JP4578555B2 - Immersion nozzle for continuous casting - Google Patents

Abstract

An immersion nozzle for continuous casting, including (1) a tubular body with a bottom, the tubular body having an inlet for entry of molten steel disposed at an upper end and a passage extending inside the tubular body downward from the inlet, and (2) a pair of opposing outlets disposed in a sidewall at a lower section of the tubular body so as to communicate with the passage, the nozzle comprising: a pair of opposing ridges horizontally projecting into the passage from an inner wall between the pair of outlets, the inner wall defining the passage.

Description

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

In a continuous casting process in which molten steel is continuously cooled and solidified to form a slab of a predetermined shape, a continuous casting immersion nozzle (hereinafter simply referred to as an “immersion nozzle”) installed at the bottom of the tundish. ) Through which molten steel is poured into the mold.
In general, the immersion nozzle is composed of a tubular body having a bottom portion with an upper end portion serving as a molten steel inflow port and a flow path extending downward from the inflow port, and a flow path is formed on a lower side surface of the tubular body. A pair of communicating discharge holes are formed to face each other. The immersion nozzle is used with its lower part immersed in molten steel in the mold. This prevents splashing of the molten molten steel and prevents oxidation by blocking contact between the molten steel and the atmosphere. Further, by using the immersion nozzle, the molten steel in the mold is rectified so that impurities such as slag and non-metallic inclusions floating on the molten metal surface are not caught in the molten steel.

In recent years, high quality and high production of steel quality in a continuous casting process have been demanded. When aiming for high production in existing facilities, it is necessary to increase the casting speed, and the idea is to increase the amount of steel passing by increasing the diameter of the flow path of the immersion nozzle or increasing the discharge hole in a limited mold. Has been made.

However, when the discharge hole is enlarged, an unbalance occurs in the flow velocity distribution in the vertical direction and / or the horizontal direction of the discharge flow discharged from the discharge hole. Then, the unbalanced flow (uneven flow) collides with the side wall of the mold so that an unstable molten steel flow is caused in the mold. As a result, the molten metal surface fluctuation due to excessive reversal flow and the steel quality deterioration due to entrainment of mold powder are caused, and it becomes a factor such as breakout.

Therefore, in Patent Document 1, for example, a pair of discharge holes formed to face the lower side surface of the tube body is divided into two or three stages in the upper and lower directions by the protrusions projecting inward, and the total number is four or six. An invention of an immersion nozzle having a discharge hole is disclosed (see FIGS. 18A and 18B). According to the submerged nozzle, a more stable and controlled discharge flow is generated that suppresses clogging, has a more uniform discharge flow rate, and significantly reduces rotation and vortex.

International Publication No. 2005/049249 Pamphlet

The inventor disclosed that the immersion nozzle described in Patent Document 1, a conventional immersion nozzle having a pair of discharge holes formed to face the lower side surface of the tube, and the discharge holes facing each other in the conventional immersion nozzle A water model test was performed on a type (see FIG. 19) in which a projecting portion projecting inwardly was provided at the center of the flow path, and the variation in the discharge flow discharged from each immersion nozzle was verified.

FIG. 20 shows the water model result of each immersion nozzle. In the figure, when the mold is viewed from the short side, the average value σ _av of the standard deviation of the left and right reversal flow rates across the immersion nozzle is plotted on the horizontal axis, the difference Δσ between the standard deviations of the left and right reversal flow rates, and the left and right reversal flow rates. The average value _Vav is taken on the vertical axis. In addition, the test body A is an immersion nozzle (4 discharge hole type) described in Patent Document 1, the test body B is a conventional immersion nozzle, and the test body C is a channel center (on the inner wall surface of the immersion nozzle and the channel width). This corresponds to an immersion nozzle provided with a protrusion at the center).
From FIG. 20 (A), the immersion nozzle having the largest difference in standard deviation Δσ between the left and right reversal flow rates, that is, the difference between the left and right reversal flow rates is the conventional type. It can be seen that the submerged nozzle provided with the protrusions has a small difference between the left and right reversal flow rates. On the other hand, from FIG. 20B, the conventional immersion nozzle and the immersion nozzle described in Patent Document 1 have a large average value V _av of the left and right inversion flow rates, and the immersion nozzle provided with a protrusion at the center of the flow path It can be seen that the average value V _av of the reversal flow velocity is small.

As the casting speed (throughput) increases, it is confirmed that the difference Δσ between the standard deviations of the left and right reversal flow rates and the average value V _av of the left and right reversal flow rates increase, but from the viewpoint of improving the quality of steel Therefore, Δσ is preferably 2 cm / sec or less, and V _av is preferably 10 cm / sec to 30 cm / sec. In this regard, Δσ is 2 cm / sec or less in all the test specimens, but as for V _av , all the test specimens are out of the range of 10 cm / sec to 30 cm / sec.

Further, in the case of the immersion nozzle (4 discharge hole type) described in Patent Document 1, as shown in the fluid analysis results shown in FIGS. 21 (A) and (B), the discharge flow from the lower discharge hole is large, There is little discharge flow from the upper discharge hole. As a result, the reversal flow velocity shows a large value of 35 cm / sec. The mold size at the time of fluid analysis is 1500 mm × 235 mm, and the casting speed is 3.0 ton / min.
In addition, since the immersion nozzle described in Patent Document 1 has four or more discharge holes, the manufacturing becomes too complicated, and when the discharge holes are blocked or melted, the balance of the discharge flow tends to be lost. There is a difficulty.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an immersion nozzle for continuous casting that is less prone to drift in the molten steel flow discharged from the discharge holes and has a small fluctuation in the molten metal surface and is easy to manufacture.

In order to achieve the above-mentioned object, the present invention provides a flow path on the lower side surface of a tubular body having a bottom, in which an upper end portion is an inlet for molten steel, and a channel extending downward from the inlet is formed therein. In a continuous casting immersion nozzle in which a pair of discharge holes communicating with each other are formed to face each other, projecting inwardly on the inner wall defining the flow path between the pair of discharge holes, the inner wall is horizontally oriented It is characterized in that the protruding ridges crossing each other are arranged to face each other.
Here, “crossing the inner wall in the horizontal direction” means a protrusion from one side end (boundary position with one discharge hole) of the inner wall to the other side end (boundary position with the other discharge hole). This means that the part extends in the horizontal direction.
In the present specification, each direction is set based on a state in which the continuous casting immersion nozzle is vertically set.

In the conventional immersion nozzle, the flow velocity distribution of the discharge flow discharged from the discharge hole is biased downward and non-uniform, but in the present invention, the discharge flow is also generated at the upper portion of the discharge hole due to the damming effect by the opposed protrusions. Can be obtained. On the other hand, the molten steel flow that passes downward between the opposing ridges is left and right evenly across the tube axis in a vertical plane parallel to the extending direction of the ridges due to the rectification effect due to the clearance between the ridges. Flow. In addition, since the discharge flow becomes uniform, the maximum velocity of the discharge flow that collides with the side wall of the mold on the short side of the mold is relaxed, and the reversal flow velocity is reduced. As a result, the molten metal surface fluctuation and mold powder entrainment due to an excessive reversal flow are eliminated, and deterioration of the steel quality can be prevented.

Further, in the continuous casting immersion nozzle according to the present invention, the discharge hole is viewed from the front, the horizontal width of the discharge hole is a ′, the vertical width is b ′, and the protrusion of the end face of the ridge portion is projected. When the height is a and the vertical width is b, it is preferable that a / a ′ = 0.05 to 0.38 and b / b ′ = 0.05 to 0.5. Furthermore, it is preferable that c / b ′ = 0.15 to 0.7, where c is a vertical distance from the upper edge of the discharge hole to ½ of the vertical width of the end face of the protrusion. To do.

In the continuous casting immersion nozzle according to the present invention, it is preferable that both end portions of the protruding portion are inclined portions that are inclined downward toward the outside. Accordingly, it is preferable that the upper end surface and the lower end surface of the discharge hole are inclined downward outward, and the inclination angle of the upper end surface and the lower end surface and the inclination angle of the inclined portion are the same angle. .
In the immersion nozzle in which the upper end surface and the lower end surface of the discharge hole are inclined downward toward the outside, when the protrusions having no inclined portions are provided at both ends in the extending direction, the discharge flow above the protrusions is projected. The flow is blocked by the strip and discharged upward. And since this flow collides with the reverse flow on the mold surface, the reverse flow velocity cannot be stabilized. For this reason, it is desirable that the inclination angles of the inclined portions formed at both ends of the ridge portion are the same as the inclination angles of the upper end surface and the lower end surface of the discharge hole.

Further, in the continuous casting immersion nozzle according to the present invention, with respect to the extending direction of the protruding portion, the width of the flow path immediately above the pair of discharge holes is L ₁ , and the protruding portion excluding the inclined portion. When the length and _{L 2,} it is preferable that L ₂ / L 1 = 0~1.

In the continuous casting immersion nozzle according to the present invention, it is preferable that an inclination angle of the upper end surface, the lower end surface, and the inclined portion is 0 to 45 °.

In the present invention, the inner wall that is defined between the pair of discharge holes and that defines the flow path projects inwardly, and the protrusions that cross the inner wall in the horizontal direction are arranged opposite to each other, so that the entire area of the discharge holes is covered. Thus, the discharge flow can be dispersed and made uniform. Thereby, the flow velocity distribution and the collision position of the discharge flow that collides with the side wall of the mold on the short side can be stabilized, and the reversal flow velocity on the mold surface can be reduced. As a result, the fluctuation of the molten metal surface is reduced, and the flow on the left and right of the immersion nozzle is close to symmetry, so that the steel quality can be improved and the production can be increased.

In addition, in the continuous casting immersion nozzle according to the present invention, it is only necessary to form the protrusions on the inner wall defining the flow path between the pair of discharge holes. A method of forming the discharge holes can be applied and manufacturing is easy.

In addition, as a method of forming the discharge hole with a normal immersion nozzle, for example, after forming a discharge hole smaller than the final shape, the discharge hole is drilled from the front direction by boring or the like, and the set cross-sectional dimension At the time of forming a ridge portion having a shape or a CIP (Cold Isostatic Pressing) molding, a portion to be a ridge portion is formed as a concave space on a cored bar at the time of molding, and a tubular body is formed in the concave space. A method of filling the clay to be formed and compressing it to form a protrusion having a set cross-sectional dimension can be employed.

The immersion nozzle for continuous casting which concerns on one embodiment of this invention is shown, (A) is a side view, (B) is a longitudinal cross-sectional view. It is a partial side view of the immersion nozzle for continuous casting. (A), (B) is a partial longitudinal cross-sectional view of the immersion nozzle for continuous casting, respectively. It is a schematic diagram for demonstrating a water model test. (A) is a graph showing the relationship between a / a ′ and Δσ, and (B) is a graph showing the relationship between a / a ′ and V _av . (A) is a graph showing the relationship between b / b ′ and Δσ, and (B) is a graph showing the relationship between b / b ′ and V _av . (A) is a graph showing the relationship between c / b ′ and Δσ, and (B) is a graph showing the relationship between c / b ′ and V _av . (A) is a graph showing the relationship between L ₂ / L ₁ and Δσ, and (B) is a graph showing the relationship between L ₂ / L ₁ and V _av . (A) is a graph showing the relationship between R / a ′ and Δσ, and (B) is a graph showing the relationship between R / a ′ and V _av . The schematic diagram of the analysis model used for fluid analysis is shown, (A) is an Example and (B) is a prior art example. The fluid analysis result of an Example is shown, (A) is explanatory drawing which shows the flow in the vertical surface of a fluid, (B) is explanatory drawing which shows the flow in the horizontal surface of a fluid. The fluid analysis result of a prior art example is shown, (A) is explanatory drawing which shows the flow in the vertical surface of a fluid, (B) is explanatory drawing which shows the flow in the horizontal surface of a fluid. It is a graph which shows the relationship between ( _{DELTA) (} theta) and _Vav . The fluid analysis result of an Example ((theta) = 0 degree) is shown, (A) is explanatory drawing which shows the flow in the vertical surface of a fluid, (B) is explanatory drawing which shows the flow in the horizontal surface of a fluid. The fluid analysis result of an Example ((theta) = 25 degrees) is shown, (A) is explanatory drawing which shows the flow in the vertical surface of a fluid, (B) is explanatory drawing which shows the flow in the horizontal surface of a fluid. The fluid analysis result of an Example ((theta) = 35 degrees) is shown, (A) is explanatory drawing which shows the flow in the vertical surface of a fluid, (B) is explanatory drawing which shows the flow in the horizontal surface of a fluid. The fluid analysis result of an Example ((theta) = 45 degrees) is shown, (A) is explanatory drawing which shows the flow in the vertical surface of a fluid, (B) is explanatory drawing which shows the flow in the horizontal surface of a fluid. The immersion nozzle for continuous casting described in Patent Document 1 is shown, (A) is a longitudinal sectional view, and (B) is a flat sectional view. It is a partial longitudinal cross-sectional view of the continuous casting immersion nozzle which provided the projection part in the flow path center part between the opposing discharge holes. (A) is a graph showing the relationship between σ _av and Δσ, and (B) is a graph showing the relationship between σ _av and V _av . The fluid analysis result of the immersion nozzle described in patent document 1 is shown, (A) is explanatory drawing which shows the flow in the vertical surface of a fluid, (B) is explanatory drawing which shows the flow in the horizontal surface of a fluid.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.

The shape of a continuous casting immersion nozzle (hereinafter simply referred to as “immersion nozzle”) 10 according to an embodiment of the present invention is shown in FIGS.
The immersion nozzle 10 includes a cylindrical tube body 11 having a bottom portion 15, and an upper end of a flow path 12 formed inside is an inflow port 13 for molten steel. On the other hand, a pair of discharge holes 14 communicating with the flow path 12 are formed on the lower side surface of the tube body 11 so as to face each other. Since the immersion nozzle 10 is required to have spalling resistance and corrosion resistance, the tube body 11 is formed of a refractory material such as alumina graphite.

The discharge hole 14 has a rectangular shape with a rounded corner portion when viewed from the front, and protrudes inwardly on an inner wall 18 between the pair of discharge holes 14 and defining the flow path 12. The protrusions 16 that cross the inner wall 18 in the horizontal direction are arranged to face each other. That is, the opposing protrusions 16 are arranged symmetrically across a vertical plane passing through the centers of the pair of discharge holes 14. The clearance between the protrusions 16 is constant, and both end portions in the extending direction are inclined portions 16a that are inclined downward toward the outside (see FIG. 3). On the other hand, the upper end surface 14a and the lower end surface 14b of each discharge hole 14 are also inclined downward toward the outside. In the present embodiment, the top of the inclined portion 16a formed on the ridge 16 and the top of the discharge hole 14 are inclined. The end surface 14a and the lower end surface 14b have the same inclination angle.

The protrusion 16 extends in the horizontal direction from one side end (boundary position with one discharge hole 14) of the inner wall 18 to the other side end (boundary position with the other discharge hole 14). As shown in FIG. 3A, the end surface of the protruding portion 16 in the extending direction is preferably a vertical surface orthogonal to the extending direction. However, when the tubular body 11 is cylindrical or the like, as shown in FIG. 3 (B), the shape of the end surface in the extending direction of the ridge portion 16 may be matched with the shape of the outer peripheral surface of the tubular body 11, thereby The discharge flow of molten steel is not affected.

In addition, it is preferable to form a concave hot water reservoir 17 at the bottom 15 of the tube body 11. The effect of the present invention is not affected even if such a recessed reservoir 17 is not provided at the bottom 15 of the tube body 11, but the molten steel poured into the immersion nozzle 10 is once received by the reservoir 17. Therefore, it is possible to disperse more uniformly and more stably in both the discharge holes 14.
In addition, the horizontal width a ′ of the discharge hole 14 does not affect the effect of the present invention regardless of whether it is the same as or different from the width of the flow path 12 (in the case of the cylindrical flow path 12).

[Water model test]
Next, a water model test carried out using a model of the immersion nozzle 10 having the above-described configuration in order to determine the optimum shape of the discharge hole 14 provided with the protruding portion 16 will be described.

First, parameters for determining the optimum shape of the discharge hole 14 provided with the ridges 16 are defined. When the discharge hole 14 is viewed from the front, the horizontal width of the discharge hole 14 is a ′, and the vertical width is b ′. The protrusion 16 has a rectangular cross section, the protrusion height of the end face of the protrusion 16 is a, the width in the vertical direction is b, and the vertical direction of the end face of the protrusion 16 from the upper edge of the discharge hole 14. Let c be the vertical distance up to ½ of the width (see FIG. 2). Here, the “rectangular cross section” includes those having rounded corners of the rectangular cross section. Also relates to the extending direction of the ridges 16, the width of the channel 12 just above the pair of discharge holes 14 length of L _1, ridges 16 excluding the inclined portion 16a (the length of the horizontal portion 16b) Is L ₂ (see FIG. 3). In addition, the downward inclination angle of the inclined portion 16a formed in the protruding portion 16 and the upper end surface 14a and the lower end surface 14b of the discharge hole 14 is θ, and the curvature radius of the corner portion of the discharge hole 14 is R.

In FIG. 4, the schematic diagram for demonstrating a water model test is shown.
The mold 21 was made 1/1 and made of acrylic resin. As for the size of the mold 21, the width in the long side direction (left and right direction in FIG. 4) was 925 mm, and the width in the short side direction (direction perpendicular to the paper surface) was 210 mm. Moreover, the water which flows into the casting_mold | template 21 from the immersion nozzle 10 was circulated using the pump so that drawing speed might correspond to 1.4 m / min.

The immersion nozzle 10 was arranged in the center of the mold 21 so that each discharge hole 14 faced the side wall 23 of the short side of the mold 21. Further, a propeller type flow velocity detector 22 is installed at a position of 325 mm from the short side wall 23 of the mold 21 (1/4 of the width in the long side direction) and 30 mm from the water surface, and the flow velocity of the reverse flow Fr is set to 3 Measured for minutes. Then, the difference Δσ in standard deviation and the average flow velocity V _av were calculated and evaluated for the measured flow velocity of the left and right reversal flows Fr.

Here, the relationship between the reversal flow rate and the casting speed (throughput) will be described.
A water model test was conducted to clarify the relationship between the difference Δσ between the standard deviations of the left and right reversal flow rates across the immersion nozzle and the throughput, and the relationship between the average value V _av of the left and right reversal flow rates and the throughput. It was confirmed that Δσ and V _av increased proportionally as it increased. At that time, the mold size and the flow channel cross-sectional area of the immersion nozzle are generally used in continuous casting of slabs, a mold having a long side direction of 700 mm to 2000 mm × short side direction of 150 mm to 350 mm, and 15 cm ^{2 to} 120 cm ² ( An immersion nozzle of φ50 mm to φ120 mm) is assumed.
If the throughput is less than 1.4 ton / min, the reversal flow rate on the molten metal surface tends to be insufficient, and if it exceeds 7 ton / min, the reversal flow rate increases, and the steel quality deteriorates due to an increase in the molten metal surface fluctuation or entrainment of mold powder. Is concerned. Therefore, the throughput is desirably 1.4 ton / min to 7 ton / min, the difference Δσ of the standard deviation of the left and right reversal flow rates is 2.0 cm / sec or less, and the average value V _av of the left and right reversal flow rates is 10 cm. / Sec to 30 cm / sec, it was found that the throughput was within the optimum range. Therefore, in the water model test results shown below, each parameter was determined based on the evaluation criteria that Δσ was 2.0 cm / sec or less and V _av was 10 cm / sec to 30 cm / sec.
In addition, the throughput value in the water model test is a value converted into molten steel with molten steel specific gravity / water specific gravity = 7.0.

FIG. 5A is a graph showing the relationship between a / a ′ and Δσ, and FIG. 5B is a graph showing the relationship between a / a ′ and V _av . In the figure, ♦ indicates the test result, and the solid line indicates the regression curve, which is the same in the following graphs. From the figure, it can be seen that Δσ is 2.0 cm / sec or less and V _av is 10 cm / sec to 30 cm / sec when a / a ′ is in the range of 0.05 to 0.38.
When a / a ′ is less than 0.05, the current blocking and rectifying effects are not sufficiently exhibited, the flow on the left and right of the immersion nozzle in the mold becomes asymmetric, and the reversal flow rate also exceeds 30 cm / sec. As a result, the molten metal surface changes drastically and adverse effects such as entrainment of mold powder occur. On the other hand, when a / a ′ exceeds 0.38, the flow velocity below the discharge hole seems insufficient, in other words, the flow velocity above the discharge hole becomes excessive, and the reverse flow velocity also exceeds 30 cm / sec. As a result, the molten metal surface changes drastically and adverse effects such as entrainment of mold powder occur.
The other parameter values when this test was implemented are as follows.
b / b ′ = 0.25, c / b ′ = 0.57, L ₂ / L ₁ = 0.83, θ = 15 °, R / a ′ = 0.14

6A is a graph showing the relationship between b / b ′ and Δσ, and FIG. 6B is a graph showing the relationship between b / b ′ and V _av . From the figure, it can be seen that Δσ is 2.0 cm / sec or less and V _av is 10 cm / sec to 30 cm / sec when b / b ′ is in the range of 0.05 to 0.5.
When b / b ′ is less than 0.05 and b / b ′ is more than 0.5, the same phenomenon as in the case of a / a ′ occurs, the molten metal surface fluctuation is severe, and there is an adverse effect such as entrainment of mold powder. Arise.
Other parameter values when this test was conducted are as follows.
a / a ′ = 0.21, c / b ′ = 0.48, L ₂ / L ₁ = 0.77, θ = 15 °, R / a ′ = 0.14

FIG. 7A is a graph showing the relationship between c / b ′ and Δσ, and FIG. 7B is a graph showing the relationship between c / b ′ and V _av . From the figure, Δσ is not sensitive to changes in the c / b ′ value. However, regarding V _av , when c / b ′ is in the range of 0.15 to 0.7, V _av is 10 cm / sec. It can be seen that it is ˜30 cm / sec.
When c / b ′ is less than 0.15 and c / b ′ exceeds 0.7, the same phenomenon as in the case of a / a ′ occurs, and the fluctuation of the molten metal surface is severe, and there is an adverse effect such as entrainment of mold powder. Arise.
Other parameter values when this test was conducted are as follows.
a / a ′ = 0.24, b / b ′ = 0.25, L ₂ / L ₁ = 0.77, θ = 15 °, R / a ′ = 0.14

8A is a graph showing the relationship between L ₂ / L ₁ and Δσ, and FIG. 8B is a graph showing the relationship between L ₂ / L ₁ and V _av . From this figure, it can be seen that when L ₂ / L ₁ is in the range of 0 to ₁ , Δσ is 2.0 cm / sec or less and V _av is 10 cm / sec to 30 cm / sec. L ₂ / L ₁ = 0 indicates that L ₂ = 0, that is, an inverted V-shaped protrusion 16 having no horizontal portion 16b. On the other hand, when L ₂ / L ₁ exceeds 1, there is a manufacturing problem that it is difficult to manufacture the immersion nozzle.
The other parameter values when this test was implemented are as follows. Further, ◇ in FIG. 8 shows the result when there is no protrusion 16 as a comparative example.
a / a ′ = 0.29, b / b ′ = 0.25, c / b ′ = 0.5, θ = 15 °, R / a ′ = 0.14

FIG. 9A is a graph showing the relationship between R / a ′ and Δσ, and FIG. 9B is a graph showing the relationship between R / a ′ and V _av , where R / a ′ = 0.5 It shows that the shape of the hole is oval or circular. From the figure, it can be seen that when R / a ′ increases, the value of Δσ slightly increases, but there is no significant change. On the other hand, with respect to V _av , when R / a ′ increases, the reversal flow rate tends to increase due to the effect of the discharge hole area becoming smaller. However, V _av is in the range of 10 cm / sec to 30 cm / sec, and it was confirmed that the protrusion works effectively even when the radius of the corner is increased.
The other parameter values when this test was implemented are as follows. The mold size in this test is 1500 mm × 235 mm, and the casting speed is 3.0 ton / min.
a / a ′ = 0.13, b / b ′ = 0.25, c / b ′ = 0.4, L ₂ / L ₁ = 1, θ = 0 °

Table 1 shows the results of water model tests carried out for the continuous casting immersion nozzle according to one embodiment of the present invention, with and without a hot water reservoir at the bottom of the tube. From the table, it can be seen that Δσ and V _av are substantially equal and within the optimum range regardless of the presence or absence of the hot water reservoir.
In addition, the parameter value at the time of implementing this test is as follows. The mold size in this test is 1200 mm × 235 mm, and the casting speed is 2.4 ton / min.
a / a ′ = 0.14, b / b ′ = 0.33, c / b ′ = 0.5, L ₂ / L ₁ = 1, θ = 0 °, R / a ′ = 0.14

[Fluid analysis]
Next, fluid analysis performed on the discharge flow of the continuous casting immersion nozzle according to the present invention and the conventional continuous casting immersion nozzle will be described.

For fluid analysis, FLUENT (fluid analysis software) manufactured by Fluent Asia Pacific Co., Ltd. was used. FIG. 10 shows an analysis model used for fluid analysis. In the figure, (A) is an example, and (B) is a conventional example. In the present analysis, as a conventional example, an immersion nozzle in which a pair of discharge holes communicating with the flow path are formed on the lower side surface of a cylindrical tubular body having a bottom portion so as to face each other is used. On the other hand, an Example provides the protrusion part which opposes in a prior art example, and the item is as follows. a / a ′ = 0.13, b / b ′ = 0.13, c / b ′ = 0.43, L ₂ / L ₁ = 0.68, θ = 15 °
The casting mold was 1540 mm in the long side direction and 235 mm in the short side direction, and the casting speed was 2.7 ton / min.

FIGS. 11A and 11B show the fluid analysis results of the example, and FIGS. 12A and 12B show the fluid analysis results of the conventional example. From these figures, it can be seen that in the example, the left and right drifts in the mold are less than in the conventional example, and the reverse flow velocity of the molten metal surface is also reduced. As a result, the molten metal surface fluctuation is reduced, and it is possible to improve the production efficiency by excellent slab quality and high speed casting.

Moreover, FIG. 13 is an average value V of the left and right reversal flow velocity when the inclination angle of the inclined portion formed on the ridge is changed with respect to the inclination angle of the upper end surface and the lower end surface of the discharge hole. _The result of having calculated the value of _av by the fluid analysis is shown. In the figure, Δθ is the difference between the inclination angle of the inclined portion formed on the ridge and the inclination angle of the upper end surface and the lower end surface of the discharge hole. When Δθ is negative, it is formed on the ridge portion. It means that the inclined portion is upward from the upper end surface and the lower end surface of the discharge hole.
From the figure, it can be seen that _Vav is the smallest when Δθ is zero, that is, when the inclined portion formed in the ridge and the upper end surface and the lower end surface of the discharge hole have the same inclination angle. Further, in the range of Δθ from −10 ° to + 7 °, V _av was 10 cm / sec to 30 cm / sec, and it was confirmed that a good reversal flow rate was exhibited.

Furthermore, in Examples, the discharge flow when the inclination angle of the inclined portion formed in the ridge and the inclination angles of the upper end surface and the lower end surface of the discharge hole are changed in synchronization was examined by fluid analysis. The results are shown in FIGS. The specifications at that time are as follows.
14A and 14B, a / a ′ = 0.13, b / b ′ = 0.25, c / b ′ = 0.4, L ₂ / L ₁ = 1, θ = 0. °, casting speed: 3.0 ton / min
15A and 15B, a / a ′ = 0.13, b / b ′ = 0.13, c / b ′ = 0.43, L ₂ / L ₁ = 0.68, θ = 25 °, casting speed: 2.7 ton / min
In the case of FIGS. 16A and 16B, a / a ′ = 0.13, b / b ′ = 0.13, c / b ′ = 0.43, L ₂ / L ₁ = 0.68, θ = 35 °, casting speed: 2.7 ton / min
In the case of FIGS. 17A and 17B, a / a ′ = 0.13, b / b ′ = 0.13, c / b ′ = 0.43, L ₂ / L ₁ = 0.68, θ = 45 °, casting speed: 2.7 ton / min
From FIG. 14 to FIG. 17 and the analysis result (FIG. 11) of θ = 15 ° shown above, when the inclination angle is 0 ° to 45 °, the deviation of the discharge flow in the mold is small, and the reverse flow velocity of the molten metal surface is also high. It can be seen that it is reduced.

Although one embodiment of the present invention has been described above, the present invention is not limited to the configuration described in the above-described embodiment, and is within the scope of matters described in the claims. Other possible embodiments and modifications are also included. For example, in the above-described embodiment, the tubular body of the continuous casting immersion nozzle is cylindrical, but includes other shapes such as a square shape. Moreover, in the said embodiment, although the inclination part is provided in the both ends of a protrusion part, an inclination part is not provided in a protrusion part, but it is good also considering the upper end surface and lower end surface of a discharge hole as horizontal. The shape of the discharge hole of the continuous casting immersion nozzle is preferably rectangular, but may be oval or elliptical.

10: immersion nozzle, 11: tube, 12: flow path, 13: inflow port, 14: discharge hole, 14a: upper end surface, 14b: lower end surface, 15: bottom, 16: protrusion, 16a: inclined portion, 16b: Horizontal portion, 17: Hot water reservoir, 18: Inner wall, 21: Mold, 22: Flow rate detector, 23: Short side wall

Claims (7)

A pair of discharge holes communicating with the flow path are opposed to a lower side surface of a tubular body having a bottom portion in which an upper end portion is an inlet of molten steel and a flow path extending downward from the inlet is formed inside. In the formed continuous casting immersion nozzle,
Immersion for continuous casting, characterized in that an inner wall that is defined between the pair of discharge holes and defines the flow path is provided with a protruding portion that protrudes inward and that crosses the inner wall in the horizontal direction. nozzle. The immersion nozzle for continuous casting according to claim 1, wherein the discharge hole is viewed from the front, the horizontal width of the discharge hole is a ', the width of the vertical direction is b', and the protrusion height of the end face of the ridge portion is A continuous casting immersion nozzle in which a / a ′ = 0.05 to 0.38 and b / b ′ = 0.05 to 0.5, where a is the vertical width and b is the vertical width. The immersion nozzle for continuous casting according to claim 2, wherein when the discharge hole is viewed from the front, a vertical distance from the upper edge of the discharge hole to ½ of the vertical width of the end face of the ridge is defined as c. C / b ′ = 0.15 to 0.7, a continuous casting immersion nozzle. The continuous casting immersion nozzle according to any one of claims 1 to 3, wherein both end portions of the protruding portion are inclined portions inclined downward toward the outside. The immersion nozzle for continuous casting according to claim 4, wherein an upper end surface and a lower end surface of the discharge hole are inclined downward toward an outer side, an inclination angle of the upper end surface and the lower end surface, and an inclination angle of the inclined portion. Submersible nozzle for continuous casting with the same angle. In the immersion nozzle for continuous casting according to claim 5 relates to the extending direction of the ridges, the width of the flow path immediately above the pair of the discharge hole L _1, of the ridges except the tilted portions An immersion nozzle for continuous casting in which L ₂ / L ₁ = 0 to _{1 when the} length is L ₂ . The immersion nozzle for continuous casting according to claim 6, wherein the upper end surface, the lower end surface, and the inclined portion have an inclination angle of 0 to 45 °.

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