll 28 by the distance of the radius of the guide roll 28.
Here, the auxiliary sheet supply unit 27 may be arranged so as to supply the auxiliary sheet 32 to the roll kiss point of the pinch roll 21 as shown in FIG. 7, or the guide roll 27 may be arranged so as to supply the auxiliary sheet 32 to the roll kiss point of the pinch roll 21. The auxiliary sheet 32 may be arranged so as to supply the auxiliary sheet 32 to the roll kiss point of 28. However, the auxiliary sheet 32 needs to have a length l or more that covers at least the lowest portion A of the dummy sheet main body 31.

Further, as shown in FIGS. 9 and 10, in the lift-type twin-drum type continuous casting apparatus, the guide roll 28 may be arranged on the upstream side of the pinch roll 21. The guide roll 28 is a driven roll. In this case, since the guide roll 28 is arranged on the most upstream side of the transport portion 20, the lowest portion A is a portion on the upstream side of the guide roll 28 where the dummy sheet main body 31 is located at the lowest position. Become.
Here, the auxiliary sheet supply unit 27 may be arranged so as to supply the auxiliary sheet 32 to the roll kiss point of the pinch roll 21 as shown in FIG. 9, or the guide roll 27 may be arranged so as to supply the auxiliary sheet 32 to the roll kiss point of the pinch roll 21. The auxiliary sheet 32 may be arranged so as to supply the auxiliary sheet 32 to the roll kiss point of 28. However, the auxiliary sheet 32 needs to have a length l or more that covers at least the lowest portion A of the dummy sheet main body 31.

The results of experiments carried out in order to confirm the effects of the present invention will be described below.
C; 0.05% by mass, Si; 0.15% by mass, Mn; 0.65% by mass, P; 0.01% by mass, S; 0.007% by mass, Al; 0.03% by mass A thin-walled slab made of carbon steel was produced using the twin-drum type continuous casting apparatus shown in the above-described embodiment.

In Examples 1-7 and Comparative Examples 1 and 2 of the present invention, the twin drum type continuous casting apparatus (curved type, without guide roll) shown in FIG. 3 was used.
In Examples 11-14 and Comparative Examples 11 and 12 of the present invention, the twin-drum type continuous casting apparatus (lifting type, without guide roll) shown in FIG. 6 was used.
In Examples 21-28 and Comparative Example 21 of the present invention, the twin-drum type continuous casting apparatus (curved type / with guide roll) shown in FIGS. 7 and 8 was used.
In Examples 31-35 of the present invention and Comparative Example 31, the twin-drum type continuous casting apparatus (lifting type / with guide roll) shown in FIGS. 9 and 10 was used.

The common conditions for the method for producing thin-walled slabs are shown below.
Cooling drum diameter: 1200 mm
Casting width: 1300 mm
Casting thickness: 2.0 mm on average
Casting speed: 50 m / min on average
Casting atmosphere: Ar + N ₂
Casting amount: 10 tons Hot water level arc angle: 40 deg
Contact arc length between molten steel and cooling drum: 419 mm
Pinch roll diameter: 250 mm
Guide roll diameter: 120 mm

In addition, the following was used as a dummy sheet for double drum type continuous casting.
Dummy sheet body: Mild steel sheet material, width 1290 mm
Auxiliary sheet: Made of iron: Sizes are listed in Tables 1 and 2.

Casting was carried out under the above conditions, and the following items were evaluated. The evaluation results are shown in Tables 1 and 2.

(1) Number of splashes attached After the casting was completed, the upper rolls of various rolls (pinch rolls, transfer rolls, guide rolls) were observed, and the number of splashes having a length of 1 mm or more attached to the upper rolls was evaluated.

(2) Meandering condition of thin-walled slab The maximum meandering amount of thin-walled slab was measured from the image during casting. "X" for the maximum meandering amount exceeding 100 mm, "△" for the maximum meandering amount exceeding 50 mm and 100 mm or less, "○" for the maximum meandering amount exceeding 20 mm and 50 mm or less, maximum meandering Those having an amount of 20 mm or less were designated as "◎".

(3) Operation status When the operation is stopped due to the occurrence of meandering, it is described as "interruption", when the meandering does not stop, it is described as "unstable", and when the meandering is suppressed, it is described as "stable".

Examples 1 to 7 of the present invention and Comparative Examples 1 and 2 use a double-drum type continuous casting apparatus having a curved shape and no guide roll.
In Comparative Example 1 in which the auxiliary sheet was not used, the splash adhered to the upper rolls of the pinch roll and the transport roll in particular, and the meandering amount of the thin-walled slab exceeded 100 mm, so that the operation was interrupted.
In Comparative Example 2 in which the length of the auxiliary sheet is shorter than the length from the auxiliary sheet supply portion to the lowest portion of the dummy sheet main body, a large amount of splash adheres to the upper roll of the pinch roll, and the meandering amount of the thin-walled slab. May exceed 100 mm, the meandering did not tend to subside, and the operation was unstable.

On the other hand, in Examples 1 to 7 of the present invention in which the auxiliary sheet covering up to the lowest portion of the dummy sheet main body was used, meandering was suppressed and stable casting could be performed. In addition, the adhesion of splash to various rolls was also suppressed.
In Examples 1 to 4 of the present invention, the length is changed by using an auxiliary sheet having the same width (1290 mm) as the dummy sheet main body. It was confirmed that the longer the length of the auxiliary sheet, the less the splash adhered to the upper rolls of the pinch roll and the transport roll, and the meandering amount of the thin-walled slab was suppressed.

Further, Examples 5, 6 and 7 of the present invention are examples in which the width of the auxiliary sheet is changed. Comparing Example 5 of the present invention with Example 7 of the present invention, when the width of the auxiliary sheet is 75% or more of the dummy sheet main body, it is possible to efficiently prevent the adhesion of splash near the center of the width and suppress meandering. It was confirmed that there was. Further, in Example 6 of the present invention in which the width of the auxiliary sheet is wider than the width of the dummy sheet main body, the splash adheres to the upper rolls of the pinch roll and the transport roll is lessened, and the meandering amount of the thin-walled slab is suppressed. Was confirmed.

Examples 11 to 14 of the present invention and Comparative Examples 11 and 12 use a double-drum type continuous casting apparatus which is a lift type and does not have a guide roll.
In Comparative Example 11 in which the auxiliary sheet was not used, the splash adhered to the upper rolls of the pinch roll and the transport roll in particular, and the meandering amount of the thin-walled slab exceeded 100 mm, so that the operation was interrupted.
In Comparative Example 12, in which the length of the auxiliary sheet is shorter than the length from the auxiliary sheet supply portion to the lowest portion of the dummy sheet main body, a large amount of splash adheres to the upper roll of the pinch roll, and the meandering amount of the thin-walled slab. May exceed 100 mm, the meandering did not tend to subside, and the operation was unstable.

On the other hand, in Examples 11 to 14 of the present invention in which the auxiliary sheet covering up to the lowest portion of the dummy sheet main body was used, meandering was suppressed and stable casting could be performed. In addition, the adhesion of splash to various rolls was also suppressed.
In Examples 11 to 14 of the present invention, the length is changed by using an auxiliary sheet having the same width (1290 mm) as the dummy sheet main body. It was confirmed that the longer the length of the auxiliary sheet, the less the splash adhered to the upper rolls of the pinch roll and the transport roll, and the meandering amount of the thin-walled slab was suppressed.

Examples 21 to 28 of the present invention and Comparative Example 21 use a twin-drum type continuous casting apparatus having a curved shape and a guide roll. In Examples 21 to 26 and Comparative Example 21 of the present invention, the auxiliary sheet was supplied from the guide roll kiss point located at the uppermost stream. On the other hand, in Examples 27 and 28 of the present invention, the auxiliary sheet was supplied from the pinch roll kiss point.

In Comparative Example 21, in which the length of the auxiliary sheet is shorter than the length from the auxiliary sheet supply portion to the lowest portion of the dummy sheet main body, a large amount of splash adheres to the upper roll of the pinch roll, and the meandering amount of the thin-walled slab. May exceed 100 mm, the meandering did not tend to subside, and the operation was unstable.

On the other hand, in Examples 21 to 28 of the present invention using the auxiliary sheet covering up to the lowest portion of the dummy sheet main body, meandering was suppressed and stable casting could be performed. In addition, the adhesion of splash to various rolls was also suppressed.
Here, Examples 21 to 24 of the present invention are examples in which the length is changed by using an auxiliary sheet having the same width (1290 mm) as the dummy sheet main body. It was confirmed that the longer the length of the auxiliary sheet, the less the splash adhered to the upper rolls of the pinch roll and the transport roll, and the meandering amount of the thin-walled slab was suppressed.

Examples 25 and 26 of the present invention are examples of changing the width of the auxiliary seat. In Example 25 of the present invention, the width of the auxiliary sheet is narrower than the width of the dummy sheet body, but it is 75% or more of the width of the dummy sheet body, and it is possible to efficiently prevent the adhesion of splash near the center of the width, and meandering. It was confirmed that it is possible to suppress. Further, in Example 26 of the present invention in which the width of the auxiliary sheet is wider than the width of the dummy sheet main body, the splash adheres to the upper rolls of the pinch roll and the transport roll is lessened, and the meandering amount of the thin-walled slab is suppressed. Was confirmed.

Further, in Examples 27 and 28 of the present invention in which the auxiliary sheet was supplied from the pinch roll kiss point, a large amount of splash was observed on the guide roll located on the upstream side of the pinch roll, but the splash on the pinch roll which is the drive roll. Since the adhesion was suppressed, the meandering of the thin-walled slab could be suppressed, and the operation could be carried out stably. It was confirmed that even if the splash adheres to the guide roll, which is the driven roll, the meandering of the thin-walled slab can be suppressed by suppressing the adhesion of the splash on the pinch roll, which is the driving roll.

Examples 31 to 35 of the present invention and Comparative Example 31 use a double-drum type continuous casting apparatus which is a lift type and has a guide roll. In Examples 31 to 33 of the present invention, the auxiliary sheet was supplied from the guide roll kiss point located at the uppermost stream. On the other hand, in Examples 34 and 35 of the present invention and Comparative Example 31, the auxiliary sheet was supplied from the pinch roll kiss point.

In Comparative Example 31, in which the length of the auxiliary sheet is shorter than the length from the auxiliary sheet supply portion to the lowest portion of the dummy sheet main body, a large amount of splash adheres to the upper roll of the pinch roll, and the meandering amount of the thin-walled slab. May exceed 100 mm, the meandering did not tend to subside, and the operation was unstable.

On the other hand, in Examples 31 to 35 of the present invention using the auxiliary sheet covering up to the lowest portion of the dummy sheet main body, meandering was suppressed and stable casting could be performed. In addition, the adhesion of splash to various rolls was also suppressed.
Here, Examples 31 to 33 of the present invention are examples in which the length is changed by using an auxiliary sheet having the same width (1290 mm) as the dummy sheet main body. It was confirmed that the longer the length of the auxiliary sheet, the less the splash adhered to the upper rolls of the pinch roll and the transport roll, and the meandering amount of the thin-walled slab was suppressed.

Further, in Examples 34 and 35 of the present invention in which the auxiliary sheet was supplied from the pinch roll kiss point, a large amount of splash was observed on the guide roll located on the upstream side of the pinch roll, but the splash on the pinch roll which is the drive roll. Since the adhesion was suppressed, the meandering of the thin-walled slab could be suppressed, and the operation could be carried out stably. It was confirmed that even if the splash adheres to the guide roll, which is the driven roll, the meandering of the thin-walled slab can be suppressed by suppressing the adhesion of the splash on the pinch roll, which is the driving roll.

From the above, according to the example of the present invention, a twin-drum type continuous casting apparatus capable of suppressing the occurrence of meandering of thin-walled slabs due to the splash deposited on the dummy sheet and stably casting. , It was confirmed that a method for producing thin-walled slabs and a dummy sheet for double-drum type continuous casting can be provided.

1 Thin-walled slab 5 Molten steel 10 Twin-drum type continuous casting device 11 Cooling drum 21 Pinch roll 27 Auxiliary sheet supply unit 30 Double-drum type continuous casting dummy sheet 31 Dummy sheet body 32 Auxiliary sheet

Claims (4)

Molten metal is supplied to the molten metal pool portion formed by a pair of rotating cooling drums and a pair of side dams, and a solidified shell is formed and grown on the peripheral surface of the cooling drum to produce a thin-walled slab. A twin-drum type continuous casting device that transports slabs by a transport unit equipped with a pinch roll that sandwiches the slab in the vertical direction.
The double-drum type continuous casting dummy sheet used at the start of casting is sandwiched between the pinch rolls and inserted between the cooling drums, and an auxiliary sheet that is laminated and arranged on one surface side of the dummy sheet body. It has a seat and
With one end of the dummy sheet main body sandwiched between the pinch rolls inserted between the cooling drums, the dummy sheet main body is located at the lowermost position on the upstream side in the conveying direction of the thin-walled slab from the conveying portion. When the part is the lowest part,
The auxiliary sheet is laminated on the surface of the dummy sheet main body facing the upper roll of the pinch roll in the region from the lowest portion to the side where the pinch roll is inserted on the downstream side in the transport direction of the thin-walled slab. Auxiliary sheet supply unit to be placed is provided,
The auxiliary sheet has a length that covers at least the lowest portion of the dummy sheet body.
The pinch roll is a twin-drum type continuous casting apparatus characterized in that the laminated dummy sheet main body and the auxiliary sheet are sandwiched and conveyed in the vertical direction. The twin drum type continuous casting apparatus according to claim 1, wherein the width of the auxiliary sheet is 75% or more of the width of the dummy sheet main body. Molten metal is supplied to the molten metal pool portion formed by a pair of rotating cooling drums and a pair of side weirs, and a solidified shell is formed and grown on the peripheral surface of the cooling drum to produce a thin-walled slab. A method for manufacturing a thin-walled slab in which a slab is transported by a transport unit provided with a pinch roll that sandwiches the slab in the vertical direction.
The double-drum type continuous casting dummy sheet used at the start of casting is sandwiched between the pinch rolls and inserted between the cooling drums, and an auxiliary sheet that is laminated and arranged on one surface side of the dummy sheet body. It has a seat and
With one end of the dummy sheet main body sandwiched between the pinch rolls inserted between the cooling drums, the dummy sheet main body is located at the lowermost position on the upstream side in the conveying direction of the thin-walled slab from the conveying portion. When the part is the lowest part,
In the region from the lowest portion to the pinch roll entry side on the downstream side in the transport direction of the thin-walled slab , at least the dummy sheet is opposed to the surface of the dummy sheet main body facing the upper roll of the pinch roll. Auxiliary sheets covering up to the lowest part of the main body are laminated and arranged.
A method for producing a thin-walled slab, which comprises sandwiching and transporting the laminated dummy sheet main body and the auxiliary sheet in the vertical direction with the pinch roll. The method for producing a thin-walled slab according to claim 3, wherein the width of the auxiliary sheet is 75% or more of the width of the dummy sheet main body.

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