JP2008238201A - Cooling grid apparatus for continuous caster, and method for producing continuously cast slab - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To impart a cooling function even to a wear-plate portion when supporting a cast slab just below a mold by a cooling grid system. <P>SOLUTION: The wear-plate 10 is provided with a cooling mechanism for extracting the heat. That is, a porous metallic body 11 is embedded as a cooling-water supply mechanism in the inner part of the wear-plate 10, so that the cooling-water is introduced into the porous metallic body 11 inside the wear plate 10 through an introducing pipe 14A and is discharged to the outside through a dischrge pipe. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cooling grid device for a continuous casting machine and a method for producing a continuous cast slab.

  In continuous casting of steel, molten steel poured from a ladle into a tundish is poured into a water-cooled mold through an immersion nozzle installed at the bottom of the tundish, and then the solidified shell formed by the mold is encircled. As the slab is cooled, it is continuously drawn below the mold to produce a continuous cast slab.

  In this case, first, in the mold, the molten steel is removed by contact with the mold to form a solidified shell. Thereafter, the slab that has passed through the mold is pulled out in the casting direction by a pinch roll while being supported by a slab support / guide device including a guide roll, a cooling grid, a cooling plate, and the like. By being supported by the slab support / guide device, swelling of the slab in the thickness direction (referred to as “bulging”) is prevented.

  This slab support / guide device includes spray nozzles such as water spray nozzles and air mist spray nozzles (hereinafter simply referred to as “spray nozzles” means both water spray nozzles and air mist spray nozzles). The slab is pulled out while being cooled by the cooling water sprayed from the spray nozzle, and eventually solidification to the center is completed. Then, it cut | disconnects to predetermined length with the slab cutting machine installed in the machine end of the continuous casting machine, and a continuous casting slab is manufactured.

  By the way, in recent years, in order to reduce the manufacturing cost, improvement of productivity has been demanded more than ever, and in the continuous casting process, the speed of the production line, that is, the drawing speed of the slab is increased. . In order to realize the high drawing speed, various problems need to be solved, and among them, a technique for cooling the slab more efficiently is required.

  Under high-speed casting, the thickness of the solidified shell immediately below the mold becomes thin, and this solidified shell breaks and breaks out, or the solidified shell does not break. Due to the pressure, bulging occurs, causing the molten steel surface in the mold to fluctuate up and down, causing mold powder to be caught in the solidified shell and causing a quality defect. That is, there is a demand for a method for efficiently cooling a slab immediately below the mold while supporting the slab so that bulging does not occur.

  Conventionally, methods for supporting a slab directly under a mold are roughly classified into three types: a roll method, a cooling plate method, and a cooling grid method (for example, see Non-Patent Document 1).

  In the roll method, a spray nozzle is installed in the gap between adjacent rolls, and the slab is supported by the roll while being cooled by the spray nozzle. In this case, from the standpoint of cooling the slab, it is desirable to increase the roll diameter to increase the roll interval and widen the area of the slab that is water-cooled. Since it spreads, there is a problem that it becomes easy to bulge. Moreover, since it supports with a roll, ie, a wire | line, there also exists a fundamental problem that the support area of a slab is small compared with the other two systems supported by a surface.

  In the cooling plate method, the entire width direction of the slab is supported by a single plate. This plate is cooled with water to cool the slab indirectly, and water is directed from the surface of the plate toward the slab. It has a function to blow out and directly cool the slab. Thus, in the cooling plate method, the entire width direction of the slab is supported by one large plate, which is a very effective method for preventing bulging of the slab, but the area for directly cooling the slab is small. Since it is small, there is a problem that the cooling efficiency of the slab is poor. In addition, when breakout occurs, there is no escape point for steam generated after the water sprayed from the plate surface cools the slab, so that steam explosion occurs and there is a problem in operation. Furthermore, since the plate is large and has an integral structure, it is also a big problem that processing and repair are difficult (see, for example, Patent Document 1).

The cooling grid method uses a cooling grid composed of a wear plate for supporting the slab and a spray nozzle installed in the gap between the wear plates, and a large number of staggered wear plates are cast. The slab is directly cooled by a large number of spray nozzles, ensuring both the support area of the slab and at the same time ensuring the direct cooling area of the slab ( For example, see Patent Document 2 and Patent Document 3.
Miyoshi et al., Iron and Steel, Vol. 60 (1974) No. 7, p. 860-867 JP-A-57-25268 Japanese Patent Laid-Open No. 2002-120054 Japanese Utility Model Publication No. 6-23647

  However, after reviewing the current cooling grid system equipment, the current cooling grid system mainly cools the slab with cooling water supplied from a spray nozzle installed in the gap between adjacent wear plates. When the wear plate for supporting the slab comes into contact with the surface of the slab, the contact portion between the slab and the wear plate is not exposed to cooling water. The problem of being sufficient was found.

The wear plate itself is not cooled by water, but is indirectly cooled by the spray water sprayed from the spray nozzles installed in the gap between the wear plates. Therefore, the contact portion of the slab with the wear plate is indirectly indirect by the wear plate. It becomes cooling.
In the cooling grid method, the area occupied by the wear plate is about 40%, that is, the area of about 40% is not directly cooled by the spray water. In the cooling grid method, since the cooling water does not hit the wear plate part, there is a problem that uniform cooling cannot be performed in the slab width direction, and there is a possibility that the slab surface may crack. It was.

  The present invention has been made in view of the above circumstances, and in carrying out the slab support directly under the mold by the cooling grid method, the wear plate portion is also provided with a cooling function and has a lower water volume than cooling by water injection. It is an object of the present invention to provide a cooling grid device for a continuous casting machine and a method for producing a continuous cast slab, which can cool the slab and has excellent slab cooling capacity.

  In order to solve the above-described problems, the present invention is installed directly under a mold of a continuous casting machine, and includes a wear plate for supporting the slab and a spray nozzle for spraying a cooling medium onto the slab. A cooling grid device for a continuous casting machine, wherein the wear plate is provided with a cooling mechanism for removing heat from the slab.

  In the above configuration, preferably, the cooling mechanism includes a porous metal body disposed on the wear plate, and a cooling medium supply / discharge mechanism that supplies and discharges the cooling medium to the porous metal body. In this case, the wear plate may be configured to have a plurality of diversion channels for diverting and flowing a cooling medium therein, and the porous metal body is disposed so as to be exposed on the slab side of the wear plate. Thus, the cooling refrigerant may be directly sprayed on the slab. Further, the wear plate may have a cooling medium branch path adjacent to the porous metal body, and the porous metal body includes a plurality of divided bodies, and the space between the divided bodies. Further, a configuration in which a gap is formed may be used.

  The present invention is also characterized in that a continuous casting machine equipped with a cooling grid device for a continuous casting machine is used, and in addition to the spray nozzle of the cooling grid device, the slab is cast while being cooled by a wear plate. A method for producing a continuous cast slab is provided.

According to the present invention, the cast slab can be efficiently cooled, and at the same time, the cooling in the cooling grid apparatus that has been non-uniform can be made uniform. As a result, it is possible to prevent the surface crack of the slab caused by the non-uniform cooling that has occurred so far.
As a result, even in continuous casting operations where the slab drawing speed has been increased in recent years, it has been possible to stably cast high-quality slabs without causing operational troubles, and industrially beneficial effects. Is brought about.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
(First embodiment)
FIG. 1 is a view showing a first embodiment of the present invention, and is a schematic view of a continuous casting machine provided with a cooling grid device according to the present invention. 2 is an enlarged perspective view of the cooling grid device in FIG.

  As shown in FIG. 1, a continuous casting machine 1 is provided with a mold 5 for cooling and solidifying molten steel 17 to form an outer shell shape of a cast piece 18. A tundish 2 for relaying and supplying molten steel 17 supplied from a ladle (not shown) to the mold 5 is installed. On the other hand, below the mold 5, a cooling grid device 6 is installed directly below the mold 5, and a plurality of opposing slab support rolls 7 are installed below the cooling grid device 6.

  The cooling grid device 6 and the slab support roll 7 are slab support / guide devices for guiding the slab 18 drawn out from the mold 5 while supporting the slab 18 downward. A pinch roll (not shown) for pulling out is included. A spray nozzle such as a water spray nozzle or an air mist spray nozzle is disposed in the gap between adjacent slab support rolls 7, and the slab 18 is cooled while being pulled out by the cooling water sprayed from these spray nozzles 12. The

  A sliding nozzle 3 for adjusting the flow rate of the molten steel 17 injected from the tundish 2 into the mold 5 is installed at the bottom of the tundish 2, and the molten steel 17 is injected into the mold 5 at the lower surface of the sliding nozzle 3. An immersion nozzle 4 made of a refractory material is installed. A plurality of transport rolls 8 for transporting the cast slab 18 are installed on the downstream side of the slab support roll 7. Above the transport roll 8, the cast slab 18 is cast. A slab cutting machine 9 for cutting a slab 18a having a predetermined length is disposed.

  As shown in FIG. 2, the cooling grid device 6 includes a large number of staggered wear plates 10 for supporting the slab 18 and water installed in the gaps between the adjacent wear plates 10. And a spray nozzle 12.

  In FIG. 2, the cooling grid device 6 is shown only in a part of the slab 18 in the width direction, but the cooling grid device 6 is installed over the entire width of the slab 18. The wear plate 10 is usually made of cast steel or cast iron.

  In FIG. 2, the water spray nozzle 12 is installed in the gap between the adjacent wear plates 10, but the water spray nozzle 12 is not necessarily used, and an air mist spray nozzle may be used.

  Moreover, although the wear plate 10 shown in FIG. 2 is a rectangular shape, it may be a lattice type as shown in Non-Patent Document 1. The point is that the wear plate 10 may have any shape as long as the support area of the slab 18 by the wear plate 10 is 20 to 60% and other parts can be cooled by the spray nozzle. Absent.

  Further, the wear plate 10 shown in FIG. 2 has a width of about 60 mm and a length of about 200 mm. However, there is no problem even if a plate having a length shorter than 200 mm exists due to the staggered arrangement. .

  Further, the installation length of the cooling grid device 6 in the casting direction is not particularly limited, and may be any number as long as at least the wear plates 10 are arranged in a staggered manner in the casting direction. However, since the cooling grid device 6 is originally a device that supports the slab 18 directly under the mold, a length of 3 m or more is not required.

3A is a front sectional view of the wear plate according to the first embodiment of the present invention, and FIG. 3B is a side sectional view thereof.
In the present embodiment, wear plate 10 includes a cooling mechanism for removing heat from the slab. That is, the porous metal body 11 is embedded in the wear plate 10, and the cooling water is introduced into the porous metal body 11 inside the wear plate 10 through the introduction pipe 14A as a cooling water supply / discharge mechanism. And discharged through the discharge pipe 14B.

The porous metal body 11 used in the present embodiment is a cooling device having excellent heat removal performance. The porous metal body 11 may be manufactured by any method such as a sintered metal or a fired metal as long as the pores are continuous and have water permeability.

  The porous metal body 11 is generally made of copper or bronze, which is generally a material having high thermal conductivity, but other materials can also be used. A plurality of materials may be used.

  Although the cooling characteristics when the cooling water flows are changed depending on the pore diameter, material filling rate, and particle / fiber diameter of the porous metal body 11, the cooling characteristics necessary for cooling the wear plate 10 of the cooling grid device 6 are satisfied. Decide these as far as you want.

  The heat removal principle of the porous metal body 11 is heat transfer using nucleate boiling of water. When heat is transferred from the heat transfer surface to the inside of the porous metal body 11, high heat extraction is realized by increasing the heat transfer area with water. Moreover, since heat removal efficiency is good, it has the characteristic that heat removal with a low amount of water is possible. In addition, since there is a material between the pores, bubbles generated by nucleate boiling are connected and it is difficult to become a film boiling region where heat transfer efficiency is poor. Therefore, high heat removal with a small flow rate can be realized by using the porous metal body.

  In the present invention, the porous metal body 11 installed inside the wear plate may be an integral body or may be divided. Moreover, you may combine the porous metal body 11 from which a material, a pore diameter, and a filling rate differ.

  In FIG. 3, the porous metal body 11 is installed in the vertical direction with respect to the wear plate 10, but it may be in the vertical direction or in an oblique direction.

  Using the continuous casting machine 1 having such a configuration, the molten steel 17 retained in the tundish 2 is injected into the mold 5 through the immersion nozzle 4 while adjusting the flow rate by the sliding nozzle 3. The molten steel 17 injected into the mold 5 is cooled in contact with the mold 5 to form a solidified shell 19. While maintaining the molten steel surface position in the mold 5 at a substantially constant position, the slab 18 having the surface as the solidified shell 19 and the inside as the unsolidified phase 20 is continuously drawn below the mold 5 to continuously cast the molten steel 17. carry out. The slab 18 from which the mold 5 has been drawn is cooled while being supported by the cooling grid device 6 and the slab support roll 7, and eventually solidifies completely to the inside. The amount of cooling water sprayed from the water spray nozzle 12 installed in the cooling grid device 6 and the amount of cooling water sprayed from the spray nozzle installed in the gap between the slab support rolls 7 are not particularly specified. The optimum range is appropriately set according to the steel type to be cast and the drawing speed of the slab. The slab 18 to be cast is cut by the slab cutting machine 9 to produce a slab 18a having a predetermined length.

  In such casting, the slab 18 is cooled by using the cooling grid device 6 having the above-described configuration, that is, the slab is cooled not only by the water spray nozzle 12 but also by the wear plate 10 while the slab is cooled. As a result, the slab 18 can be efficiently cooled, and at the same time, the cooling in the cooling grid device 6 that has been non-uniform can be improved. It becomes possible to prevent the surface cracking of the slab 18 resulting from the non-uniform cooling that has occurred so far.

(Second Embodiment)
FIG. 4A is a front sectional view of a wear plate according to a second embodiment of the present invention, and FIG. 4B is a side sectional view thereof.
In the present embodiment, the wear plate 10 has a plurality of branch channels 31 in which cooling water is shunted and allowed to flow.

  That is, a plurality of branch channels 31 are provided inside the wear plate 10, and the porous metal body 11 is installed in each branch channel 31. The cooling water that has entered from the introduction pipe 14A flows into the porous metal body 11 through the branch flow path 31 therein, merges again, and is then discharged outside through the discharge pipe 14B.

(Third embodiment)
FIG. 5 (A) is a front sectional view of a wear plate according to a third embodiment of the present invention, and FIG. 5 (B) is a side sectional view thereof.
In the present embodiment, the porous metal body 11 is disposed so as to be exposed on the slab side of the wear plate 10, whereby the cooling water is directly blown onto the slab.

  That is, the porous metal body 11 is exposed on the surface of the slab and is in direct contact with the slab. In this case, the cooling water that has entered from the introduction pipe 14A flows to the porous metal body 11, and the slab is sprayed with fine mist-like cooling water, which is cooled by the evaporation heat of the water.

(Fourth embodiment)
FIG. 6 (A) is a front sectional view of a wear plate according to a fourth embodiment of the present invention, and FIG. 6 (B) is a side sectional view thereof.

In the present embodiment, wear plate 10 has a plurality of diversion channels 31 for diverting and flowing cooling water therein, and porous metal body 11 is disposed exposed on the slab side of wear plate 10. Thus, the cooling water is sprayed directly on the slab.

  That is, a plurality of branch channels 31 are provided inside the wear plate 10, and the porous metal body 11 is installed in each branch channel 31. The cooling water that has entered from the introduction pipe 14 </ b> A flows into the porous metal body 11 through the branch channel 31 therein.

  In addition, the porous metal body 11 is exposed on the surface of the slab, and is in direct contact with the slab. Fine mist-like cooling water is sprayed on the slab, and the evaporation heat of water Cooling.

(Fifth embodiment)
FIG. 7A is a front sectional view of a wear plate according to a fifth embodiment of the present invention, and FIG. 7B is a side sectional view thereof.
In the present embodiment, the wear plate 10 has a cooling water branch 32 adjacent to the porous metal body 11.

  That is, when installing the porous metal body 11 in the cooling channel water in the wear plate 10, the porous metal body 11 thinner than the thickness of the cooling channel is installed in contact with the surface on the slab side, A cooling water branch 32 is provided on the anti-slab side of the porous metal body 11. In this case, since the pressure loss in the cooling water channel is reduced, the flow rate of the cooling water can be increased.

(Sixth embodiment)
FIG. 8A is a front sectional view of a wear plate according to a sixth embodiment of the present invention, and FIG. 8B is a side sectional view thereof.
The porous metal body 11 is composed of a plurality of divided bodies, and a gap 33 is formed between the divided bodies.

That is, when the porous metal body 11 is divided and installed in the cooling water channel of the wear plate 10, a gap 33 is left between the porous metal bodies 11.
Depending on the conditions of the cooling target, the bubbles evaporated inside the porous metal body 11 are condensed in a water channel where the porous metal body 11 is not installed, and evaporate inside the next porous metal body 11. Thus, the nucleate boiling region can be used more effectively.

  The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the idea of the present invention.

It is a figure which shows 1st Embodiment of this invention, Comprising: It is the schematic of the continuous casting machine provided with the cooling grid apparatus which concerns on this invention. It is an expansion perspective view of the cooling grid apparatus in FIG. (A) is a front sectional view of a wear plate concerning a 1st embodiment of the present invention, and (B) is the side sectional view. (A) is a front sectional view of a wear plate concerning a 2nd embodiment of the present invention, and (B) is the side sectional view. (A) is a front sectional view of a wear plate concerning a 3rd embodiment of the present invention, and (B) is the side sectional view. (A) is a front sectional view of a wear plate concerning a 4th embodiment of the present invention, and (B) is the side sectional view. (A) is a front sectional view of a wear plate concerning a 5th embodiment of the present invention, and (B) is the side sectional view. (A) is a front sectional view of a wear plate concerning a 6th embodiment of the present invention, and (B) is the side sectional view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Continuous casting machine 2 Tundish 3 Sliding nozzle 4 Immersion nozzle 5 Mold 6 Cooling grid apparatus 7 Cast piece support roll 8 Conveyance roll 9 Cast piece cutting machine 10 Wear plate 11 Porous metal body 12 Water spray nozzle 14A Inlet pipe 14B Exhaust pipe 18 Casting 19 Solidified shell 20 Unsolidified phase 31 Minute flow path 32 Branching path 33 Gap

Claims (7)

A cooling grid device for a continuous casting machine, which is installed immediately below the mold of the continuous casting machine, and includes a wear plate for supporting the slab and a spray nozzle for spraying a cooling medium onto the slab,
A cooling grid device for a continuous casting machine, wherein the wear plate is provided with a cooling mechanism for removing heat from the slab. The cooling mechanism is
A porous metal body disposed on the wear plate;
A cooling grid device for a continuous casting machine according to claim 1, further comprising a cooling medium supply / discharge mechanism that supplies and discharges the cooling medium to and from the porous metal body.   The cooling grid device for a continuous casting machine according to claim 2, wherein the wear plate has a plurality of diversion channels for diverting a cooling medium into the wear plate.   4. The continuous casting machine according to claim 2, wherein the porous metal body is disposed so as to be exposed on a slab side of the wear plate, and thereby the cooling refrigerant is sprayed directly on the slab. 5. Cooling grid device.   The cooling grid device for a continuous casting machine according to claim 2, wherein the wear plate has a branch path for a cooling medium adjacent to the porous metal body.   The cooling grid device for a continuous casting machine according to claim 2, wherein the porous metal body is composed of a plurality of divided bodies, and a gap is formed between the divided bodies.   While using the continuous casting machine provided with the cooling grid apparatus for continuous casting machines of any one of Claims 1 thru | or 6, in addition to the spray nozzle of the said cooling grid apparatus, cooling a slab also with a wear plate A method for producing a continuous cast slab characterized by casting.

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