JP2014046314A - Cast piece cooling system in continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable quick replacement such as enabling maintenance in an off-line, without having influence on productivity.SOLUTION: A plurality of spray type cooling systems are arranged in the extraction direction of a cast piece 6 for secondarily cooling the cast piece 6 extracted from a casting mold 2 for continuous casting. An appropriate number of spray type cooling systems 21 are set as one block B, and are constituted so that cooling water and air can be supplied by one cooling water pipe 23 and an air pipe 22 for every block. Attachment to and detachment from a main piping, of the respective cooling water pipe 23 and air pipe 22 for every block, is executed via a coupler 25 executed by rotation on the tip side of a lever 25a with the base end side as a fulcrum. Since the productivity is improved by shortening of a replacement time, off-line maintenance can be executed without reducing the productivity, and nonuniform cooling of the cast piece caused by blocking-up of a nozzle can be prevented, and an axial crack and bending of a round billet cast piece can be reduced.

Description

  The present invention relates to a spray-type slab cooling device installed as a secondary cooling device for continuous casting equipment.

  In continuous casting of steel, the molten steel in the ladle is once poured into the tundish, then poured into the water-cooled mold 2 through the immersion nozzle 1 installed at the bottom of the tundish, and then the molten steel surface is cooled. The solidified shell 3 is formed. The solidified shell 3 pulled out from the mold 2 is secondarily cooled while being guided and supported by the cooling grid or the support roll 4 directly below the mold and further by the guide roll 5 below the mold 2 to grow the solidified shell 3 to grow the slab 6. (See FIG. 1). In addition, 7 in FIG. 1 is a spray nozzle for secondary cooling.

  In this continuous casting, particularly when casting a steel type that is likely to be axially cracked at the center of the slab, in order to reduce axially centered cracking, an end-solidification cooling zone 8 is provided at the final solidification position and the slab 6 is further removed. In some cases, control is performed so that compressive stress is generated by cooling the substrate and preventing the generation of tensile stress at the central solidification interface.

  Thus, in continuous casting of steel, the cooling of the slab is very important for the formation and growth of a uniform solidified shell and the improvement of quality. The cooling water for secondary cooling of the slab is branched from the main pipe to the pipe for each of the plurality of segments, and then water or gas / liquid mixed with air via each spray type cooling device constituting the segment. Sprayed on the slab as mixed mist.

  In the cooling system as described above, dirt accumulated in the piping, foreign matter accumulated in the water tank, or the like may be mixed, and the nozzle of the cooling device may be blocked due to these. When nozzle clogging occurs, cooling of the slab becomes uneven and quality defects such as bending of the slab occur, so prevention of nozzle clogging is essential in continuous casting of steel.

  In order to prevent nozzle blockage, it is important to remove the nozzle blockage off-line, but the spray type cooling device having the nozzle group is configured with a guide mechanism for holding the slab (roller apron). The roller apron is composed of a plurality of segments A (see FIG. 1), and it is necessary to remove and install the spray cooling device for off-line maintenance on a segment basis. The plurality of spray type cooling devices 11 constituting this segment are integrated with the segment A, and as shown in FIG. 6, each spray type cooling device 11 is connected to a separate cooling water pipe 12 and air pipe 13. Therefore, it takes a long time to attach and detach, resulting in a decrease in productivity.

  For this reason, once the spray-type cooling device is installed, it is rarely removed to perform off-line maintenance. Therefore, there is a case where the nozzle is blocked during continuous casting, and a technique for suppressing the blocking of the nozzle has been proposed.

  For example, Patent Document 1 discloses a technique for detecting nozzle blockage from the opening of a flow rate adjustment valve and the amount of cooling water in each cooling system. Patent Document 2 discloses a technique for measuring the pressure of a spray jet flow with a load cell via a pressure receiving plate installed on a dummy bar, and detecting nozzle blockage from the change in the measured pressure. Patent Document 3 discloses a technique for detecting nozzle blockage from the temperature difference between the cooling water temperature inside the nozzle and the original piping.

  The techniques disclosed in these Patent Documents 1 to 3 are techniques for detecting the clogged state of the nozzles and suppressing the clogging of the nozzles by performing maintenance before serious clogging occurs. Since it cannot be managed, it is necessary to check each nozzle.

  In other words, the techniques disclosed in Patent Documents 1 to 3 cannot reduce the time required for replacing the spray cooling device, even though the time for checking the nozzles and the inspection cycle can be shortened. . Further, since it is not a technique for preventing the nozzle clogging itself, it is not a drastic measure.

  With respect to the above problem, in Patent Document 4, the cooling water outlet cross-sectional area decreases during operation to form a predetermined jet amount distribution, and the jet outlet cross-sectional area increases when the cooling water jetting is interrupted. A technique for preventing clogging of a nozzle by using a spray nozzle having a nozzle is disclosed.

  However, since the technique disclosed in Patent Document 4 is a technique for preventing clogging of nozzle tips (cooling water ejection ports), clogging that occurs at the orifice portion cannot be prevented.

  That is, in any of the techniques of Patent Documents 1 to 4, in order to suppress nozzle clogging, nozzle clogging is removed off-line or scale accumulated in the cooling water piping of the spray-type cooling device. It is necessary to carry out maintenance such as removal of accumulated foreign matter.

JP 2006-175464 A JP 2010-172921 A JP 2003-170256 A JP 2002-59248 A

  The problem to be solved by the present invention is that there is no technology that can completely prevent nozzle clogging of a spray cooling device used for continuous casting of steel, so it is necessary to maintain the spray cooling device offline, At that time, it takes a long time to attach and remove the spray type cooling device.

  An object of the present invention is to provide a spray-type cooling device that can be quickly replaced so that it can be maintained off-line without affecting productivity.

That is, the present invention
In order to secondary-cool the slab drawn from the continuous casting mold, a spray-type cooling device arranged in the drawing direction of the slab,
Appropriate number of spray type cooling devices are made into one block, and each block is constructed so that cooling water and air can be supplied by one cooling water pipe and air piping. The main feature is that each pipe is attached to and detached from the main pipe via a coupler that can be rotated by turning the distal end of the lever with the base end as a fulcrum.

  In the present invention, it is possible to attach / detach the cooling water pipe and the air pipe to / from the main pipe by simply rotating the lever for each block, thereby reducing the replacement time. Productivity is improved. This makes it possible to perform offline maintenance without reducing productivity, prevent uneven cooling of the slab due to nozzle clogging, and reduce the rounding and bending of the round billet slab. become.

It is a schematic block diagram of the continuous casting installation provided with the slab cooling device of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic of the slab cooling device of this invention, (a) is the figure seen from the slab drawing direction, (b) is the figure seen from the cross-sectional direction of the slab. It is the figure which showed an example of the coupler which comprises the slab cooling device of this invention, (a) is an external view, (b) is a perspective view, (c) is a longitudinal cross-sectional view. It is a figure showing an example of the effect of the present invention, and shows color check evaluation. It is the figure which showed an example of the effect of this invention, and shows bending evaluation. It is the schematic seen from the slab drawing direction in the schematic of the conventional slab cooling device.

  The purpose of the present invention is to provide a spray-type cooling device for secondary cooling of a slab to a segment of a support roll for the purpose of enabling quick replacement so that off-line maintenance is possible without affecting productivity. Instead of replacing units, it was realized by making it possible to replace multiple spray-type cooling devices in a batch independent of the segment.

  That is, according to the present invention, a plurality of spray-type cooling devices are configured as one block so that cooling water and air can be supplied by one cooling water pipe and air piping, so that batch replacement can be performed. Can be exchanged independently. The cooling medium sprayed by the cooling device of the present invention may be either water alone or a gas-liquid mixed mist mixed with air.

  Therefore, the time required for the replacement can be greatly shortened as compared with the replacement in the segment unit in which the cooling water pipe and the air pipe to be attached and detached for each spray cooling device are integrally attached. As a result, the spray cooling device can be replaced in a short time and can be maintained off-line, so that nozzle blockage of the spray cooling device can be effectively suppressed.

  In addition, it is possible to easily replace the cooling nozzle by inspecting nozzle tip clogging in advance and preparing a replacement block for which maintenance has been completed. In addition, it is possible to easily inspect the spray angle of the spray sprayed from the nozzle at the time of offline maintenance and correct the misalignment of the spray angle toward the center.

Examples of the present invention will be described below.
The slab cooling device of the present invention is a spray-type cooling device 21 for secondary cooling of a slab drawn from a continuous casting mold, and has a structure as shown in FIG. 2, for example.

  22 is an air pipe arranged on the outer peripheral side, and has an annular double pipe structure in which a cooling water pipe 23 is arranged on the inner peripheral side, so that air is supplied from the air pipe 22 and cooling water is supplied from the cooling water pipe 23. It has become.

  For example, as shown in FIG. 2B, gas-liquid mixed mist is ejected from 12 gas-liquid two-fluid nozzles 24 arranged radially inward. Hereinafter, this spray type cooling device is referred to as a spray ring.

  In addition, conventionally, as shown in FIG. 6, instead of connecting the cooling water pipe and the air pipe for each spray ring, in the present invention, as shown in FIG. One spray ring 21 is used as one block B, and one cooling water pipe 23 and one air pipe 22 are provided for each block, and the cooling water pipes 23 and the air pipes 22 are cooled to three spray rings 21 one by one. Water and air are supplied.

  Further, in the conventional spray ring shown in FIG. 6, the cooling water pipe and the air pipe are connected by screw joints. In the present invention, the cooling water pipe 23 and the air pipe 22 for each block are connected to the main spray ring. The attachment / detachment to / from the pipe is performed via a coupler 25 that can be rotated by turning the distal end side of the lever 25a with the proximal end side as a fulcrum as shown in FIG.

  In the present invention, the block B and the segment base 26 are fixed by driving a cotter pin 27 between the lower part of the block B and the segment base 26, and the block B and the segment base 26 can be easily attached and detached.

  Next, in order to confirm the effect of the device of the present invention having the above-described configuration, a test for exchanging the cooling device for each casting was performed.

  Hereinafter, the test results will be described. The test was performed on a round billet slab shaft at the final solidification position of a round billet slab 30 to 35 m from the meniscus of a 41 m long billet cast slab having a radius of curvature of 10.5 m. The apparatus of the present invention was applied to perform strong cooling for reducing the center crack. The casting conditions and steel types at that time are as follows.

Casting conditions Round billet slab size: 191mm and 225mm outside diameter
Casting speed: 1.8 to 3.6 m / min
Number of strands: 4-6

・ Steel grade
C: 0.05 mass%, Si: 0.30 mass%, Mn: 1.30 mass%, P: 0.013 mass%, S: 0.002 mass%, balance: Fe + impurity

  In this test, four sets of blocks each having three spray rings arranged at intervals of 400 mm were set so that the intervals between the blocks were 400 mm.

  In order to investigate the quality of the round billet slab continuously cast by applying the apparatus of the present invention, for axial cracking, a dye penetration test, so-called color check, defined in JIS Z 2343 of the billet cross section end face is performed, The length of the crack was taken as the color check indication range (mm), and the average value was evaluated. The result is shown in FIG.

  As can be seen from FIG. 4, the color check instruction range (mm) was 1.1 mm (n number: 3664 evaluation) when the conventional cooling device shown in FIG. 6 was applied. By applying the cooling device of the present invention, it was greatly reduced to 0.3 mm (n number: 84 evaluations).

  As for the bending, the billet bending amount was measured at a frequency of six from the central portion of the steady casting portion per charge, and evaluated as the bending amount per 1 m of billet. The result is shown in FIG.

  As can be seen from FIG. 5, the bending amount per meter of billet was 3.7 mm per meter when the conventional cooling device shown in FIG. 6 was applied, but the cooling device of the present invention was applied. As a result, the slab was reduced to 1.5 mm per 1 m, and a slab having no variation could be obtained.

  As a result, the time required for off-line maintenance to prevent the plug ring from being attached and detached and to prevent clogging, which previously took 18 hours to replace the segment, is greatly reduced to 4 hours by adopting the spray ring of the present invention. I was able to. Therefore, it became possible to replace the spray ring without affecting the productivity.

  In addition, after casting, the spray ring can be removed and maintenance can be easily performed off-line to remove nozzle obstructions and foreign matter in the piping. As a result, nozzle clogging does not occur and uniform slab cooling is stable. Casting is now possible.

  It goes without saying that the present invention is not limited to the above-described examples, and the embodiments may be appropriately changed within the scope of the technical idea described in each claim.

  In the above-described embodiment, the example in which the present invention is applied to the cooling at the end of solidification used for reducing the axial center crack of the round billet slab during continuous casting of the round billet slab has been described. The same applies to the secondary cooling spray cooling device.

  Moreover, in the said Example, since it interferes with the support roll 9 arrange | positioned at the coagulation | solidification end cold zone 8, the number of the spray rings 21 fixed to one block B was set to three, However, The number is adjustable according to a connection. Needless to say.

  The present invention as described above can be applied to any type of continuous casting, such as a vertical type and a vertical bending type, as well as a curved type.

2 Mold 6 Slab 21 Spray cooling device (spray ring)
22 Air piping 23 Cooling water piping 24 Nozzle 25 Coupler 25a Lever B Block

Claims (2)

In order to secondary-cool the slab drawn from the continuous casting mold, a spray-type cooling device arranged in the drawing direction of the slab,
Appropriate number of spray type cooling devices are made into one block, and each block is constructed so that cooling water and air can be supplied by one cooling water pipe and air piping. A slab cooling device in continuous casting, wherein each pipe is attached to and detached from the main pipe via a coupler that can be rotated by turning the distal end side of a lever with the base end side as a fulcrum.   The slab cooling device for continuous casting according to claim 1, wherein the slab cooling device ejects only cooling water or gas-liquid mixed mist.

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