JPH0526591B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a continuous casting immersion nozzle used for casting molten metal from a tundish into a mold in continuous steel casting.

Prior Art A submerged nozzle used for the purpose of preventing oxidation of molten steel in continuous steel casting is used by being attached to a tundish in the state shown in FIG. 2, for example. That is, the immersion nozzle 9 is attached to the tundish via an upper nozzle 10 held by the tundish (not shown) and a sliding nozzle 6 connected to the upper nozzle. The sliding nozzle 6 consists of a fixed plate 7 and a sliding plate 8, and can control the flow rate of molten steel by adjusting the mutual alignment of the nozzle holes.

Problems to be Solved When this sliding nozzle 6 is used with the nozzle hole not fully open but partially constricted to control the flow rate of molten steel, the nozzle hole of the sliding plate 8 of the sliding nozzle 6 and the immersion nozzle A void A is created in the nozzle hole at the top of 9 due to the drift of the molten steel flow. This cavity is under negative pressure, and if the sealing between the nozzles is insufficient, air will flow in during casting. In particular, pressure is applied from above and below between the fixed plate 7 and the sliding plate 8, but cracks may occur in these plates due to thermal shock in the early stages of use, and air may flow in through the cracks. Often. Further, when the sliding plate 8 is slid, molten steel may get caught, and the sliding surface may become rough, resulting in insufficient sealing between the fixed plate 7 and the sliding plate 8.

As a result, if air flows into the negative pressure generating area mentioned above, the quality of the molten steel will deteriorate due to oxidation and changes in composition, and if the immersion nozzle material contains carbon, the inner wall of the nozzle will be oxidized and decarburized. , the strength will decrease and the steel will be abnormally damaged by the flow of molten steel.

An object of the present invention is to provide an immersion nozzle for continuous casting that can prevent the generation of a negative pressure portion as described above, thereby preventing air from flowing into the nozzle.

Means for Solving the Problems The above object of the present invention is to provide a hollow part in the side wall extending in the circumferential direction and longitudinal direction of the nozzle at the upper part of the nozzle side wall, and to provide a gas outlet hole communicating from the hollow part into the inside of the nozzle. A gas supply hole is provided in the nozzle side wall for the hollow portion, and the gas outlet hole is downwardly directed from the outside to the inside of the nozzle side wall so as to prevent molten steel from flowing into the gas outlet hole. and the length of the hole in the nozzle circumferential direction is 1 mm or more
This is achieved using a continuous casting immersion nozzle characterized by a diameter of 30 mm or less.

When an inert gas is supplied to the hollow portion from the gas supply hole, the inert gas flows into the upper part of the submerged nozzle from the gas outlet hole. When a sliding nozzle is used with a part of the nozzle hole constricted to control the flow rate of molten steel, this inert gas flows into the void area created by the drift of the molten steel flow and corrects that part. Maintain pressure and prevent air from entering from outside the nozzle.

The number of the gas supply holes may be one, but two, three or more are provided so that the inert gas can be equally supplied to the entire area of the hollow part and the gas can be blown as equally as possible from each outlet hole. may be provided in a radial arrangement.

In a commonly used submerged nozzle, the hollow portion and gas outlet hole are preferably provided within a range of 250 mm from the upper socket of the nozzle in the longitudinal direction of the nozzle. This is because if it is provided below this, even if inert gas is blown into it, there is a risk that the gas will not smoothly reach the above-mentioned void generation area.

The gas outlet hole extends downward from the outside to the inside of the nozzle side wall and has a length of 1 mm or more and 30 mm or less in the nozzle circumferential direction so as to prevent molten steel from flowing into the gas outlet hole. has been done. By having an opening of such a size, it is possible to prevent molten steel from flowing into the gas outlet hole, and with such a size, the strength of the nozzle will not be impaired if the number of holes and the hole interval are appropriately selected. From this point of view, it is more preferable that the length of the opening in the longitudinal direction of the nozzle is 2 mm or less. Further, it is desirable that a plurality of the gas outlet holes be provided in the circumferential direction as a whole.

The position and number of the gas outlet holes can be determined as appropriate depending on the range of the negative pressure generation area during steel casting.

In addition, a hollow part is further provided at the lower end of the hollow part in the nozzle side wall described above, and a gas outlet hole is also provided in the latter hollow part to prevent the nozzle hole from being blocked by non-metallic inclusions adhering to the nozzle inner wall. Good too.

The above-mentioned hollow part on the upper part of the nozzle side wall and the gas outlet hole connected thereto are made of bamboo, wood, resin, etc., which disappear or shrink due to heat during nozzle firing or heating drying.
It is obtained by making a solid or hollow object such as metal into a shape corresponding to the hollow part or gas outlet hole, and embedding it in clay during nozzle molding. The gas supply holes can be formed in the same manner, but they may also be formed by machining after the nozzle is formed.

Embodiment An embodiment of the present invention will be described below with reference to FIG.

The illustrated immersion nozzle 1 uses a mixture of alumina graphite and zirconia graphite obtained by kneading each of alumina and zirconia and graphite with a resin binder and then drying the mixture as a nozzle raw material. It is filled into a mold and formed, and during the molding, a cardboard with a thickness of 0.5 mm in the shape of the hollow part 3 and the gas outlet hole 4 at the upper part of the nozzle side wall 2 is embedded together in the mold, and 1000 kgf/cm ²
The molded body is subjected to reduction firing, and then gas supply holes 5 are bored, and the hollow part 3 created when the cardboard is burned away during firing is made to communicate with the gas outlet hole 4. be.

Nozzle 1 has a total length of approximately 680 mm and an inner diameter of approximately 70 mm.
It is.

The hollow portion 3 extends downward L=190 mm from a position L=50 mm below the nozzle upper socket, and its cross section is a circular band with an average diameter D=90 mm. Hollow part 3 as a whole extends from the nozzle upper socket in the longitudinal direction of the nozzle.
It is within the range of 250mm.

The gas outlet holes 4 are provided in two stages in the longitudinal direction of the nozzle, and each stage has 24 outlet holes 4 arranged at equal intervals in the circumferential direction of the nozzle with a slight downward slope. The opening dimensions of No. 4 are approximately 8 mm in the circumferential direction of the nozzle and approximately 0.5 mm in the longitudinal direction of the nozzle.

One gas supply hole 5 is bored at a position L'=190 mm below the nozzle socket.

The nozzle 1 was installed under the sliding nozzle of the tundish, and while nitrogen gas was supplied from the gas supply hole 5 at 20/min, 5 charges were used in continuous casting. As a result, with the conventional nozzle, the nozzle blockage phenomenon occurred at the end of 5-charge use, and the amount of oxygen in the molten steel tended to increase, but with the above-mentioned nozzle 1, there was no blockage, and the fluctuations in the molten steel composition were extremely small. Nakatsuta. Also, nozzle 1 after use.
When observed, there was no oxidation decarburization of the nozzle material, and there was little erosion. This is apparently because the nitrogen gas flowed into the cavity-generating region within the nozzle to maintain a positive pressure there and prevent air from entering from outside.

Effects of the Invention The continuous immersion casting nozzle of the present invention includes a gas outlet hole that communicates into the nozzle from a hollow portion provided in the upper part of the nozzle side wall. Therefore,
When pouring molten steel into a mold during continuous steel casting, inert gas can be sent into the upper part of the nozzle hole to maintain positive pressure, preventing negative pressure that tends to occur in the upper part and the associated air leakage. can do.
In particular, since the gas outlet hole has an opening having a length in the nozzle circumferential direction of 1 mm or more and 30 mm or less, a large amount of inert gas that can sufficiently prevent the generation of negative pressure can be sent. This prevents air from flowing into the nozzle and prevents abnormal melting damage due to oxidation of molten steel and oxidation of the nozzle structure during continuous casting. Since the gas outlet hole extends downward from the outside to the inside of the nozzle side wall, the inflow of molten steel can be effectively prevented even if the gas outlet hole has a relatively large circumferential length as described above.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of one embodiment of the present invention, and FIG. 2 is an explanatory diagram of the occurrence of voids in the nozzle in a continuous casting process using a conventional immersion nozzle. DESCRIPTION OF SYMBOLS 1... Immersion nozzle, 2... Nozzle side wall, 3... Hollow part, 4... Gas outlet, 5... Gas supply hole.

Claims (1)

[Scope of Claims] 1. A hollow part is provided in the side wall extending in the circumferential direction and longitudinal direction of the nozzle in the upper part of the nozzle side wall, and gas outlet holes communicating from the hollow part into the nozzle are distributed, and A gas supply hole is provided in the nozzle side wall, and the gas outlet hole extends downward from the outside to the inside of the nozzle side wall so as to prevent molten steel from flowing into the gas outlet hole. An immersion nozzle for continuous casting, characterized in that the length in the circumferential direction is 1 mm or more and 30 mm or less. 2. The nozzle according to claim 1, wherein the hollow part and the gas outlet hole are provided within a range of 250 mm from the upper socket of the nozzle in the longitudinal direction of the nozzle.