KR100423947B1 - submerged entry nozzle for continous casting - Google Patents

Abstract

The present invention forms a symmetrical flow of molten steel in the mold during continuous casting by minimizing the range of the flow rate and pressure change in the nozzle for the continuous casting immersion nozzle to reduce the height difference of the hot water, according to the position of the separator The present invention relates to an immersion nozzle structure capable of producing a cast of good quality with a uniform solidification cell thickness by ensuring a stable flow phenomenon of molten steel in a mold according to a change in the minimum cross-sectional area of an appropriate discharge portion, the width and the angle of a separator.

According to this configuration, the cylindrical pipe-shaped upper end portion 21a from the nozzle inlet portion to the discharge portion and the primary conversion portion 22a having a constant internal cross-sectional area, and the secondary conversion portion 23 with the internal cross-sectional area gradually increasing and the It is a technique for continuous casting immersion nozzle, characterized in that the inner cross-sectional area is composed of a peripheral ring portion 24a gradually increasing, and the separator 25a for inducing a symmetrical flow of molten steel in the center of the end of the peripheral ring portion. .

Description

Submerged entry nozzle for continous casting

The present invention relates to an immersion nozzle for continuous casting of molten steel, and more particularly, by supplying molten steel into a mold without a rapid change in flow rate inside the immersion nozzle, inducing uniform distribution of the discharge flow and ensuring a uniform solidification cell thickness. The present invention relates to an immersion nozzle structure suitable for continuous casting, which can produce quality castings.

The immersion nozzle for molten steel casting is used between tundish and mold during continuous casting of steel, and plays a major role in improving the quality of cast steel by preventing the mixing of the molding agent by preventing oxidation of molten steel and vortex prevention of molten steel. Will be

Immersion nozzles for continuous casting of slab generally have a thickness of 50 to 80 mm, and the inside of the inner wall of the immersion nozzle corresponding to this mold has a width of 20 to 40 mm and an exit volume of 100 mm or more. Immersion nozzles are used.

In the slab continuous casting machine, the molten steel flow in the mold is directly or indirectly related to the prevention of mixing of the casting agent due to the stability of the water surface behavior, ensuring the uniform cooling capacity of the surface of the cast steel, and the prevention of breakout due to the inflow of the casting agent. In order to ensure stable operation during continuous casting of the sleeve, it is essential to secure a strict flow form. For this purpose, various types of immersion nozzles have been used.

Such a nozzle has a large change in cross-sectional area from the inlet to the discharge part, so that the flow rate decreases and increases in the nozzle, and the discharge flow rate becomes nonuniform as the variation in the flow velocity in the longitudinal and transverse directions inside the nozzle is uneven. It is difficult to keep the hot water surface of the molten steel in the mold difficult to generate a drift due to the transverse flow rate difference.

As a result, there is a delay of solidification locally and the thickness of the solidification cell becomes thinner than other parts. As a result of tension, vertical cracking occurs on the surface of the slab. There is a need for the shape of the immersion nozzle can be made.

As a means for solving the above-described problems, for example, in Japanese Patent Laid-Open No. 2000-23326 (hereinafter referred to as "first invention 1"), the shape of the discharge portion 26 is as shown in Figs. 1A and 2B. It consists of the angle a = 0-60, the angle b = 30-80 degree, and T / t = 75-200%, and the cylindrical pipe upper end part 21 and the discharge part 26 in the inner wall 10 of the immersion nozzle. It consists of a primary conversion portion 22 extending toward the side and the peripheral ring portion 24 having the same diameter as the end of the conversion portion.

And in International Application No. PCT / CA95 / 00228 (hereinafter referred to as "Selection 2"), the total convergence angle c = 2.0 to 8.6 ° of the front wall as shown in Figs. 3a and 3b, preferably 5.3 °, the total convergence of the side walls. The angle d = 16.6 to 6 degrees, preferably 10.4 degrees, and the deflection portion is configured similarly to the nozzle of 10 to 80 degrees, preferably 30 degrees.

In the above-described first invention, in the shape where the upper portion 61 of the separator 25 is deflected, molten steel collides with the separator 25 when the molten steel passes through the molten metal and scatters to the outside of the mold. No symmetrical flow of molten steel into the mold can be induced, resulting in drift in the mold.

In addition, even if the bottom angle b is in the range of 30 to 80 °, the flow velocity in the outer circumferential portion 62 rapidly increases, making it difficult to maintain the original angle due to wear caused by molten steel. The flow phenomenon of molten steel is different.

In addition, when the T / t is 100% or less, as shown in FIG. 9, the location of the collision point F with respect to the mold wall is closer to the surface of the molten steel, so that the flow velocity and area of the molten steel flow S1 having a reverse flow form are increased. The height difference from the water surface S0 becomes 10 mm or more, and stable operation cannot be performed.

On the other hand, the invention 2 of FIGS. 3A and 3B has a small cross-sectional area variation, but the flow velocity of the center portion in the transverse direction of the submerged nozzle is increased by increasing the transverse length of the submerged nozzle at 5 ° or more. ) And the nozzle inner wall-side flow velocity 52a are generated to generate a drift. This is because the flow velocity in the center is greater than that in the nozzle inner wall, and the flow of molten steel is concentrated on the separator 25 and the flow phenomenon in the mold generates a small size double roll flow. Since the position is close to the water surface S0, the height difference of the water surface by the molten steel flow S1 which has a counterflow form appears large.

As described above, in the shape of the immersion nozzle, the change in the cross-sectional area inside the nozzle, the length in the lateral direction, and the shape of the separator make the flow phenomenon of the molten steel unstable, which makes the mold surface instability unstable.

The present invention is to solve the above-mentioned problems, and to adjust the minimum cross-sectional area of the discharge portion, the angle of the separator, the width of the separator appropriately, such as to have a cross-sectional area gradually increasing in surface area from the upper end of the cylindrical pipe toward the discharge portion By immersing the nozzle, the phenomenon of molten steel flow in the mold can be secured stably, and it is possible to provide a casting immersion nozzle suitable for continuous casting. There is this.

Figure 1a is a front sectional view of a conventional immersion nozzle

FIG. 1B is a side cross-sectional view of FIG. 1A

FIG. 2 is an enlarged side view of part “A” of FIG. 1B;

Figure 3a is a front sectional view of another conventional immersion nozzle

3B is a side cross-sectional view of FIG. 3A

Figure 4a is a cross-sectional view according to the section 2-2 of the present invention Figure 4b

4B is a cross-sectional view taken along the cross section of FIG. 4A 1-1.

5 is a cross-sectional view taken along section 3-3, 4-4, 5-5, 6-6, 7-7 of FIGS. 4A and 4B;

6 is a cross sectional view along section 21, 22, 23, 24 of FIGS. 4A and 4B;

Figure 7 is an enlarged view of the lower end of the immersion nozzle in accordance with the present invention

8 is an enlarged view of a lower end of another immersion nozzle different from the shape of the separator and FIG. 7 associated with the present invention.

Figure 9 is a schematic diagram of the molten steel flow shape in the mold produced by the immersion nozzle of the present invention

Explanation of symbols for main parts of the drawings

21a: Pipe type upper end 22a: Primary conversion part

23: secondary conversion unit 24a: peripheral ring

25a: separator 26a: discharge part

A: Minimum area of discharge part h: Separator height

L: Separator Width F: Collision Point

31: inlet section area S1, S2, S3: flow of molten steel

In order to achieve the above object, the present invention provides a cylindrical pipe-shaped upper end and a primary conversion part having a constant internal cross-sectional area and a secondary conversion part and an internal cross-sectional area which gradually increase in internal cross-sectional area from the inlet part of the nozzle to the discharge part. It consists of a peripheral ring to increase, and consists of a continuous casting immersion nozzle characterized in that it comprises a separator for inducing a symmetrical flow of molten steel in the center of the end of the peripheral ring.

4A and 4B show the structure of the immersion nozzle according to the embodiment of the present invention, wherein the cylindrical pipe-shaped upper end portion 21a and the inner cross-sectional area of the nozzle from the inlet to the discharge portion of the nozzle are increased or constant. ) And a secondary conversion portion 23 whose inner cross-sectional area gradually increases, and a peripheral ring portion 24 a whose inner cross-sectional area gradually increases, and the discharge portion 26a for inducing the flow of molten steel into the mold and the discharge port. It consists of a structure including a separator (25a) to induce a symmetrical flow of the molten steel in the center of the end.

In the immersion nozzle of the present invention having the above structure, as shown in FIGS. 5 and 6, the internal cross-sectional area gradually increases from the cylindrical pipe-shaped upper end portion 21a toward the discharge portion 26a (ie, 31 in FIG. 5). To 35 and gradually increase the internal cross-sectional area as shown in 36 to 39 of FIG. 6).

That is, the cylindrical inlet portion 27 has a cross-sectional area of 95 to 98% based on the hole cross-sectional area 31, which is a 3-3 cross section. In this area, the cross-sectional area is reduced from the initial inlet, so that the flow rate is slightly increased, but little pressure fluctuation occurs, and it is composed of a cylindrical pipe-shaped upper end portion 21a having an inner cross-sectional area 36 which hardly changes up to 4-4 sections.

In addition, the primary conversion portion 22a forming a 5-5 cross-sectional area from the 4-4 cross section is a conversion portion for guiding the cylindrical pipe-shaped upper portion 21a to the slit discharge portion, the characteristic of which is reduced in thickness and increased in length. In order to induce the flow of molten steel from the circular shape to the slit-type discharge part 26a, it is rectangular as shown in FIG. The change in the internal cross-sectional area at this site converges in the range of 90 to 100% based on the inlet cross-sectional area 31, so that the fluctuations in the flow rate and pressure hardly occur.

The secondary conversion unit 23a is characterized in that the thickness decreases and the length increases, that is, the internal cross-sectional area is divergent in the range of 100 to 140% based on the internal cross-sectional area 31 of the inlet. This causes a decrease in flow velocity before the molten steel rushes to the peripheral ring 24a.

The divergence of the internal cross-sectional divergence exceeding the above range causes rapid fluctuations in the flow velocity and pressure of the primary conversion section 22a and the secondary conversion section 23a of the immersion nozzle. In detail, the phenomena caused by this result in a rapid pressure fluctuation in the nozzle while the fluid passes through the high pressure barrier. The pressure wave is generated by the generated pressure fluctuation, which is transmitted to the nozzle top. The pressure wave delivered to the lower side is caused by pulsation at the outlet, which causes the discharge flow rate to be uneven due to the uneven flow rate change, making it difficult to maintain the constant surface of the molten steel in the mold intermittently. Generate drift.

In areas that increase after cross-sectional area reduction (ie, primary and secondary conversion units), variations in speed and pressure occur according to internal cross-sectional area changes. In other words, the speed at the change point 5a increases and an area where the fluctuations in the pressure become uneven is generated. This phenomenon is as described above. In order to solve this effectively, it is desirable to minimize the difference in the cross-sectional area change amount. In detail, when the length of the primary conversion unit 22a is 253 mm, the amount of change in the cross-sectional area of the primary conversion unit 22a is −0.15 mm ² . The difference between the amount of change in cross-sectional area the same manner as 2 debit affected part (23a) is 1.91mm + ² when the affected area 1 debit (22a) and second debit affected part (23a) of the cross-sectional area change amount is 2.07mm ^2.

That is, in order to minimize the difference in the cross-sectional area change amount, the difference in the cross-sectional area change amount may be reduced only by sufficiently securing the length of the secondary conversion unit 23a.

The immersion nozzle according to the present invention eliminated the cause of the drift by minimizing the change of the cross-sectional area to 6 mm ² or less by minimizing the flow velocity and pressure change inside the nozzle.

That is, by securing the length of the secondary conversion unit 23a to a predetermined length or more, it is possible to alleviate the sudden pressure fluctuation of the molten steel when entering the shift section. In other words, when a cross-sectional area change occurs, a distance that can alleviate the fluctuation of the pressure of the molten steel inside the nozzle is secured.

Peripheral annulus 24a keeps the length of cross-sectional area constant, and the length of long-side portion is constant or increased, that is, the inner cross-sectional area emits constant cross-sectional area 31 in the range of 105 to 150%. It is done. This decreases the flow velocity in the nozzle without maintaining or increasing constant until immediately before the separator 25a installed at the bottom and eliminating the transverse flow difference, thereby preventing the molten steel from flowing through the separator.

3A and 3B, the divergence angle of the side wall of the periphery annular portion 24 is 6 ° or more, so that the flow velocity deviation of the central flow 51a inside the nozzle and the flow 52a on the inner wall side of the nozzle is generated, thereby causing the deflection. Provided the cause.

The immersion nozzle according to the present invention maintains the internal cross-sectional area from the inlet portion 27 to the discharge portion 26a within a predetermined range to minimize the flow velocity deviation between the central flow 51 inside the nozzle and the flow 52 on the inner wall. Therefore, it is possible to prevent the drift during the split flow induction of the molten steel by the separator.

The following is described according to the embodiment.

Table 1 shows the cross-sectional area change inside the immersion nozzle to confirm the effect of the present invention.

Examples of this invention One 2 3 4 5 6 Internal cross section [based on cross section 100 of Fig. 5] (Fig. 5) 32 cross section 97 97 97 97 97 97 (Fig. 5) 33 cross section 94 90 98 90 98 98 (Fig. 5) 34 cross section 120 110 110 120 120 140 (Fig. 5) Cross section of 35 120 120 120 130 130 150 Internal cross-sectional area change amount (mm ² ) Round pipe section 21a -0.31 -0.31 -0.31 -0.31 -0.31 -0.31 Primary conversion section 22a -0.34 -0.32 +0.11 -1.32 +0.11 +0.11 Secondary converter (23) +3.31 +1.74 +1.53 +2.61 +2.80 +5.34 Peripheral affected part (24a) +0.00 +0.79 +0.79 +0.79 +0.79 +0.79

Species Examples of this invention One 2 3 One 2 3 4 5 6 Cross-sectional area change amount (mm ² ) Round pipe section 21a -0.04 -0.24 -0.51 -0.31 -0.31 -0.31 -0.31 -0.31 -0.31 Primary conversion section 22a 2.57 -0.22 -18.9 -0.34 -0.32 +0.11 -1.32 +0.11 +0.11 Secondary converter (23) -2.91 - - +3.31 +1.74 +1.53 +2.61 +2.80 +5.34 Peripheral lesions (24a) 0.48 +5.76 5.49 +0.00 +0.79 +0.79 +0.79 +0.79 +0.79 Difference in cross-sectional area change between sections (mm ² , absolute value) Round pipe part-primary conversion part 2.61 0.02 18.39 0.03 1.01 0.42 1.01 0.42 0.42 Primary transform unit-secondary transform unit 5.48 - - 3.64 3.06 1.41 3.93 2.69 5.23 Secondary converter-main converter 3.39 5.98 24.39 3.31 0.95 0.74 1.82 2.01 4.56 Height difference at the water surface (mm) 7.4 9.4 8.6 3.8 2.8 2.3 4.1 3.3 5.2 Remarks Separator Width (L) = 80mm, Separator Angle (α) = 60 °

Velocity and pressure distribution in the immersion nozzle according to the present invention are simulated using a computer by the finite volume method (FVM). And pressure fluctuations were small, preferably 6 mm ² or less. As the difference in the cross-sectional area between sections increases, the fluctuations in the flow velocity and pressure inside the immersion nozzle increase proportionally.In the case of more than 6mm ² , the flow velocity difference in the transverse direction occurs within the immersion nozzle, which provides the cause of the drift. And a pressure wave is generated as the pressure changes rapidly, and the phenomenon shown therein is as described above.

As shown in Figs. 7 and 8, the separator 25a has a forming angle in the range of 0 ° ≦ α ≦ 120 °, and the height h of the separator is 30 to 150 mm while the width of the separator is in the range of 30 mm ≦ L ≦ 120 mm. The upper and lower curvatures 42 and 44 are formed in the range, and the minimum cross-sectional area A according to the height h of the separator is in the range of 125 to 200% based on the inlet cross-sectional area 31, and the minimum The cross-sectional area (A) is the area at the shortest distance between the discharge part upper surface 41 and the separator upper curvature 42, which changes according to the height h of the separator, and the curvature of the lower part in the separator 25a is the width of the separator. It is characterized by consisting of a height of 5 to 20mm.

During thin sleeve casting, the flow of molten steel (S1, S2, S3) in the mold through the separator 25a of the immersion nozzle forms a downward flow through the separator. In addition, the discharge section minimum cross-sectional area A and the exit speed change according to the height h of the separator 25a, and the flow size of the molten steel downward in the mold varies according to the size of the exit speed.

That is, the minimum cross-sectional area A of the discharge part of the discharge part determines the exit speed of the immersion nozzle discharge part, and the flow of molten steel by the separator varies according to the size of the exit speed.

The molten steel in the mold through the separator 25a of the immersion nozzle generally forms a double roll flow, and the flow phenomenon is shown in FIG. 9 according to the minimum cross-sectional area A of the discharge part, the angle α of the separator, and the width L of the separator. Go through the same route.

That is, the flow of molten steel discharged along the inner wall 10 of the immersion nozzle rises by colliding with the mold wall at the top of another flow S2 in the mold and again forming a reverse flow near the bath surface. Its reverse flow is different from the height of the surface of the water surface according to the speed size and increases the instability of the surface of the mold in accordance with the magnitude of the rising surface speed. Such instability of molten steel, in particular, instability in the hot water surface causes many problems such as uneven heat transfer toward the mold side and difficulty in forming a constant solidification cell.

The flow S2 of molten steel discharged from the center of the discharge portion has the largest flow velocity among the discharged flows, and collides with the mold wall to form a downflow. The size of the flow (S2) affects the formation of the reverse flow of the molten steel flow (S1), the phenomenon appearing as described above.

In addition, the flow (S3) flowing along the separator wall 43 forms a downward flow, but collides with the flow (S2) of the molten steel and the stagnant region of the lower portion to reverse the direction of the flow to form an upward flow. This upflow rate affects the formation of a solidified layer inside the mold. By removing the area of the upstream from the bottom of the separator or reducing the speed of the upstream, the impact on the solidification layer of the cast can be minimized.

Flow of the molten steel (S1, S2, S3) mentioned above to confirm the effect of the present invention is the flow phenomenon of the molten steel through the separator 25a of the immersion nozzle discharge section minimum cross-sectional area (A), the angle of the separator (α) As a result of the numerical analysis using the computer by the finite volume method according to the change of the width (L) of the separator, the height difference in the water surface is shown in the following table (Table 3).

Width of separator (L) 30 mm 45 mm 60 mm 80 mm 100 mm 120 mm Minimum cross section area (A) of the discharge port (at α = 60 °) 125% 2.6 2.9 3.5 4.2 5.4 7.4 145% 2.6 1.9 2.0 4.2 5.0 6.9 170% 2.7 3.5 4.3 4.8 5.9 7.1 200% 2.7 3.7 4.4 5.2 6.1 7.4 Separator Angle (α) (A = 120%) 0 ° 2.6 2.5 2.9 3.5 4.5 5.6 15 ° 2.6 1.1 2.0 3.7 5.3 6.4 30 ° 2.6 1.2 2.3 3.8 5.4 6.5 60 ° 2.6 1.9 2.7 4.2 6.0 6.9 120 ° 2.8 3.6 3.9 4.9 6.4 8.0 Remarks The shape of the immersion nozzle is applied to Example 3 of the present invention (Table 2).

The flow of molten steel in the mold changes depending on the length of the minimum cross-sectional area A and the width L of the separator. The flow rate changes according to the minimum cross-sectional area (A). As the minimum cross-sectional area A approached 125%, the molten steel flow rate of the reverse flow at the collision point F increased, resulting in a large difference in height of the water surface SO. In addition, when the minimum cross-sectional area (A) is out of an appropriate size or more, the discharge flow rate is reduced and the collision point (F) is closer to the water surface, so that the reverse flow region on the water surface is widened, thereby increasing the height difference of the water surface. As the minimum cross-sectional area A of the discharge portion changes, the discharge flow velocity changes and the position of the collision point F changes according to the size of the discharge velocity, thereby changing the height difference on the water surface according to the speed and area of the reverse flow.

As the discharge flow rate is larger than the minimum cross-sectional area of the discharge portion of 125% or less, the position of the collision point F becomes closer to the hot water surface and the height difference increases as the side of the separator 25a becomes larger.

The flow phenomenon of molten steel in the discharge section minimum area 145% is a double roll flow, but the flow rate of the reverse flow is small due to the downward flow of molten steel. As it was not large, the height difference on the water surface was most stable.

When the discharge flow rate is lowered at the discharge area minimum 170% or more, the location of the collision point F due to the change in the width of the separator does not change significantly, and the flow phenomenon of the molten steel in the mold forms a small double roll flow. As a result, the collision point was closer to the floor, resulting in a greater height difference at the floor. In addition, the discharge flow rate difference between the left and right sides of the separator is generated in the discharge section minimum cross-sectional area of 200% or more, and the effects thereof are as described above.

As shown in (Table 3), the smaller the separator width (L), the lower the flow of vertical downflow, and the larger the double roll flow. In addition, the location of the collision point (F) of the molten steel flow in the mold was changed according to the separator width (L) and the angle (α), and the smaller the separator angle (α) and the separator width (L), the collision point (F) is the water level ( Deepening from S0), the flow velocity of the reverse flow at the floor was reduced, and the area of the congestion area and the upward flow at the bottom of the separator was reduced so that the height difference at the floor was reduced. On the other hand, the larger the angle of the separator (α) and the width of the separator (L), the closer the collision point was from the floor, resulting in a greater height difference on the floor.

When the separator width (L) is 120 mm or more and the angle (α) is 120 ° or more, the position of the collision point (F) is closer to the floor, the speed and area of the reverse flow increases, and the height difference on the floor is 10 mm or more. The influence is as described above.

As described above, the molten steel discharged from the inside of the immersion nozzle has a minimum cross-sectional area of the discharge port.

(A) That is, the position of the collision point (F) was changed according to the discharge flow rate, the separator width (L) and the angle (α), the speed and area of the reverse flow reversed after the collision and the congestion area of the bottom of the separator and It can be seen that the height difference at the water surface varies according to the size of the upward flow.

The direction of the molten steel flow in the mold was determined by the discharge speed and the separator width (L) by the discharge section minimum cross-sectional area A rather than the influence of the angle. As shown in Table 3, at the same cross-sectional area and the same width of the separator, the direction of the molten steel flow in the mold did not show a significant difference at an angle of more than 30 °.

Table 4 shows the results of the actual casting experiment by making the immersion nozzle into a refractory.

Experimental conditions, Mold: 20-6 Crown Mold (Mould side: 1240mm)

Casting Speed: 4.5m / min

Depth of Depth: 150mm

As shown in Table 4, the conventional immersion nozzle has a large cross-sectional area change and a large flow velocity and pressure fluctuation, and a flow velocity difference occurs in the transverse direction and the longitudinal direction to generate a drift during the split flow of molten steel through the separator. In addition, the collision point F of the reverse flow was close to the surface S0 to increase the height difference of the surface. In the immersion nozzle according to the present invention, the flow velocity in the interior is gradually reduced, and the pressure fluctuation is constant, so that no drift occurs in the split flow through the separator, thereby minimizing the change in the molten steel of the molten steel in the mold.

In addition, the flow velocity and direction of the molten steel are appropriately adjusted according to the discharge flow rate and the width and angle of the separator according to the minimum cross-sectional area of the discharged portion to ensure the stability of the molten steel flow in the mold. As it was maintained within the height difference of 10 mm from the hot water surface, which is the limit value of the standing crack of the slab surface, stable operation was achieved.

As described above, the immersion nozzle of the present invention minimizes the range of the flow velocity and pressure change inside the nozzle to form a symmetrical flow of molten steel in the mold of the thin slab continuous casting, thereby reducing the difference in the height of the water bath according to the position of the separator. The stable phenomena of molten steel in the mold can be secured according to the appropriate minimum cross-sectional area, the width of the separator, and the quality of the cast can be produced with uniform solidification cell thickness.

Claims (5)

From the inlet of the nozzle toward the discharge part, the cylindrical pipe-shaped upper end portion 21a and the primary conversion portion 22a having a constant internal cross-sectional area, the secondary conversion portion 23 and the internal cross-sectional area of which the internal cross-sectional area is gradually increased. An immersion nozzle for continuous casting, characterized in that it comprises a separator 25a for symmetrical flow of molten steel in the center of the end of the peripheral ring portion gradually increasing. The method of claim 1, The cross-sectional area is 95 to 98% of the cylindrical pipe-shaped upper end portion 21a, 90 to 100% of the primary conversion portion 22a, 100 to 140% of the secondary conversion portion 23, and the peripheral ring portion based on the inlet cross-sectional area. An immersion nozzle for continuous casting, characterized in that (24a) is 110 to 150%. The method of claim 1, The immersion nozzle for continuous casting, characterized in that the absolute value of the difference in cross-sectional area variation between each section does not exceed 6mm ² . The method of claim 1, The formation angle of the separator 25a is 0 ° ≤α≤120 °, the width of the separator is 30mm≤L≤120mm, the height of the separator is 30-150mm, and the curvature is formed on the top and the bottom of the separator. Immersion nozzle for continuous casting The method of claim 4, wherein The curvature of the lower portion of the separator is a continuous casting immersion nozzle, characterized in that consisting of a height of 5 to 20mm in the width of the separator.