JP4851199B2 - Immersion nozzle - Google Patents

Description

  The present invention relates to an immersion nozzle used for continuous casting, and more particularly to a drift of molten steel discharge flow and a splash phenomenon at the start of casting.

In the conventional immersion nozzle, at the start of casting, the lower part of the immersion nozzle is used for the purpose of suppressing the so-called splash phenomenon that the molten steel poured into the immersion nozzle is ejected so as to jump up by vigorously hitting the bottom surface. The discharge hole to be perforated is provided slightly above the bottom surface, and a so-called hot water reservoir having a substantially cylindrical shape is formed.
However, when molten steel having a velocity gradient in the mold thickness direction is poured into the immersion nozzle, or when a velocity gradient in the mold thickness direction is generated in the molten steel poured into the immersion nozzle, the molten steel in the pool portion due to a pressure difference, the molten steel flow across the basin portion to the mold thickness direction occurs (see FIG. 6 (a)). The transverse molten steel flow (refer to FIG. 6 (b)) to induce a rotational flow with axis parallel to the mold width direction, as a result, the drift of the mold thickness direction of molten steel discharge flow from the discharge hole of the immersion nozzle It will occur.
Then, due to the drift of the molten steel discharge flow, the shell in the vicinity of the mold corner portion already solidified / formed is remelted, and as a result, a so-called solidification delay, which is non-uniform shell growth, is generated.
When this solidification delay is significant, there is a concern about so-called breakout in which the shell is broken and the molten steel flows out of the shell.
In addition, it has already been clarified that the drift of the molten steel discharge flow does not depend on the opening / closing direction of the slide plate for adjusting the flow rate of the molten steel poured into the immersion nozzle (Non-Patent Document 1 and Non-Patent Document 1). Patent Document 2).

  For the purpose of preventing the drift of the molten steel discharge flow in the mold thickness direction, for example, the inner wall of the immersion nozzle is formed in a mogul shape (uneven shape), and the molten steel flow in the immersion nozzle is used as a strong turbulent flow field. Technology has been proposed. However, according to the present technology, the manufacturing cost of the immersion nozzle is greatly increased, and the effect of making the molten steel flow a strong turbulent flow field is lost in a relatively short period of time due to deposits on the inner wall. It is supposed to end up.

Further, as this type of technology, for example, there is one described in Patent Document 1.
The configuration described in Patent Document 1 is as follows. That is, a hemispherical recess is formed at the bottom of the immersion nozzle. According to this, the molten steel flowing down the immersion nozzle rises by reversing the inside of the immersion nozzle again by the hemispherical bottom, so that the molten steel flowing further collides with the inverted molten steel. As a result, the flow of molten steel is calmed down.
According to the above configuration, the flow rate of the molten steel discharged from the immersion nozzle is made uniform, the amount of outflow from the left and right discharge ports becomes equal, and vortices and excessive upward flow are not generated.

JP-A-2-1658551 Kenji Ichikawa, 2 others, “About the flow in a submerged nozzle tube [Results of water model experiment on tundish SN; 3rd report]”, Refractory, Refractory Technology Association, January 1990, Vol. 42, No. 1 , P.43-46 A. R. ARManderas, “Dynamics of two-phase downwards flow in submerged entry nozzle and its influence on the two-phase flow in the mold ”, Int. J. International Journal of Multiphase Flow, Netherlands, ELSEVIER, 2005, Vol. 31, p.643-665

Conventionally, in general, it has been a problem to improve the flow of molten steel in a mold in many ways.
The configuration of Patent Document 1 has been quite useful in solving this problem, but the development of a more useful immersion nozzle has been desired.

  The present invention has been made in view of such various points, and its main purpose is to suppress the splash phenomenon at the start of casting and reduce the drift in the mold thickness direction of the molten steel discharge flow. Is to provide.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

According to the 1st viewpoint of this invention, the immersion nozzle comprised as follows is provided.
A pair of opposing discharge holes are drilled in the vicinity of the inner bottom surface of the nozzle, and a recess extending in the nozzle radial direction is formed in the inner bottom surface of the nozzle.
The vertical cross section in the longitudinal direction of the recess is rectangular or trapezoidal.
The side of the vertical cross section in the longitudinal direction of the recess is parallel to the longitudinal direction of the immersion nozzle or is inclined more than 0 degree and 50 degrees or less with respect to the longitudinal direction of the immersion nozzle .
The concave portion is an inner angle of a vertical cross section in the longitudinal direction, and is formed so that a portion far from the inner bottom surface of the nozzle is 90 degrees or more and 140 degrees or less.
The ratio h / D, which is the ratio of the depth h of the vertical cross section in the longitudinal direction of the concave portion to the inner diameter D of the immersion nozzle, is in the range of 0.1 ≦ h / D ≦ 1.0.
Y / Y which is a ratio of the width y of the lower side of the vertical cross section in the longitudinal direction of the concave portion and the opening width Y of the inner circumferential side opening end of the discharge hole is 0.4 ≦ y / Y ≦ 1.0. Is within the range.
And the direction of the discharge port is a direction connecting the opening center of the center point and the discharge hole of the nozzle inner diameter in a plan view, a longitudinal direction of the recess, the angle θ2 formed by the the direction of the discharge hole, the Θ2 / θ3, which is the ratio of the angle θ3 formed by the surface connecting the side of the inner peripheral opening end of the discharge hole and the axis of the immersion nozzle, is in the range of 0 ≦ θ2 / θ3 ≦ 1.0 Is within.
However, the “rectangular shape or trapezoidal shape” includes those in which arcs are formed at the corners.

  Thereby, the splash phenomenon at the start of casting can be suppressed, and the drift of the molten steel discharge flow in the mold thickness direction can be greatly reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view of an immersion nozzle according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line 2-2 in FIG. 3 is an enlarged view of portion A in FIG. 1, and FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. FIG. 5 is a view similar to FIG.

  In the present embodiment, a continuous casting immersion nozzle (hereinafter simply referred to as an immersion nozzle) 100 is formed in a substantially cylindrical shape with a bottom, as shown in FIGS. A pair of opposed discharge holes 2 and 2 are perforated (see also FIG. 4).

As shown in FIG. 1, the discharge holes 2 and 2 have a substantially rectangular vertical cross section in the drilling direction, and as shown in FIG. 2, the discharge holes 2 and 2 expand in a fan shape as they move away from the axis of the immersion nozzle 100. 4 is formed slightly obliquely downward.
Further, in the present embodiment, the immersion nozzle 100 is configured such that the lower side of the inner peripheral side opening ends 2a and 2a of the discharge holes 2 and 2 and the nozzle inner bottom surface 1 are the axis of the immersion nozzle 100 as shown in FIG. It is comprised so that it may correspond in a direction.

  As shown in FIGS. 1, 2, and 4, the nozzle inner bottom surface 1 extends in the diameter direction of the immersion nozzle 100, and its longitudinal length substantially coincides with the inner diameter D of the immersion nozzle 100. A recess 4 is provided.

The vertical cross section of the concave portion 4 in the longitudinal direction is formed in a rectangular or trapezoidal shape as shown in FIGS. The “rectangular shape or trapezoidal shape” includes those in which arcs are formed at the corners as shown in FIGS. 1 and 3.

As shown in FIG. 3, the side 4a of the vertical section of the concave portion 4 in the longitudinal direction is parallel to the longitudinal direction of the immersion nozzle 100 (that is, the vertical direction) or 0 degrees with respect to the longitudinal direction of the immersion nozzle 100. And is inclined to the outside by 50 degrees or less. In other words, when the outer side inclination angle θ1 of the side edge 4a is not less than 0 degrees and not more than 50 degrees and the outer side inclination angle θ1 is 0 degree (the side edge 4a in the vertical section of the longitudinal direction of the recess 4 is In the case of being parallel to the longitudinal direction of the immersion nozzle 100) , it can be said that the vertical cross section of the concave portion 4 is rectangular. In other words, the concave portion 4 is formed so that the inner corner of the longitudinal section in the longitudinal direction and the far side with respect to the nozzle inner bottom surface 1 is 90 degrees or more and 140 degrees or less.

  Further, as shown in the figure, h / D which is a ratio of the depth h of the vertical cross section in the longitudinal direction of the recess 4 and the inner diameter D of the immersion nozzle 100 is 0.1 ≦ h / D ≦ 1. It is comprised so that it may become in the range of 0.

  Further, as shown in this figure, y / is the ratio of the width y of the lower side of the vertical section of the recess 4 in the longitudinal direction and the opening width Y of the inner peripheral side opening ends 2a and 2a of the discharge holes 2 and 2. Y is configured to be within a range of 0.4 ≦ y / Y ≦ 1.0. In the figure, the ratio y / Y is about 0.3.

In the present embodiment, as shown in the figure, an arc having a radius R1 within the range of 0 ≦ R1 ≦ y / 2 may be formed at the corner of the vertical section of the recess 4 in the longitudinal direction. . For example, the lower side of the vertical cross section in the longitudinal direction of the concave portion 4 may be a complete arc without a flat portion (in this case, R1 is about y / 2). In the present embodiment, the radius R1 is about y / 3 as shown in FIG.
Note that, as described above, the symbol y is the width of the lower side of the vertical section of the recess 4 in the longitudinal direction. However, when the corner of the vertical section is formed in an arc shape as shown in FIG. y is defined as the distance between the first virtual intersection of the lower side and the one side 4a and the second virtual intersection of the lower side and the other side 4a.

For example, as shown in FIG. 5, the direction of the discharge holes 2, 2, which is a direction connecting the center point of the inner diameter of the immersion nozzle 100 and the center of the discharge holes 2, 2 in plan view, and the length of the recess 4 surface connecting the direction, the angle θ2 formed by the direction toward said discharge port 2-2, sides of the discharge holes 2.2 on the inner peripheral side opening end 2a, 2a and the axis of said immersion nozzle 100 , Θ2 / θ3, which is a ratio of the angle θ3 formed by the above, is configured to be in a range of 0 ≦ θ2 / θ3 ≦ 1.0. In the present embodiment, the ratio θ2 / θ3 is substantially zero as shown in FIG.

  Next, the operation of this embodiment will be described.

  The immersion nozzle 100 according to the present embodiment is used as a guide for pouring molten steel temporarily stored in a tundish (not shown) into a mold for forming a slab shell, for example, in a continuous casting machine. Is.

The immersion nozzle 100 is detachably attached to the tundish tank bottom in advance before the start of casting, and is attached so that the discharge holes 2 and 2 substantially face the narrow surface of the mold.
Next, the tundish to which the immersion nozzle 100 is attached is lowered to a predetermined position, whereby the immersion nozzle 100 is inserted into the mold to an appropriate depth.
Next, a dummy bar (not shown) for pulling out the slab is inserted into the continuous casting machine.
Then, a slide valve (not shown) provided at the bottom of the tundish is appropriately opened. As a result, molten steel held in the tundish starts to be poured into the mold through the immersion nozzle 100.
Next, the slab formed by cooling in the mold is drawn out to the dummy bar at an appropriate casting speed. Thereby, continuous casting is started.

Hereinafter, the molten steel flow in the immersion nozzle 100 according to the present embodiment will be described in comparison with a comparative example. FIG. 6 is a longitudinal sectional view of a conventional immersion nozzle, schematically showing a molten steel flow in the nozzle, and FIG. 7 is a view similar to FIG. The molten steel flow in the nozzle is schematically represented. 6 and 7 , for convenience of explanation, the outer peripheral side opening end of the discharge hole that appears inside the inner peripheral side opening end in the drawing is omitted.

In the conventional immersion nozzle as shown in FIG. 6 (a), when molten steel having a velocity gradient in the mold thickness direction is poured, or when a velocity gradient in the mold thickness direction is generated in the molten steel for some reason, Due to the pressure difference of the molten steel generated in the hot water pool portion, a molten steel flow that crosses the hot water pool portion in the mold thickness direction is generated. Then, as shown in FIG. 6 (b), this transverse molten steel flow induces a rotating flow having an axis parallel to the mold width direction, and as a result, the molten steel discharge flow from the discharge hole of the immersion nozzle has a mold thickness direction. Drift will occur.
On the other hand, as shown in FIG. 7 , the immersion nozzle 100 according to the present embodiment is not formed with a hot water reservoir as in the comparative example, and instead, the nozzle inner bottom surface 1 is radially arranged as described above. A recess 4 extending in the shape of the recess 4 is provided with a width (y) smaller than at least the opening width Y of the inner peripheral opening ends 2a and 2a of the discharge holes 2 and 2 (also in FIG. 3). See also). Therefore, even if molten steel having a velocity gradient in the mold thickness direction is poured, or even if a molten steel having a velocity gradient in the mold thickness direction is generated in the molten steel for some reason, the rotational flow is induced. The crossed molten steel flow is very difficult to generate, and the molten steel discharge flow is discharged in the form of the discharge holes 2 and 2 in the drilling direction. Thereby, compared with the said conventional immersion nozzle, the immersion nozzle 100 which concerns on this embodiment can reduce significantly the drift of the mold thickness direction of a molten steel discharge flow. In addition, the concave portion 4 is appropriately provided in the inner bottom surface 1 of the nozzle so that the splash phenomenon at the start of casting described above can be suppressed.

  Hereinafter, a test for confirming the technical effect of the submerged nozzle 100 according to the present embodiment, that is, a first confirmation test for evaluating the drift and splash phenomenon in the mold thickness direction of the molten steel discharge flow, and the solidification delay described above. Will be described with reference to the second confirmation test. Each numerical range described above is reasonably supported by the following first and second confirmation tests that are closely related to each other.

<First confirmation test>
In this test, as shown in Table 1 below, various recesses with different shapes and sizes were formed in the bottom surface inside the nozzle, and a discharge experiment using water instead of molten steel was conducted. The drift in the thickness direction and the splash phenomenon were evaluated, and the shape and size of the recesses were comprehensively evaluated based on these evaluations.

(Evaluation of drift)
The evaluation of “drift” in Table 1 is specifically performed as follows. FIG. 8 is a front view of the immersion nozzle.
That is, as shown in FIG. 8 , the flow rate of the water discharge flow discharged from the discharge hole of the immersion nozzle was measured at 9 points in a checkerboard shape using an appropriate flow rate detection device (for example, an electromagnetic current meter). An example of the measurement results shown in FIGS.
And among the measurement results, the speed difference between the lower right column and the lower left column is calculated (see the thick circle in FIG. 8 ), and when the absolute value is less than 0.2 m / s, “○ (no drift) ”), And when it was 0.2 m / s or more, it was evaluated as“ × (with drift) ”.

(Evaluation of splash phenomenon)
Here, as described above, the `` splash phenomenon '' refers to a phenomenon that the molten steel poured into the immersion nozzle at the start of casting is discharged so as to jump up by vigorously hitting the bottom surface. Not only that, but also includes a phenomenon in which molten steel is vigorously discharged downward from the discharge hole of the immersion nozzle and jumps up through the upper end surface of the dummy bar and the narrow surface of the mold that are inserted in advance into the mold. .
The “scattering height” in Table 1 relates to the former phenomenon, and the “bubble dive depth” in Table 1 also relates to the latter phenomenon. The latter phenomenon was indirectly evaluated by evaluating the strength of the water flow discharged downward from the discharge hole (bubble dive depth). Note that these splash phenomena are not preferable because of a decrease in productivity.

The evaluation of the “scattering height” in Table 1 is specifically performed as follows. FIG. 11 is a side view of the immersion nozzle.
That is, as shown in FIG. 11 , the arrival height of water droplets discharged and scattered upward from the discharge hole of the immersion nozzle was measured visually with reference to the upper side of the outer peripheral opening end of the discharge hole.
And when this reach | attainment height was less than 15 cm, it was set as "(circle) (scattering height small)", and when it was 15 cm or more similarly, it evaluated as "* (scattering height high)".

On the other hand, the evaluation of the “bubble dive depth” in Table 1 is specifically performed as follows.
That is, as shown in FIG. 11 , a water tank whose water surface height is adjusted so that the vertical distance to the lower end of the immersion nozzle is 5 cm is installed below the immersion nozzle, and downward from the discharge hole of the immersion nozzle. The arrival depth of the bubbles in which the water discharge flow discharged vigorously was measured was measured visually with reference to the water surface.
And when this reach | attainment depth was less than 35 cm, it was set as "(circle) (bubble dive depth small)", and when it was 35 cm or more similarly, it evaluated as "* (bubble dive depth is large)."
In addition, the observation object which records this reaching depth is the bubble entrained by the water discharge flow,
The diameter was limited to 5 mm or more.

  The “comprehensive evaluation” in Table 1 above is based on whether or not all the evaluations regarding the “drift”, “scattering height”, and “bubble dive depth” are good (that is, “◯”). Is to be judged.

<First Confirmation Test (A): Ratio h / D>
In as the recesses 4 of the immersion nozzle 100 is described above with reference to FIGS. 6 and 7 with respect to the principles of the relief / effect of suppressing the splash phenomenon of the foregoing and drift of the mold thickness direction of the molten steel discharge flow according to the embodiment is there.
This test is a test for confirming the influence of the ratio h / D on the splash phenomenon (see also FIG. 3). The test results of this test are shown in FIG. 12.
In this test, the ratio y / Y is 0.5, the outer inclination angle θ1 is 0 degree, the ratio θ2 / θ3 is 0, the ratio x / X is 0, and the radius R1 is 0 mm. The water flow rate was set to 550 L / min, respectively.
According to this figure, it can be seen that the splash phenomenon is satisfactorily suppressed when the ratio h / D is particularly 0.1 or more.
On the other hand, as the ratio h / D increases, it becomes difficult to ensure the strength against breakage of the immersion nozzle. Therefore, it can be said that the ratio h / D is preferably 1.0 or less in actual operation.

<First Confirmation Test (B): Ratio y / Y (1)>
This test is a test for confirming the influence of the ratio y / Y on the effect of reducing the drift (see also FIG. 3). The test results of this test are shown in FIG. 13.
In this test, the ratio h / D is 0.3, the outer inclination angle θ1 is 0 degree, the ratio θ2 / θ3 is 0, the ratio x / X is 0, and the radius R1 is 0 mm. The water flow rate was set to 550 L / min, respectively.
According to the figure, it can be seen that the effect of reducing the drift is excellent when the ratio y / Y is in the range of 0 ≦ y / Y ≦ 1.0 (see FIGS. 6 and 7) . See also).

<First Confirmation Test (C): Ratio y / Y (2)>
This test is a test for confirming the influence of the ratio y / Y on the effect of suppressing the splash phenomenon (see also FIG. 3). The test results of this test are shown in FIG. 14.
As in the first confirmation test (B), the ratio h / D is 0.3, the outer inclination angle θ1 is 0 degrees, the ratio θ2 / θ3 is 0, and the ratio h / D is 0. x / X was set to 0, the radius R1 was set to 0 mm, and the water flow rate was set to 550 L / min.
According to the figure, it can be seen that the effect of suppressing the splash phenomenon is excellent when the ratio y / Y is in the range of 0.4 ≦ y / Y ≦ 1.0.

Then, the ratio y / Y is why it is not possible to satisfactorily suppress the splash phenomenon described above if not within the above range will be described with reference to FIGS. 15 and 16. 15 and 16 are similar to FIGS. 6 and 7 , respectively.
That is, when the ratio y / Y as shown in FIG. 15 (a) is in the large case (more specifically than 1.0, the hot water reservoir portion substantially cylindrical described above the bottom of the immersion nozzle is formed ), A rotating flow having an axis parallel to the mold width direction is generated in the same manner as in FIG. 6 (a), and in the direction (diagonal direction) indicated by the white arrow in this figure (FIG. 15 (a)). It is because molten steel is discharged vigorously. Therefore, as shown in FIG. 14 , when the ratio y / Y is 1.0 or more, both the scattering height and the bubble dive depth are remarkably large values.
On the other hand, if the ratio y / Y as shown in FIG. 15 (b) is less than 0.4, since the recess is not sufficiently secured, molten steel is subtracted its momentum by the recess to be secured This is because the ink is discharged directly from the discharge hole downward. Therefore, as shown in FIG. 14 , when the ratio y / Y is less than 0.4, the bubble dive depth is a remarkably large value.
In contrast, if the ratio y / Y as shown in Figure 16 is 0.4 ≦ y / Y ≦ 1.0, rotational flow as shown in FIG. 15 (a) to have become hard to occur, By appropriately securing the concave portion, the molten steel is appropriately branched / dispersed before being discharged from the discharge hole, and the momentum is reduced by colliding with the inner peripheral surface of the immersion nozzle. And the bubble dive depth are suppressed at the same time.

  In light of the test results of the first confirmation tests (B) and (C), the effect of reducing the drift is particularly when the ratio y / Y is in the range of 0.4 ≦ y / Y ≦ 1.0. It can be seen that the above-described splash phenomenon is satisfactorily suppressed.

<First Confirmation Test (D): Outside Inclination Angle θ1>
This test is a test for confirming the influence of the outer inclination angle θ1 on the effect of reducing the drift (see also FIG. 3). The test results of this test are shown in Figure 17.
In this test, the ratio h / D is 0.3, the ratio y / Y is 0.5, the ratio θ2 / θ3 is 0, the ratio x / X is 0, and the radius R1 is 0 mm. The water flow rate was set to 550 L / min.
According to this figure, it can be seen that the effect of reducing the above-described drift is satisfactorily achieved when the outer inclination angle θ1 is in the range of 0 ≦ θ1 [degree] ≦ 50.

Next, a description will be given of a reason why the outer inclination angle θ1 is preferred in terms of the effect of reducing the drift of the in the range of the Figure 18. Figure 18 is a view similar to FIG.
That is, as shown in FIG. 18 (a), when the outer inclination angle θ1 is larger than 50 degrees, the side 4a of the recess 4 opens to the left and right, so that the molten steel having a velocity gradient in the mold thickness direction is obtained. When a molten steel poured for some reason has a velocity gradient in the mold thickness direction, the molten steel flow crosses the recess in the mold thickness direction due to the pressure difference of the molten steel generated in the recess. occurs because thereby (FIG. 6 (a) and (b) see also together).
Although not shown, when the outer inclination angle θ1 is smaller than 0 degree (in the negative case), the concave portion has a shape that expands toward the back, so that the processing is extremely difficult and the productivity of the immersion nozzle is remarkable. Since it falls, it is not preferable.
On the other hand, if the outer inclination angle .theta.1 as shown in FIG. 18 (b) is in the range of 0 ≦ .theta.1 [degrees] ≦ 50 (substantially 0 ° in the figure), the sides of the recess (side surface) described above since it will be formed so as to block the "molten steel flow across the mold thickness direction (see FIG. 6 (a))", since the effect of reducing the flow distortion is effectively achieved. As a result, it is considered that the inside of the recess is in a state where molten steel is stagnated.

<First Confirmation Test (E): Ratio θ2 / θ3>
This test is a test for confirming the influence of the ratio θ2 / θ3 on the effect of reducing the drift (see also FIG. 3). The test results of this test are shown in Figure 19.
In this test, the ratio h / D is 0.3, the ratio y / Y is 0.5, the outer inclination angle θ1 is 0 degrees, the ratio x / X is 0, and the radius R1 is The water flow rate was set to 0 mm and 550 L / min, respectively.
According to this figure, it can be seen that the effect of reducing the above-mentioned drift is satisfactorily achieved when the ratio θ2 / θ3 is in the range of 0 ≦ θ2 / θ3 ≦ 1.0.

Next, the reason why it is preferable that the ratio θ2 / θ3 is within the above range will be described with reference to FIGS. 20 and 21 . 20 and 21 are both similar to FIG.
That is, as shown in FIG. 20, when the ratio θ2 / θ3 is in the range of 0 ≦ θ2 / θ3 ≦ 1.0 (about 0.5 in the figure), the side (side surface) of the recess is the above-mentioned “ (in other words so as to block the molten steel flow across the mold thickness direction (see FIG. 6 (a)) ", the direction of the molten steel flow to be to cross into the mold thickness direction, the longitudinal direction of the recess, but a large angle to each other This is because the effect of reducing the drift is effectively achieved. As a result, it is considered that the inside of the recess is in a state where molten steel is stagnated.
On the other hand, as shown in FIG. 21, when the ratio θ2 / θ3 is larger than 1.0 (about 2.0 in the figure), the direction of the molten steel flowing across the mold thickness direction and the longitudinal direction of the recess ( This is because the angle formed by intersecting the extending direction) is small, so that it is difficult to sufficiently block the molten steel flow to be crossed. As a result, the above-mentioned drift occurs as described above.

  As described above, the technical effect of the immersion nozzle 100 according to the above embodiment was confirmed through the first confirmation tests (A) to (E). In addition to the above tests, the inventors of the present invention described below. Also report that the test was conducted.

<Test 1 : Radius R1>
This test is a test for investigating the influence of the radius R1 on the effect of reducing the drift (see also FIG. 3). The test results of this test are shown in Figure 22.
In this test, the ratio h / D is 0.3, the ratio y / Y is 0.5, the outer inclination angle θ1 is 0 degrees, the ratio θ2 / θ3 is 0, and the ratio x / X was set to 0, and the water flow rate was set to 550 L / min.
According to the figure, it can be seen that the effect of reducing the above-mentioned drift is excellent even if the radius R1 is set to any value within the range of at least 0 ≦ R1 ≦ y / 2.

<Second confirmation test>
In this test, medium carbon steel was actually cast using a conventional immersion nozzle (comparative example) and an immersion nozzle (example) according to the present invention. At that time, a mold having a slab width of 1240 mm and a slab thickness of 240 mm was used, and a casting speed was set to 1.4 m / min or 1.6 m / min.
And the vertical section of the longitudinal direction of the cast slab was observed, and the immersion nozzle according to the present invention was evaluated based on the degree of solidification delay. FIG. 23 is an explanatory diagram relating to the degree of solidification delay, and FIG. 24 is a diagram showing the test results of this test.

The “coagulation delay” is obtained by measuring as follows. That is, as shown in FIG. 23 , first, the cast slab is cut in a direction perpendicular to the longitudinal direction. Second, the distance between the hot water pattern (white band) appearing in this vertical section and the slab wide surface is measured. More specifically, the distance is measured at two locations: a location 5 cm away from the slab narrow surface along the slab wide surface and a location where the hot water pattern appears closest to the slab wide surface. To do. In the figure, the distance measured at the former location corresponds to symbol A, and the distance measured at the latter location corresponds to symbol B. Third, the distance obtained by subtracting the distance B from the distance A is divided by the distance B to obtain the “coagulation delay degree”.
In addition, said "solidification delay degree" is calculated | required based on the result obtained by measuring the distance between a hot water pattern and a slab wide surface as mentioned above, and a hot water pattern and a slab narrow surface. It is conceivable that it is obtained based on the result obtained by measuring the distance between them. In the graph shown in FIG. 24 , any of these solidification delays is plotted.

According to FIG. 24, when the immersion nozzle according to the present invention is used, the degree of solidification delay (especially, the maximum) is significantly improved at any casting speed as compared with the conventional immersion nozzle. I understand.

As described above, in the above-described embodiment, the immersion nozzle 100 for continuous casting is configured as follows.
That is, a pair of opposed discharge holes 2 and 2 are formed in the vicinity of the nozzle inner bottom surface 1, and a concave portion 4 extending in the nozzle radial direction is formed in the nozzle inner bottom surface 1.
The vertical cross section in the longitudinal direction of the recess 4 is rectangular or trapezoidal.
The side 4a of the vertical cross section in the longitudinal direction of the recess 4 is parallel to the longitudinal direction of the immersion nozzle 100, or is inclined to the outside of more than 0 degree and 50 degrees or less with respect to the longitudinal direction of the immersion nozzle , The concave portion 4 is formed so that the inner angle of the vertical cross section in the longitudinal direction is 90 ° or more and 140 ° or less on the side far from the nozzle inner bottom surface 1.
The ratio h / D, which is the ratio of the depth h of the vertical section in the longitudinal direction of the concave portion 4 to the inner diameter D of the immersion nozzle 100, is in the range of 0.1 ≦ h / D ≦ 1.0.
The ratio y / Y between the width y of the lower side of the vertical cross section of the concave portion 4 and the opening width Y of the inner peripheral opening ends 2a and 2a of the discharge holes 2 and 2 is 0.4 ≦ It is in the range of y / Y ≦ 1.0.
And direction towards the discharge hole 2 is a direction connecting the opening center of the center point and the discharge hole 2.2 of the nozzle inner diameter in a plan view, a longitudinal direction of the recess 4, the angle θ2 formed by the discharge hole 2 and direction towards the the surface connecting the sides and the axis of said immersion nozzle 100 of the inner peripheral side opening end 2a of the discharge hole 2, the angle .theta.3 formed by, the ratio a is .theta.2 / .theta.3 of 0 ≦ It is in the range of θ2 / θ3 ≦ 1.0.
As described above, the “rectangular or trapezoidal shape” includes those in which arcs are formed at the corners.

Thereby, the splash phenomenon at the start of casting can be suppressed, and the drift of the molten steel discharge flow in the mold thickness direction can be greatly reduced (see Table 1).
Moreover, this effect is produced without being influenced by the opening and closing direction of the slide plate for adjusting the molten steel flow rate.

  As described above, the preferred embodiment of the present invention has been described. However, the immersion nozzle according to the present invention can be appropriately changed as follows.

  That is, in the above-described embodiment, the immersion nozzle 100 is configured such that the nozzle inner bottom surface 1 and the lower sides of the inner peripheral side opening ends 2a and 2a of the discharge holes 2 and 2 substantially coincide with each other in the axial direction of the immersion nozzle 100. However, the present invention is not limited to this, and both may be different in the axial direction.

The longitudinal cross-sectional view of the immersion nozzle which concerns on one Embodiment of this invention. FIG. 2 is a sectional view taken along line 2-2 in FIG. 1. The A section enlarged view in FIG. FIG. 4 is a sectional view taken along line 4-4 in FIG. The figure similar to FIG. The longitudinal cross-sectional view of the conventional immersion nozzle. The figure similar to FIG. The front view of an immersion nozzle. The figure which shows an example of the measurement result of the flow velocity of a water discharge flow. The figure which shows an example of the measurement result of the flow velocity of a water discharge flow. The side view of an immersion nozzle. The figure which shows the test result of a 1st confirmation test (A). The figure which shows the test result of a 1st confirmation test (B). The figure which shows the test result of a 1st confirmation test (C). Similar to Figure 6. Similar to Figure 7. The figure which shows the test result of a 1st confirmation test (D). Similar to Figure 6. The figure which shows the test result of a 1st confirmation test (E). The figure similar to FIG. The figure similar to FIG. The figure which shows a reference test result. Explanatory drawing of a coagulation delay degree. The figure which shows the test result of a 2nd confirmation test.

DESCRIPTION OF SYMBOLS 1 Nozzle inner bottom face 2 Discharge hole 2a Inner peripheral side opening end 4 of a discharge hole Recessed part 4a Side edge of the vertical cross section of the recessed part in the longitudinal direction θ1 Outer inclination angle θ2, θ3 Angle 100 Immersion nozzle

Claims (1)

A pair of opposed discharge holes are drilled in the vicinity of the nozzle inner bottom surface, and a recess extending in the nozzle radial direction is provided in the nozzle inner bottom surface,
The vertical cross section in the longitudinal direction of the recess is rectangular or trapezoidal,
The side of the vertical cross section in the longitudinal direction of the recess is parallel to the longitudinal direction of the immersion nozzle or is inclined outwardly from 0 degree to 50 degrees or less with respect to the longitudinal direction of the immersion nozzle ,
The concave portion is an internal angle of a vertical cross section in the longitudinal direction, and is formed so that the one far from the inner bottom surface of the nozzle is 90 degrees or more and 140 degrees or less,
H / D, which is the ratio of the depth h of the vertical cross section in the longitudinal direction of the concave portion and the inner diameter D of the immersion nozzle, is in the range of 0.1 ≦ h / D ≦ 1.0,
Y / Y which is a ratio of the width y of the lower side of the vertical cross section in the longitudinal direction of the concave portion and the opening width Y of the inner circumferential side opening end of the discharge hole is 0.4 ≦ y / Y ≦ 1.0. Within the range of
And the direction of the discharge port is a direction connecting the opening center of the center point and the discharge hole of the nozzle inner diameter in a plan view, a longitudinal direction of the recess, the angle θ2 formed by the the direction of the discharge hole, the Θ2 / θ3, which is the ratio of the angle θ3 formed by the surface connecting the side of the inner peripheral opening end of the discharge hole and the axis of the immersion nozzle, is in the range of 0 ≦ θ2 / θ3 ≦ 1.0 An immersion nozzle, characterized in that