JP3027645B2 - 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 an immersion nozzle for continuous casting and, more particularly, to a novel improvement for preventing casting defects caused by entrainment of mold powder which increases in frequency with increasing casting speed.

[0002]

2. Description of the Related Art Generally, in continuous casting, a mold 1 is provided with a gate 2 as shown in FIG. 7, and the gate 2 is formed by a short side wall 3 and a long side wall of the mold. During casting, the nozzle body 4 of the immersion nozzle is inserted into the gate 2. The nozzle body 4 has a predetermined inner diameter D, and a discharge hole 5 for discharging the molten metal is provided at a tip end thereof. The discharge hole 5 opens toward the mold short side wall 3 and is formed downward at a predetermined discharge angle θ as shown in FIG.
In addition, a box 6 having a predetermined depth H is provided at a bottom portion that constitutes the tip of the nozzle body 4. The depth H of the box 6 refers to the distance from the inner lower end portion 5a of the discharge hole 5 to the inner front end surface 4a of the nozzle body 4. Therefore, in the continuous casting process, the nozzle body 4 of the immersion nozzle is inserted into the gate 2 and the molten metal is continuously discharged from the discharge hole 5. An elongated product having a predetermined sectional shape is continuously manufactured while the molten metal is cooled and solidified at a drawing speed. Such operations are continuously performed in one mold, which is generally called continuous casting.

[0003]

The conventional continuous immersion nozzle for continuous casting has the following problems because it is constructed as described above. That is, in continuous casting,
In order to improve the productivity, it is necessary to increase the casting speed. However, in order to increase the casting speed, it is necessary to increase the flow rate of the molten metal discharged from the discharge hole 5 of the nozzle body 4, and when the discharge speed of the molten metal is increased, as shown in FIG. It collides with the short side wall 3 of the mold, and a part thereof becomes reverse flow, and the mold powder 7 formed on the molten metal surface of the mold 1 is rolled downward. Such entanglement increases as the discharge speed from the discharge holes 5 increases, resulting in a defect due to mold powder in the final product, which causes a problem that the quality of the final product deteriorates. As a means to solve such problems,
For example, a method of applying an electromagnetic field to molten steel discharge flow and forcibly reducing the discharge speed by this electromagnetic force (Japanese Patent Laid-Open No. 2-89)
544), a method in which the number of discharge holes is increased to increase the cross-sectional area of the discharge holes to reduce the flow velocity of the discharge flow (Japanese Patent Application Laid-Open No. 55-88347), or the discharge angle of a nozzle. The method of turning down was devised. However, the method using electromagnetic force such as an electromagnetic brake,
In addition to an increase in equipment costs, a sufficient effect cannot be obtained unless an appropriate electromagnetic force corresponding to the respective casting speed is applied, resulting in a disadvantage in that the operation management becomes complicated. In addition, when the number of discharge holes is increased, the shape of the nozzle becomes complicated, and the manufacturing cost of the nozzle increases. Although the method in which the discharge hole of the nozzle is directed downward has an effect up to a certain casting speed, high-speed casting (a molten steel passage amount of 4
(t / min or more) was not sufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and in particular, has been developed to prevent a casting defect caused by entrainment of a mold powder, which occurs more frequently as the casting speed increases. It is an object to provide a casting immersion nozzle.

[0005]

According to the present invention, there is provided an immersion nozzle for continuous casting according to the present invention, comprising a nozzle body located inside a short side wall of a mold, and formed on a side wall of the nozzle body and facing downward toward the short side wall of the mold. In a continuous casting immersion nozzle having a discharge hole opened at the bottom and a concave box at the bottom of the nozzle body, the depth of the box is H, the inner diameter of the nozzle body is D, and the discharge angle of the discharge hole is θ. As H ≧ 0.20
D, θ ≧ 15 °.

[0006]

In the immersion nozzle for continuous casting according to the present invention, the discharge hole formed in the side wall of the nozzle body having an inner diameter D located inside the short side wall of the mold is opened downward toward the short side wall of the mold. The discharge angle θ of the discharge hole is set to θ ≧ 15 °, and the nozzle body is configured to have a relation of H ≧ 0.20D with respect to the depth H of a box formed in a concave shape at the bottom of the nozzle body. In addition, it is possible to effectively prevent the entrainment of the mold powder, whose occurrence frequency increases as the casting speed increases.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a continuous casting immersion nozzle according to the present invention will be described below in detail with reference to the drawings. The same or equivalent parts as those in the conventional example will be described using the same reference numerals. FIG. 1 shows a nozzle body 4 of a continuous casting immersion nozzle of the present invention. The nozzle body 4 has an inner diameter D
And a discharge hole 5 formed on this side wall and opening downward toward the short side wall of the mold (see FIG. 7).
The discharge hole 5 is directed downward at a discharge angle θ. A concave box 6 having a depth H is formed at the lower bottom of the discharge hole 5.

[0008] The depth H of the box 6 is
Means the distance from the inner lower end portion 5a to the inner tip surface 4a of the nozzle body 4, and in the present invention, the depth of the box 6 is set to H ≧ 0.20D, discharge angle θ ≧ 1
It is established with a relationship of 5 ゜.

Such a relationship, that is, H ≧ 0.20D, θ ≧
The experiment that led to the 15 ° relationship will be described in detail below.

FIG. 2 is a graph showing the results obtained by an experiment using a water model. The horizontal axis represents H / D,
The vertical axis is the average flow velocity (average surface flow velocity) near the surface of the mold 1 where the mold powder 7 is assumed to be formed.
As a result, when the discharge angle θ was 0 °, that is, when the discharge angle was horizontal, there was no change in the surface flow velocity, but when the discharge angle θ was
When ゜ was set, the average surface flow velocity decreased most when the H / D was around 0.2, and thereafter, the state was maintained even when the H / D was increased. When the discharge angle θ is further increased,
For example, when the angle is 30 ° downward, the average surface flow velocity is
The value further decreased from the case of ゜, and peaked when the H / D was around 0.3. Thereafter, even when the H / D was increased, the state was maintained.

Therefore, the discharge angle θ is increased, and
By increasing the box depth H, the surface flow velocity can be effectively reduced. However, as is clear from this experiment, even if the box depth exceeds a certain value, a further reduction in flow velocity can be obtained. It turned out that it was not possible. Therefore, it has been found that the surface speed can be effectively reduced by setting the depth of the box to H ≧ 0.20D and the discharge angle downward at 15 ° or more.

FIGS. 3 to 5 are diagrams showing how the conventional nozzle and the nozzle of the present invention affect the surface flow velocity by changing the casting speed. 3 to 5, the horizontal axis represents the distance from the center of the nozzle to the short side wall of the mold, and the vertical axis represents the average surface flow velocity near the surface of the mold 1 where the mold powder 7 is assumed to be formed. . As a conventional immersion nozzle, an immersion nozzle having a relationship of H = 0.06D and θ = 30 ° is used, and as an immersion nozzle of the present invention, a relationship of H = 0.34D and θ = 30 ° is used. Using an immersion nozzle, the casting speed is 1.4 m / min, 1.6 m / min,
The comparison was made for the case of 2.0 m / min. As a result, even when the casting speed is increased, the surface flow velocity is smaller when the immersion nozzle of the present invention is used, and the peak of the surface flow velocity does not exceed about 10 cm / s. It has been found that the surface flow velocity can be kept lower when the immersion nozzle of the invention is used. Furthermore, it has been found that the immersion nozzle of the present invention can form a stable molten metal surface without changing the surface flow velocity even if the casting speed is changed so greatly.

Here, using a conventional immersion nozzle and the immersion nozzle of the present invention, it is verified how much mold powder is contained in the final product. In this verification, the inner diameter of the nozzle was 80 mm, the shape of the discharge hole of the nozzle was a vertical ellipse (85 × 75 mm), the mold size was 250 × 1325 mm, and the drawing speed was 1.8 m / m.
In, continuous casting of low carbon Al guild steel was performed. Incidentally, as a conventional immersion nozzle, the discharge angle is θ = 15 °,
H / D = 0.06, and the immersion nozzle of the present invention θ =
30 °, H / D = 0.34 (box depth H is 27m
m).

As a result, as shown in FIG. 6, the use of the immersion nozzle of the present invention succeeded in reducing the entrainment of the mold powder, and the interposition considered to be caused by the mold powder in the final product. 8 things
2% could be reduced.

[0015]

The immersion nozzle for continuous casting according to the present invention has the following features.
With the above configuration, the following effects can be obtained. That is, when the depth of the box is H, the inner diameter of the nozzle is D, and the discharge angle of the discharge hole is θ, H ≧
By configuring the immersion nozzle of the present invention in a relationship of 0.20D, θ ≧ 15 °, even if the casting speed is increased, the entrainment of the mold powder is effectively prevented without increasing the surface flow velocity in the mold. can do. As a result, an unprecedented superior effect, such as the ability to effectively prevent casting defects due to entrainment of the mold powder, could be exhibited.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a nozzle main body of a continuous casting immersion nozzle of the present invention.

FIG. 2 is a graph comparing the average surface flow velocities with different nozzle ejection angles in a water model experiment.

FIG. 3 is a graph comparing the surface flow rates of a conventional immersion nozzle and the immersion nozzle of the present invention at a forging speed of 1.4 m / min.

FIG. 4 is a graph comparing the surface flow rates of the conventional immersion nozzle and the immersion nozzle of the present invention at a forging speed of 1.6 m / min.

FIG. 5 is a graph comparing the surface flow rates of a conventional immersion nozzle and the immersion nozzle of the present invention at a forging speed of 2.0 m / min.

FIG. 6 is a graph showing the inclusion index caused by powder using a conventional immersion nozzle and the immersion nozzle of the present invention.

FIG. 7 is a diagram showing a flow of a molten metal in a mold.

FIG. 8 is a sectional view showing a nozzle body of a conventional continuous casting immersion nozzle.

[Explanation of symbols]

 3 Short side wall of mold 4 Nozzle body 5 Discharge hole 6 Box H Depth of box D Inner diameter of nozzle θ Discharge angle

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshio Nakajima 11-1 Showa-cho, Kure City, Hiroshima Prefecture Inside Kure Research Laboratory of Nisshin Steel Co., Ltd. (56) References JP-A-2-127950 (JP, A) JP-A-4-41059 (JP, A) JP-A-3-193250 (JP, A) JP-A-5-96351 (JP, A) JP-A-4-134251 (JP, U) (58) Fields investigated ( Int.Cl. ⁷ , DB name) B22D 11/10 330 B22D 41/50 520 B22D 41/50 540

Claims (1)

(57) [Claims] 1. A nozzle body (4) located inside a mold short side wall (3), and a discharge hole formed in a side wall of the nozzle body (4) and opening downward toward the mold short side wall. (5) In a continuous casting immersion nozzle having a concave box (6) at the bottom of the nozzle body, the depth of the box (6) is H, the inner diameter of the nozzle body (4) is D, When the discharge angle of the discharge hole is θ, H ≧ 0.20
D, a continuous immersion nozzle for continuous casting, characterized in that θ ≧ 15 °.