JPS6376753A - Box type submerged nozzle for high cleanliness steel - Google Patents

Abstract

PURPOSE:To obtain a submerged nozzle for continuously casting high cleanliness steel by inserting a wall face body as surrounding discharging holes in a lower end part of a cylindrical body and arranging discharging holes to sideward and downward respectively at the side wall facing to the discharging holes for molten steel flow staying zone of space part and the center of bottom wall. CONSTITUTION:The refractory wall face body 4 is inserted as surrounding the discharging holes 2 in the lower end part of refractory cylindrical body 1, to form the space part 3. In the wall face body 4, the side face discharging holes 7 are penetrated at the side wall 4b near the height at upper limit position of the holes 2 as facing to the holes 7 at the side wall 4b and further the downward discharging hole 8 is arranged as concentric with the cylindrical body 1 at center of the bottom wall 4c. At the time of pouring the molten steel, the molten steel flowed out from the holes 2 through flowing down passage 9 is rapidly reduced in speed by colliding to the walls 4b and staying in the space part 3, to discharge from the holes 8. At the same time, the prevention of sticking and the working of floating promotion for deposit in the molten steel developing in the staying zone of space part 3 is executed by flow of the holes 7. In this way, this submerged nozzle, by which the cast slab having good quality by continuous casting is stably poured, is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a submerged nozzle for injecting molten steel into a mold during continuous steel casting.

(Conventional technology) Recent years? Continuous casting is widely used in casting No. 8 steel from the viewpoints of productivity, casting yield, energy saving, etc. In this continuous casting, molten steel is injected into a mold through a submerged nozzle, and is continuously drawn out while being cooled and solidified by the mold and a secondary cooling zone to produce a red-hot slab.

In this state, the molten metal quickly solidifies into slabs, which not only improves the cleanliness of the molten steel itself, but also prevents uneven solidification due to uneven flow of the injection flow caused by the immersion nozzle, or interference with floating of inclusions. However, it is difficult to stably cast a good slab by casting, inserting, etc., and this is an important technical problem for workers involved in the work.

Therefore, in order to solve the problem during No. 29 casting and perform stable casting, a discharge passage is provided on both sides of the lower end of the immersion nozzle, and a passage is provided on the outer periphery of the discharge passage, as in, for example, Japanese Utility Model Application Publication No. 49-139322. An immersion nozzle (in which a sealed flow box having a
(hereinafter simply referred to as a flow box nozzle), or as shown in JP-A-51-54836, a 5in2 system containing 1.0 to 10.0% CaO inside a conventional outer fireproof material. Immersed nozzle lined with refractory material to prevent nozzle clogging (hereinafter simply referred to as lined nozzle)
etc. have been proposed.

(Problems to be Solved by the Invention) However, even if these immersion nozzles are used, they are not sufficient for achieving high cleanliness and stable casting for the following reasons. First, in the flow box nozzle, the discharge flow of the molten metal becomes a short-circuit flow through the gap, and the aimed discharge flow cannot be relaxed. In addition, in a nozzle in which the discharge flow is mainly lateral or upward flow, uneven solidification due to washing and development of the solidified shell or disturbance of the molten metal surface may occur, leading to the insertion of powder or inclusions.

Furthermore, even if a molten metal retention area is simply formed in order to reduce the discharge flow rate of the molten metal, the AQ□0 in the molten metal retention area. Adhesion of the system may occur, and conversely, serious quality defects may occur due to these peelings and contamination. On the other hand, with lined renozzles, in addition to not being able to achieve sufficient deceleration and relaxation of the discharge flow, the inner lined refractory material cannot sufficiently capture inclusions and reform the shape, but conversely, it is difficult to wash and develop solidified shells. It has disadvantages such as non-uniform solidification due to the discharge flow or insertion of inclusions resulting in casting failures and quality problems.

The present invention aims to alleviate the discharge flow, which is a drawback of conventional immersion nozzles, to make the IG hardness uniform, to prevent surface disturbance, and to stabilize high-quality slabs by suppressing the promotion and insertion of inclusions. There is a box type immersion nozzle that enables casting.

(Means for Solving the Problems) Hereinafter, a box-type immersion nozzle for highly clean steel according to the present invention will be described. Prior to the present invention, the inventors of the present invention obtained the following knowledge by studying the problems of conventional submerged nozzles and conducting various actual temperature experiments. In order to stably cast high-quality slabs in continuous casting, first of all, (1) the discharge flow rate of the immersion nozzle should be set to a sufficiently moderate upward or downward flow. ■By forming voids, the discharge flow is most effectively buffered by collisions, and extreme stagnation areas result in quality problems due to deposition and peeling of deposits.

■On the other hand, capturing inclusions in the retention area is effective;
In addition, it is also effective to modify the properties of inclusions by utilizing this region.
Furthermore, this modification and the gentle upward flow caused by the relaxed downward flow promote the floating action of inclusions. (2) It was found that appropriate stirring of the molten metal surface is essential in order to capture floating inclusions and lubricate the mold.

The present invention was achieved based on these findings, and the outlet sides of the discharge holes of the cylindrical body are each surrounded by a wall surface.

Among them, a wall surface parallel to the discharge hole of the cylindrical body has a cavity formed in contact with the cylindrical body, and furthermore, the lower part of the cavity communicates with another cavity, and the molten metal retention area of the cavity is discharged. By providing a discharge hole in the side wall facing the hole and providing a downward discharge hole centered on the axis of the cylindrical body in the bottom wall, or by further providing a CaO-containing refractory on the inner wall surface of the cavity. By providing a plate lining, a downward flow with a moderate flow velocity was created, and a submerged nozzle was realized that solved the above technical problems at once.

(for production) Hereinafter, further detailed description will be given based on the embodiment shown in the figures.

FIG. 1(a) shows a cross-sectional view of a box-type immersion nozzle for continuous casting according to the present invention, FIG. 1(b) shows a cross-sectional view taken along the line A-A', and FIG. An example is shown in Figure 2(b).
-A' cross-sectional view is shown, and FIG. 3 is a cross-sectional view when a CaO-containing refractory plate is lined inside.

In the figure, 1 is a cylindrical body made of a refractory made of, for example, alumina-C, 5L-C, or ZrO2, and is provided with a discharge hole 2 having a suitable downward angle at its lower end. In addition, the discharge hole 2 has a cavity 3 surrounding the discharge hole 2.
is provided by the wall body 4.

This wall body 4 is made of a refractory material, and has an upper wall 4a and a side wall 4b.
, and a bottom wall 4c, the lower end of the cylindrical body 1 is fitted into the upper wall 4a, and furthermore, the tapered portion 5a of the slug line portion 5 is engaged and locked.

In this state, the cylindrical body has a side wall 4 parallel to the discharge hole of the cylindrical body.
b in the same manner and engages integrally with the upper wall 4a to form a cavity 3, and the lower part of the cavity 3 communicates with each other cavity, and the bottom u4c has a cylindrical body 1. axis x-x'
A downward discharge hole 8 centered at is bored. Note that 9 in the figure is a molten steel flow path.

In addition, a discharge hole 7 is bored in the side wall 4b of the wall body 4 forming the cavity 3 at a portion facing the discharge hole 2 and at a height near the upper limit portion of the discharge hole 2. The discharge hole 7 in this side wall and the downward discharge hole 8 centered on the axis x-x' of the cylindrical body 1 as shown in FIG. 1(a).
is not limited to a circular shape, but may be an ellipse or a rectangle. Incidentally, as shown in FIG. 1(b), the side discharge hole 7 may be formed at the lower end of the side wall 4b, and a downward discharge hole 8 may be provided centered on the axis of the cylindrical body 1.

The molten steel poured into the immersion nozzle 1 in this way flows out from the discharge hole 2 at a considerable speed, but it is rapidly decelerated due to the synergistic effect of collision with the side wall 4b and relaxation by the i8 molten metal retention area in the cavity 3. and is poured out from the downward discharge hole 8. In addition, a retention area is always generated in the cavity 3 and the wall body 4 is covered with Al.
1,0. Forms deposits on the system. If this adhesion grows considerably, it will cause quality problems due to peeling and insertion, so this adhesion prevention and AQ20. The floating of system precipitates is promoted and the mold surface powder is melted and adjusted all at once by the flow through the side discharge holes 7 of the small volume hood. As shown in Fig. 1, the discharge flow from the discharge hole 2 is made to collide with the side wall 4b, and the discharge flow from both sides collides again with the guidance of the bottom wall 4c to form a center downward flow, thereby reducing the discharge. The synergistic effect of the flow and the side discharge flow makes floating and removal of inclusions more effective.

The downward flow thus decelerated and relaxed descends to become a relaxed upward flow, which is further added to the side discharge flow to achieve ideal bath agitation and floating and solidification of inclusions and the like. In addition, in order to further improve the flotation and removal of these inclusions, a third
As shown in the figure, CaO-containing refractory plates 11a-b as shown in Table 1 are fixed to the wall surface forming the cavity 3 by mortar, baking, or other common means. These CaO-containing refractory plates 11a to 11b have a CaO content of 50 to
It is necessary to contain 95%, but if it is less than 50%, the effect of promoting 11,0° inclusions and improving the quality cannot be achieved. On the other hand, if it is more than 95%, the melting resistance and strength will be insufficient, so 50 to 95% is desirable.

With this configuration, Al1120. On the other hand, 12 Cab: 7 AΩ20. The synergistic effect of lowering the melting point, reforming, and relaxing the discharge flow results in extremely excellent flotation and removal.

The CaO-containing refractory plates 11(a) and 11(b) may be coated with a moisture-proofing agent such as paraffin, or formed from a chloride compound, and converted into CaO by heating at 800 to 1200°C during drying. Compounds such as the following may also be used.

(Example) Next, the box-type immersion nozzle of the present invention was used in AQ quilt j8 S'A
Table 2 and Fig. 4 compare the results of continuous casting using the conventional method with a box-type case consisting of a cavity and a lateral discharge flow. It is clear that the nozzle of the present invention has a higher It is very effective in distributing and slowing down the downward discharge flow, and the quality obtained is also very good.

Furthermore, Table 3 shows cases in which the inner surface was lined with a CaO-containing refractory plate, and it can be seen that the water droplets were excellent in all cases.

Table 1 Table 2 Table 3 (Effects of the invention) As described above, by using the box-type immersion nozzle for producing highly clean W4 of the present invention, the injection and discharge flow can be increased, the downward flow can be applied, and the deceleration can be sufficiently reduced. In addition to stable casting, high quality can be achieved by suppressing quality impediments such as inclusions.
Furthermore, the simple combination structure allows for easy attachment and detachment, making it possible to simplify manufacturing and facilitate installation.

[Brief explanation of the drawing]

FIG. 1(a) shows a cross-sectional view of a box-type immersion nozzle for continuous casting according to the present invention, and FIG. 1(b) shows a cross-sectional view taken along the line A-A',
FIG. 2(a) shows a sectional view of another box-shaped immersion nozzle according to the present invention, FIG.
The figure shows an immersed nozzle lined with a CaO-containing refractory plate, and FIG. 4 shows the relative softness of the box-shaped immersed nozzle of the present invention and a conventional box-shaped immersed nozzle. Explanation of symbols 1... Cylindrical body, 2... Discharge hole, 3... Cavity part, 4... Wall body, 5... Slab line part, 7... Side discharge hole, 8.・・Downward discharge hole, 9・・
- Molten steel flow path, 11a, b... CaO-containing refractory plate. Fig. 1 Fig. 2 (a) (a) Child Fig. 4 (α) (b) vF abutment degree (α7 min) Feeding speed (m7 min) (C) νu1 speed (m/f>)

Claims (2)

[Claims] (1) The outlet side of the discharge hole of the cylindrical body is surrounded by a wall surface, and the wall surface parallel to the discharge hole of the cylindrical body has a cavity formed in contact with the cylindrical body. A discharge hole is formed in the side wall that communicates with another cavity at the bottom and faces the discharge hole in the molten metal retention area of the cavity, and a downward discharge hole centered on the axis of the cylindrical body is provided in the bottom wall. A box-type immersion nozzle for high-clean steel, which is characterized by being equipped with. (2) The outlet side of the discharge hole of the cylindrical body is surrounded by a wall surface, and the wall surface parallel to the discharge hole of the cylindrical body is provided with a cavity formed in contact with the cylindrical body. The lower part communicates with another cavity, and a discharge hole is bored in the side wall facing the discharge hole in the molten metal retention area of the cavity, and the bottom wall has a discharge hole facing downward around the axis of the cylindrical body. A box-shaped immersion nozzle for highly clean steel, characterized in that a discharge hole is provided and the inner wall surface of the cavity is lined with a CaO-containing refractory plate.