JP3903497B2 - Method and apparatus for preventing floating of debris in vacuum degassing tank - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for preventing a brick from being raised due to joint cracks in a brick in a vacuum degassing tank.
[0002]
[Prior art]
The vacuum degassing method includes an RH method and a DH method. The RH method and the DH method are exactly the same in that the molten steel sucking mechanism is different and the molten steel is sucked into the vacuum chamber and vacuum refining is performed. Therefore, the RH method will be described here. FIG. 7 is a schematic diagram of an RH type vacuum degassing apparatus. A vacuum degassing tank (hereinafter referred to as a degassing tank) 1 has two dip tubes 3 a and 3 b at the lower part thereof, and these two dip tubes 3 a and 3 b are immersed in the molten steel 5 of the molten steel pan 4. Then, the gas inside the degassing tank 1 is sucked from the exhaust pipe 7 formed in the upper part of the degassing tank 1 to make the degassing tank 1 vacuum. Thereafter, the molten steel 5 is sucked into the degassing tank 1 through the dip tube 3a using the pressure difference from the atmospheric pressure, and Ar gas G which is an inert gas is blown from the dip tube 3a. Thereby, the molten steel 5 is circulated in the direction of the arrow 2 through the path of the dip tube 3a → degassing tank 1 → immersion tube 3b, and the molten steel 5 is stirred and mixed in the degassing tank 1 by the Ar gas G. 5 is decarburized, degassed, deoxidized, and inclusions floated to refine the molten steel.
[0003]
5 and 6 are a longitudinal sectional view and a bottom view of a conventional degassing tank 1 used in the RH method. The degassing tank 1 is composed of an upper lid 1a, a body tank 1b, and a lower tank 1c, and has two dip tubes 3a and 3b that take in and discharge molten steel at the bottom of the lower tank. And the upper cover 1a, the trunk | drum tank 1b, and the lower tank 1c are joined by the flange F among each. Each of the upper lid 1a, the trunk tank 1b, and the lower tank 1c has a structure in which an indeterminate refractory material and a refractory brick 11 are lined with a predetermined thickness inside the iron shell 10, respectively. Of these, the lower tank. 1c, reflux condenser 9a on the lower surface thereof, and 9b is formed, the dip tube 3a thereto, 3b are joined by a flange F _3. The dip tubes 3a and 3b have a structure in which an amorphous refractory layer is formed on the outside of the tube and a fixed refractory brick is lined on the inside of the tube, and a flange is attached to one end of the tube. Reference numeral 12 denotes a tank fixing bracket.
[0004]
Although not shown in the drawing, the dip tube 3a has a large number of Ar gas blowing pipes embedded therein, and Ar gas can be blown into the molten steel rising inside the dip tube 3a.
[0005]
In the degassing tank 1 having such a structure, in the degassing step of molten steel, as described above, the hot molten steel circulates in the lower tank 1c while being vigorously stirred by Ar gas bubbles. At this time, since the laying part 13 of the lower tank 1c is located between the dip pipe (molten steel riser pipe) 3a and the dip pipe (molten steel fall pipe) 3b, the molten steel flows vigorously. Brick is heavily worn. The brick of this laying part 13 is washed with molten steel at 1600 ° C. in the degassing process, and since the fluctuation of the thermal load is reduced to 800 ° C. during the rest period, the brick repeatedly expands and contracts, its horizontal joints, Cracks are likely to occur in vertical joints.
[0006]
When a crack occurs in the vertical joint, there arises a problem that the molten steel penetrates into the cracked portion and causes individual bricks constituting the floor portion 13 to float. For this reason, although it changes with operation conditions, it was necessary to replace the floor brick for every 400 to 500 charges.
[0007]
Japanese Utility Model Publication No. 64-30350 (Technology 1) and Japanese Utility Model Application Laid-Open No. 4-13037 (Technology 2) are disclosed as techniques for preventing the above-mentioned bricks from floating up. The technology 1 is “the floor brick is a land- approaching structure or a combination structure of doweled bricks”, and the technology 2 is “the upper part of the reflux tube of the degassing tank has the left and right sides from the inner side to the outer side. By constructing a cylinder by alternately placing a number of tall hexahedron bricks that are wedge-shaped wide and inclined from the upper side to the lower side, the left and right sides of the lower part of the reflux tube are A large number of wedge-shaped hexahedron bricks, which are wide and wide from the inner surface to the outer surface, are stacked in several stages to construct a cylinder. "
[0008]
[Problems to be solved by the invention]
In the degassing process of the molten steel, the inside of the tank is evacuated simultaneously with the start of the process, and the molten steel flows into the tank through the dip tube as the degree of vacuum increases. At this time, if the brick has joint openings or joint cracks, the joint is in a vacuum state, so the molten steel is inserted into the joints. Repeated degassing process increases the amount of bullion inserted, thereby raising the brick. If the brick is constructed as in the above technique 1 or technique 2, the life of the brick will be longer than that of the previous brick, but this will cause cracks in the horizontal and vertical joints of the brick. However, there is a problem that molten steel penetrates into the crack, expands the crack, and finally the brick rises.
[0009]
An object of the present invention is to provide a method and apparatus for preventing molten steel from entering a crack and solving the problem of the brick rising even if a crack occurs in the horizontal joint and vertical joint of the brick. .
[0010]
[Means for Solving the Problems]
The present invention achieves the above object by the following method and apparatus.
[0011]
In that method, an inert gas is supplied to the joint crack portion of the laying brick of the vacuum degassing tank having a pair of reflux pipes whose upper ends are opened inside the tank at the bottom of the tank, and the gap between the joint cracks is determined by the pressure in the tank. Is also maintained at a high positive pressure.
[0012]
In the above method, Ar gas may be used as the inert gas.
The apparatus is provided with an annular tube having a plurality of nozzle ports for discharging an inert gas around a reflux tube of a vacuum degassing tank having a pair of reflux tubes whose upper ends open inside the tank at the bottom of the tank, A pipe for supplying an inert gas is provided in the annular pipe.
[0013]
"Action"
Method: By supplying an inert gas to the joint crack portion of the laying brick in the vacuum degassing tank and maintaining the joint crack portion gap at a positive pressure, it is possible to prevent the molten steel from entering the joint crack portion gap. The brickwork will not be lifted.
[0014]
The use of Ar gas as an inert gas is convenient because Ar gas is used for stirring and mixing of molten steel and can be sufficiently secured in terms of quantity.
[0015]
Apparatus: Ar gas enters the annular pipe through the pipe and fills the horizontal joint where cracks are generated from a plurality of nozzle openings. If a crack occurs in the vertical joint, the Ar gas filled in the horizontal joint is discharged into the molten steel in the degassing tank through the crack in the vertical joint, and the molten steel is prevented from entering the cracked joint.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a longitudinal sectional view of a lower tank for carrying out the present invention, and FIG. 4 is a view taken along arrow BB in FIG. 1c is lower tank 10 steel shell of the lower tank 1c, F ₂ is the joint flange of the barrel tank, F ₃ is the joint flange of the dip tube. 20 is a lining side wall brick stacked inside the side wall of the iron skin 10, 21 is an opening for circulating the molten steel, 22 is an arc shaped brick arranged on the inner periphery of the opening 21, and 23 is an arc shaped molding. It is a fan-shaped cross-section shaped brick disposed on the outer periphery of the brick 22. A rectangular shaped brick 27 is disposed on the bottom surface of the lower tank other than the area occupied by the arc-shaped brick 22 and the fan-shaped cross-section brick 23. The arc-shaped molded brick 22, the fan-shaped cross-section molded brick 23, and the molded brick 27 that form the bottom surface of the lower tank are collectively referred to as a spread brick 13.
[0017]
About 2 mm thick fireproof coating material is applied to the mating surface of each adjacent brick 13, or about 2 mm thick ceramic paper is interposed. The refractory coating material and the ceramic paper form a horizontal joint 25 and a vertical joint 26. 24a is a fireproof coating material that fills the space formed between the lower iron skin 10 and the brick 13; 24b is a fireproof coating that fills the space between the middle brick 13 and the iron skin 10; It is a material.
[0018]
In the lower tank 1c configured as described above, in order to supply the inert gas to the horizontal joint 25 and the vertical joint 26 of the brick 13, the following piping means is provided. This will be described with reference to FIGS.
[0019]
Annular pipes 30 and 30 are respectively disposed through the fireproof coating material 24a on the iron shell 10 side and the fireproof coating material 24b at the center so as to surround the two openings 21 and 21 for circulating the molten steel. It is. As shown in FIG. 2, the annular tube 30 is provided with a plurality of nozzle ports 30a for discharging an inert gas. Although FIG. 2 shows an example in which the number of nozzle openings 30a is four, five or more nozzle openings may be provided. A part of the annular pipe 30 interferes with the formed bricks 22, 23, 27. In this part, the corresponding formed bricks 22, 23, 27 are divided and processed, and the gap is filled with a fireproof coating material. .
[0020]
A supply pipe 31 is connected to the steel pipe 10 side of the annular pipe 30, and this supply pipe 31 is attached to the inert gas main pipe 32 so as to be removable through the core 10. As the annular tube 30, an easily machined small diameter copper tube (outer shape: 5 to 6 mm, inner diameter: 2 to 3 mm) provided with a plurality of nozzle ports of 1.5 to 2 mmφ is used.
[0021]
Since it is difficult to predict when cracks will occur in the horizontal joints 25 and vertical joints 26 of the brick 13, the annular pipe 30 with the supply pipe 31 is the first brick so that cracks may occur at any time. It is disposed at the time of loading and is connected to the inert gas main pipe 32 from the beginning of use of the lower tank 1c.
[0022]
The mounting position of the annular pipe 30 is selected in order to minimize division processing of the brick 13 that interferes in the middle, and the mounting position of the annular pipe 30 may be set higher than the mounting position.
[0023]
If comprised as mentioned above, the inert gas supplied to the annular pipe will fill the horizontal joint where the crack has occurred from the plurality of nozzle openings, and if the vertical joint cracks, the horizontal joint will be filled. Ar gas is discharged into the molten steel in the degassing tank through the crack in the vertical joint, and the molten steel is prevented from entering the cracked joint.
[0024]
【The invention's effect】
According to the present invention, when the cracks generated in the horizontal joint and the vertical joint of the floor brick continue, the inert gas is discharged into the molten steel inside the vacuum degassing tank through the vertical joint, so that the molten steel penetrates into the vertical joint. Can be prevented. As a result, the replacement period can be greatly extended as compared with the conventional construction bricks, and the repair cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal cross-sectional view showing a state in which an inert gas supply annular pipe is disposed inside a brick of a lower tank according to the present invention.
FIG. 2 is a perspective view of an annular tube for supplying an inert gas according to the present invention.
FIG. 3 is a longitudinal sectional view of a lower tank.
4 is a cross-sectional view taken along the line BB in FIG.
FIG. 5 is a longitudinal sectional view of a vacuum degassing tank.
6 is a cross-sectional view taken along the line AA in FIG.
FIG. 7 is a schematic view of an RH type vacuum degassing tank.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vacuum degassing tank 1c Lower tank 3a, 3b Immersion pipe 10 Iron skin 13 Cover brick 20 Side wall brick 21 Opening 22 for circulating molten steel Arc-shaped brick 23 Fan-shaped cross-section brick 24a, 24b Fireproof coating material 25 Horizontal joint 26 Vertical joint 27 Cuboid shaped brick 30 Annular pipe 31 Supply pipe 32 Inert gas main pipe

Claims (3)

Inert gas is supplied to the joint cracks of the laying brick of the vacuum degassing tank having a pair of reflux pipes whose upper ends are open inside the tank at the bottom of the tank, and the positive pressure is higher than the pressure in the tank. A method for preventing the rising of bricks in a vacuum degassing tank. The method of claim 1, wherein the inert gas is Ar gas and the brick debris floating prevention method of the vacuum degassing tank. An annular tube having a plurality of nozzle ports for discharging an inert gas is disposed around the reflux tube of the vacuum degassing vessel having a pair of reflux tubes whose upper ends are open to the inside of the vessel at the bottom of the vessel. An anti-brick lift device for vacuum degassing tanks, which is provided with piping to supply inert gas.

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