JP2000117403A - Immersion nozzle for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an immersion nozzle for continuous casting, with which the clogging of the nozzle can be prevented over a long term without executing the blowing of inert gas. SOLUTION: In the immersion nozzle for continuous casting, concentrically arranging a nozzle hole 2 with the nozzle body and supplying molten metal into a mold from a tundish, at least three eccentric nozzle holes 4, 5, 6 having the same diameter as the nozzle hole 2 and the axes L1, L2, L3 paralleled with axial line L0 of the nozzle hole 2 and with mutually different positions, are interposed by suitably separating in the longitudinal direction of the nozzle body 1 at the intermediate part in both ends of the nozzle hole 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a continuous casting immersion nozzle for supplying molten metal from a tundish into a mold.

[0002]

2. Description of the Related Art In order to gently supply molten metal into a mold, an immersion nozzle for continuous casting installed at the bottom of a tundish, which is a container for receiving molten metal, has an oxide-based immersion nozzle on the inner peripheral surface of the nozzle hole. Adhesion and accumulation of inclusions cause nozzle blockage. In order to prevent this nozzle blockage, it is common to blow an inert gas such as Ar or N ₂ from the inner peripheral surface of the nozzle hole, but a part of the blown gas becomes bubbles to form in the slab. Inevitably entrapped, these bubbles are found in ultra-low carbon steel (carbon content less than 0.01 wt%) by blistering on the product surface or by internal flaws (ultrasonic flaw test in strict quality requirements) )
There is a defect that causes the occurrence. Conventionally, as an immersion nozzle for continuous casting which avoids the above-mentioned problems caused by blowing an inert gas, one or a plurality of swelling portions are provided at an intermediate portion between both ends of a nozzle hole, and an oxide-based swelling portion is provided on the swelling portion. One that preferentially adheres inclusions (for example, Al ₂ O ₃ ) (see Japanese Utility Model Publication No. 57-18043), a convex or concave portion on the inner surface of the nozzle hole, or a convex or concave portion continuous in a spiral shape on the inner surface. A turbulent flow generated at the upper and lower portions of the convex portion or in the vicinity of the concave portion to wash away the adhered oxide-based inclusions (see Japanese Utility Model Application Laid-Open No. 61-72361), or a plurality of stepped portions in the nozzle hole A turbulent flow is generated at the step to wash away the adhered oxide-based inclusions (see Japanese Utility Model Laid-Open No. 4-6351).

[0003]

However, in the conventional immersion nozzle for continuous casting, in which a swelling portion is provided at a part of the nozzle hole, the molten metal stays in the swelling portion and traps oxide-based inclusions. Is not good, and when a concave or convex portion (step portion) is provided in a part of the nozzle hole, turbulent flow is generated only in the vicinity of the step portion having a small diameter, the force is small, and the step size is small. Oxide-based inclusions adhering to the nozzle hole surface other than in the vicinity of the portion are not sufficiently washed off, and as a result, there is a problem that the nozzle is clogged early. Therefore, an object of the present invention is to provide a continuous casting immersion nozzle that can prevent nozzle blockage for a long time without blowing inert gas.

[0004]

In order to solve the above-mentioned problems, a continuous casting immersion nozzle according to the present invention has a nozzle hole provided coaxially with a nozzle body, and continuously feeds molten metal from a tundish into a mold. In the immersion nozzle for use, at least three eccentric nozzle holes having the same diameter as the nozzle hole, the axes parallel to the axis of the nozzle hole, and different from each other in the middle of both ends of the nozzle hole are appropriately separated in the longitudinal direction of the nozzle body. It is characterized by being interposed. It is preferable that the axes of the eccentric nozzle holes having different positions are shifted from each other by a predetermined angle in the same direction on the same circumference centered on the axis of the nozzle hole.

The connection between the nozzle hole and the eccentric nozzle hole is 30 to 90 ° (90 ° = perpendicular to the axis) with respect to the axis of the nozzle hole.
It is desirable to do this through an inclined nozzle hole having an axis that intersects at an angle of? If the axis of the inclined nozzle hole is less than 30 ° with respect to the axis of the nozzle hole, the length of the inclined nozzle hole becomes extremely long, or the amount of deviation of the eccentric nozzle hole becomes extremely small. It is not possible to give the flow a swirl. A more desirable angle is 45-90 °. The amount of deviation of the axis of the eccentric nozzle hole from the axis of the nozzle hole is 1/10 to 1/10 of the inner radius of the nozzle when the thickness of the nozzle (= radius outside the nozzle−radius inside the nozzle (radius of the nozzle hole)) does not become less than 20 mm. 1/2 is desirable. The deviation is
If it is less than 1/10 of the inner radius of the nozzle, the molten metal flow cannot have a swirl property, and if it exceeds １ ／, the nozzle thickness is less than 20 mm in a normal immersion nozzle, and the strength of the nozzle is reduced. Run out. A more desirable deviation is
It is 1/8 to 1/3 of the inner radius of the nozzle.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. 1, 2, 3 and 4
Is a longitudinal sectional view showing an example of an embodiment of a continuous casting immersion nozzle according to the present invention, a sectional view taken along line II-II in FIG. 1,
FIG. 1 is a drawing taken along line III-III in FIG. 1 and FIG.
FIG. 4 is a sectional view taken along line IV-IV. In the figure, reference numeral 1 denotes a nozzle main body made of an appropriate refractory material. The nozzle main body 1 has an axial center opening at one end (the upper end in FIG. 1) and the other end (FIG. 1).
A nozzle hole 2 having a closed lower end is provided coaxially. The nozzle hole 2 is communicated with the outside via a discharge port 3 provided at the other end of the nozzle body 1. An intermediate portion between both ends (the upper and lower ends in FIG. 1) of the nozzle hole 2 has the same diameter as the nozzle hole 2 and
Axis L ₁ , which is parallel to the axis L ₀
L ₂ , L ₃ , that is, one end in the same direction (a counterclockwise direction in FIG. 2) on the same circle (1/7 of the radius of the nozzle hole) around the axis L ₀ of the nozzle hole 2. Three eccentric nozzle holes 4, 5, 6 having axes L ₁ , L ₂ , L _3, which are provided at predetermined angles (120 ° in the illustrated example), are arranged in the longitudinal direction of the nozzle body 1 as needed. (in the illustrated are equally spaced) is interposed in spaced, connecting the nozzle hole 2 and the eccentric nozzle holes 4, 5, 6, 30 to 90 ° to the axis L ₀ of the nozzle holes 2 ( This is done through inclined nozzle holes 7, 8, 9, 10, 11, 12 having axes that intersect at an angle of 60 ° in the illustration. In FIG. 1, reference numeral 2a denotes a slag line portion provided on the outer peripheral portion on the other end side of the nozzle body 2, made of a suitable refractory having excellent corrosion resistance to molten slag powder.

In the continuous casting immersion nozzle having the above structure, the molten metal supplied from the opening of the nozzle hole 2 is supplied from the nozzle hole 2 to each of the eccentric nozzle holes 4, 5, 6, and each of the eccentric nozzle holes 4, 5. When flowing into the nozzle holes 2 from the nozzle holes 5, 6, a large turbulence is generated due to the sudden change of the flow direction, and a swirl flow is generated.
The inner peripheral surfaces of 6, 7, 8, 9, 10, 11, 12 are strongly cleaned. For this reason, the oxide-based inclusions are
Adhesion and accumulation on the inner peripheral surfaces of 4, 5, 6, 7, 8, 9, 10, 11, and 12 are prevented.

Here, the immersion nozzle according to the present invention (Example 1) and the immersion nozzle (Example 2) provided with four eccentric nozzle holes in substantially the same manner as the above are each provided in a tundish in an existing continuous casting machine. And the actual use for continuous casting of ultra-low carbon steel (casting weight: 500 t / nozzle), the thickness of oxide inclusions and the quality of steel slabs were as shown in Table 1, respectively.

[0009]

[Table 1]

For comparison, an immersion nozzle provided with two eccentric nozzles (Comparative Example 1) in substantially the same manner as in Example 1;
An immersion nozzle provided with the same three eccentric nozzle holes as in Example 1 and provided with the axis of each eccentric nozzle hole at the same position (Comparative Example 2), and an immersion nozzle having no eccentric nozzle hole (only a straight nozzle hole) (Comparative Example 3), an immersion nozzle provided with one to three concave portions or convex portions in the nozzle hole (Comparative Examples 4 to 6),
An immersion nozzle that blows Ar gas into the nozzle hole (Comparative Example 7) and an immersion nozzle that has one recess or protrusion in the nozzle hole and blows Ar gas into the nozzle hole (Comparative Example 8) were implemented. When the embodiment was used in the same manner as in Examples 1 and 2, the thickness of the oxide-based inclusions and the quality of the slab were as shown in Tables 1, 2, and 3, respectively.

[0011]

[Table 2]

[0012]

[Table 3]

As can be seen from Tables 1 to 3, the number of eccentric nozzle holes is three or more and the positions of the respective axes are different from each other, so that the thickness of the oxide-based inclusions is 1
mm or less, and the slab quality becomes good.

[0014]

As described above, according to the immersion nozzle for continuous casting of the present invention, when the molten metal flows from the nozzle hole into each eccentric nozzle hole and from each eccentric nozzle hole into the nozzle hole, Abruptly changing the flow direction causes large turbulence, and the inner peripheral surface of the nozzle hole is strongly washed, preventing oxide-based inclusions from adhering and accumulating on the inner peripheral surface of the nozzle hole. Therefore, nozzle clogging can be prevented for a long period of time without blowing inert gas. Also, by providing the axis of each eccentric nozzle hole in the same direction on the same circumference centered on the axis of the nozzle hole, shifting the required angle in order from the one on one end side,
Since the swirling flow is generated, the above effect can be further promoted.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of an embodiment of an immersion nozzle for continuous casting according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Nozzle body 2 Nozzle hole 4 Eccentric nozzle hole 5 Eccentric nozzle hole 6 Eccentric nozzle hole L ₀ axis L ₁ axis L ₂ axis L ₃ axis

Continued on the front page (72) Inventor Toshiro Oya 1st Minamito, Ogakie-cho, Kariya-shi, Aichi Prefecture Toshiba Cell Mix Co., Ltd. Mix Co., Ltd. Kariya Works F-term (reference) 4E004 FB10 4E014 DB04

Claims (2)

[Claims] In a continuous casting immersion nozzle for supplying a molten metal from a tundish into a mold, a nozzle hole is provided coaxially with the nozzle body, and an intermediate portion at both ends of the nozzle hole has the same diameter as the nozzle hole. An immersion nozzle for continuous casting, characterized in that at least three eccentric nozzle holes having axes different from each other and parallel to the axis of the nozzle hole are appropriately separated in the longitudinal direction of the nozzle body. 2. The eccentric nozzle holes are provided with different axes at different positions in the same direction on the same circumference centered on the axis of the nozzle holes in the same direction in order from the one on one end side by a required angle. The immersion nozzle for continuous casting according to claim 1, wherein: