JP2007245213A - Method of and device for pulverizing molten steel outflowing due to breakout in continuous casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of and a device for pulverizing molten steel in order to prevent a steel slab, holding device and the like from being adhered with molten steel outflowing due to a breakout in continuous casting. <P>SOLUTION: A cooling medium is sprayed to the molten steel outflowing from a cast slab due to a breakout, along the outer surface of the cast slab, through spouts of cooling nozzles, which are arranged in gaps in a cooling, holding, and guiding device for a cast-slab and/or in gaps in a drawing and bending device, along the outer surface of the cast slab. The cooling, holding, and guiding device for a cast-slab and/or the drawing and bending device is attached with a molten-steel pulverizing device, which is provided with a cooling medium spraying mechanism and a cooling medium supplying mechanism. In the pulverizing device, the cooling medium spraying mechanism has a cooling medium pressurizing mechanism for pressurizing the cooling medium and supplying the medium to the cooling nozzles, and the cooling medium supplying mechanism supplies the cooling medium, which is prepared by mixing cooling water and gas, to the cooling medium pressurizing mechanism. The spouts of the cooling nozzles are opened along the outer surface of the cast slab. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for pulverizing molten steel in order to prevent molten steel flowing out at a breakout during continuous casting from adhering to a slab support device or the like.

  The continuous casting machine has main parts such as ladle support, tundish, tundish support, mold, slab cooling support guide, drawing, cutting, etc. that produce slabs from molten steel, and incidental equipment such as transportation, refining, water treatment, etc. Various types have been developed from the initial vertical type, horizontal type, and curved type, and arc curved types suitable for mass-produced steel types have been frequently used in recent years.

  FIG. 5 schematically shows a curved continuous casting equipment, and a curved slab continuous casting machine 100 is provided with a mold 500 for cooling and solidifying the molten steel 1100 to form the outer shell shape of the slab slab 1200. A tundish 200 for relaying and supplying molten steel 1100 supplied from a ladle (not shown) to the mold 500 is installed at a predetermined position above the mold 500.

  On the other hand, a plurality of pairs of slab support rolls including a support roll 600, a guide roll 700, and a pinch roll 800 are arranged below the mold 500, and the slab slab 1200 drawn out from the mold 500 includes these slabs. While being supported by the support roll, it is drawn downward in the casting direction (arrow e direction).

  Among these, the pinch roll 800 is a drive roll for pulling out the slab cast slab 1200 at the same time as supporting the slab cast slab 1200. A secondary cooling zone in which a spray nozzle (not shown) such as a water spray nozzle or an air mist spray nozzle is arranged in the gap between the slab support rolls adjacent in the casting direction is configured. The slab slab 1200 is cooled while being pulled out by cooling water sprayed from (also referred to as “secondary cooling water”).

  A sliding nozzle 300 for adjusting the flow rate of the molten steel 1100 injected from the tundish 200 into the mold 500 is installed at the bottom of the tundish 200, and the molten steel 1100 is injected into the mold 500 on the lower surface of the sliding nozzle 300. An immersion nozzle 400 made of a refractory material is installed.

  A plurality of conveyance rolls 900 for conveying the cast slab slab 1200 are installed on the downstream side of the slab support roll. Above the conveyance roll 900, a slab slab to be cast is provided. A slab cutting machine 1000 for cutting a slab slab 1200a having a predetermined length from 1200 is disposed.

  The molten steel 1100 injected into the tundish 200 is injected into the mold 500 from the tundish 200 through the immersion nozzle 400, and the molten steel 1100 cast into the mold 500 is cooled by the mold 500 to form a solidified shell 1300, The slab slab 1200 having an unsolidified layer 1400 is continuously drawn downward while being supported by a plurality of pairs of slab support rolls including a support roll 600, a guide roll 700, and a pinch roll 800.

  Mold powder (not shown) is added on the molten steel surface of the mold 500. While the slab slab 1200 is drawn, it is cooled by the secondary cooling zone. The cooled slab slab 1200 increases the thickness of the solidified shell 1300 and eventually completes the solidification to the center at the solidification completion position 1500.

  The slab slab 1200 thus cast is cut by a slab cutting machine 1000 to obtain a slab slab 1200a. The slab slab 1200a is conveyed to the next hot rolling step.

  Since a plurality of pairs of slab support rolls including a support roll 600, a guide roll 700, and a pinch roll 800 disposed below the mold 500 are bulged by molten steel static pressure, a plurality of rolls are continuously cast. Are formed and arranged continuously to form a roll band.

  Immediately below the mold 500, since the solidified shell is thin and non-uniform, breakout is likely to occur. Therefore, in order to prevent the occurrence and uniformly cool (secondary cooling), a slab is provided between the roll groups. A water-cooling nozzle for cooling is arranged. In addition, since the molten steel static pressure is high immediately below the mold 500, a large-diameter roll is used.

  In the drawing / bending device, on the downstream side of the secondary cooling zone, hydraulically and electrically driven rolls are arranged above and below in the thickness direction of the slab and the slab is drawn out.

  In recent years, in order to improve productivity, it has been required to increase the casting speed, and the slab solidified shell that comes into contact with these rolls is remarkably thinned, and there is a concern that the frequency of occurrence of breakout will increase.

  When a breakout occurs at one end, the molten steel scatters around a plurality of pairs of slab support rolls consisting of a support roll 600, a guide roll 700, and a pinch roll 800, causing damage to piping for greasing and cooling, poor roll rotation, Various troubles such as an abnormal load on the roll due to gold biting are caused, and a lot of incidental facilities are replaced and productivity is lowered.

  Patent Document 1 relates to a bullion outflow prevention device in a continuous casting machine, and describes that the damage of bullion outflow when a breakout occurs is reduced by a molten steel outflow prevention plate shown in FIG.

  In FIG. 4, the slab slab 1200 cast by the mold 500 is pulled out along the arrow e, and the molten steel outflow prevention plate 1600 is pressed against each of the left and right short sides of the slab slab 1200.

  A portion of the molten steel outflow prevention plate 1600 that comes into contact with the slab slab 1200 is attached with a rotating roller so as not to generate rubbing on the surface of the slab slab 1200, and the plate surface to which the molten steel 1100 adheres during breakout is: The cooling water sprayed on the slab slab 1200 does not accumulate, and the expanded metal has a high effect of capturing molten steel.

The molten steel outflow prevention plate 1600 is disposed on the short side of the slab cast piece 1200 so as not to interfere with the slab cooling support guide device and the segment frame of the drawing / bending device. It is also possible to attach a plurality of slab cast pieces 1200 in the drawing direction.
JP-A-6-99258

  However, when molten steel spill prevention plates or similar are used, they are placed in a narrow space between the slab cooling support guide device and the drawing / bending device, so that these devices can be protected from molten steel. Sometimes it can't be done.

  That is, the molten steel that has flowed down to the molten steel outflow prevention plate is partially solidified by cooling corresponding to its heat capacity, but is scattered around by an impact when it collides with the molten steel outflow prevention plate.

  When the amount is large, it further scatters by colliding with the molten steel spill prevention plate below and adheres to the slab cooling support guide device, the roll or bearing of the drawing / bending device, and the like. In particular, when a breakout occurs on the curved portion side of the arc-curved continuous casting equipment, such a phenomenon increases the equipment damage.

  Therefore, an object of the present invention is to solve the above-described problems and to provide a method and apparatus for reducing equipment damage due to breakout during continuous casting.

The object of the present invention can be achieved by the following means.
1. A method for pulverizing molten steel, characterized by spraying a cooling medium onto molten steel leaked from a slab by breakout during continuous casting.
2. 2. The molten steel grinding method according to 1, wherein the cooling medium is sprayed onto the molten steel along the outer surface of the slab.
3. 2. The pulverization of molten steel according to 1, wherein the cooling medium is jetted along the outer surface of the slab from a jet nozzle of a cooling nozzle disposed in a gap between the slab cooling support guide device and / or the drawing / bending device. Method.
4). Further, the cooling medium is sprayed on the bearing box and its periphery and / or the roll surface, and the spray film by spraying the cooling medium is continuously formed around the slab and continuously in the casting direction. The method for pulverizing molten steel according to claim 1.
5). A slab cooling support guide device and / or a drawing / bending device equipped with a molten steel crushing device having a cooling medium ejection mechanism and a cooling medium supply mechanism, wherein the cooling medium ejection mechanism is a cooling device in the molten steel crushing device. A cooling medium pressurizing mechanism that pressurizes and supplies the cooling medium to the nozzle and the cooling nozzle, the cooling medium supply mechanism supplying the cooling medium to the cooling medium pressurizing mechanism, and an outlet of the cooling nozzle Is a slab cooling support guide device and / or a drawing / bending device, wherein the slab cooling support guide device and / or the drawing / bending device are open along the outer surface of the slab.
6). 6. The slab cooling support guide device and / or drawing / bending device according to claim 5, wherein the cooling medium is water or water and gas.

According to the present invention, since the cooling film by the cooling medium is formed on the four circumferences of the slab directly under the mold, the following effects can be obtained.
1 Molten steel that is about to pass through the cooling film is pulverized and rapidly solidified, and adhesion of the metal to the slab cooling support guide device and / or the drawing / bending device is prevented.
2 As a result, segment replacement becomes unnecessary, and long-term production stoppage due to recovery is avoided.
3 The steam explosion is prevented because the cooling medium does not directly enter the part where the molten steel leaks in the slab.
Since the cooling film by 4 cooling media is formed in the four rounds of a slab, the said 1 effect is acquired with respect to the molten steel leak in which position of a slab outer periphery.
5 When molten steel does not leak, when the cooling medium is ejected, solidification of the surface of the slab is promoted and prevention of molten steel leakage is suppressed.

  The present invention is characterized in that a high-pressure cooling medium is sprayed on the molten steel flowing out by breakout, and is pulverized and rapidly solidified.

  FIG. 1 is a schematic diagram for explaining a molten steel crushing method according to an embodiment of the present invention, and FIG. 2 shows an enlarged view of molten steel crushing. In these drawings, 1 is a mold, 2 is a slab cooling support guide device, 3 is a segment frame, 4 is a cooling device, 41 is a cooling nozzle, 42 is a spout, 5 is a slab, 6 is a roll, and 7 is a break. Molten steel ejected by the out, 71 is a pulverized steel droplet, e is an arrow indicating the casting direction, f is an arrow indicating the ejection direction of the cooling medium ejected from the cooling nozzle, and g is a cooling film. In addition, the cooling device 4 is arrange | positioned so that the secondary cooling device (not shown) for cooling the slab cast piece 5 may be arrange | positioned between the rolls of 6, but it may not interfere.

  In the slab cooling support guide device 2, the cooling device 4 is disposed in each of the plurality of gaps of the segment frame 3, and a high-pressure cooling medium is ejected along the outer surface of the slab 5 to support the slab cooling. A cooling film g continuously covering the slab slab 5 in the guide device 2 is formed.

  As the cooling medium, cooling water or cooling water and gas are used. When using cooling water and gas, either arrange the cooling water jet nozzle and the gas jet nozzle independently, or supply water and gas to one nozzle from a separate system pipe like a two-fluid nozzle, It is possible to make an air mist by blowing gas into water at the nozzle outlet. FIG. 2 shows a case where water is used as the cooling medium.

  When the molten steel 7 breaks out from the slab slab 5 collides with the cooling film g, the molten steel 7 is crushed into fine steel droplets 71. Since the steel droplets 71 are almost solidified at the time of being crushed by the cooling film g, even if they collide with the roll 6 or the segment frame 3, they do not adhere to these devices and are not damaged. It is also restrained from spreading and spreading damage.

  In the method for pulverizing molten steel according to the present invention, the cooling medium is ejected from the ejection port 42 of the cooling nozzle 41 so as to be parallel to the outer surface of the slab 5. Is prevented from entering and triggering a water vapor explosion.

  The jet direction of the cooling medium may be parallel to the outer surface of the slab 5, and may be any of the casting direction, the reverse casting direction, or the direction perpendicular to the casting direction in FIG. 3 (FIG. 3).

  Furthermore, when the cooling medium is sprayed on the bearing box and the periphery thereof and / or the roll surface, and the spray film formed by spraying the cooling medium is continuously formed around the slab and continuously in the casting direction, the molten steel is formed on the roll itself and It is preferable that it is prevented from adhering to the bearing portion.

  Further, the cooling device 4, the cooling nozzle 41, and the ejection port 42 are formed so that the cooling film g is formed between the roll 6 and the segment frame 3 and at least 1 m in the casting direction from directly below the mold 1. It is preferable to arrange in.

  The spout 42 is preferably slit-shaped so that a uniform cooling film is formed. A cooling liquid or mist can be used as the cooling medium.

  The equipment capacity of the cooling device 4 is determined such that the kinetic energy per unit time of the cooling medium is larger than the kinetic energy per unit time of the molten steel.

  Hereinafter, the case where a cooling film is formed directly under a mold of a continuous casting machine (about, a portion corresponding to 4 pitches at a roll pitch interval of 260 mm between 1 m and 2 m below the molten metal surface) will be specifically described.

  When cooling water is used as a cooling medium and molten steel is pulverized with cooling water from a slit-shaped jet outlet having the same width as the broken hole, the following is obtained.

If a 10mm square fracture occurs in the solidified wall 2m below the mold surface, the kinetic energy per unit time of the molten steel that breaks out is 83.5 (J / s) from E _k = 1/2 · mv ² It becomes.

Molten steel ejection speed v = √ (2gh) = 6.26 (m / s)
However, g = 9.80665 (m / sec ² ), h = 2 (m)
Molten steel m = ρAv (kg / s) = 4.26 (kg / s)
However, ρ (molten steel density) = 6.8 × 10 ³ (kg / m ³ ), A (cross-sectional area) = 0.0001 (m ² )

When pulverizing molten steel with cooling water from a slit-shaped outlet having a lateral width of 10 mm and a height of 3 mm, the kinetic energy per unit time of the molten steel must be greater than the kinetic energy per unit time of the molten water. (1) Formula is materialized.
E _k (cooling water) = 1/2 · mv ² = 1/2 × ρAv × v ² ≧ 83.5 (J / s) (1)
Here, from A = 0.00003 (m ² ) and ρ = 1.0 × 10 ³ (kg / m ³ ), the expression (2) is obtained as the cooling water ejection speed v (m / s).

v ≧ 17.7 (m / s) (2)
The required amount of cooling water (Q) is Q = Av ≧ 0.335 (m ³ / s).

At a casting speed of 1 m / min, the cooling water amount is 0.335 m / s between the time of raising the mold molten steel surface level from the tundish to the mold at the start of casting for 1 minute and the casting length of 11 minutes up to 10 m. When the present invention is carried out, 221 m ³ is required as the cooling water amount.

  When carrying out the method for pulverizing molten steel according to the present invention, it is possible to reduce the amount of cooling medium used by operating the cooling device in accordance with the casting state. That is, when casting is not steady, such as cast slabs at the start of casting or continuous casting of different steel types, the casting length is discharged to 10 m to form a cooling film. When changing the width, water is discharged only during that period.

  On the other hand, when the casting is in a steady state, control is performed so that water is discharged when the breakout detection device detects a breakout. In addition, after drainage, it is possible to use trench drainage that is drained into the scale pit and returned to the power treatment pond.

The figure explaining the grinding method of the molten steel which concerns on one Example of this invention. The elements on larger scale of FIG. The figure explaining the grinding method of the molten steel which concerns on the other Example of this invention. Conventional example. The figure explaining a continuous casting machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold | mold 2 Casting piece cooling support guide apparatus 3 Segment frame 4 Cooling device 41 Cooling nozzle 42 Jetting port 5 Casting piece 6 Roll 7 Molten steel 71 Steel droplet e Arrow which shows casting direction f It shows the ejection direction of the cooling medium ejected from a cooling nozzle Arrow g Cooling film 100 Curved slab continuous casting machine 200 Tundish 500 Mold 600 Support roll 700 Guide roll 800 Pinch roll 900 Transport roll 1000 Slab cutting machine 1100 Molten steel (conventional example)
1200, 1200a Slab slab 1300 Solidified shell 1400 Unsolidified layer 1500 Solidification completion position 1600 Molten steel outflow prevention plate

Claims (6)

  A method for pulverizing molten steel, characterized by spraying a cooling medium onto molten steel leaked from a slab by breakout during continuous casting.   The method for pulverizing molten steel according to claim 1, wherein the cooling medium is sprayed onto the molten steel along the outer surface of the slab.   2. The molten steel according to claim 1, wherein the cooling medium is ejected along the outer surface of the slab from an outlet of a cooling nozzle disposed in a gap between the slab cooling support guide device and / or the drawing / bending device. Grinding method.   Furthermore, a cooling medium is sprayed on a bearing box and its periphery, and / or the roll surface, and the injection film by spraying a cooling medium is formed continuously in the periphery of a slab and also in the casting direction. The method for pulverizing molten steel according to any one of the above.   A slab cooling support guide device and / or a drawing / bending device equipped with a molten steel crushing device having a cooling medium ejection mechanism and a cooling medium supply mechanism, wherein the cooling medium ejection mechanism is a cooling device in the molten steel crushing device. A cooling medium pressurizing mechanism that pressurizes and supplies the cooling medium to the nozzle and the cooling nozzle, the cooling medium supply mechanism supplying the cooling medium to the cooling medium pressurizing mechanism, and an outlet of the cooling nozzle Is a slab cooling support guide device and / or a drawing / bending device, wherein the slab cooling support guide device and / or the drawing / bending device are open along the outer surface of the slab. 6. The slab cooling support guide device and / or drawing / bending device according to claim 5, wherein the cooling medium is water or water and gas.

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