JP3458226B2 - Immersion nozzle for continuous casting - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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, a continuous casting immersion nozzle installed at the bottom of a tundish, which is a container for receiving molten metal, has an oxide system on the inner peripheral surface of the nozzle hole. Nozzle blockage occurs due to adhesion and accumulation of inclusions. In order to prevent this nozzle clogging, it is generally practiced 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 a bubble in the slab. Inevitably taken in, these bubbles are found in ultra-low carbon steel (carbon content less than 0.01 wt%), causing swelling defects on the product surface or internal defects (ultrasonic flaw detection test for products with strict quality requirements). )
There is a problem that causes the occurrence of. Conventionally, as a dipping nozzle for continuous casting that avoids the above-mentioned problems due to blowing of an inert gas, one or a plurality of bulging portions are provided in the middle portion of both ends of the nozzle hole, and an oxide-based swelling portion is provided in the bulging portion. Inclusions (for example, Al ₂ O ₃ ) are preferentially attached (see Japanese Utility Model Publication No. Sho 57-18043), convex portions or concave portions on the inner surface of the nozzle hole, or convex portions or concave portions continuous in a spiral shape on the inner surface. Provided to cause turbulent flow near the upper and lower parts of the convex portion or at the concave portion to wash away the adhered oxide inclusions (see Japanese Utility Model Laid-Open No. 61-72361), or a plurality of stepped portions in the nozzle hole. It is known that a turbulent flow is generated at the step and the adhered oxide inclusions are washed away (see Japanese Utility Model Laid-Open No. 4-6351).

[0003]

However, in the conventional dipping nozzle for continuous casting in which a bulge is provided in a part of the nozzle hole, molten metal stays in the bulge and traps oxide inclusions. If the concave portion or the convex portion (step portion) is provided in a part of the nozzle hole, the turbulent flow occurs only near the diameter difference step portion, and the force is small, There is a problem that the oxide inclusions adhering to the nozzle hole surface other than the vicinity of the portion are not washed off well, resulting in early nozzle clogging. Therefore, it is an object of the present invention to provide a continuous casting immersion nozzle capable of preventing nozzle clogging for a long period of time without blowing an inert gas.

[0004]

In order to solve the above-mentioned problems, the continuous casting immersion nozzle of the present invention has a nozzle hole provided coaxially with the nozzle body, and continuous casting for supplying molten metal from a tundish into a mold. In the immersion nozzle, at least three eccentric nozzle holes having an axis having the same diameter as the nozzle hole and parallel to the axis of the nozzle hole and different in position from each other are appropriately separated in the longitudinal direction of the nozzle body. It is characterized by being intervened with. It is preferable that the axis lines of the eccentric nozzle holes, which are different in position from each other, are provided on the same circumference centered on the axis of the nozzle hole in the same direction and shifted in order from the one end side by a required angle.

The connection between the nozzle hole and the eccentric nozzle hole is 30 to 90 ° with respect to the axis of the nozzle hole (90 ° = right angle to the axis).
It is desirable to do so through an inclined nozzle hole having axes intersecting at an angle of. When the axis line of the inclined nozzle hole is less than 30 ° with respect to the axis line 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, and the molten metal The flow cannot be swirled. A more desirable angle is 45 to 90 °. Eccentricity with respect to the axis of the nozzle hole The amount of deviation of the axis of the nozzle hole is 1/10 to 10% of the inner radius of the nozzle when the nozzle wall thickness (= outer radius of nozzle-inner radius of nozzle (radius of nozzle hole)) is not less than 20 mm. 1/2 is desirable. The amount of bias is
If it is less than 1/10 of the inner radius of the nozzle, the molten metal flow cannot be swirled, and if it exceeds 1/2, the nozzle wall thickness becomes less than 20 mm in a normal immersion nozzle, and the strength of the nozzle is reduced. Run out. A more desirable bias is
It is 1/8 to 1/3 of the inner radius of the nozzle.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION 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 the line II-II in FIG.
The III-III line drawing figure 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 body made of an appropriate refractory material, and an axial center portion of the nozzle body 1 is open at one end (upper end in FIG. 1) and at the other end (FIG.
A nozzle hole 2 having a closed lower end) is provided coaxially, and the nozzle hole 2 is communicated with the outside through a discharge port 3 provided at the other end of the nozzle body 1. The nozzle hole 2 has the same diameter as the nozzle hole 2 at the intermediate portion of both ends ((upper and lower ends in FIG. 1) of the nozzle hole 2).
Axis L ₁ of different of the axis L ₀ and position to each other in parallel,
L ₂ , L ₃ , that is, one end side in the same direction (counterclockwise direction in FIG. 2) on the same circle (radius 1/7 of the radius of the nozzle hole) centering on the axis L ₀ of the nozzle hole 2 Three eccentric nozzle holes 4, 5 and 6 having axis lines L ₁ , L ₂ and L ₃ which are sequentially displaced from each other by a required angle (120 ° in the figure) are provided in the longitudinal direction of the nozzle body 1. The nozzle holes 2 and the eccentric nozzle holes 4, 5, 6 are connected to each other at equal intervals (in the drawing, at regular intervals), and the connection between the eccentric nozzle holes 4, 5 and 6 is 30 to 90 ° with respect to the axis L ₀ of the nozzle hole 2 ( This is done through inclined nozzle holes 7, 8, 9, 10, 11, 12 having axes intersecting at an angle of 60 ° in the illustrated case. In FIG. 1, reference numeral 2a is a slag line portion provided on the outer peripheral portion on the other end side of the nozzle body 2 and made of an appropriate refractory material having excellent corrosion resistance to molten slag powder.

In the continuous casting immersion nozzle having the above-mentioned structure, the molten metal supplied from the opening of the nozzle hole 2 is transferred from the nozzle hole 2 to the eccentric nozzle holes 4, 5, 6 and also to the eccentric nozzle holes 4, 4. When flowing into the nozzle holes 2 from 5, 5 and 6, a large turbulent flow is generated due to the abrupt change of the flow direction, and a swirling flow is generated, and each nozzle hole 2, 4, 5,
The inner peripheral surfaces of 6, 7, 8, 9, 10, 11, 12 are strongly washed. Therefore, the oxide-based inclusions are
Adhesion and accumulation on the inner peripheral surfaces of 4,5, 6, 7, 8, 9, 10, 11, 11 are prevented.

Here, the aforementioned immersion nozzle according to the present invention (Embodiment 1) and the immersion nozzle (Embodiment 2) having four eccentric nozzle holes in substantially the same manner as the immersion nozzle in an existing continuous casting machine are used. When it was installed in the bottom of No. 2 and was used for continuous casting of ultra-low carbon steel (casting weight: 500 t / nozzle), the thickness of oxide inclusions and the quality of the billet were as shown in Table 1.

[0009]

[Table 1]

Further, for comparison, an immersion nozzle having two eccentric nozzles (Comparative Example 1), similar to Example 1,
An immersion nozzle having the same three eccentric nozzle holes as in Example 1 and provided with the axes of the respective eccentric nozzle holes at the same position (Comparative Example 2), and an immersion nozzle having no eccentric nozzle holes (only straight nozzle holes) (Comparative Example 3), an immersion nozzle having 1 to 3 recesses or protrusions 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 it was carried out and used in the same manner as in Examples 1 and 2, the thickness of oxide inclusions and the quality of the billet were as shown in Table 1, Table 2 and Table 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, whereby the thickness of the oxide-based inclusions is 1.
mm or less, and the slab quality is 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 holes into the eccentric nozzle holes and from the eccentric nozzle holes into the nozzle holes, Since the turbulent flow is generated due to the abrupt change of the flow direction, and the inner peripheral surface of the nozzle hole is strongly cleaned, oxide-based inclusions are prevented from adhering to and accumulating on the inner peripheral surface of the nozzle hole. Therefore, it is possible to prevent the nozzle clogging for a long period of time without blowing the inert gas. Further, by providing the axis line of each eccentric nozzle hole in the same circumference centered on the axis line of the nozzle hole in the same direction by sequentially shifting from the one end side by a required angle,
Since a swirling flow is generated, the above effect can be further promoted.

[Brief description of drawings]

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

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

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

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

[Explanation 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

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Etsuhiro Hasebe No. 1 Minamifuji, Ogakie-cho, Kariya city, Aichi Toshiba Ceramics Co., Ltd. Kariya factory (56) Reference JP-A-8-294757 (JP, A) JP HEI 9-141407 (JP, A) JP 11-47896 (JP, A) JP 6-269913 (JP, A) JP 5-177312 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/10 330 B22D 41/50 520

Claims (2)

(57) [Claims] 1. A continuous casting immersion nozzle, comprising a nozzle body coaxially with a nozzle body, for supplying molten metal from a tundish into a mold, wherein the nozzle hole has the same diameter as the nozzle hole at an intermediate portion between both ends. An immersion nozzle for continuous casting, characterized in that at least three eccentric nozzle holes having axis lines parallel to the axis line of the nozzle hole and different in position from each other are provided at appropriate intervals in the longitudinal direction of the nozzle body. 2. The axes of the eccentric nozzle holes, which are different in position from each other, are provided on the same circumference centered on the axis of the nozzle hole in the same direction, offset from each other by a required angle in order from one end side. The immersion nozzle for continuous casting according to claim 1.