KR20010056388A - Apparatus for cooling the strip in twin roll strip casting machine - Google Patents

Abstract

PURPOSE: An apparatus for cooling steel billet in a twin roll strip casting machine is provided to manufacture a strip having superior quality by rapidly cooling the steel billet at straightly below the casting roll so as to uniformly maintain edge shape of the steel billet, restrain oxidation and prevent skewness thereof to the utmost. CONSTITUTION: The apparatus comprises a pair of left and right fixing blocks (10) vertically fixed to straightly below casting rolls; a pair of left and right moving blocks (10a) assembled movably back and forth for the fixing blocks (10); a pair of cooling rolls (11,11a) each of which are idle drivenly assembled to the fixing and moving blocks (10,10a) so as to correspond to the front and back surfaces of a strip (7); rotary unions (12) circulating and supplying cooling water to the side of the cooling rolls (11,11a); operating cylinders (13) moving the moving blocks (10a) back and forth; position detectors (14) detecting back and forth moving distances of the moving blocks (10a); and force detectors (15) measuring adhesive forces between the cooling rolls (11,11a) and the strip (7).

Description

Cast iron cooling device of twin roll type sheet casting machine {APPARATUS FOR COOLING THE STRIP IN TWIN ROLL STRIP CASTING MACHINE}

The present invention relates to an apparatus for cooling a cast steel cast in a twin-roll sheet caster, and more particularly, having a cooling roll for quenching the cast steel cast directly under the casting roll to maintain the edge shape of the cast steel uniformly, The present invention relates to a slab cooling apparatus of a twin roll type sheet casting machine capable of restraining and at the same time preventing musk of a slab while drawing a slab.

In general, the twin-roll type sheet casting machine 100 is shown by each other by a driving device not shown through a molten steel injection nozzle 3 in the tundish (2) receiving the molten steel from the ladle (1). Molten steel is injected between the twin rolls (hereinafter referred to as casting rolls) rotating in the opposite direction to form molten steel between the casting rolls 4 and 4a and the edge dam 5 which face each other by injecting molten steel, and rotating them. It is a facility for casting the thin plate (7) while forming a solidified shell by rapidly solidifying the molten steel through the contact between the casting roll (4) (4a) and the molten steel.

The method of manufacturing a thin plate using the twin roll-type thin plate casting machine 100 is a new casting method that allows the hot rolling in the slab softening method to be omitted since the cast is manufactured by directly casting a cast steel having a thickness of about 2 to 6 mm. Accordingly, the manufacturing cost is reduced compared to the slab playing method, and the quality of the cast steel is very excellent due to the particle size refinement or segregation reduction due to the non-equilibrium state due to rapid solidification.

However, due to rapid solidification, molten steel is generally solidified for less than 0.3 seconds, so non-uniform solidification tends to occur in the width direction of the cast steel, and such non-uniform solidification may cause cracks on the surface of the cast steel. .

In addition, in particular, uncoagulation occurs frequently in the edge portion of the cast steel. When the fraction of the columnar top is excessively small compared to the center portion in the width direction due to the uncoagulation phenomenon of the edge portion, the mechanical strength of the cast steel edge becomes low, The heat rises as the heat is released back to the column.

Therefore, when such edge portion is not solidified, edge bulging occurs due to iron static pressure caused by molten steel of the equiaxed portion, and the thickness of the slab edge portion is excessively thicker than that of other portions. In case of coiling in (8), when the edge builder pressure is generated and the coil is released, the wave of cast iron edge becomes too severe, which causes serious problem in applying the cold rolling and heat treatment process.

In addition, if the edge portion is not solidified, edge crack may occur due to the strength decrease of the edge portion, and in extreme cases, it may cause plate breakage, so it is completely suppressed for stable operation in the twin roll type sheet casting machine (100). It is essential.

Conventional techniques for preventing such non-solidification of the edge is a method of adjusting the crown disclosed in Korean Patent Publication (B1) 10-0215728, which is formed when a solidified shell is formed on a casting roll which is a cooling drum, Since the coagulation shell does not move at the same time, the coagulation shell receives contraction force as the coagulation shell grows, and the edge cast of the cooling drum is lifted from the cooling drum.

When the solidification shell is continuously raised, an air gap of several tens of micrometers is generated between the cooling drum and the solidification shell, which leads to a serious delay in heat transfer, and thus an edge non-solidification phenomenon occurs.

As a method for suppressing this phenomenon, it is effective to narrow the gap of the cooling drum at the edge so that the part having the less solidification part is pressed. Therefore, by providing a concave crown to the cooling drum, the edge part has a relatively small roll gap so that the edge solidification part The non-solidification at the edge part was reduced by making the ratio the same as the center part. However, the edge non-solidification was not fundamentally eliminated by these conventional methods, and thus 100% of the edge non-solidification was not completely eliminated. As a result of this, more fundamental measures are required.

In Japanese Patent Laid-Open No. 11-10289, as shown in Fig. 1, a cooling block 6 capable of cooling the slab edges by gas is mounted directly below the casting rolls 4 and 4a, and the cooling is performed. In the block 6, a flow path through which gas can be injected is formed to propose cooling of the slab edge by gas injection. This is a technique of achieving complete solidification of the slab edge by rapidly cooling the unsolidified molten steel in the casting rolls 4 and 4a by cooling the slab edge, thus eliminating edge bulging and edge fracture.

However, it is difficult to achieve sufficient cooling in the case of cooling the cast steel by gas, and it is almost impossible to cool the flash lamp that may occur when edge jams are caused by a skull or the like momentarily on the cast steel edge.

As described above, the edge non-solidification can be suppressed to a certain level by the conventional technology, but in the case of the method using the roll crown, edge non-solidification occurs due to casting variables. Cooling method is not enough to be applied in case of high casting speed of 60mpm or higher, and cooling efficiency can be increased when using lower temperature gas such as liquid helium. It is expensive and difficult to apply in actual operation. In addition, if an instant edge flash occurs due to a skull or the like during casting, the cooling block 6 may be caught and the cooling block 6 may be damaged or, in severe cases, cast pieces may be torn. There was a problem that it is difficult to produce a thin plate of excellent quality by employing.

Accordingly, the present invention has been made to solve the above problems, the object of the present invention is to quench the casting slab directly below the casting roll to maintain the edge shape of the cast steel uniformly, while suppressing the oxidation of the cast steel and at the same time The present invention aims to provide a cast cooling device of a twin roll type sheet casting machine which is capable of producing a thin plate of excellent quality by preventing the musk of the cast during maximum drawing.

1 is a schematic view showing a twin-roll sheet caster according to the prior art,

Figure 2 is a schematic diagram showing a twin-roll sheet caster employing a cast cooling device according to the present invention,

Figure 3 is a block diagram showing a slab cooling apparatus of a twin-roll sheet caster according to the present invention.

* Explanation of symbols for the main parts of the drawings *

2 ... tundish 4,4a ... casting roll

5 ...... edge dam 7 ...... thin plate

10 ..... fixed block 10a .... moving block

11,11a ... cooling roll 12 ..... rotary union

13 ..... Operation cylinder 14 ..... Position detector

15 ..... Force Detectors 19 ..... Roll Shafts

The present invention as a technical configuration for achieving the above object,

A pair of casting rolls rotated in opposite directions, an edge dam installed at both ends of the casting roll to form a molten pool, and molten steel is passed between the casting rolls while supplying an atmospheric gas to the upper portion of the molten steel to cast thin plates. In the double roll type sheet casting machine,

A pair of left and right fixed blocks fixedly installed vertically under the casting roll; and a pair of left and right moving blocks assembled together so as to be movable forward and backward with respect to the fixed block; and idling and driving to the fixed and movable blocks. A pair of cooling rolls respectively assembled to correspond to the front and rear surfaces of the thin plate; and a rotary union for circulating and supplying cooling water to the cooling roll; and an operation cylinder for moving the moving block forward and backward; and the moving block. The position detector for detecting the forward and backward movement distance of the; and, the force detector for measuring the adhesive force between the cooling roll and the thin plate; by providing a slab cooling apparatus of a twin roll type sheet caster.

Hereinafter, with reference to the accompanying drawings the present invention will be described in more detail.

Figure 2 is a schematic diagram showing a twin roll thin plate casting machine employing a slab cooling apparatus according to the present invention, Figure 3 is a block diagram showing a slab cooling apparatus of a twin roll thin plate casting machine according to the present invention, as shown, The slab cooling apparatus 90 of the present invention is mounted directly under a pair of casting rolls 4 and 4a for casting a thin plate, and is cast while passing through a nip portion of the casting rolls 4 and 4a. By rapidly cooling the thin plate 7, such a device 90 is fixed, moving block 10, 10 a, cooling roll 11, 11 a, rotary union 12, operation cylinder 13, position detector. 14 and the force detector 15 and the like.

That is, the fixing block 10 is a pair of left and right in the roll width direction perpendicular to the pair of casting rolls (4) (4a) directly below the pair of casting rolls that rotate in opposite directions to cast the thin plate (7) On the other hand, the fixed block 10 and the movable block 10a corresponding to each other are installed in a left and right pair so as to be movable forward and backward by the operation cylinder 13 on a sliding frame not shown.

In addition, the cooling rolls 11 and 11a are assembled between both ends of the fixed block 10 corresponding to each other in the roll width direction and between the pair of moving blocks 10a to allow idle driving. By assembling each other, the front and rear surfaces of the thin plate 7 to be cast while passing between the casting rolls 4 and 4a are respectively disposed to correspond to each other.

Here, the fixed block 10 and the moving block 10a are disposed to correspond to the one side casting roll 4 and the other side casting roll 4a which is fixed when the upper plate is cast so as to form a roll portion during casting.

At this time, the cooling rolls 11 and 11a should be disposed as close as possible to the casting rolls 4 and 4a, but the nip and the thin plates between the casting rolls 4 and 4a through which the thin plates 7 pass. If the distance between the nips between the cooling rolls 11 and 11a for cooling 7) is long, the molten steel positive pressure at the edge unsolidified portion is increased based on the following equation (1).

F = ρg h

Where F is the positive static pressure, ρ is the density, g is the acceleration of gravity, and h is the distance from the melt surface.

That is, when the iron positive pressure increases, the force applied by the solidification shell increases, so that when the unsolidified molten steel of the slab edge remains to a certain length, the iron static pressure is deformed without the solidification shell of the slab, which causes edge bulging.

Therefore, the cooling rolls (11) (11a) is located within a predetermined length in the nip of the casting rolls (4) (4a) to be cooled in contact with the front, rear of the thin plate (7) before edge bulging occurs. As a result of the casting experiment, the nip distance between the casting rolls 4 and 4a and the cooling rolls 11 and 11a at the top is slightly different depending on the thickness of the thin piece cast to be cast. 7) In case of casting, it is better to set within about 400mm.

On the other hand, the smaller the maximum diameter of the cooling rolls (11) (11a), the shorter the distance to the nip between the casting rolls (4) (4a), thereby reducing edge static pressure on the solidification shell, thereby reducing edge bulging. Although there is an advantage, at least the cooling rolls 11 and 11a are equipped with a cooling hole 19a through which coolant is introduced and circulated, and a rotary union 12 for circulating the cooling water supplied to the cooling hole 19a. This should be determined in the range of possible diameters.

For example, in the process of casting the thin plate 7 as the casting rolls 4 and 4a having a diameter of 1000 to 1500 mm, the cooling rolls 11 and 11a having a diameter of approximately 200 mm are fixed and moving blocks 10 and 10a. ), The nip distance between the casting rolls 4, 4a and the cooling rolls 11, 11a is about 400 mm, and thus the cooling rolls 11, 11a having a diameter of 200 mm or less must be employed.

In addition, the cooling rolls 11 and 11a mounted on the fixed and movable blocks 10 and 10a are constituted by a pair of roll members facing each other to cool the thin plates to be cast. (7) Insufficient cooling effect, residual molten steel is not completely solidified, radiant heat phenomenon or edge bulging may occur, so it is composed of a plurality of roll members that are continuous under the same direction as thin plate advancing direction. While cooling the thin plate, the temperature exiting the cooling rolls 11 and 11a should be reduced as much as possible.

The rotary union 12 supplies cooling water to the cooling hole 19a formed in the cooling rolls 11 and 11a to cool the surface of the cooling rolls 11 and 11a in contact with the hot plate surface. It is configured to communicate with one end of the roll shaft 19, which is a passage through which the coolant is supplied, so that the coolant of which the water temperature is increased due to the water cooling action can be recycled in the roll.

The rotary union 12 has a structure similar to that of another rotary union (not shown), which cools the roll surface by supplying cooling water to the casting rolls 4 and 4a used for sheet casting. Description will be omitted below.

In addition, the operation cylinder 13 is not shown so that the cooling rolls (11) (11a) evenly contact the thin plate surface by moving the moving block (10a) forward or backward with respect to the fixed block 10 is fixed position. The rod ends are connected to one side of the left and right pairs of the movable blocks 10a which are slidably assembled on the slide frame, and the operation cylinder 13 is fixed to the fixed base 13a.

Here, the working fluid supply line 13b of the working cylinder 13 is connected to an operating motor (not shown) for supplying a working fluid to move the left and right pairs of moving blocks 10a forward and backward simultaneously with the same pressure. It is good to be configured.

On the other hand, the position of the front and the detection end 14a of the moving block 10a correspond to each other in each body of the fixed position working cylinder 13 so as to detect the moving distance of the moving block 10a moving forward and backward. The detector 14 is mounted, and between the rod end of the operation cylinder 13 and the front surface of the moving block 10a, the cooling roll 11 contacting the surface of the thin plate 7 by the advancement of the moving block 10a. Force detectors 15 are mounted respectively so that the adhesive force between 11a and the thin plate 7 can be measured and transmitted to the cab from time to time.

Referring to the operation and effect of the present invention having the above configuration is as follows.

First, the molten steel supplied to the tundish 2 through the ladle 1 is supplied between the pair of casting rolls 4 and 4a through the injection nozzle 3 to form a molten pool, and then the casting roll 4 (4a) is rotated in opposite directions to start casting the thin plate (7).

At this time, when casting starts and the tip of the thin plate 9 passes through the casting rolls 4 and 4a, the gap between the casting rolls 4 and 4a can promote solidification of the molten steel at the thin plate tip. The phosphorus nip is made larger than the plate thickness to be cast, and then after a certain time has elapsed, the phosphorus nip is narrowed to the nip size of the casting rolls 4 and 4a for obtaining the target thin plate thickness.

That is, during the initial nip of the casting rolls 4 and 4a, the cold roll 11 in which the thin plates 7 cast due to excessive flushing of cast steel edges is disposed directly below the casting rolls 4 and 4a. There is a risk of damaging and damaging it), the adhesive portion of the initial thin plate tip is very fragile, there is a risk of short circuit if the initial flush is caught by the cooling roll (11) (11a).

Therefore, the nip size between the cooling rolls 11 and 11a may be set sufficiently large at the beginning of the casting compared with the nip size of the casting rolls 4 and 4a.

The operation of adjusting the nip size of the cooling rolls (11) (11a) before and after the moving block (10a) based on the detection signal transmitted from the position detector (14) for detecting the position of the moving block (10a). The advancing is performed by advancing forward and backward the rod end of the operation cylinder 13.

The sheet casting operation is continuously performed, using the position detector 14 which detects the position of the moving block 10a at a time when the nip size of the casting rolls 4 and 4a reaches a target value. The movement with respect to the fixed block 10 positioned by the operating cylinder 13 until the nip size between the casting rolls 4 and 4a and the nip size between the cooling rolls 11 and 11a are equal to each other. When the block 10a is advanced, the surface between the fixed block 10 and the cooling rolls 11 and 11a respectively mounted to the movable block 10a is narrowed and the surface of the thin plate 7 which is cast downward is in contact. You lose.

At the same time, the cooling rolls 11 and 11a contacting the thin plate surface are assembled to the fixed and movable blocks 10 and 10a so as to be idle-dried, and the cooling water is circulated and supplied by the rotary union 12. Like the casting rolls 4 and 4a, the thin plates 7 are rapidly cooled and drawn out without being directed to the coiler 8 by the cooling rolls 11 and 11a which are rotated in opposite directions. It begins to wind up in (8).

At this time, since the cooling rolls 11 and 11a are fixed to the casting blocks 4 and 4a and mounted on the moving blocks 10 and 10a to form a nip located within 400 mm from the nips of the casting rolls 4 and 4a, the cooling rolls 11 and 11a are cast and lowered. It is possible to rapidly cool the cast steel before edge bulging occurs in the thin plate.

In addition, since the plurality of cooling rolls (11) (11a) is installed in the moving, fixed block (10) (10a) in a plurality of directly below the same direction as the casting direction of the thin plate can be sufficiently cooled even when the thin plate is cast at high speed It is possible to sufficiently cool the thin plates passing through the cooling rolls 11 and 11a without fear of radiant heat or edge bulging.

When the total temperature of the thin plate 7 cast by the thin plate cooling is reduced, not only complete removal of edge non-coagulation occurred during casting but also thin plate oxidation by temperature decrease can significantly reduce the amount of oxidation scale. The pickling process, which is a post process, can be performed more smoothly.

On the other hand, since the cooling rolls 11, 11a and the thin plate 9 cannot be sufficiently contacted even after moving to the normal casting position, the rod end of the working cylinder 13 and the moving block 10a are not. As the force detector 15 mounted between the front surfaces of the sheet, the adhesive force of the cooling rolls 11 and 11a in contact with the thin plate surface is measured, and the measured values are inadequate and the thin plate 7 and the cooling roll 11 ( If it is determined that 11a) is not in sufficient contact, the rod end of the operation cylinder 13 is further advanced to increase the contact force between the cooling rolls 11, 11a and the thin plate so as not to adversely affect the plate thickness change. Control to press the cast.

In this case, the cooling effect of the thin plate by the cooling roll is increased, as well as the thin plate shape is corrected to some extent by the compression of the slab edge even when instantaneous edge flush occurs due to the skull during casting, etc. It is possible to prevent the phenomenon that the thin plate 7 is torn due to the discharge roll, and the portion where the flush is generated is compressed, so that the cast iron edge is relatively good and the winding in the coiler is good. It is possible to prevent the wave from being generated in the loose edge portion.

According to the present invention as described above, by rapidly cooling a thin plate to be cast with a plurality of cooling rolls continuous in the thin plate advancing direction directly below the pair of casting rolls, to completely suppress the edge non-solidification that can occur during casting Since defects such as edge bulging and edge tearing can be removed at the source, the shape and quality of the thin plate can be significantly improved as compared with the conventional one, and the casting safety can be significantly improved.

In addition, even when edge flush of cast steel is generated instantaneously due to skulls generated during casting, the shape of cast steel can be improved by compressing the flush to improve the shape of the cast steel. In short, the pickling time and pickling degree in the pickling process, which is a post process, are improved, thereby obtaining an effect of manufacturing a thin plate of excellent quality.

Claims (6)

A pair of casting rolls 4 and 4a which rotate in opposite directions to each other, an edge dam 5 provided at both ends of the casting rolls 4 and 4a to form a molten pool, and an atmosphere above the molten pool. In a twin roll type sheet casting machine for casting a thin plate 7 by passing molten steel between the casting rolls 4 and 4a while supplying gas, A pair of left and right fixed blocks 10 which are vertically fixed directly below the casting rolls 4 and 4a; and a pair of left and right moving blocks which are assembled to be movable forward and backward with respect to the fixed block 10; 10a); and a pair of cooling rolls 11 and 11a respectively assembled to the fixed and movable blocks 10 and 10a so as to be idle-dried so as to correspond to the front and rear surfaces of the thin plate 7. A rotary union 12 for circulating and supplying cooling water to the cooling rolls 11 and 11a; and an operation cylinder 13 for moving the moving block 10a forward and backward; and the front of the moving block 10a. , Position detector 14 for detecting the reverse movement distance: and a force detector 15 for measuring the adhesive force between the cooling roll (11) (11a) and the thin plate (7); Cast iron cooling device of sheet casting machine. The method of claim 1, The fixed block 10 and the movable block 10a are paired with one side casting roll 4 which is fixed to form a roll 닢 part during sheet casting, and the other side casting roll 4a which is moved during casting. Cast iron cooling device for roll type sheet casting machine. The method of claim 1, The cooling rolls (11) (11a) is in contact with the front and rear surfaces of the thin plate (7) before the edge bulging occurs at the edge of the thin plate (7) to reduce the cooling roll (4) (4a) and the top A slab cooling apparatus for a twin roll sheet caster, characterized in that the distance between the nips between the cooling rolls (11) (11a) is set within about 400 mm. The method of claim 1, The cooling rolls 11 and 11a can sufficiently cool the thin plates 7 escaping at high speed during high-speed casting, and continue in the same direction as the traveling direction of the thin plates 7 so as to prevent radiative heat phenomenon or edge bulging. Cast iron cooling device of a twin-roll thin plate casting machine, characterized in that consisting of a plurality of roll members. The method of claim 1, The nip size between the cooling rolls 11 and 11a is set sufficiently large in comparison with the nip size of the casting rolls 4 and 4a at the beginning of casting, and the nip size of the casting rolls 4 and 4a is targeted. When the value is set to 1, the moving block 10a is advanced until the same as the nip size between the casting rolls 4 and 4a so as to surface the cooling rolls 11 and 11a and the thin plate 7. It is controlled so that the contact with each other cast iron cooling device of a twin-roll sheet caster. The method of claim 1, When the cooling rolls 11 and 11a are determined to be in insufficient contact with the thin plate 7 and the cooling rolls 11 and 11a due to insufficient contact force measured by the force detector 15, the operation cylinder ( 13) to further advance the rod end to increase the contact force between the cooling roll (11) (11a) and the thin plate so as not to adversely affect the plate thickness change to control the pressing of the thin plate (7) with a constant force Slab cooling device of double roll type sheet casting machine.