JPH06328210A - Immersion nozzle for continuous casting - Google Patents

Abstract

PURPOSE:To prevent erosion near the discharging hole of a nozzle and to improve the durability of the nozzle by opening the discharging holes on a side surface near the tip part of the nozzle and an auxiliary discharging hole at the tip part. CONSTITUTION:The art near the tip part of the hollow tubular nozzle 11 is used by inserting to a mold. In order to spout molten steel, at the side surface near the tip part of the nozzle 11, the discharging holes 13 inclined at a fixed angle are opened so as to form a well part 15 having the depth W from the bottom wall 12 in the inner surface of the nozzle tip part. Further, at the tip part in the axial direction of the nozzle 11, the auxiliary discharging hole 14 having the inner diameter D smaller than the inner diameter Di of the nozzle 11 is provided. The diameter D of the auxiliary discharging hole 14 is set to be in the range of 40-70% of the inner diameter Di of the nozzle 11. By this method, the spouting speed of the molten steel from the discharging hole is restrained to be slow and rising of the molten steel from the surface thereof can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a continuous casting immersion nozzle, which suppresses the rise of molten steel in a mold, improves the quality of the steel material produced and prevents the occurrence of operational troubles such as breakouts. The purpose is to reduce the melting loss in the vicinity of the discharge hole in the immersion nozzle and increase the durability.

[0002]

2. Description of the Related Art The structure of an immersion nozzle for continuous casting, which has been widely used in the past, is generally a discharge hole for ejecting molten steel Y into a mold 3 on a side surface near the tip of the nozzle 1 as shown in FIG. 2 needs to prevent solidification of the molten steel surface YH by continuing to supply the molten steel surface YH to the molten steel surface YH,
It is opened so that it opens diagonally downward. In addition, there is also known one in which the discharge holes opened on the side surface near the tip of the nozzle are formed in a plurality of two or three steps along the side surface in the length direction of the nozzle (JP-A-1-1577751). ing. Further, in order to suppress the rise of molten steel in the mold, the discharge angle of the discharge hole opened diagonally downward, which is opened on the side surface near the nozzle tip, is formed in two stages, and a direct magnetic field is applied to the mold. A method of forming molten metal and controlling the flow of molten steel by electromagnetic force is already known.

[0003]

However, among the above-mentioned objects, the discharge hole 2 for ejecting molten steel, as shown in FIG. 2, is formed so as to be opened obliquely downward on the side surface near the tip of the nozzle 1. In the case of using the immersion nozzle opened in the mold 3, molten steel Y ejected from the discharge hole 2 of the immersion nozzle in the mold 3 collides with the wall surface of the mold 3 and then becomes an upward flow due to the upward reversal flow phenomenon to the mold wall surface. As a result, the molten steel Y rises in the vicinity of the mold wall as shown in FIG.

This swelling becomes more remarkable when the casting speed is increased in a bloom having a small mold cross-sectional area. When the height of the swelling increases, the molten layer of the flux called mold powder in the swelling portion is interrupted, resulting in lack of lubrication due to the flux between the mold 3 and the slab. In order to improve lubricity, a flux F called mold powder is added to the molten steel surface YH in a thickness of about 10 to 15 / mm.

However, if the rising height of the molten steel Y exceeds a certain limit, the above-mentioned lubrication between the mold 3 and the slab becomes extremely uneven or insufficient, and the slab mold is constrained, resulting in the worst case. No flux is supplied between the mold and the slab, and the slab sticks to the mold,
The so-called restrained breakout occurs, and due to the above-mentioned non-uniform lubrication, the initial solidification of the shell in the mold also becomes non-uniform, causing slab defects such as slab longitudinal crack starting from the undeveloped part of the shell. It will be easier.

The above-mentioned swelling phenomenon becomes more remarkable as the casting speed becomes faster, and as the casting speed increases, the flow velocity in the vicinity of the meniscus becomes faster and the corrugation of the molten metal surface becomes large, and the surface of the mold 3 becomes continuous during the continuous casting operation. The flux F that has been melted in No. 3 is re-engaged in the molten steel Y and is captured under the surface layer of the slab, so that not only product defects such as sliver flaws remain on the product surface after rolling, but also the entrained flux F Is caught in the negative pressure portion 2a in the upper part of the discharge hole 2 of the immersion nozzle and melts the upper part in the discharge hole 2 of the immersion nozzle, and the immersion nozzle falls off during casting and the subsequent work is continued. It is often impossible to do so and the cost of the product rises.

Further, the discharge holes opened on the side surface near the tip of the nozzle are formed in two or three stages along the side surface in the length direction of the nozzle.
In the case where the mold is constituted by a plurality of stages, the portion to be immersed in the mold becomes long, and as a result, it is not applicable when the length of the mold is relatively short.

Further, in the case of the method of controlling the flow of molten steel by the electromagnetic force by forming a direct current magnetic field in the mold, not only the equipment cost is large and the number of strands is large as in the bloom continuous casting apparatus, This method cannot be adopted if there is no space around the mold.

[0009]

Therefore, in the present invention, by solving the various problems in the above-mentioned prior art and suppressing the rise of the flux molten layer in the vicinity of the mold wall, the flux between the mold and the slab is reduced. The lubricity of the immersion nozzle is constantly improved to prevent the occurrence of restraint breakout, eliminate the slab defects, and improve the durability of the immersion nozzle to improve the continuous index (1) of the immersion nozzle in continuous casting.
This is intended to reduce the product cost by extending the number of charges that can be cast with a dipping nozzle of a book.

That is, specifically, a tubular nozzle to be inserted into a mold, a discharge hole for jetting molten steel is formed on a side surface near the tip of the nozzle, and the tip of the nozzle in the axial direction is formed. And an auxiliary discharge hole having a diameter smaller than the inner diameter of the nozzle.

According to the present invention, the diameter of the auxiliary discharge hole formed at the tip of the nozzle in the axial direction is 40 to 70% of the inner diameter of the nozzle.
The present invention also relates to a submerged nozzle for continuous casting, which is characterized in that it is set within the range.

[0012]

When molten steel is supplied into the mold from the inserted tubular nozzle, a portion of the molten steel is opened from the auxiliary discharge hole having a diameter smaller than the inner diameter of the nozzle, which is opened at the axial tip of the nozzle. Not only decreases the molten steel jet pressure from the discharge hole opened on the side surface near the nozzle tip, but also eliminates the negative pressure in the upper half of the discharge hole on the side surface of the nozzle, making it positive. As a result of increasing the molten steel jetting area, the jetting velocity of the molten steel from the discharge hole can be moderately suppressed, and swelling on the molten steel surface can be suppressed. In addition, as a result of the positive pressure being applied to the upper half of the discharge hole on the side surface of the nozzle described above, the flux that has melted on the molten steel surface is not sucked in, preventing melt damage around the discharge hole and improving the durability of the nozzle. Can be made.

[0013]

The concrete contents of the present invention will be described below with reference to FIG.
11, a hollow tubular nozzle 11 is provided. On the side surface near the tip of the nozzle 11, in order to jet molten steel, the bottom wall 1 is formed on the inner surface of the nozzle tip.
2 to form a well portion 15 having a depth W from the bottom wall 1
2, a discharge hole 13 inclined by a certain angle (a) is formed, and a diameter (D) smaller than the inner diameter (Di) of the nozzle 11 is formed in the bottom wall 12 at the tip of the nozzle 11 in the axial direction. The auxiliary discharge hole 14 is opened.

The above-mentioned ratio of the size of the auxiliary discharge hole 14 to the discharge hole 13 has a certain effective relationship for suppressing the rise of the molten surface of the molten steel. 11 inner diameter (Di) of 45
The range of% -65% was most effective. Further, the depth (height) of the well portion 15 at the bottom is also related to some extent in order to suppress the swelling of the molten surface of the molten steel. Similarly, according to our experimental results, if it is 8.0 mm or more, It turns out that a sufficient effect can be obtained.

[0015]

As described above, according to the present invention, the discharge hole 13 for jetting the molten steel is formed on the side surface of the nozzle 11 near the tip end, and the tip end in the axial direction of the nozzle 11 is smaller than the inner diameter (Di) of the nozzle 11. Since the auxiliary discharge hole 14 having the diameter is opened, when the molten steel is supplied into the mold from the inserted tubular nozzle 11, the auxiliary discharge hole 14 formed at the axial tip (bottom wall 12) of the nozzle 11 is opened. A part of the molten steel flows out from the nozzle 11 and not only the molten steel jetting pressure from the discharge hole 13 formed in the side surface near the tip of the nozzle 11 decreases, but also the negative half 13a in the upper half of the discharge hole 13 on the nozzle side surface. As a result of eliminating the pressure and increasing the positive pressure to increase the molten steel jet area, the jet velocity of the molten steel jetted from the discharge holes 13 can be gently suppressed, and the rise of the molten steel surface can be suppressed.

Further, as a result of positive pressure being applied to the upper half portion 13a in the discharge hole 13 on the side surface of the nozzle 11 described above, suction of the molten flux on the molten steel surface is eliminated, and melt damage around the discharge hole is prevented. Therefore, various beneficial effects such as the durability of the nozzle 11 can be improved.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a main portion of a tip (lower end) portion of a continuous casting immersion nozzle which is an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of an essential part showing a state of use of a conventionally known immersion nozzle for continuous casting.

[Explanation of symbols]

 11 Nozzle 12 Bottom Wall 13 Discharge Hole 14 Auxiliary Discharge Hole 15 Well Part

Claims (2)

[Claims] 1. A tubular nozzle to be inserted into a mold, wherein a side face near the tip of the nozzle is provided with a discharge hole for jetting molten steel, and the nozzle is provided at the tip in the axial direction of the nozzle. An immersion nozzle for continuous casting, characterized in that an auxiliary discharge hole having a diameter smaller than the inner diameter is opened. 2. The continuous according to claim 1, wherein the diameter of the auxiliary discharge hole formed at the tip of the nozzle in the axial direction is set to be within the range of 40 to 70% of the inner diameter of the nozzle. Immersion nozzle for casting.