JP2000202593A - Seal material for preventing leakage of molten steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal material preventing the leakage of molten steel, which has the sealness for preventing the leakage of the molten steel from the starting time of continuously casting the molten steel to the starting time of drawing out a cast slab and with which the defective working of a pump for cooling water, etc., can be reduced because the excess load at the starting time of drawing out is not developed to a solidified shell. SOLUTION: The seal material 10 for preventing the leakage of the molten steel which is inserted into a gap 17 between a dummy bar head 15 set in a mold 13 and the inner wall of a mold 13 at the starting time of continuously casting the molten steel 12, includes air or a oxidizing agent in the inner part thereof and composed of combustible material consisting essentially of paper, pulp, combustible fiber or wood piece, etc., and provided with the sealness for preventing the leakage of the molten steel 12 from the gap 17 at the starting time of pouring the molten steel 12 and the combustiblity which collapses the seal material by burning and carburizing in the interval after the molten steel 12 prevented from the leakage solidifies, till the starting time of drawing out the solidified cast slab.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing material for preventing molten steel from leaking from a gap between a dummy bar head and an inner wall of a mold at the start of casting.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, at the start of continuous casting of molten steel 50, a dummy bar head 51 for pulling out a tip of a slab and a mold 52 for cooling supplied molten steel 50 are provided. In order to prevent the molten steel 50 from leaking from the gap 53, the non-combustible sealing material 54 made of a refractory material or the like is used.
Is filled in advance, and then the molten steel 50 is supplied into the mold 52 via the immersion nozzle 55 to start continuous casting. Then, in order to increase the strength of the solidified shell (shell) 56, a cold material made of a small piece of iron or the like is previously arranged at the tip of the dummy bar head 51, and the molten steel 50
Is generally employed to maintain the connection state well.

[0003]

However, in the case of the prior art, the mold 52 is provided with a taper that reduces the diameter in the casting direction, and a non-combustible sealing material 54 made of a refractory material is used. Since the sealing material 54 remains as a solid in the gap 53 between the mold 51 and the mold 52, the sealing material 54 becomes an obstacle, and when the dummy bar head 51 is moved to pull out the tip of the slab from the mold 52, the molten steel 5
An excessive load is applied to the portion of the solidified shell 56 formed by solidification of 0. Therefore, the dummy bar head 51 and the solidified shell 5
There has been a problem that the joint with the steel sheet 6 is separated to interrupt the casting, or the solidified shell 56 is broken, and the molten steel 50 leaks from the shell. Further, there is a problem that the sealing material 54 remaining in an unburned state mixes into the drainage of the cooling water, causing a malfunction of a drainage pump for circulating or removing the cooling water. The present invention has been made in view of such circumstances, and has a sealing property to prevent leakage of molten steel from the start of continuous casting of molten steel to the start of drawing of a slab, and to apply an excessive load at the start of drawing to a solidified shell. It is an object of the present invention to provide a sealing material for preventing molten steel from leaking, which is capable of extinguishing (or reducing) the operation failure of a drainage pump, etc.

[0004]

According to the present invention, there is provided a sealing material for preventing molten steel from leaking, comprising a combustible material containing air or an oxidizing agent therein. This can promote the combustion of the combustible material when it is arranged in the gap where the inflow of air from the outside is restricted. The flammable material containing air or an oxidant inside has a sealing property to prevent leakage of molten steel from a gap between the dummy bar head and the inner wall of the mold at the start of molten steel injection and a high temperature between the start of drawing of the slab. Since it has flammability that burns and collapses due to the heat of the molten steel, it is possible to prevent leakage of the molten steel, and solid matter that becomes an obstacle at the time of drawing the slab from the lower part of the mold does not remain in the gap and solidified. It can be pulled out without applying an excessive load to the part of the brittle solidified shell. At the start of molten steel injection, the sealing property that prevents the leakage of molten steel from the gap depends on the length of the solidified ingot of molten steel that adheres to the periphery of the slab tip pulled out from the lower part of the mold, the frequency of molten steel leakage, etc. Can be evaluated. In addition, the combustibility of burning, carbonizing, and collapsing until the start of drawing of the solidified slab is dependent on the amount of solid matter remaining on the periphery of the tip of the slab to be drawn and the pulling force required to pull out the dummy bar. It can be evaluated according to the size and the like.

[0005] Here, the combustible material may be a paper material having a porosity necessary for maintaining the flammability. In this case, the necessary sealability and flammability as a sealing material for preventing molten steel leakage are properly adjusted according to the holding time from the start of casting to the start of drawing and the degree of the gap between the dummy bar head and the inner wall of the mold. The porosity can be adjusted in a state of being balanced. In addition, the combustibility is adjusted by impregnating the combustible material with a combustible oil, for example, kerosene, light oil, oil or the like in a predetermined amount, for example, in a range of 2% by weight or more and 50% by weight or less. Combustion can be facilitated. Further, a number of spaces filled with air are formed in the combustible material, and the spaces are filled with a predetermined amount, for example, 10
% Or more and 80% or less, the combustibility of the combustible material can be further enhanced. Further, the combustible material may be provided with a hole or a space through which gas generated by carbonization or combustion escapes to adjust the combustion state of the molten steel leakage prevention seal material.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIGS. 1 (a), (b), (c)
FIG. 2 is an explanatory view of a method of using a sealing material for preventing molten steel leakage according to an embodiment of the present invention, FIG. 2 is an explanatory view of a method of manufacturing corrugated paper, and FIG. 3 shows the relationship between the temperature of the sealing material and the molten steel holding time. FIG. 4 is a graph showing the relationship between the gap between the inner wall of the mold and the dummy bar head and the ingot.

As shown in FIGS. 1 (a) to 1 (c), a continuous casting apparatus 11 to which a sealing material 10 for preventing molten steel from leaking according to an embodiment of the present invention is used. A mold 13 that is arranged to be reduced in the casting direction according to the amount and water-cools the supplied molten steel 12 from the surroundings,
A dummy bar head 15 arranged to close the bottom in the mold 13 and pulled down with the lower end of the slab having the solidified shell 14 of the molten steel 12 in a connected state, and arranged above the mold 13 during continuous casting, And a submerged nozzle 16 for supplying the molten steel 12 into the mold 13.

[0008] The sealing material 10 for preventing molten steel leakage is a small plate-like piece inserted so as to close the gap 17 between the inner wall of the mold 13 and the dummy bar head 15 and is made of corrugated paper 20 which is an example of a combustible material. . As shown in FIG. 2, the corrugated paperboard 20 is formed by corrugating a thick cardboard 21 suitable for a material such as a lightweight daily necessity, a container for containing foodstuffs, and a pattern paper for work. Flat paper material 22 on one side
Are laminated paper having a predetermined strength. The corrugated paperboard 20 thus formed is a corrugated paperboard 2
Since a large number of spaces 23 for holding air serving as an oxygen source are provided between the flat paper material 1 and the flat paper material 22, the paper material suitable for securing the flammability as the molten steel leakage prevention seal material 10 is provided. Material. Here, small pieces of the corrugated paper 20 having a thickness of 2 to 5 mm are appropriately overlapped, and this is
into the gap 17 in the range of 2 mm while being compressed appropriately.
It is arranged so as to have a porosity necessary for providing necessary combustion properties and sealing properties. If this compression is excessive,
The porosity is insufficient, and the flammability in the subsequent start period (the period from the start of the injection of the molten steel 12 to the start of the drawing of the slab) becomes insufficient. Conversely, when the degree of compression is small, the sealing performance in the gap 17 is reduced, and the leakage of the molten steel 12 from the gap 17 is increased. For the above reasons, for example, if the porosity is 20% or more,
%, Preferably in a range of 30% or more and 70% or less.

It is also possible to insert a combustion aid such as an oxidizing agent or oil serving as an oxygen source into a part or all of the space 23 of the corrugated paperboard 20. Thereby, the ignitability can be improved and the required flammability can be secured. Further, alumina, silica,
By filling a suspension or colloid liquid containing a refractory component such as mullite, and drying and using the same, it is possible to adjust the sealability and the flammability to a required level. As a simpler method, the corrugated paperboard 20 can be immersed in a combustion aid such as flammable oil as it is, and then lifted up to remove the excess and leave the space 23 containing air.

In the present embodiment, a case where corrugated paper 20 is used as a flammable material for sealing material 10 for preventing molten steel from leaking will be described.
Contains oxidizer components such as air or manganese oxide inside, combustible fibers such as polyester, nylon, cotton, silk, paper,
A material mainly composed of pulp or wood pieces may be used. If you want to let air inside,
It is preferable to form a large number of communicating holes, spaces, grooves and the like inside or outside of the combustible material. As a result, the air necessary for combustion is introduced from the outside, or the combustible material is ignited and burned by the air held in the space, thereby forming the gap 1.
7, the required flammability can be ensured. Further, the gas generated by carbonization or combustion is discharged to the outside via these holes and spaces, so that the combustibility is further improved.

The mold 13 is made of copper, for example, having a cooling water passage for cooling the molten steel 12 therein. The mold length is, for example, 700 to 900 mm, and the length of the long side at the upper end of the rectangular casting section is set. 120-400mm, short side length 1
It is a casting mold having a diameter of about 00 to 300 mm, and has a taper such that a casting cross section is reduced in the casting direction. For example, in the case of manufacturing a cast piece belonging to bloom, the length of the long side or the short side of the casting cross section is 0.5 mm or more with respect to the casting direction length of the mold 13 of 900 mm and 2
In the case of a slab belonging to a slab, the length of the long side or short side of the horizontal section is 3 mm or more with respect to the casting direction length of the mold of 900 mm and 6 mm.
It is a slope that contracts downward in the range of not more than mm.

[0012] As shown in FIG.
Has a deformed recess 24 formed in a horizontal direction in order to mechanically join the upper end portion and the lower end portion of the slab made of molten steel 12 solidified first. Is a connecting member for connecting the solidified cast slab tip portion at the deformed recess 24 and pulling it out in the vertical direction.

Next, a method of using the sealing material 10 for preventing leakage of molten steel applied to the continuous casting apparatus 11 will be described with reference to FIG. As shown in FIG.
As a preparation before the start of continuous casting, the dummy bar head 15 is arranged at a predetermined position in the mold 13. At this time, the gap 1 between the upper side surface of the dummy bar head 15 and the inner wall surface of the mold 13 is set.
The distance d of 7 is in the range of 3 to 10 mm. Next, about 2 to 3 small pieces of corrugated paper 20 having a thickness of 2 to 5 mm are overlapped and pressed into the gap 17 to be filled in a laminated and compressed state. Then, the coolant 26 such as iron powder and iron pieces is
The immersion nozzle 16 laid on the upper surface of the dummy bar head 15 and attached to the lower part of the tundish is installed at a predetermined position in the mold 13 to complete the preparation operation before molten steel injection. In some cases, it is possible to omit the use of such a coolant 26 and start continuous casting.

At the start of continuous casting as shown in FIG. 1B, the molten steel 12 is discharged at a predetermined flow rate through the discharge hole 25 of the immersion nozzle 16 by using a molten steel flow control device such as a sliding nozzle or a stopper head (not shown). Then, the molten metal surface 27 in the mold 13 is gradually raised to a predetermined position. During this time, the sealing material 10 for preventing the molten steel from leaking, the upper portion of which is covered with the coolant 26 and inserted into the gap 17.
Prevents leakage of molten steel 12 from gap 17. Then, since the molten steel leakage preventing seal material 10 is heated by the high-temperature molten steel 12, the temperature becomes higher than about 250 ° C. 10 to 40 seconds after the injection of the molten steel 12 is started, and combustion starts.

FIG. 3 shows a case where corrugated paper 20 is used as a combustible material (symbol: ○) and a case where cardboard 21 is used.
It is the graph which measured the temperature change of the sealing material in the case where (symbol: x) is used, respectively. As shown in FIG. 3, when the cardboard 21 having no space is used, the temperature 50 seconds after the start of pouring, which is the time of starting the drawing of the slab, is only about 120 to 130 ° C. It can be seen that combustion is difficult and the slab is kept unburned even after the start of drawing. On the other hand, when the corrugated paper 20 is used, after the start of injection, the upper end immediately reaches a temperature of about 250 ° C. or higher and combustion starts, and the combustion propagates downward. The temperature of the sealing material in FIG. 3 is measured at a position 15 mm below the upper end position of the sealing material in contact with the molten steel, and such a measured temperature is lower than the actual maximum temperature. In addition, the ignition point is the spontaneous ignition temperature under a condition where there is sufficient oxygen in the atmosphere,
The sealing material is inserted into the narrow gap, and the value becomes different under the condition where the supply of oxygen is restricted. In the results of this experiment,
The combustion of the sealing material has started in a combustion zone of about 250 ° C. or higher indicated by a broken line in FIG.

As shown in FIG. 1C, the corrugated paper 20
The molten steel leakage prevention seal material 10 using flammable material as a flammable material, by 40 seconds after the start of casting to start drawing the slab,
It disappears by combustion or is finally carbonized and remains in a collapsed state of extremely low strength. Therefore, molten steel 12
When the dummy bar head 15 mechanically fastened at the portion of the deformed recess 24 to the solidified lower end of the cast slab is moved in the casting direction to a position immediately below the inclined mold 13, a sealing material for preventing molten steel leakage. No excessive load is caused by the solid residue of 10 or the like. Therefore, it is possible to prevent troubles occurring in the early stage of casting such as breakage of the solidified shell 14 and leakage of molten steel due to the movement of the dummy bar head 15.

FIG. 4 shows the length h of the metal insert 28 at the start of pulling out the dummy bar head 15 which is an index of the sealing property of the sealing material 10 for preventing molten steel leakage (FIG. 1).
(C)) and the distance d of the gap 17 between the mold (MD) 13 and the dummy bar head (DB) 15 were determined by flammable corrugated paper 20 (symbol: ○) and cardboard 21 (symbol: ×). It is the graph each shown about the case where it was made into a material. As can be seen from FIG. 4, when the corrugated paperboard 20 is used, the length h of the ingot 28 increases sharply when the gap d of the gap 17 exceeds 8 mm, and when the cardboard 21 is used, The length h of the bullion 28 increases in a range where the distance d exceeds 15 mm. Thus, gap 1
When the distance d of 7 is 8 mm or less, the necessary sealing property can be maintained by using the sealing material 10 for preventing leakage of molten steel using the cardboard paper 20 as a flammable material. Moreover, the cardboard paper 20 in which the space 23 is formed can be ignited by the air or the oxidizing agent filled in the space 23 and can be burned until the drawing is started. Therefore, when using a submersible pump that circulates the cooling water during the continuous casting operation, it is possible to prevent troubles such as the remaining of the sealing material being suspended in the cooling water and causing the submersible pump to operate improperly.

On the other hand, when a pile of cardboards 21 having a small porosity and a high degree of filling is used as a sealing material for preventing the leakage of molten steel, even if the sealing property can be maintained, the casting is started. Even at the time of starting withdrawal after 40 seconds, it is difficult to perform combustion because a flow path for introducing air for combustion or air from the outside is not secured.
Therefore, the sealing material remaining in the unburned state in the gap 17 becomes a resistance, and the dummy bar head 15 is moved to the mold 13.
An excessive load is generated when the steel sheet is pulled downward from the bottom of the steel sheet, thereby increasing the frequency of troubles such as molten steel leakage in the early stage of casting. In addition, the residue of the sealing material is mixed in the drainage of the cooling water, which causes a malfunction of the pump.

The embodiment of the present invention has been described above. However, the present invention is not limited to this embodiment, and any change in conditions without departing from the gist is within the scope of the present invention. For example, in the present embodiment, an example in which corrugated paper is used as the combustible material has been described. However, wood powder obtained by grinding wood chips or the like adjusted to have a predetermined porosity when filled in a gap, or this wood powder It is also possible to use a mixture of a binder and a binder. Then, in order to adjust the flammability, while maintaining a predetermined amount of porosity, a combustible additive such as easily combustible oil or coal or an oxidizing agent serving as an oxygen source is contained therein, or a predetermined space is formed. Straws or pipe-like small pieces for this purpose may be dispersed.

[0020]

In the sealing material for preventing molten steel from leaking according to the first to fifth aspects, a combustible material containing air or an oxidizing agent is used. Thereby, the combustion of the combustible material in the case where it is arranged in the narrow gap where the inflow of air from the outside is restricted can be promoted. The combustible material has a sealing property that prevents the molten steel from leaking from a gap between the dummy bar head and the inner wall of the mold at the start of molten steel injection, and burns due to the heat of the molten steel at a high temperature until the start of drawing of the slab. And flammability that causes carbonization and collapse, so that leakage of molten steel can be effectively prevented, and solids and the like that become obstacles when the slab is pulled out from the lower part of the mold do not remain in the gaps and solidify. The part of the freshly solidified shell can be pulled out without applying an excessive load. In addition, operation failure of the drain pump can be suppressed.

In particular, in the sealing material for preventing molten steel from leaking, since the combustible material is a paper material having a porosity necessary to maintain its flammability, the sealing material for preventing molten steel from leaking is used. Can be adjusted to an appropriate state in which the necessary sealing properties and flammability are balanced. Further, in the sealing material for preventing molten steel from leaking according to the third aspect, the combustible material is impregnated with the combustible oil in advance, so that the combustibility can be easily improved. In the sealing material for preventing molten steel from leaking according to the fourth aspect, since a large number of spaces including air are formed in the combustible material, the combustibility of the combustible material can be further enhanced. In the sealing material for preventing molten steel from leaking according to claim 5, since the combustible material is provided with holes and spaces through which gas generated by carbonization or combustion escapes, air is discharged from the surroundings to the combustible material as the gas is discharged. Introduced, the flammability can be more efficiently improved.

[Brief description of the drawings]

1 (a), 1 (b) and 1 (c) are illustrations of a method for using a sealing material for preventing molten steel leakage according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a method for manufacturing corrugated paper.

FIG. 3 is a graph showing a relationship between a temperature of a sealing material and a molten steel holding time.

FIG. 4 is a graph showing a relationship between a gap between an inner wall of a mold and a dummy bar head and a metal insert.

FIG. 5 is an explanatory diagram of a usage state of a sealing material in a conventional example.

[Explanation of symbols]

Reference Signs List 10 sealing material for preventing molten steel leakage 11 continuous casting device 12 molten steel 13 mold 14 solidified shell 15 dummy bar head 16 immersion nozzle 17 gap 20 corrugated cardboard (flammable material) 21 cardboard 22 paper material 23 space portion 24 deformation dent 25 discharge hole 26 cooling Lumber 27 Hot surface 28 Bullion holder

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Fumiko Hirabayashi 1-3-1 Oya, Yawatahigashi-ku, Kitakyushu-shi, Fukuoka Prefecture Astec Irie Co., Ltd. (72) Inventor Kimoto ▲ Hiro ▼ Fukuoka Prefecture 1-3-1, Otani, Ward-ku Astec Irie

Claims (5)

[Claims] 1. A sealing material for preventing molten steel from leaking into a gap between a dummy bar head disposed in a mold and an inner wall of the mold at the start of continuous casting of molten steel. , Made of a flammable fiber, or a flammable material mainly composed of wood pieces, etc., at the start of the injection of the molten steel, a sealing property for preventing leakage of the molten steel from the gap, and after the molten steel solidified to prevent leakage is solidified. A sealing material for preventing molten steel from leaking, which has a combustibility of burning, carbonizing, and collapsing until the start of drawing of the solidified slab. 2. The sealing material for preventing molten steel from leaking according to claim 1, wherein the combustible material is made of a paper material having a porosity to maintain the flammability. 3. The sealing material according to claim 1, wherein said flammable material is impregnated with flammable oil. 4. The sealing material for preventing molten steel from leaking according to claim 1, wherein the combustible material has a plurality of spaces including air. . 5. The sealing material for preventing molten steel from leaking according to claim 1, wherein the combustible material is provided with holes and spaces through which gas generated by carbonization or combustion escapes. Seal material for preventing leakage.