JP6569550B2 - Twin-drum type continuous casting apparatus, cooling drum, and method for producing thin-walled slab - Google Patents

Description

  The present invention relates to a twin-drum type continuous casting device that supplies molten metal to a molten metal pool portion formed by a pair of cooling drums and a pair of side weirs to produce a thin-walled cast piece. The present invention relates to a cooling drum used and a method for manufacturing a thin cast slab.

  As a method for producing a thin metal slab, for example, as shown in Patent Literatures 1 to 3, a cooling drum having a water-cooling structure is provided inside, and a molten metal pool part formed between a pair of rotating cooling drums is used. Molten metal is supplied, solidified shells are formed and grown on the peripheral surface of the cooling drum, the solidified shells formed on the peripheral surfaces of the pair of cooling drums are joined to each other at the drum kiss point, and pressed down to a predetermined thickness. A twin-drum continuous casting method for producing a thin-walled slab is provided. Such a twin drum type continuous casting method is applied to various metals.

  When starting casting in the above-described twin-drum type continuous casting method, for example, as shown in Patent Documents 1 to 3, a dummy sheet is sandwiched between cooling drums, and a pair of cooling drums and a pair of side weirs are used. The cooling drum is rotated while supplying the molten metal to the formed molten metal reservoir, and a thin cast piece is formed so as to be connected to the dummy sheet. The dummy sheet and the thin wall connected to the dummy sheet are formed between the cooling drums. The slab is pulled out.

  Here, since the casting conditions such as the amount of molten metal supplied to the molten metal reservoir and the temperature of the cooling drum are not stable at the start of casting, the thin cast slab formed to be connected to the dummy sheet The strength was insufficient, and there was a concern that the thin cast piece would break when the dummy sheet was pulled out.

For this reason, for example, in Patent Document 1, when the slab is transported, the auxiliary sheet is welded to the dummy sheet, and the slab is placed on the auxiliary sheet and transported. Techniques for suppressing breakage have been proposed.
In Patent Document 2, a linear, net-like, or thin plate-like reinforcing material selected from W, Ta, and Mo is disposed at the end of the dummy sheet, and the reinforcing material is cast with molten metal. Thus, a technique for improving the strength of the thin cast piece at the start of casting has been proposed.
Further, in Patent Document 3, the thickness of the position corresponding to the pouring nozzle is increased in the metal plate attached to the tip of the dummy sheet, so that the solidified shell at the center of the width is melted by the discharge flow from the pouring nozzle. Techniques for suppressing this have been proposed.

JP 04-356333 A JP 05-293605 A Japanese Patent Application Laid-Open No. 07-232244

By the way, in the cooling drum used for the above-mentioned twin-drum type continuous casting apparatus, the central part in the axial direction of the peripheral surface has a crown shape that is retreated inward in the radial direction. In other words, the shape of the cooling drum is adjusted such that the cooling drum is thermally expanded during casting and the cooling drum is thermally expanded to have a flat peripheral surface.
Here, at the start of casting, since the temperature of the cooling drum is low, the casting is performed in a state in which the central portion in the axial direction of the peripheral surface has a crown shape that is retracted radially inward.

  Then, the solidified shell formed at the central portion in the axial direction of the cooling drum is positioned radially inward from the solidified shell formed at the end portion in the axial direction, and the solidified shell at the central portion in the axial direction is located at the drum kiss point. It is not sufficiently crimped, and an unsolidified portion is formed inside the width center portion of the thin cast piece obtained. When the thin cast piece is pulled out with the unsolidified part formed as described above, the solidified shell at the center of the width of the thin cast piece is broken, and the unsolidified part leaks to the outside of the thin cast piece. There was a risk that it would become stuck and casting could not be continued. Further, the thin cast slab in which the unsolidified part is removed and the perforated part is formed may be twisted, and the slab cannot be transported.

  The present invention has been made in view of the above-described situation, and suppresses the occurrence of an unsolidified portion in the center of the width of the manufactured thin cast piece at the start of casting, thereby stabilizing the casting. It is an object of the present invention to provide a twin-drum type continuous casting apparatus that can be carried out, a cooling drum used in the double-drum type continuous casting apparatus, and a method for producing a thin-walled slab using the twin-drum type continuous casting apparatus And

  In order to solve the above problems, a twin-drum continuous casting apparatus according to the present invention has a pair of rotating cooling drums and a pair of side weirs, and a fusion formed by the pair of cooling drums and the pair of side weirs. A twin-drum continuous casting apparatus for supplying a molten metal to a metal reservoir and forming and growing a solidified shell on a peripheral surface of the cooling drum to produce a thin cast piece, wherein the cooling drum is formed on the peripheral surface. A central portion in the axial direction has a crown shape that is retreated inward in the radial direction, and at least one of the pair of cooling drums is provided at both axial ends of the peripheral surface in a state before starting casting. A heat insulating material is provided, and the cooling drum provided with the heat insulating material is provided with a heat insulating material removing means for removing the heat insulating material of the cooling drum that has passed through the molten metal reservoir after the start of casting. It is characterized in that it is.

According to the twin-drum type continuous casting apparatus having this configuration, since at least one of the pair of cooling drums is provided with the heat insulating material at both ends in the axial direction of the peripheral surface, the casting starts. The formation of a solidified shell at the axial end of the cooling drum having a crown shape at the time is suppressed, and the solidified shell at the axial central portion can be sufficiently crimped at the drum kiss point. Generation | occurrence | production of the solidification part can be suppressed. Therefore, it becomes possible to carry out casting stably at the start of casting.
In addition, since the heat insulating material removing means for removing the heat insulating material of the cooling drum that has passed through the molten metal reservoir after the start of casting is provided, after the temperature of the cooling drum rises, the axial end of the cooling drum A solidified shell is formed also in the portion, and a thin cast piece having a predetermined width can be stably manufactured.

Here, in the twin-drum continuous casting apparatus of the present invention, it is preferable that the heat insulating material has a structure in which a heat insulating sheet is attached to a peripheral surface of the cooling drum.
In this case, the above-described heat insulating material can be disposed relatively easily by selecting the material, thickness, width, and the like of the heat insulating sheet. Further, it can be removed relatively easily by the heat insulating material removing means, and after the temperature of the cooling drum has risen, the thin cast slab can be stably produced.

Further, when the maximum depth of the crown shape of the cooling drum is hc and the depth of the crown shape at the end in the axial center of the heat insulating material is he, 0.3 ≦ (hc−he ) /Hc≦0.7 is preferably provided with the heat insulating material.
In this case, even in various crown-shaped cooling drums, the heat insulating material can be properly disposed, and the occurrence of an unsolidified portion in the center portion of the thin cast piece can be reliably suppressed.

The cooling drum of the present invention is a cooling drum used in the above-described twin-drum type continuous casting apparatus, and has a crown shape in which a central portion in the axial direction of the peripheral surface is retreated inward in the radial direction. A heat insulating material is disposed at both ends in the axial direction.
In the cooling drum having this configuration, since the heat insulating material is disposed at both ends in the axial direction of the peripheral surface, formation of a solidified shell at the axial end of the cooling drum having a crown shape at the start of casting is suppressed. can do.

  The method for producing a thin slab according to the present invention supplies molten metal to a molten metal reservoir formed by a pair of rotating cooling drums and a pair of side weirs, and forms and grows a solidified shell on the peripheral surface of the cooling drum. A thin-walled slab manufacturing method for manufacturing a thin-walled slab, wherein a dummy sheet is sandwiched between the pair of cooling drums of the above-described twin-drum type continuous casting apparatus, and a molten metal is placed in the formed molten metal reservoir. At the start of casting, the formation and growth of a solidified shell in the region where the heat insulating material is disposed in the cooling drum is suppressed.

  In the method for manufacturing a thin cast piece of this configuration, at the start of casting, by suppressing the formation and growth of a solidified shell in the region of the cooling drum where the heat insulating material is disposed, The solidified shell formed on the portion can be sufficiently crimped, and the occurrence of an unsolidified portion in the central portion of the width of the thin slab can be suppressed. Thereby, it becomes possible to carry out casting stably at the start of casting.

  As described above, according to the present invention, at the start of casting, it is possible to suppress the occurrence of an unsolidified portion inside the width center portion of the manufactured thin-walled slab and to perform casting stably. A twin-drum type continuous casting apparatus, a cooling drum used in the twin-drum type continuous casting apparatus, and a method for producing a thin cast slab using the twin-drum type continuous casting apparatus can be provided.

It is a schematic explanatory drawing which shows the twin drum type continuous casting apparatus which is embodiment of this invention. It is a schematic explanatory drawing of the cooling drum used for the twin drum type continuous casting apparatus shown in FIG.

Hereinafter, a twin-drum continuous casting apparatus, a cooling drum, and a method for producing a thin cast piece according to an embodiment of the present invention will be described with reference to the accompanying drawings. In addition, this invention is not limited to the following embodiment.
In this embodiment, molten steel is used as the molten metal, and a thin cast piece made of steel is manufactured. Examples of steel types include 0.001% C polar carbon steel, 0.05% C low carbon steel, 0.2% C medium carbon steel, 1.0% C high carbon steel, SUS304 steel, SUS430 steel (note that ,% Is% by mass).

  As shown in FIG. 1, the twin-drum continuous casting apparatus 10 according to this embodiment rotates in contact with a pair of cooling drums 20 (20A, 20B) and the peripheral surfaces of these cooling drums 20 (20A, 20B). Side weir disposed at the widthwise ends of the driving brush roll 11 (11A, 11B), the pinch roll 13 (13A, 13B) for conveying the thin cast piece, and the pair of cooling drums 20 (20A, 20B) 14, and a tundish 16 and an immersion nozzle 17 for supplying the molten steel 3 to the molten steel reservoir 15 defined by the pair of cooling drums 20 (20 </ b> A and 20 </ b> B) and the side weir 14.

  In this twin-drum type continuous casting apparatus 10, the molten steel 3 comes into contact with the rotating cooling drum 20 (20A, 20B) and is cooled, so that the solidified shell is formed on the peripheral surface of the cooling drum 20 (20A, 20B). 5 grows, and the solidified shells 5, 5 formed on the pair of cooling drums 20 (20 </ b> A, 20 </ b> B) are pressed against each other at the drum kiss point, whereby a thin cast piece having a predetermined thickness is cast.

  Here, in the twin-drum continuous casting apparatus 10 according to the present embodiment, at the start of casting, as shown in FIG. 1, as shown in FIG. 1, the dummy sheet 18 is sandwiched between a pair of cooling drums 20 (20 </ b> A, 20 </ b> B). A reservoir portion 15 is formed. Note that a reinforcing portion extending toward the molten steel pool portion 15 is provided at the end of the dummy sheet 18. The dummy sheet 18 is sandwiched between pinch rolls 13 (13A, 13B). By winding up the dummy sheet 18, a thin cast slab formed continuously with the end of the dummy sheet 18 is continuously formed. Will be manufactured.

Then, in the state before the start of casting, the cooling drum 20 (20A, 20B) has a radial central portion in the direction of the axis O in consideration of thermal expansion during casting, as shown in FIG. The crown is retracted inward.
Here, in this embodiment, in at least one cooling drum 20A of the pair of cooling drums 20 (20A, 20B), as shown in FIG. It is arranged.

  Here, in this embodiment, as shown in FIG. 2, the maximum depth of the crown shape of the cooling drum 20A is hc, and the depth of the crown shape at the end on the center side in the axis O direction of the heat insulating material 21 is he. In this case, it is preferable that the heat insulating material 21 is disposed so as to satisfy 0.3 ≦ (hc−he) /hc≦0.7. That is, the width for disposing the heat insulating material 21 is set according to the crown shape of the cooling drum 20A.

In this embodiment, this heat insulating material 21 is set as the structure which stuck the heat insulation sheet on the surrounding surface of 20 A of cooling drums.
In addition, it is preferable that the heat conductivity in 300 to 400 degreeC is 0.1 W / (m * K) or less. There is no particular limitation on the lower limit of the thermal conductivity.
Further, the thickness of the heat insulating sheet needs to be thinner than the thickness of the solidified shell 5 formed on the peripheral surface of the cooling drum 20 when pressed by the cooling drum 20, and is more appropriate for the compressibility of the heat insulating sheet. Although the range of thickness changes, specifically, it can be exemplified as 1.0 mm or less. Moreover, in order to ensure heat insulation and intensity | strength, it is preferable that the thickness of a heat insulation sheet shall be 0.25 mm or more.

  In addition, it can illustrate that this heat insulation sheet is affixed on the surrounding surface of the cooling drum 20A with a commercially available double-sided tape. Moreover, when dividing | segmenting and sticking to a some heat insulation sheet, the slight clearance gap (for example, 2 mm or less) may arise in the joint part of the heat insulation sheet.

Here, in the present embodiment, as described above, the brush roll 11 (11A, 11B) that rotates in contact with the peripheral surface of the cooling drum 20 (20A, 20B) is provided.
The brush roll 11 (11A, 11B) is positioned on the opposite side of the molten steel reservoir 15 of the cooling drum 20 (20A, 20B) and is supported in parallel with the cooling drum 20 (20A, 20B). The brush roll 11 (11A, 11B) is in contact with the peripheral surface of the cooling drum 20 (20A, 20B) and the cooling drum 20 at a contact point with the cooling drum 20 (20A, 20B). (20A, 20B) and the roll direction of the brush roll 11 (11A, 11B) are rotationally driven so that the rotational speed is higher than that of the cooling drum 20 (20A, 20B). It is set as the structure.
And in this embodiment, the brush roll 11A arrange | positioned so that the cooling drum 20A with which the heat insulating material 21 was arrange | positioned removes the heat insulating material 21 of the cooling drum 20A which passed the molten steel pool part 15 after the casting start. It becomes a heat insulating material removing means.

  Next, the manufacturing method of the thin cast piece which is this embodiment using the twin drum type continuous casting apparatus 10 mentioned above is demonstrated.

First, as shown in FIG. 1, a dummy sheet 18 is sandwiched between a pair of cooling drums 20 (20 </ b> A, 20 </ b> B) to form a molten steel pool portion 15.
The molten steel 3 is supplied from the tundish 16 to the molten steel reservoir 15 via the immersion nozzle 17, and the pair of cooling drums 20 (20A, 20B) are directed in the rotation direction R, that is, the pair of cooling drums 20 ( Each cooling drum 20 (20A, 20B) is rotated so that the region where 20A and 20B) are close to each other is directed in the drawing direction of the thin cast slab (downward in FIG. 1).

Then, the solidified shell 5 is formed on the peripheral surface of the cooling drum 20 (20A, 20B). At the start of casting, the temperature of the cooling drum 20 (20A, 20B) did not rise sufficiently, and as shown in FIG. 2, the central portion of the peripheral surface in the direction of the axis O was retracted radially inward. It is in a state.
Here, in this embodiment, as shown in FIG. 2, one cooling drum 20 </ b> A is provided with the heat insulating material 21 at both ends of the circumferential surface in the axis O direction. In the provided region, the formation of the solidified shell 5 is suppressed, and the solidified shell 5 grows preferentially in the central portion in the axis O direction.

  Then, the solidified shell 5 grows on the peripheral surface of the cooling drum 20 (20A, 20B), and the solidified shells 5, 5 formed on the pair of cooling drums 20 (20A, 20B) are pressure-bonded at the drum kiss point. The At this time, although the central portion in the axis O direction of the cooling drum 20 (20A, 20B) is retracted radially inward, the formation / growth of the solidified shell 5 at the end in the axis O direction is suppressed. The solidified shells 5 and 5 formed at the central portion in the axis O direction of the drum 20 (20A, 20B) can be sufficiently pressed together.

Thus, a thin cast piece is formed so as to be connected to the dummy sheet 18, and the thin cast piece formed to be connected to the end of the dummy sheet 18 is continuously manufactured by winding up the dummy sheet 18. It becomes possible.
Then, after the temperature of the cooling drum 20 (20A, 20B) rises and the crown shape is eliminated, the heat insulating material 21 of one cooling drum 20A is removed by the brush roll 11A, so that the cooling drum 20A The formation / growth of the solidified shell 5 at the end portion in the direction of the axis O is not suppressed, and the shape of the end portion in the width direction of the thin cast piece is also stabilized.

  According to the twin-drum continuous casting apparatus 10, the cooling drum 20A, and the thin-walled slab manufacturing method according to the present embodiment configured as described above, both ends of the circumferential surface in the direction of the axis O in one cooling drum 20A. Since the heat insulating material 21 is disposed in the cooling drum 20A having the crown shape at the start of casting, formation of the solidified shell 5 at the end portion in the axis O direction can be suppressed. As a result, the solidified shells 5 and 5 formed in the central portion in the direction of the axis O that has been retreated radially inward can be sufficiently pressed together at the drum kiss point, and the occurrence of an unsolidified portion in the central width portion of the thin cast slab Can be suppressed. Therefore, it becomes possible to carry out casting stably at the start of casting.

  Further, since the brush roll 11A is provided as a heat insulating material removing means for removing the heat insulating material 21 of the cooling drum 20A that has passed through the molten steel pool portion 15 after the start of casting, the temperature after the molten steel pool portion 15 has risen is increased. After the heat insulating material 21 can be removed from the cooling drum 20A and the casting conditions are stabilized, the solidified shell 5 is also formed at the end of the cooling drum 20A in the axis O direction. A slab can be manufactured stably.

  Moreover, in this embodiment, since the heat insulating material 21 is set as the structure which stuck the heat insulating sheet to the surrounding surface of 20 A of cooling drums, by selecting the material, thickness, width, etc. of a heat insulating sheet, the above-mentioned It becomes possible to arrange the heat insulating material 21 relatively easily. Moreover, it can remove comparatively easily with the brush roll 11A which is a heat insulating material removal means, and after the temperature of the cooling drum 20A rises, a thin cast piece can be manufactured stably.

Here, in the present embodiment, as the heat insulating sheet, for example, a sheet having a thermal conductivity of 0.1 W / (m · K) or less from 300 ° C. to 400 ° C. is used, so that the heat insulating property at the operating temperature is excellent. Therefore, the formation / growth of the solidified shell 5 in the region where the heat insulating material 21 is disposed can be reliably suppressed.
Moreover, since the thickness of the heat insulation sheet is thinner than the thickness of the solidified shell formed on the peripheral surface of the cooling drum 20A, for example, 1.0 mm or less, the cooling drum 20 (20A, 20B) is at the drum kiss point. It is possible to securely press the solidified shells 5 and 5 formed at the central portion in the axis O direction.
Furthermore, in this embodiment, since the heat insulation sheet is stuck on the circumferential surface of the cooling drum 20A by a commercially available double-sided tape, it can be easily removed by the brush roll 11A.

  Furthermore, in this embodiment, when the maximum depth of the crown shape of the cooling drum 20A is hc, and the depth of the crown shape at the end on the center side in the axis O direction of the heat insulating material 21 is he, 0.3 ≦ The heat insulating material 21 is arranged so as to satisfy (hc-he) /hc≦0.7, and the width for arranging the heat insulating material 21 is set according to the crown shape of the cooling drum 20A. Therefore, also in the cooling drum 20A of various crown shapes, the heat insulating material 21 can be properly disposed, and the occurrence of an unsolidified portion in the width center portion of the thin cast piece can be reliably suppressed.

As mentioned above, the twin drum type continuous casting apparatus, the cooling drum, and the method for manufacturing the thin cast piece according to the embodiment of the present invention have been specifically described, but the present invention is not limited to this, and the present invention is not limited thereto. Changes can be made as appropriate without departing from the technical idea.
For example, in this embodiment, although it demonstrated as what manufactures the thin cast piece of steel, it is not limited to this, You may make into the thin cast piece of aluminum or another metal.

Moreover, although this embodiment demonstrated what provided the pinch roll, there is no limitation in arrangement | positioning of these rolls etc., You may change a design suitably.
Furthermore, although this embodiment demonstrated as a structure which arrange | positions a heat insulating material by affixing a heat insulating sheet, it is not limited to this, You may apply an amorphous heat insulating material.
In the present embodiment, the heat insulating material is disposed only on one cooling drum, but the heat insulating material may be disposed on both of the pair of cooling drums.

In the following, the results of experiments conducted to confirm the effects of the present invention will be described.
A cooling drum having a diameter of 600 mm and a width of 800 mm was prepared. In the crown shape, the maximum depth hc was 150 μm.

In the example of the present invention, in one cooling drum, a heat insulating sheet (SC paper 1260-I manufactured by Nippon Thermal Ceramics Co., Ltd., thickness 0.25 mm) was attached to an end portion in the axial direction of the peripheral surface with a commercially available double-sided tape. . Table 1 shows the relationship between the maximum crown-shaped depth hc of the cooling drum and the crown-shaped depth he at the end of the heat insulating material on the axial center side.
On the other hand, in the comparative example, the heat insulating material was not provided.

  By using the twin drum type continuous casting apparatus having the structure shown in FIG. 1 equipped with the cooling drum described above, low carbon steel (mass%, C: 0.04 to 0.06%, Si: 0.01 to 0.05%) , Mn: 0.4 to 0.6%, P: 0.01 to 0.02%, S: 0.002 to 0.005%, the balance being Fe and inevitable impurities). Casting was performed 10 times, and the number of times of casting stop was evaluated. The evaluation results are shown in Table 1.

In the comparative example, casting stoppage occurred 8 times out of 10 castings. Specifically, in a thin cast piece connected to a dummy sheet, a hole is generated in the center in the width direction, and an unsolidified part adheres to a pinch roll or a subsequent cast piece conveying device, or a hole is formed. The thin cast slab was twisted and interfered with the pinch roll and the subsequent slab transport equipment, making it impossible to transport the thin cast slab.
In addition, perforation occurred also about 2 times which could continue casting. Of these, the casting was continued because the twisted thin slab did not interfere with the pinch rolls and subsequent slab transport equipment. The other one time, the unsolidified part was completely dropped from the thin slab and did not adhere to the pinch roll or the subsequent slab conveying equipment, so the casting was continued.

  In the example of the present invention, in the thin cast piece connected to the dummy sheet, a defect occurred in the region where the heat insulating material was disposed, but the central portion in the width direction was sound. And in the area | region after casting length 1.9m, there was no defect | deletion of the edge part of the width direction, and the thin cast piece was able to be cast favorable. In 10 castings, casting was stopped 0 times, and all castings were completed.

  From the above, according to the example of the present invention, at the start of casting, it is possible to suppress the occurrence of an unsolidified portion in the center of the width of the manufactured thin cast piece and perform casting stably. It was confirmed that.

3 Molten steel (molten metal)
5 Solidified Shell 10 Twin Drum Type Continuous Casting Device 11A Brush Roll (Insulating Material Removal Means)
20 Cooling drum 21 Insulation

Claims (5)

A pair of rotating cooling drums and a pair of side weirs are provided. Molten metal is supplied to a molten metal reservoir formed by the pair of cooling drums and the pair of side weirs, and a solidified shell is provided on the peripheral surface of the cooling drum. A twin-drum continuous casting device that forms and grows to produce thin-walled slabs,
The cooling drum has a crown shape in which a central portion in the axial direction of the peripheral surface is retreated inward in the radial direction, and at least one cooling drum of the pair of cooling drums is in a state before starting casting. Heat insulating material is disposed at both axial ends of the peripheral surface,
The cooling drum provided with the heat insulating material is provided with heat insulating material removing means for removing the heat insulating material of the cooling drum that has passed through the molten metal pool after the start of casting. Drum type continuous casting equipment.   2. The twin-drum continuous casting apparatus according to claim 1, wherein the heat insulating material has a structure in which a heat insulating sheet is attached to a peripheral surface of the cooling drum. When the maximum depth of the crown shape of the cooling drum is hc, and the depth of the crown shape at the end on the axial center side of the heat insulating material is he,
0.3 ≦ (hc−he) /hc≦0.7
The twin-drum type continuous casting apparatus according to claim 1 or 2, wherein the heat insulating material is disposed so as to satisfy the above. A cooling drum used in the twin-drum continuous casting apparatus according to any one of claims 1 to 3,
The cooling drum according to claim 1, wherein a central portion in the axial direction of the peripheral surface has a crown shape that is retreated inward in the radial direction, and heat insulating materials are disposed at both ends in the axial direction of the peripheral surface. Thin-walled slab for supplying a molten metal to a molten-metal reservoir formed by a pair of rotating cooling drums and a pair of side weirs, and forming and growing a solidified shell on the peripheral surface of the cooling drum to produce a thin-walled slab A manufacturing method of
A dummy sheet is sandwiched between the pair of cooling drums of the twin-drum type continuous casting apparatus according to any one of claims 1 to 3, and a molten metal is supplied to a formed molten metal reservoir,
A method for producing a thin-walled slab characterized by suppressing formation / growth of a solidified shell in a region of the cooling drum where the heat insulating material is disposed at the start of casting.

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