JPS6114051A - Immersion nozzle for continuous casting - Google Patents

Abstract

PURPOSE:To decrease the infiltration depth of the molten steel in a casting mold and to discharge uniformly the molten steel from an immersion nozzle by curving the top end of the immersion nozzle to a semispherical shape, forming a slit to the top end and providing a pair of molten steel outflow holes to both ends of the slit. CONSTITUTION:The top end of the immersion nozzle 5 is curved to the semispherical shape and the slit 5a is formed to the top end. A pair of the circular molten steel outflow ports 5b are provided to both ends of the slit 5a. A pair of the holes 5b may be ellptical, etc. except the circular shape and the angle thereof is inclined in a horizontal or prescribed range. The molten steel is uniformly discharged from the holes 5b by using such immersion nozzle 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a submerged nozzle for continuous casting.

[Prior art and its problems]

As shown in Fig. 6, tundish 1 for continuous casting
The molten steel in the tundish 1 is passed through an immersion nozzle 2 that projects downward and is installed vertically into the bottom wall of the tundish 1, and is poured into the mold 3.
Continuously cast inside.

Conventionally, an immersion nozzle has a plurality of circular molten steel outflow holes facing upward or downward at the bottom of its side wall, but it is designed to prevent molten steel from scattering in the initial stage of casting, and to reduce the level of molten steel in the mold during steady casting. In order to facilitate management, two molten steel outflow holes 2a of the immersion nozzle 2 are provided at the lower part of the side wall of the immersion nozzle 2, facing each other, as shown in FIG. 7(A) or (B). There is one in which each of the outflow holes 2a is inclined downward within a range of 30 degrees.

FIG. 6 shows the flow state of the molten steel in the mold 3 and the unsolidified slab when the molten steel is poured into the mold 3 by the immersion nozzle 2 shown in FIG. 7(A).

The penetration depth of the molten steel flow into the unsolidified slab is related to whether or not inclusions that have flowed into the molten steel in the unsolidified slab are captured, and the shallower the penetration depth, the more likely the inclusions will be captured. This improves the cleanliness of the slab.

The penetration depth becomes deeper as the slab drawing speed and slab size increase. For example, 250 cabinets x 2100mm
When a slab of size 1 is cast at a slab drawing speed of 1 m/min, the penetration depth reaches a maximum of about 3 m.

Further, as shown in FIG. 8, if the molten steel flow becomes uneven for some reason, the penetration depth will be reduced by 20 to 40%.
It gets deeper.

Immersion nozzle 2 aimed at shallowing the penetration depth
As shown in FIGS. 9(A) and (B),
The inner surface and the molten steel outflow hole 2a are made oval, or
As shown in FIG. 10, there is one in which the inner surface is elliptical and the molten steel outflow hole 2a is box-shaped.

However, even if this type of immersion nozzle 2 is used, the penetration depth can only be reduced by about 20 to 30%, and no great effect can be obtained, and the above-mentioned drifting of the molten steel flow cannot be prevented from occurring. I can't. Further, since the internal cross section of the immersion nozzle 2 is larger than necessary, inclusions easily adhere to and grow on the inner surface of the immersion nozzle 2, which adversely affects the quality of the slab.

In addition, there is a method of blowing an inert gas into the submerged nozzle as a means of reducing the penetration depth, but this method can only reduce the penetration depth by about 20%.

The immersion nozzle has two molten steel outflow holes on the side and bottom of the wall.
In addition to the above-mentioned problems, since the molten steel is divided into two parts and cast into the mold in the immersion nozzle, the solidified slab at the crater end becomes corrugated as shown in FIG. For this reason, the timing of completion of solidification in the width direction of the slab is different, which causes internal defects and tends to deteriorate the quality of the slab.

A submerged nozzle that solved the above-mentioned problems was published in Japanese Patent Application Laid-open No. 5
It is disclosed in Japanese Patent No. 0-36317 (hereinafter referred to as prior art). As shown in FIGS. 12 and 13, the submerged nozzle 2 according to the prior art has a flat tip, and the tip is provided with a slit 4 having a width of 6 to SO fin. Although this method allows molten steel to flow out, it has the following problems.

(1) The molten steel flow is not uniform in all directions of the slit.

(2) When casting alkylated steel, the molten steel flow is not uniform as mentioned in (1), so a part of the slit 4 (other than both ends and the center of the slit) is blocked by alumina, causing the molten steel to flow. This can lead to drifting of currents or even shutdown of operations.

('3) As shown in FIG. 14, since the molten steel flows downward, the melting of the powder on the molten steel may be hindered, or the surface of the molten steel may solidify.

As a result of (4) and (3), not only defects occur on the surface of the slab, but also breakouts are more likely to occur.

[Purpose of the invention]

Therefore, an object of the present invention is to provide a submerged nozzle for continuous casting that can reduce the penetration depth of molten steel in a mold and can uniformly flow out molten steel.

[Summary of the invention]

At the immersion nozzle of the tundish, which is vertically attached to the bottom wall of the tundish and projects downward, the molten steel in the tamp is poured into the mold provided below the tundish. The tip is curved into a hemispherical shape, a slit is formed in the tip, and a pair of molten steel outflow holes are provided at both ends of the slit.

[Structure of the invention]

One embodiment of this invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a main part showing an embodiment of the immersion nozzle of the present invention, and FIG. 2 is a side view of the same main part. The tip of the nozzle 5 is curved into a hemispherical shape, and a sulin 5a is formed at the tip, and a pair of circular molten steel outflow holes 5b are provided at both ends of the nozzle 5a. 1
The shape of the pair of molten steel outflow holes δb may be oval or the like other than circular, and the angle thereof may be horizontal or inclined within a range of ±10°.

The length 5a may extend slightly from the tip of the immersion nozzle 4 to the side wall of the immersion nozzle 5. In this case, 1
A pair of molten steel outflow holes 5b are formed in the side wall.

When such an immersion nozzle 5 is used, the molten steel flows out to the potter through the slit 5a and the molten steel outflow hole 5b, as shown in FIG. Moreover, as shown in Figure 4,
Since the flow of molten steel in the mold 3 extends to the upper surface of the molten steel in the mold, the powder on the molten steel is easily melted, and there is no possibility that the surface of the molten steel will solidify. Furthermore, since the penetration depth of the molten steel in the mold becomes shallow, the shape of the solidified slab at the crater end becomes flat as shown in FIG. Therefore, the completion times of solidification in the width direction of the slab are approximately equal, so that internal defects are not induced and a slab of excellent quality can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, the penetration depth of the molten steel flow into the mold is shallower than that of the immersion nozzle of the prior art, so that inclusions are not captured and the molten steel is not trapped by the immersion nozzle. Since the molten steel flows out uniformly from the molten steel, it is possible to prevent the immersion nozzle from clogging, and since the molten steel flow also reaches the top surface of the molten steel,
Smooth melting of powder can be achieved. Therefore, a cast slab with few internal defects and excellent surface quality can be obtained. These effects are further enhanced by injecting an inert gas into the submerged nozzle at the same time as the molten steel is poured.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part of an embodiment of the present invention, FIG. 2 is a side view of the same main part, and FIG. Figure 4 is an explanatory diagram showing the flow state of molten steel when molten steel is cast using the immersion nozzle of the present invention, and Figure 5 is an explanatory diagram showing the solidification casting of the crater end when the immersion nozzle of the present invention is used. The cross-sectional views showing the shape of the pieces, Figures 6 and 8, show the flow state of molten steel when molten steel is cast using a conventional immersion nozzle.
2 explanatory diagrams, Figure 7 (AJ, (B), Figure 9 (At
, (Figures 8 and 10 are sectional views of main parts of a conventional immersion nozzle, Figure 11 is a sectional view of a solidified slab at the crater end when a conventional immersion nozzle is used, and Figure 12 is a sectional view of a solidified slab at the crater end.
FIG. 13 is a sectional view of the main part of the immersion nozzle of the prior art, FIG. 13 is a side view of the main part, and FIG. 14 is an explanation showing the flow state of molten steel when molten steel is poured using the immersion nozzle of the prior art. It is a diagram. In the drawing, 1...Tanditshu 2.
...Immersion nozzle 2a... Molten steel outflow hole 3...
Mold 4... Slit 5... Immersion of this invention] 5a... Slit Zipper 5b...
Molten steel outflow hole

Claims (1)

[Scope of Claims] An immersion nozzle, which is vertically attached to a bottom wall of a tundish and projects downward, for pouring molten steel in the tundish into a mold provided below the tundish; A continuous casting immersion device characterized in that the tip of the nozzle is curved into a hemispherical shape, a slit is formed at the tip, and a pair of molten steel outflow holes are provided at both ends of the slit. nozzle.