JPH05169212A - Immersion nozzle for continuous casting - Google Patents

Abstract

PURPOSE:To prevent the casting defect caused by entrapment of mold powder increasing frequency of the development according to the increase of the casting speed related to an immersion nozzle for continuous casting. CONSTITUTION:In the immersion nozzle for continuous casting having a nozzle body 4 positioned at the inside of a short side wall in a mold, a discharging hole 5 formed at the side wall of the nozzle body 4 and opened downward to the short side wall in the mold and a recessed box 6 at the bottom part of the nozzle body, in the case of using H for a depth of the box 6, D for an inner diameter of the nozzle body 4 and theta for an discharging angle of the discharging hole, this nozzle is the constitution having the relations H>=0.20D and theta>=15 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dipping nozzle for continuous casting, and more particularly to a novel improvement for preventing casting defects caused by entrainment of mold powder, which frequently occurs with increasing casting speed.

[0002]

2. Description of the Related Art Generally, in continuous casting, as shown in FIG. 7, a gate 1 is provided in a mold 1, 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 sprue 2. The nozzle body 4 has a predetermined inner diameter D, and a discharge hole 5 for discharging the molten metal is provided at the tip 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.
Further, a box 6 having a predetermined depth H is provided at the bottom portion which 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 tip 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 sprue 2, the molten metal is continuously discharged from the discharge hole 5, and the molten metal is cooled and solidified in the mold 1 to a certain degree, and the molten metal is cooled to a predetermined position below the mold 1. The elongated product having a predetermined cross-sectional shape is continuously manufactured while the molten metal is cooled and solidified at the drawing speed. It is generally called continuous casting that such a work is continuously performed by one mold.

[0003]

Since the conventional continuous casting immersion nozzle is constructed as described above, the following problems exist. That is, in continuous casting,
It is necessary to increase the casting speed in order to improve the productivity. However, in order to increase the casting speed, it is necessary to increase the flow velocity of the molten metal discharged from the discharge hole 5 of the nozzle body 4, and if the molten metal discharge speed is increased, the molten metal discharged from the discharge hole 5 is It collides with the mold short side wall 3 and a part thereof becomes a reverse flow, and the mold powder 7 formed on the molten metal surface of the mold 1 is wound downward. Such entrainment increases as the ejection speed from the ejection holes 5 increases, and defects due to the mold powder occur in the final product, resulting in a problem that the quality of the final product deteriorates. As a means for solving such problems,
For example, an electromagnetic field is applied to the molten steel discharge flow, and the discharge speed is forcibly reduced by this electromagnetic force (Japanese Patent Laid-Open No. 2-89).
No. 544), a method of decreasing the flow velocity of the discharge flow by increasing the number of the discharge holes to increase the cross-sectional area of the discharge holes (Japanese Patent Laid-Open No. 55-88347), or the discharge angle of the nozzle. It was devised such as a way to turn down. However, the method using electromagnetic force such as electromagnetic brake is
There are drawbacks that the equipment cost is high, and sufficient effect cannot be obtained unless an appropriate electromagnetic force corresponding to each casting speed is applied, resulting in complicated operation management. In addition, when the number of ejection holes is increased, the nozzle shape becomes complicated and the manufacturing cost of the nozzle increases. And, although the method of making the nozzle discharge hole downward is effective up to a certain casting speed, high-speed casting (molten steel passage amount 4
(t / min or more) was not sufficient.

The present invention has been made to solve the above problems, and in particular, it is intended to prevent a casting defect caused by the inclusion of mold powder, which is frequently generated with an increase in casting speed. An object is to provide a dipping nozzle for casting.

[0005]

An immersion nozzle for continuous casting according to the present invention comprises a nozzle main body located inside a short side wall of a mold and a side wall of the nozzle main body and directed downward toward the short side wall of the mold. In a continuous casting dip nozzle having a discharge hole opened in 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 continuous casting immersion nozzle according to the present invention, the discharge hole formed in the side wall of the nozzle body having the inner diameter D located inside the mold short side wall is opened downward toward the mold short side wall, By constructing the nozzle body with the relation that the discharge angle θ of the discharge hole is θ ≧ 15 ° and H ≧ 0.20D with respect to the depth H of the box formed in the bottom of the nozzle body. In addition, it is possible to effectively prevent the entrainment of the mold powder, which occurs more frequently as the casting speed increases.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the continuous casting immersion nozzle according to the present invention will now be described in detail with reference to the drawings. It should be noted that the same or equivalent portions as those of 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. This nozzle body 4 has an inner diameter D
And a discharge hole 5 which is formed in the side wall and is opened downward toward the mold short side wall (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 bottom of the discharge hole 5 on the lower side.

The depth H of the box 6 is determined by the discharge hole 5
Is the distance from the inner lower end portion 5a of the nozzle body 4 to the inner tip surface 4a of the nozzle body 4, and in the present invention, in order to effectively prevent the entrainment of mold powder even in high speed casting, the depth of the box 6 is set to H ≧ 0.20D, discharge angle θ ≧ 1
It is established with a relationship of 5 degrees.

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

FIG. 2 is a graph showing the results obtained by the experiment using the water model, where the horizontal axis is H / D,
The vertical axis represents the average flow velocity (average surface flow velocity) near the molten metal surface of the mold 1 in which the mold powder 7 is supposed to be formed.
As a result, when the discharge angle θ was 0 °, that is, when the discharge angle θ was horizontal, no change was observed in the surface flow velocity, but the discharge angle θ was set downward 15
The average surface velocity was the lowest when the H / D was around 0.2 when the angle was set to 0, and thereafter the state was maintained even if the H / D was increased. When the discharge angle θ is further increased,
For example, in the case of 30 ° downward, the average surface velocity is θ = 15
It further decreased from the case of ° and reached a peak near H / D of 0.3, and thereafter, that state was maintained even if H / D was increased.

Therefore, the discharge angle θ is increased, and
By increasing the box depth H, the surface flow velocity can be effectively reduced, but as is clear from this experiment, even if the box depth is set to a certain value or more, it is possible to obtain a further velocity reduction effect. It turned out that I couldn't. Therefore, it was found that the surface velocity can be effectively reduced by setting the depth of the box to H ≧ 0.20D and setting the discharge angle downward to 15 ° or more.

3 to 5 are views comparing 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 molten metal surface of the mold 1 in which the mold powder 7 is supposed 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. Casting speed 1.4m / min, 1.6m / min,
Comparison was made for the case of 2.0 m / min. As a result, even if the casting speed is increased, the surface velocity is smaller when the immersion nozzle of the present invention is used, and the peak of the surface velocity does not exceed about 10 cm / s. It has been found that the surface flow velocity can be suppressed lower when the immersion nozzle of the invention is used. Further, 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 when the casting speed is greatly changed.

Here, it is verified how much the mold powder is contained in the final product by using the conventional immersion nozzle and the immersion nozzle of the present invention. In this verification, as the immersion nozzle, 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, the low carbon Al guild steel was continuously cast. The conventional dipping nozzle has a discharge angle of θ = 15 °,
H / D = 0.06 and θ = for the immersion nozzle of the present invention.
30 °, H / D = 0.34 (box depth H is 27 m
m).

As a result, as shown in FIG. 6, by utilizing the immersion nozzle of the present invention, the inclusion of mold powder was successfully reduced, and the mold powder in the final product is considered to be the cause of the intervention. 8 things
It could be reduced by 2%.

[0015]

The immersion nozzle for continuous casting according to the present invention is
Since it is configured as described above, the following effects can be obtained. That is, assuming that 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 so as to have a relationship of 0.20D and θ ≧ 15 °, even if the casting speed is increased, the surface flow velocity in the mold is not increased and the entrainment of mold powder is effectively prevented. can do. As a result, it was possible to exert an excellent effect that has never been seen, such as effectively preventing a casting defect caused by the inclusion of mold powder.

[Brief description of drawings]

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

FIG. 2 is a graph comparing average surface flow velocities by changing the discharge angle of a nozzle in a water model experiment.

FIG. 3 is a graph comparing the surface flow velocities of the 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 velocities 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 velocities of the 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 due to powder using the conventional immersion nozzle and the immersion nozzle of the present invention.

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

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

[Explanation of symbols]

 3 Mold short side wall 4 Nozzle body 5 Discharge hole 6 Box H Box depth D Nozzle inner diameter θ Discharge angle

Front page continued (72) Inventor Yoshio Nakajima 11-1 Showamachi, Kure City, Hiroshima Prefecture Kure Research Institute, Nisshin Steel Co., Ltd.

Claims (1)

[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 opened downward toward the mold short side wall. In the continuous casting immersion nozzle having (5) and 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, and H ≧ 0.20 where θ is the discharge angle of the discharge hole
An immersion nozzle for continuous casting, characterized by having a relationship of D, θ ≧ 15 °.