KR19990054403A - Nozzle inside vacuum method and apparatus in twin roll sheet casting device - Google Patents

Abstract

The present invention is a twin roll type sheet casting apparatus for solidifying molten steel to produce a thin plate by releasing most of the heat into the roll by contacting the roll with molten metal supplied between the rolls, and the molten steel discharged through the nozzles installed between the rolls. In the nozzle and vacuum method and apparatus in a twin-roll thin plate casting apparatus for suppressing the defect of the slab by the gas mixed into the slab, that is, the gas mixed into the slab positively and the oxidation of the molten steel in the nozzle by the gas In order to prevent the inflow of external gas by installing a device around the upper nozzle that primarily blocks gas that can flow into the nozzle, the primary device can not completely block the inflow of gas, thus connecting the upper nozzle and the lower nozzle. Pump the gas flowing into the nozzle through the part gap with a vacuum pump Will the hayeoseo to keep the ball in ecology.

Description

Nozzle internal vacuum method and apparatus in twin roll sheet casting device

The present invention is a twin roll type sheet casting apparatus for solidifying molten steel to produce a thin plate by releasing most of the heat into the roll by contacting the roll with molten metal supplied between the rolls, and the molten steel discharged through the nozzles installed between the rolls. In the nozzle and vacuum method and apparatus in a twin-roll thin plate casting apparatus for suppressing the defect of the slab by the gas mixed into the slab, that is, the gas mixed into the slab positively and the oxidation of the molten steel in the nozzle by the gas It is about.

A schematic diagram of a general twin roll sheet casting process is shown in FIG. 1.

The molten steel 3 supplied between the pair rolls 1 through the immersion nozzle composed of the upper nozzle 5 and the lower nozzle 6 solidifies while losing heat in the direction of the center of the roll. The roll is released by the rotation of the twin roll 1.

In the prior art, Japanese Patent Laid-Open No. 7-68357 shows an example of the use of an immersion nozzle for a twin roll 1 type sheet casting apparatus, which is composed of an upper nozzle 5 and a lower nozzle 6. The molten steel 3 supplied from the tundish 4 is supplied to the lower nozzle 6 after passing through the upper nozzle 5, and the molten steel pool 3 between the pair rolls 1 through the discharge port of the lower nozzle 6. To be supplied.

In Japanese Laid-Open Patent Publication No. 7-68357, the gas inside the nozzle is raised as the molten steel in the lower nozzle 6 increases as the casting proceeds by processing a degassing hole in the nozzle and mounting a filler such as a wire rod between the holes. Is pushed up and out through the wire rod installed in the hole.

When the height of the molten steel reaches the hole position, the hole is automatically sealed by the solidification of the molten steel that passes through the wire rod, thereby obtaining a blocking effect from the outside air.

According to the conventional method as described above, as the molten steel height inside the nozzle is increased, the gas inside the nozzle may be discharged to some extent. However, when the nozzle length W1 is larger than 400 mm and the casting speed is about 70 mpm or more, it becomes difficult to fill the lower nozzle 6 with the molten steel 3.

Of course, opening the stopper 21 mounted on the initial tundish 4 as much as possible and increasing the inner diameter W2 of the upper nozzle 5 may raise the height of the molten steel accumulated in the lower nozzle 6 to a certain height. During the casting, it is difficult to control the height of the molten steel 3 between the pair rolls 1, so that it may take a considerable time to obtain a steady state casting condition or may cause an operation interruption.

In addition, in the case of the immersion nozzle consisting of the upper nozzle (5) and the lower nozzle (6) it is very difficult to be completely sealed conditions such as the connection portion of the upper and lower nozzles and the connection portion of the upper nozzle and the tundish (4).

However, in the case of casting, the lower nozzle (6) takes a negative pressure inside the nozzle, so if the nozzle is not completely sealed, the external gas (mainly air) continues to flow into the gap between the connecting parts, thereby making the inside of the lower nozzle (6) an oxidizing atmosphere. do.

Therefore, when the lower nozzle 6 is not completely filled by the molten steel 3, two bad effects can be caused in casting.

First, the upper nozzle 5 is gas entrapment into the molten steel which is generated by not being completely immersed by the molten steel 3 in the lower nozzle 6. The gas thus mixed is supplied to the molten metal pool 3 through the discharge port 17b of the lower nozzle 6 and may be mixed into the cast steel. In order to prevent gas mixing by the molten steel discharged from the upper nozzle 5, the minimum molten steel height in the lower nozzle 6 should be about 30 mm higher than the upper nozzle discharge port 17a. .

The second is oxidation of the molten steel inside the nozzle by the gas remaining inside the lower nozzle 6. The molten steel oxidized in this way becomes a scum-like material after being supplied to the molten pool, and then aggregates with each other to become large and mixed into the slab 2 in the middle of casting, thereby casting defects such as cracks in the slab. Will cause.

The present invention is installed around the upper nozzle to block the gas that can be introduced into the nozzle primarily to prevent the inflow of external gas, even if the primary device is not completely blocked the inflow of gas connection between the upper nozzle and the lower nozzle The purpose of the present invention is to produce a high quality product by pumping gas introduced into the nozzle through the part gap with a vacuum pump to maintain the inside of the nozzle in a vacuum state throughout the casting.

1: Schematic diagram of a twin roll continuous sheet casting device

2: Detailed view of the vacuum apparatus inside the nozzle

Figure 3: Top view of the excerpt of the middle cover and the brick

<Description of Symbols on Main Parts of Drawing>

1. Roll 2. Cast

3. molten steel 4. tundish

5. Upper Nozzle 6. Lower Nozzle

7. Gasket 8. Baffle

9. Middle cover 10. Top cover

11. pour box 12. pore box

13. Pipe 14. Lake

15. Maltar 16. Brick

17a. Upper nozzle outlet 17b. Lower Nozzle Toe Exit

18. Vacuum pump 19. Hole in middle cover

20.Edge Dam 21.Stopper

22. Gas Chiller 23. Well Block

24. Bracket W1. Lower nozzle length

W2. Upper nozzle inner diameter

The present invention is a hose to the pipe 13 installed through the pore box 12 and the mortar 15 and the upper cover 10 in order to prevent the gas intrusion into the molten steel and to discharge the gas already invaded to maintain a vacuum state 14 is connected to the end of the hose (14) by installing a vacuum pump 18, the operation of the vacuum pump 18, the gas invaded into the lower nozzle (6) pipe 13 and the hose (14) ) To maintain the inside of the lower nozzle (6) in a vacuum state by discharging to the outside, and the well block (23) in the tundish (4) in order to primarily prevent gas infiltration into the lower nozzle (6). A nozzle pore box 12 is installed around the upper nozzle 5 seated on the), and the pore box 12 is fixed to the pore box support 11 installed under the tundish 4, and the pore box 12 At the bottom, the lower nozzle 6 supporting bracket 24 is connected.

In addition, a pipe 13 connected to the vacuum pump 18 was also installed in the pore box 12 to maintain the inside of the pore box 12 in a vacuum.

A gasket 7 is installed between the bracket 24 and the pore box 12 to prevent external gas from entering.

Looking inside the lower nozzle 6, a baffle 8 is installed at the bottom, which minimizes the momentum of the molten steel discharged through the upper nozzle 5 outlet, that is, minimizes the turbulence of the molten steel and then lower nozzle ( 6) It is installed to supply molten steel to the discharge port 17b, and the upper nozzle is lowered to the upper part of the belly pool 8.

The middle cover 9 is installed at the top of the baffle 8, and the middle cover 9 is processed with a hole 19 as a passage for pumping the gas present in the lower portion of the middle cover.

The size of this hole 19 is enough about 5-20 mm in diameter.

Brick 16 is installed around the upper nozzle 5 of the upper part of the middle cover 9, The detail of this brick is shown in FIG.

The purpose of installing the brick 16 is that when the gas is completely pumped through the hole 19, the molten steel 3 is discharged through the hole 19 by the vacuum pumping pressure and comes out of the upper surface of the middle cover 9, and thus If the height of the molten molten steel (3) is lower than the height of the brick (16), the molten steel continues to accumulate on the upper surface of the middle cover, so that the heat of the molten steel is released to the outside while the molten steel accumulates, thereby securing the time required to solidify the molten steel. have.

Eventually, when the molten steel 3 is hardened, the lower region of the middle cover 9 is completely blocked from the outside and maintains a vacuum state, thereby preventing oxidation of the molten steel 3 in the lower nozzle 6 and mixing of gas into the molten metal pool. Will be.

In addition, by applying an adhesive material that withstands high temperatures such as mortar 15 on the upper surface of the upper cover 10, the gas flowing into the nozzle through the gap between the upper cover 10 and the lower nozzle 6 body. You can block.

Pipes (13) necessary to extract the vacuum is installed in two places directly below the pore box (12) and the top cover (10). The pipe 13 installed in the pore box 12 has a purpose to primarily pump the gas introduced into the pore box from the outside, and the pipe installed directly under the upper cover 10 is not found in the pore box 12. Secondly pump the gas which is not pumped and flowed in.

In particular, since the temperature of the gas pumped through the pipe 13 installed directly under the upper cover 10 is considerably high, this gas may cause problems in the operation of the pump if it is directly introduced into the vacuum pump 18.

Therefore, the gas cooling device 22 is installed in the middle of the pumping hose 14 for the purpose of lowering the temperature of the hot pumped gas.

The capacity of the vacuum pump 18 used as an apparatus for maintaining the vacuum in the nozzle is sufficient in the range of 0.5 to 3 kPa. Of course, the smaller the volume in the nozzle, the smaller the capacity of the vacuum pump 18 is.

The present invention as described above is installed around the upper nozzle to block the gas to be introduced into the nozzle primarily to prevent the inflow of external gas, even if the primary device is not completely blocked the flow of gas in the upper nozzle and lower By pumping the gas flowing into the nozzle through the gap between the connection part of the nozzle with a vacuum pump, the inside of the nozzle is maintained in a vacuum ecology, thereby producing a quality cast.

Claims (3)

The hose 14 is installed in the pipe 13 installed through the pore box 12 and the mortar 15 and the upper cover 10 to prevent gas intrusion into the molten steel and to discharge the gas that has already invaded to maintain the vacuum state. And a vacuum pump 18 is installed at the end of the hose 14 so that the gas invaded into the lower nozzle 6 by the operation of the vacuum pump 18 is connected through the pipe 13 and the hose 14. The inside of the lower nozzle (6) by discharging to the outside to maintain the inside of the vacuum vacuum nozzle method in the twin-roll thin plate casting. The gas cooling device 22 is installed in the middle of the hose 14 in order to cool the hot gas heat while discharging the gas infiltrated into the lower nozzle 6. A nozzle internal vacuum method in a twin-roll thin sheet casting apparatus. The nozzle pore box 12 is installed around the upper nozzle 5 seated on the well block 23 in the tundish 4 to prevent gas infiltration into the lower nozzle 6 primarily. The box 12 is fixed to the pore box support 11 installed under the tundish 4, and the lower nozzle 6 supporting bracket 24 is connected to the lower portion of the pore box 12. Edo vacuum apparatus in the nozzle in the twin-roll thin plate casting apparatus, characterized in that it is configured to maintain the vacuum inside the pore box 12 by installing a pipe (13) connected to the vacuum pump (18).