JP2019217518A - Cooling roll, twin roll type continuous casting device, and method for producing thin slab - Google Patents

Abstract

To provide cooling rolls capable of suppressing the generation of a hot band or the like caused by the entrainment of a largely grown bullion and a semi-solidified layer and capable of stably performing casting, a twin roll type continuous device provided with the cooling rolls, and a method for producing a thin slab.SOLUTION: Each cooling roll 20 is used for a twin roll type continuous casting device where a molten metal is fed to a molten metal pool part formed of the pair of rotating cooling rolls 20 and a pair of side weirs, and a solidified shell is formed and grown to a circumferential face of each cooling roll 20 to produce a thin slab. A recessed part 21 is provided at a boundary part between the circumferential face and a side face at an edge part in a width direction of each cooling roll 20.SELECTED DRAWING: Figure 5

Description

  The present invention supplies a molten metal to a molten metal pool formed by a pair of cooling rolls and a pair of side weirs, and forms and grows a solidified shell on the peripheral surface of the cooling roll to produce a thin cast slab. The present invention relates to a cooling roll used in a twin-roll continuous casting apparatus, a twin-roll continuous casting apparatus using the cooling roll, and a method for producing a thin cast slab.

  As a method of manufacturing a thin metal slab, a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs is provided with a pair of cooling rolls having a water cooling structure inside and rotating in opposite directions to each other. A solidified shell is formed and grown on the peripheral surface of the cooling roll, and the solidified shells formed on the outer peripheral surfaces of the pair of cooling rolls are pressed against each other at a roll kiss point to obtain a thin wall having a predetermined thickness. A twin-roll continuous casting apparatus for producing slabs is provided. Such a twin-roll continuous casting apparatus is applied to various metals.

  In the twin roll type continuous casting apparatus described above, the molten metal is continuously supplied from the molten metal container disposed above the cooling roll to the molten metal pool section via the immersion nozzle. The molten metal is discharged from the immersion nozzle arranged at the center of the molten metal pool toward the peripheral surface of the cooling roll, and flows toward the pair of side dams along the peripheral surface of the cooling roll. The molten metal solidifies and grows on the peripheral surface of the rotating cooling roll to form a solidified shell, and the solidified shell on the peripheral surface of each cooling roll is pressed at a kiss point.

The side weir serving as the side wall of the molten metal pool slides on the side surface of the rotating cooling roll to seal and hold the molten metal during casting of a thin cast piece. Here, since the cooling roll needs to take out a large amount of heat in a very short time in contact with the molten metal, the roll has an internal water cooling structure. This cooling roll is composed of a roll main body and an outer peripheral sleeve mounted on the outer peripheral portion, and a copper alloy having a high thermal conductivity is used as a material of the outer peripheral sleeve.
Here, the side weir is preheated before casting and is also heated from the outside during casting. However, since the side weir is always slid with the cooling roll, heat is removed from the cooling roll and cooled. When this cooling is excessive, the molten metal solidifies on the side weir surface by contacting the side weir that has become low in temperature, and the resulting solidified layer adheres and grows on the side weir surface. This is called bullion.

The ingot thus formed on the side weir surface may grow into a thick wall, and may be drawn into the pair of cooling rolls together with the thin cast piece cast on the peripheral surface of the cooling roll. .
When the base metal is drawn between the pair of cooling rolls together with the thin slab, the base metal is pressed between the cooling rolls together with the thin slab, so that the thickness locally increases. In addition, when the metal is bitten by the pair of cooling rolls, the distance between the pair of cooling rolls temporarily increases, and the thickness of the thin cast slab becomes thicker. This causes the occurrence of a so-called hot band, which results in a high temperature, and a resulting thickness fluctuation of the thin cast slab, a quality defect such as a surface flaw, a breakage of the plate, and a trouble in operation such as a molten metal leak.

  Further, in the twin-roll continuous casting apparatus described above, when the solidified shell is broken down by a pair of cooling rolls, the tip of the solidified shell breaks and becomes a floating crystal. Floating crystals stay in the vicinity of the side weir where stagnation is likely to occur, and the fluidity is eventually impaired to form a slurry-like semi-solid layer. When this semi-solidified layer is rolled into a thin cast slab, a hot band or the like is generated similarly to the base metal, and it becomes impossible to carry out casting stably.

Therefore, in this twin-roll type continuous casting apparatus, in order to uniformly promote solidification on the peripheral surface of the cooling roll to produce a sound thin plate, the generation and growth of the base metal and semi-solidified layer on the side weir surface are required. Prevention is one of the most important issues in the process.
Therefore, for example, Patent Literatures 1 and 2 propose techniques for suppressing the generation of metal on the side weir surface.

In Patent Document 1, by vibrating a side weir slidably in contact with an end surface of a cooling roll, solidified shell (metal) adhered to an inner surface of the side weir is dropped off at an early stage, and entrainment into a thin cast slab is suppressed. There has been proposed a twin-roll continuous casting apparatus capable of stably producing a homogeneous thin cast piece without breaking the thin cast piece.
Patent Document 2 discloses a vibrating device that vibrates a side weir in a sliding contact surface with an end surface of a cooling roll, vibrates the side weir during an unsteady state of casting, and vibrates the side weir during a steady state. Methods for stopping vibration have been proposed.

JP-A-60-184450 JP 05-237603 A

By the way, in both Patent Documents 1 and 2, the vibration direction of the side weir is within the sliding surface between the side weir and the end face of the cooling roll, and since the end face of the cooling roll is always in contact with the side weir, the vibration from the cooling roll is removed. Heat was inevitable, the temperature of the side weir decreased, and the generation and growth of metal on the side weir surface could not be sufficiently suppressed.
Further, in Patent Document 1, the side weir is vibrated so that the solidified shell (metal) adhered to the inner surface of the side weir is dropped off at an early stage. In addition, the metal or semi-solidified layer cannot be dropped off at an early stage, and the metal or semi-solidified layer may grow on the side weir surface.

  The present invention has been made in view of the above-described circumstances, and can suppress generation of a hot band or the like due to entrainment of a large grown metal and a semi-solid layer, and can perform stable casting. It is an object of the present invention to provide a cooling roll, a twin-roll continuous casting apparatus equipped with the cooling roll, and a method for producing a thin cast slab.

  In order to solve the above problem, the cooling roll according to the present invention supplies molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side dams, and supplies a molten metal to a peripheral surface of the cooling roll. A cooling roll used in a twin-roll continuous casting apparatus for forming and growing a solidified shell to produce a thin cast slab, wherein a recess is provided at a boundary between a peripheral surface and a side surface of a width direction end of the cooling roll. It is characterized by having.

  According to the cooling roll having this configuration, during casting, the molten metal is inserted into the concave portion provided at the boundary between the peripheral surface and the side surface at the widthwise end of the cooling roll and solidifies, and the flash-shaped solidified portion is formed. It is formed. When the burr-like solidified portion slides on the side weir along with the rotation of the cooling roll, the burr-like solidified portion is integrated with the base metal or semi-solidified layer on the surface of the side weir and rolled into the thin cast slab. In this way, by causing the metal or semi-solidified layer on the side weir surface to be rolled into a thin cast slab before growing large, the occurrence of hot bands can be suppressed and casting can be performed stably. It becomes.

Here, in the cooling roll of the present invention, the concave portion has a length in the roll width direction of 0.1 mm or more and 0.5 mm or less, and a length in the roll radial direction of 0.3 mm or more and 3 mm or less. It is preferable that the circumferential length be in the range of 1 mm or more and 30 mm or less.
In this case, since the size of the concave portion is specified as described above, the molten metal can be accurately inserted into the concave portion, and the bur or semi-solid layer on the side weir surface can be formed by the burr-like solidified portion. It can be rolled into thin cast slabs before growing large. Further, it is possible to suppress the quality of the end portion shape of the thin cast slab from being greatly reduced.

Further, in the cooling roll of the present invention, it is preferable that a plurality of the concave portions are periodically arranged in the circumferential direction at the boundary portion.
In this case, since a plurality of concave portions provided at the boundary between the peripheral surface and the side surface at the width direction end of the cooling roll are periodically arranged in the boundary portion in the circumferential direction, the metal on the surface of the side weir is provided. And the semi-solidified layer can be accurately caught in the slab before growing large.

Further, in the cooling roll of the present invention, it is preferable that the concave portions periodically arranged are arranged at intervals of 30 mm or more and 250 mm or less in a circumferential direction.
In this case, the metal or semi-solid layer on the surface of the side weir can be accurately involved in the slab before growing large.

In the cooling roll of the present invention, the recess formed at one end in the width direction of the cooling roll and the recess formed at the other end in the width direction of the cooling roll are arranged at different positions in the circumferential direction. It is preferred that
In this case, at the same location in the longitudinal direction of the thin cast slab, it is possible to suppress the ingot of the base metal or the semi-solidified layer at both ends of the width of the thin cast slab. The influence can be suppressed and casting can be performed stably.

The twin-roll continuous casting apparatus of the present invention supplies molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side dams, and forms a solidified shell on the peripheral surface of the cooling roll. A twin-roll continuous casting apparatus for producing a thin cast slab by growing the slab, characterized by including the cooling roll described above.
According to the twin-roll type continuous casting apparatus of this configuration, since the above-described cooling roll is provided, the metal or semi-solidified layer on the side weir surface is rolled into a thin cast piece before growing large, so that hot rolling is performed. Generation of a band can be suppressed, and stable casting can be performed.

Here, in the twin-roll continuous casting apparatus of the present invention, one of the cooling rolls and the other are formed such that the recess formed in one of the cooling rolls and the recess formed in the other cooling roll do not face each other at the roll kiss point. And a cooling roll are preferably arranged.
In this case, the metal or semi-solidified layer caught in the solidified shell of one cooling roll and the metal or semi-solidified layer caught in the solidified shell of the other cooling roll are prevented from facing each other at the roll kiss point. Thus, the influence on the thin cast slab due to the incorporation of the base metal and the semi-solidified layer can be suppressed, and the casting can be stably performed.

The method of casting a thin cast slab of the present invention comprises supplying a molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side dams, and forming a solidified shell on a peripheral surface of the cooling roll. A method for casting a thin cast slab which is grown to produce a thin cast slab, characterized by using the cooling roll described above.
According to the method of casting a thin cast slab of this configuration, since the above-described cooling roll is used, the metal or semi-solidified layer on the side weir surface can be rolled into the slab before it grows large, and hot Generation of a band can be suppressed, and stable casting can be performed.

Here, in the method of casting a thin cast slab of the present invention, when the molten metal pool portion has a contact length L in the circumferential direction of the molten metal and the cooling roll, a plurality of the periodically arranged plurality of the molten metal are formed. It is preferable that the interval between the concave portions is L or less.
In this case, the metal or semi-solidified layer on the surface of the side weir can be accurately caught in the slab before it grows greatly from the roll kiss point to the surface of the molten metal.

  As described above, according to the present invention, it is possible to suppress generation of a hot band or the like due to entrainment of a large-grown base metal and a semi-solid layer, and a cooling roll capable of performing stable casting. It is possible to provide a twin-roll continuous casting apparatus provided with a roll and a method of manufacturing a thin cast slab.

It is an explanatory view showing an example of a twin roll type continuous casting device which is an embodiment of the present invention. FIG. 2 is a partially enlarged explanatory view of the twin-roll continuous casting apparatus shown in FIG. 1. It is explanatory drawing which shows the flow of the molten metal surface of the molten steel pool part in the twin roll type continuous casting apparatus shown in FIG. It is explanatory drawing which shows the generation | occurrence | production area | region of the metal in the side weir in the twin roll type continuous casting apparatus shown in FIG. It is explanatory drawing of the cooling roll which is embodiment of this invention. (A) is a side view, (b) is one end view, and (c) is the other end view. It is a partially expanded explanatory view of the cooling roll shown in FIG. FIG. 6 is an explanatory sectional view of a concave portion of the cooling roll shown in FIG. 5. It is explanatory drawing which shows arrangement | positioning of a pair of cooling roll in the twin roll type continuous casting apparatus shown in FIG. 5 is a graph showing the results of measuring the surface temperature of a slab in Example 1 of the present invention. It is a graph which shows the surface temperature measurement result of the cast piece in a comparative example. FIG. 3 is a schematic explanatory view of a thin cast piece obtained by Example 1 of the present invention. It is a schematic explanatory drawing of the thin cast piece obtained by the comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, the metal to be cast will be described as steel. Note that the present invention is not limited to the following embodiments.

In the present embodiment, molten steel is used as the molten metal, and the thin cast slab 1 made of steel is manufactured. In addition, as a steel type, for example, 0.001-0.01% C ultra low carbon steel, 0.02-0.05% C low carbon steel, 0.06-0.4% C medium carbon steel, 0.5 ~ 1.2% C high carbon steel, austenitic stainless steel represented by SUS304 steel, ferritic stainless steel represented by SUS430 steel, 3.0 ~ 4.0% Si directional electromagnetic steel, 0.1 ~ 6.5% Si non-oriented electrical steel or the like (% is mass%).
In the present embodiment, the width of the thin cast slab 1 to be manufactured is in the range of 200 mm to 1800 mm, and the thickness is in the range of 0.8 mm to 5 mm.

Next, the twin-roll continuous casting apparatus 10 according to the present embodiment will be described.
The twin-roll continuous casting apparatus 10 shown in FIG. 1 includes a pair of cooling rolls 20 (20A, 20B), pinch rolls 12, 12, 13, and 13 for supporting the thin cast slab 1, and a pair of cooling rolls 20 (20A , 20B), and the molten steel 3 supplied to the molten steel pool 16 defined by the pair of cooling rolls 20 (20A, 20B) and the side weir 15. There is provided a tundish 18 to be held, and an immersion nozzle 19 for supplying molten steel 3 from the tundish 18 to the molten steel pool 16.

Here, as shown in FIG. 2, the molten steel pool portion 16 is defined by arranging the side weir 15 on the end face of the cooling roll 20.
As shown in FIG. 3, the molten metal surface of the molten steel pool portion 16 has a rectangular shape surrounded on all sides by a pair of side weirs 15, 15 and a pair of cooling rolls 20 (20 </ b> A, 20 </ b> B). An immersion nozzle 19 is provided at the center of the rectangular hot water surface.
As shown in FIG. 4, the sliding portion of the side weir 15 in the molten steel pool 16 with the molten steel 3 has a substantially inverted triangular shape.

  As shown in FIG. 3, the flow of the molten steel 3 in the molten steel pool 16 flows from the immersion nozzle 19 toward the peripheral surface of the cooling roll 20, and along the peripheral surface of the cooling roll 20, the pair of side weirs 15 Flow to each. The contact point between the cooling roll 20 and the side weir 15 is a dead zone for the flow of the molten steel 3, and is a region (stagnant region) D where the molten steel 3 does not flow sufficiently and stagnates.

As shown in FIG. 5, in the cooling roll 20, a concave portion 21 that is recessed in the roll radial direction and the roll width direction is provided at the boundary between the peripheral surface and the side surface at the width direction end.
In the present embodiment, as shown in FIG. 5, it is preferable that a plurality of recesses 21 are periodically arranged in the circumferential direction at the boundary between the circumferential surface and the side surface of the end in the width direction of the cooling roll 20.

As shown in FIGS. 6 and 7, the concave portion 21 has a length a in the roll width direction of 0.1 mm or more and 0.5 mm or less, and a length b in the roll radial direction of 0.3 mm or more and 3 mm or less. It is preferable that the length c in the circumferential direction is in the range of 1 mm or more and 30 mm or less.
Further, it is preferable that the circumferential interval p (the interval between the center positions of the concave portions 21 as shown in FIG. 6) of the periodically arranged concave portions 21 is in the range of 30 mm or more and 250 mm or less.
In the present embodiment, when the circumferential contact length L between the molten steel 3 and the cooling roll 20 in the molten steel pool portion 16 is set to be equal to or less than L in the circumferential direction of the plurality of concave portions 21 that are periodically arranged. It is preferred that

  Further, in the present embodiment, the recesses 21 are disposed so as to equally divide one round (360 °), and are disposed at intervals of 8 ° or more and 40 ° or less in terms of the central angle. Is preferred.

  Further, in the cooling roll 20 of the present embodiment, as shown in FIG. 5, a concave portion 21 formed on one end side in the width direction of the cooling roll 20 (left side in FIG. 5), and the other end side in the width direction of the cooling roll 20. It is preferable that the recess 21 formed on the right side (in FIG. 5) is arranged at a position different from each other in the circumferential direction. That is, as shown in FIG. 5B and FIG. 5C, the concave portion 21 formed on the other end surface is disposed between the concave portions 21 formed on one end surface in the width direction of the cooling roll 20. Is preferred.

  Further, in the twin-roll continuous casting apparatus 10 of the present embodiment, as shown in FIG. 8, the concave portion 21 formed on one cooling roll 20A and the concave portion 21 formed on the other cooling roll 20B are formed. It is preferable that one cooling roll 20A and the other cooling roll 20B are arranged so as not to face each other at the roll kiss point.

  Further, in the twin-roll continuous casting apparatus 10 of the present embodiment, the concave portion 21 formed on one widthwise end of one cooling roll 20A and the concave portion formed on the other widthwise end of one cooling roll 20A. 21, the concave portion 21 formed on one end side in the width direction of the other cooling roll 20B, and the concave portion 21 formed on the other end side in the width direction of the other cooling roll 20B are arranged so as not to coincide at the roll kiss point. Is preferred.

  In the twin-roll continuous casting apparatus 10, molten steel 3 is supplied from a tundish 18 to a molten steel pool section 16 through a dipping nozzle 19. In the molten steel pool section 16, the molten steel 3 contacts the rotating cooling rolls 20 (20 </ b> A, 20 </ b> B) and is cooled, whereby the solidified shells 5 and 5 grow on the peripheral surface of the cooling roll 20. Then, the solidified shells 5, 5 formed on the pair of cooling rolls 20 (20A, 20B) are pressed together at the roll kiss point, thereby casting the thin cast piece 1 having a predetermined thickness.

At this time, since the side weir 15 is always slid with the cooling roll 20, heat is removed from the cooling roll 20 and cooled. For this reason, as shown in FIG. 4, in the area S near the sliding line with the cooling roll 20 on the surface of the side weir 15, metal grows and deposits.
Further, as shown in FIG. 3, at the contact point between the cooling roll 20 and the side weir 15, a dead zone for the flow of the molten steel 3 is formed, and a region where the molten steel 3 does not flow sufficiently and stagnates (stagnation region). D. For this reason, the floating crystals existing in the molten steel pool portion 16 stay in the stagnant region D to form a semi-solid layer. If the base metal or semi-solidified layer is caught in the thin cast piece 1 in a state of large growth, a hot band or the like is generated, and it becomes impossible to perform casting stably.

  Therefore, in the present embodiment, as described above, by providing the recess 21 at the boundary between the peripheral surface and the side surface of the width direction end of the cooling roll 20, the molten steel 3 is inserted into the recess 21 and solidified. The formed burr-like solidified portion is integrated with the metal or semi-solid layer formed on the surface of the side weir 15, and the metal or semi-solid layer is involved in the thin cast slab 1 before growing large. It is configured as follows.

  Here, the reason why the size and arrangement of the concave portions 21 in the cooling roll 20 are defined as described above will be described.

By setting the length a of the recess 21 in the roll width direction to 0.1 mm or more, the molten steel 3 can be reliably inserted into the recess 21 against the surface tension of the molten steel 3. Further, by setting the length a of the recess 21 in the roll width direction to 0.5 mm or less, it is possible to suppress the end shape of the thin cast slab 1 from being disturbed.
From the above, in the present embodiment, it is preferable that the length a of the recess 21 in the roll width direction be in the range of 0.1 mm or more and 0.5 mm or less.

By setting the length b of the concave portion 21 in the roll radial direction to 0.3 mm or more, the molten steel 3 can be reliably inserted into the concave portion 21 against the surface tension of the molten steel 3. Further, by setting the length b of the recess 21 in the roll radial direction to 3 mm or less, it is possible to suppress the end shape of the thin cast slab 1 from being disturbed.
From the above, in the present embodiment, it is preferable that the length b of the concave portion 21 in the roll radial direction be in the range of 0.3 mm or more and 3 mm or less.

By setting the circumferential length c of the recess 21 to 1 mm or more, the molten steel 3 can be reliably inserted into the recess 21 against the surface tension of the molten steel 3. In addition, by setting the circumferential length c of the concave portion 21 to 30 mm or less, it is possible to suppress the end shape of the thin cast slab 1 from being disturbed.
From the above, in the present embodiment, it is preferable that the circumferential length c of the concave portion 21 be in the range of 1 mm or more and 30 mm or less.

By setting the interval p in the circumferential direction of the concave portions 21 arranged periodically to 30 mm or more, the metal and semi-solidified layer existing between the adjacent concave portions 21 grow to some extent, and are inserted into the concave portions 21 and solidified. By the formed burr-like solidified portion, the thin cast slab 1 can be accurately wound. Further, by setting the interval p in the circumferential direction of the concave portion 21 to 250 mm or less, formation of a coarse metal and a semi-solid layer can be suppressed.
From the above, in the present embodiment, it is preferable that the interval p in the circumferential direction between the periodically arranged concave portions 21 is in the range of 30 mm or more and 250 mm or less.

Further, when the circumferential contact length L between the molten steel 3 and the cooling roll 20 in the molten steel pool portion 16 is set to be less than or equal to L, the circumferential interval p of the plurality of concave portions 21 that are periodically arranged is L or less. It is preferable because formation of a coarse metal and a semi-solidified layer reaching from the roll kiss point to the molten metal surface can be suppressed.
In addition, it is more preferable that the interval p in the circumferential direction of the concave portion 21 is not less than L × (１ ／) and not more than L × (１ ／).

  According to the present embodiment having the above-described configuration, since the concave portion 21 is provided at the boundary between the peripheral surface and the side surface at the end in the width direction of the cooling roll 20, the molten steel 3 is placed in the concave portion 21 during casting. When the burr-like solidified portion slides with the side weir 15 with the rotation of the cooling roll 20, the burr-like solidified portion is formed. Is integrated into the thin cast slab 1 and the metal or semi-solidified layer can be engulfed in the thin cast slab 1 before growing large, and it is possible to suppress the generation of hot bands. Become.

  In addition, it is preferable that the concave portion 21 formed on one end side in the width direction of the cooling roll 20 and the concave portion 21 formed on the other end side in the width direction of the cooling roll 20 are arranged at different positions in the circumferential direction. . In this case, at the same position in the longitudinal direction of the thin slab 1, it is possible to suppress the ingot of the base metal or the semi-solidified layer from being wound on both ends of the width of the thin slab 1, and the thin slab due to the inclusion of the base metal or the semi-solidified layer 1 can be suppressed and casting can be performed stably.

  Further, in the present embodiment, one cooling roll 20A and the other cooling roll 20A are so arranged that the recess 21 formed in one cooling roll 20A and the recess 21 formed in the other cooling roll 20B do not face each other at the roll kiss point. It is preferable that the roll 20B and the roll 20B are arranged. In this case, the metal or semi-solidified layer wound on the solidified shell 5 of one cooling roll 20A and the metal or semi-solidified layer wound on the solidified shell 5 of the other cooling roll 20B come into contact at the roll kiss point. It is possible to suppress the influence on the thin cast slab 1 due to the incorporation of the base metal or the semi-solidified layer, and to perform the casting stably.

As described above, the cooling roll, the twin-roll continuous casting apparatus, and the method for manufacturing a thin cast slab which are the embodiments of the present invention have been specifically described. However, the present invention is not limited to this, and the technical It can be changed as appropriate without departing from the spirit.
For example, in the present embodiment, as shown in FIG. 1, a twin-roll continuous casting apparatus provided with pinch rolls has been described as an example. However, the arrangement of these rolls and the like is not limited, and the design may be changed as appropriate. You may.
Further, the shape of the concave portion 21 is not limited to the shape illustrated in the drawing. Further, the arrangement of the concave portions 21 is not limited to the present embodiment.

  Hereinafter, the results of experiments performed to confirm the effects of the present invention will be described.

  Using a twin-roll continuous casting apparatus having the configuration shown in FIG. 1, 0.05% C, 0.6% Si, 1.5% Mn, 0.03% Al, the balance Fe, and impurities were determined by mass%. A thin cast slab made of steel having the following composition was cast. The liquidus temperature of steel having this composition was 1517 ° C, and the temperature of molten steel injected into the molten steel pool portion was set to 1547 to 1567 ° C so that the degree of superheat was 30 to 50 ° C.

Here, the cooling roll has a diameter of 600 mm and a width of 800 mm, and is composed of an internal water-cooled roll main body and a copper sleeve mounted on the outer periphery thereof. did. Then, as shown in Table 1, a concave portion was provided at the boundary between the peripheral surface and the side surface at the end in the width direction of the cooling roll.
Then, a thin cast slab having a thickness of 2 mm was cast at a molten steel depth of 212 mm in the molten steel pool portion and a peripheral speed of the cooling roll of 50 m / min.

The surface temperature of the thin cast slab just below the cooling roll is measured with a radiation thermometer, and when a peak that is higher than 30 ° C. from the steady state temperature occurs, it is determined that a hot band has occurred, and the number of times the hot band has occurred is determined. Counted. Table 1 shows the evaluation results.
FIG. 9 shows the temperature measurement result of Example 1 of the present invention, and FIG. 10 shows the temperature measurement result of Comparative Example. Further, FIG. 11 shows the state of metal infiltration in the thin cast slab of Example 1 of the present invention, and FIG. 12 shows the state of metal ingot in thin cast slab of the comparative example.

In the comparative example in which the concave portion was not provided in the cooling roll, a large amount of hot band was generated because the grown metal was irregularly involved.
On the other hand, in the example of the present invention in which the concave portion was provided in the cooling roll, the number of occurrences of hot bands was greatly reduced.
In particular, in Examples 1 to 4 of the present invention in which the size of the concave portion and the interval in the circumferential direction were within the desired ranges, there was no hot band.

  From the above results, it has been confirmed that according to the present invention, it is possible to suppress the occurrence of frequent occurrence of hot bands or the like due to the large grown metal or semi-solidified layer being caught in the slab, and it is possible to stably cast.

1 Thin cast slab 3 Molten steel (molten metal)
5 Solidified shell 10 Twin roll continuous casting device 15 Side dam 16 Molten steel pool (molten metal pool)
20 cooling roll 21 recess

Claims (9)

Twin rolls for supplying molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs, and forming and growing a solidified shell on the peripheral surface of the cooling rolls to produce thin cast slabs A cooling roll used in a continuous casting apparatus,
A cooling roll, wherein a recess is provided at a boundary between a peripheral surface and a side surface at an end in a width direction of the cooling roll.   The concave portion has a length in a roll width direction of 0.1 mm or more and 0.5 mm or less, a length in a roll radial direction of 0.3 mm or more and 3 mm or less, and a circumferential length of 1 mm or more and 30 mm or less. The cooling roll according to claim 1, wherein the cooling roll is within the range.   The cooling roll according to claim 1, wherein a plurality of the concave portions are periodically arranged in the boundary portion in the circumferential direction.   4. The cooling roll according to claim 3, wherein the concave portions periodically arranged are disposed at intervals of 30 mm or more and 250 mm or less in a circumferential direction. 5.   The concave portion formed on one end side in the width direction of the cooling roll and the concave portion formed on the other end side in the width direction of the cooling roll are arranged at different positions in the circumferential direction. The cooling roll according to any one of claims 1 to 4. A twin roll that supplies molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side dams, and forms and grows a solidified shell on the peripheral surface of the cooling roll to produce a thin cast slab. Type continuous casting apparatus,
A twin-roll continuous casting apparatus comprising the cooling roll according to any one of claims 1 to 5.   The one cooling roll and the other cooling roll are arranged so that the recess formed in one cooling roll and the recess formed in the other cooling roll do not face each other at a roll kiss point. 7. The twin-roll continuous casting apparatus according to 6. A thin metal casting is manufactured by supplying molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs, and forming and growing a solidified shell on the peripheral surface of the cooling roll to produce a thin cast slab. A method of casting pieces,
A method of casting a thin cast slab, comprising using the cooling roll according to claim 1.   When the molten metal pool portion has a circumferential contact length L between the molten metal and the cooling roll, a circumferential interval between the plurality of recesses periodically arranged is not more than L. The method for casting a thin cast piece according to claim 8.

Images