JPH11239852A - Immersion nozzle for continuous casting and continuous casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an immersion nozzle for continuous casting and a continuous casting method, with which the clogging of the immersion nozzle is prevented and the lowering of molten steel surface temp. is restrained and the stable continuous operation is achieved by shallowing the invading depth of inclusion and a cast slab having a little defect can be produced. SOLUTION: The molten steel flowing from a flowing rate control device 13 is introduced to the inside of the circular arc-state inner peripheral wall 20 of the immersion nozzle for continuous casting while deviating the center part of the immersion nozzle for continuous casting and inclining by a little in the longitudinal direction to give the circular flow 21 along the circular arc-state inner peripheral wall 20 to the molten steel. As the other way, the molten steel flowing from the flow rate control device 13 is introduced toward the circular arc-state inner peripheral wall 20 of the immersion nozzle for continuous casting from the center part of the immersion nozzle for continuous casting by inclining to the peripheral direction thereof to give the circular frow 21 along the circular arc-state inner peripheral wall 20 to the molten steel. The molten steel is poured into a mold by circulating with the immersion nozzle for continuous casting and also, an electromagnetic stirring in the mold is executed to circulate the molten steel in the mold in the vertical plane to the drawing out direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting of steel, which prevents clogging of an immersion nozzle due to inclusion of inclusions, prevents a decrease in the surface temperature of molten steel in a mold, and prevents molten steel from flowing from an immersion nozzle. The present invention relates to an immersion nozzle for continuous casting and a continuous casting method that achieves stable operation by reducing the discharge flow velocity of the steel to reduce the depth of penetration of inclusions and enables the production of high quality cast slabs.

[0002]

2. Description of the Related Art In continuous casting of steel, when pouring molten steel from a ladle into a mold, the molten steel is usually poured from a ladle into a tundish, and then poured from the tundish into a mold through an immersion nozzle. A slab or a round or square billet is manufactured continuously.

[0003] By the way, in pouring into a mold for slab, in order to secure the surface temperature of molten steel poured into the mold,
As the immersion nozzle, a multi-hole nozzle such as a bottomed two-hole nozzle whose discharge port is provided in the short side direction of the mold is generally used.

[0004] In the case of a thin slab, a decrease in the surface temperature of the slab causes the surface of the surface of the slab to be covered in the mold and the solidified shell to be fixed to the immersion nozzle. It must be avoided because it causes problems such as inability to obtain. When the above multi-hole nozzle is used, the molten steel injected into the mold becomes a molten steel flow toward the short side of the mold, and collides with the short piece to form an upward flow in the direction of the molten metal. Supplied to the molten metal surface, a decrease in the molten metal surface temperature is suppressed. However, when the casting speed increases, a phenomenon called so-called shaving, in which mold powder is caught in the molten steel, occurs, and defects in cast slab quality are likely to occur.

When a two-hole nozzle is used for billet casting, the distance between the discharge hole and the inner wall of the mold is short.
The collision of the molten steel flow causes the re-melting of the solidified shell, making the casting unstable, and the growth of the solidified shell uneven in the circumferential direction of the billet, which tends to cause slab defects such as vertical cracks. Therefore, a single-hole straight nozzle without a bottom is usually used in billet casting.

FIG. 6 is a schematic view showing pouring by a single-hole straight nozzle. Here, reference numeral 61 denotes a tundish, 62 denotes a flow control device, 63 denotes a single-hole straight nozzle, 64 denotes a pouring flow, and 65 denotes a mold. As shown in the figure, when the single-hole straight nozzle 63 is used, the pouring flow 64 is a molten steel flow directed downward, so that the supply of high-temperature molten steel to the molten metal surface is small, and the temperature of the molten metal surface is not decreased. Will be noticeable. In order to prevent this, an electromagnetic stirring device is installed, and electromagnetic stirring in the mold is performed in which the molten steel in the mold is swirled in a plane perpendicular to the drawing direction.

FIG. 7 is a schematic diagram showing stirring of molten steel by an electromagnetic stirrer. Here, reference numeral 63 denotes a single-hole straight nozzle, 64 denotes a pouring flow, 65 denotes a mold, 66 denotes a swirling flow,
7 is an unmelted mold powder, 68 is a molten mold powder, 69 is an electromagnetic stirring device, and 70 is a molten metal surface.

The application of the swirling flow 66 by the electromagnetic stirrer 69 makes the temperature of the molten steel in the mold 65 uniform and suppresses a decrease in the temperature of the molten metal. However, particularly in the casting of a round billet having a circular cross section, the application of the swirl flow 66 causes the molten metal surface 70 to be concave at the center of the mold as shown in FIG. Entrapment of the mold powder 67 is likely to occur, and a slab defect may occur.

[0009] Furthermore, pouring with a submerged nozzle has the following problems. Inclusions adhere to the immersion nozzle and clog the immersion nozzle, and stable operation cannot be performed for a long time. When a single-hole straight nozzle is used, the flow of the pouring flow is deep, and it is difficult to float and remove inclusions that have entered the mold, particularly in casting with a small-section mold. Also, 2
When a hole nozzle is used, a so-called one-sided flow with a different pouring amount from the two-hole nozzle is likely to occur under the influence of the drift in the immersion nozzle, resulting in a quality defect of the cast slab.

As a measure for preventing clogging of the immersion nozzle,
A method of injecting an inert gas such as Ar gas using a porous plug provided on the inner wall of an immersion nozzle has been used. Is still a problem.

As a measure for reducing the depth of inclusion penetration, Japanese Patent Publication No. 6-16930 discloses a method in which the discharge flow rate from the single-hole straight nozzle is reduced by expanding the discharge hole of the single-hole straight nozzle in a tapered shape. Have been. However, in this method, it is difficult to form an upward flow even if the downward discharge flow rate can be reduced, and a decrease in the temperature of the molten metal surface is inevitable.

As a countermeasure against one-sided flow, Japanese Patent Laid-Open Publication No.
No. 498 discloses a method of imparting swirl to molten steel in an immersion nozzle using an electromagnetic stirring device. This method
Since a shearing force acts on the inner wall of the immersion nozzle, it is expected that this is also effective in preventing inclusions from adhering to the inner wall of the immersion nozzle. However, the cooling water of the electromagnetic stirrer may come into contact with the scattered molten steel and cause a large disaster such as a steam explosion. The security measures for that are quite extensive,
In particular, in the case of casting a billet with a small-section mold, it is practically difficult to install an electromagnetic stirrer in a narrow space around an immersion nozzle. Also, it is difficult for this method to form an upward flow to the molten metal surface, and a decrease in the molten metal surface temperature is inevitable.

[0013]

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the prior art, the present invention provides a swirling flow to molten steel by a submerged nozzle, forms a rising flow in a mold direction in a mold, and discharge velocity. Achieve stable continuous operation by preventing nozzle clogging caused by inclusion of inclusions inside the immersion nozzle, suppressing a decrease in the temperature of the molten metal, and reducing the depth of penetration of inclusions It is another object of the present invention to provide a continuous casting immersion nozzle and a continuous casting method that enable the production of cast pieces with less quality defects.

[0014]

Means for Solving the Problems The present inventors have studied the structure of a continuous casting immersion nozzle (hereinafter also referred to as an immersion nozzle) and conducted a continuous casting test to solve the above problems, and obtained the following findings. Obtained.

(A) The application of the swirling flow to the molten steel by the immersion nozzle can be performed by the following means. (a) First Means-The molten steel that has flowed in from the flow control device is guided by removing the center of the arc-shaped inner peripheral wall of the immersion nozzle and tilting it in the longitudinal direction of the arc-shaped inner peripheral wall.

(B) Second Means The molten steel flowing from the flow control device is guided to the center of the arc-shaped inner peripheral wall of the immersion nozzle. -From the center to the arc-shaped inner peripheral wall, the molten steel is guided by being inclined in the circumferential direction of the arc-shaped inner peripheral wall.

(C) Third Means A plug having a plurality of twisted passages from top to bottom is provided inside the immersion nozzle.

(B) By applying the swirling flow by the above means,
It is possible to form an upward flow in the direction of the molten metal surface and reduce the discharge flow velocity. (C) In addition to the above-mentioned means (a) or (b), the provision of the tapered portion which is reduced downward following the arc-shaped inner peripheral wall and the straight-shaped portion following the same promotes the application of the swirling flow.

(D) In addition to the above-mentioned means, by forming the lowermost inner surface of the immersion nozzle in a divergent shape, the formation of an upward flow in the direction of the molten metal surface and a decrease in the discharge flow velocity are further promoted. (E) The molten steel is injected into the mold while applying a swirl flow to the molten steel using the immersion nozzle having the above means, and the molten steel is swirled in a horizontal plane in the mold in a direction opposite to or the same as the swirl flow. By performing the electromagnetic stirring in the mold, it is possible to suppress the surface defects of the slab or to secure the temperature of the molten metal.

The present invention is based on the above findings, and the gist is as follows. (1) Connect to the bottom of the tundish downstream of the flow controller,
A continuous casting immersion nozzle for injecting molten steel into a mold, wherein the molten steel flowing from the flow rate control device is removed from the central portion of the arc-shaped inner peripheral wall of the continuous casting immersion nozzle, and the length of the arc-shaped inner peripheral wall is reduced. An immersion nozzle for continuous casting, which has a function of inducing the liquid steel to incline in a direction and impart a swirling flow along an arc-shaped inner peripheral wall to molten steel.

(2) An immersion nozzle for continuous casting, which is connected downstream of the flow control device at the bottom of the tundish and injects molten steel into a mold, wherein the molten steel flowing from the flow control device is used for the continuous casting. From the center of the arc-shaped inner peripheral wall of the immersion nozzle, it was provided with a function of guiding toward the arc-shaped inner peripheral wall by inclining in the circumferential direction of the arc-shaped inner peripheral wall, and imparting a swirling flow along the arc-shaped inner peripheral wall to molten steel. An immersion nozzle for continuous casting, characterized in that:

(3) A tapered portion following the arc-shaped inner peripheral wall and contracting downward, and a straight-shaped portion following the tapered portion and directed downward.
Item 6. The immersion nozzle for continuous casting according to item 2 or.

(4) A continuous casting immersion nozzle connected to the flow rate control device at the bottom of the tundish for injecting molten steel into a mold, wherein the continuous casting immersion nozzle is provided with an inside extending downward from above. An immersion nozzle for continuous casting, comprising a plug having a plurality of passages twisted toward each other.

(5) The immersion nozzle for continuous casting according to any one of the above (1) to (4), wherein the lowermost part of the immersion nozzle for continuous casting is divergent toward the discharge port. nozzle.

(6) Using the continuous casting immersion nozzle according to any one of the above-mentioned items (1) to (5), while applying a swirling flow to the molten steel in the continuous casting immersion nozzle, A continuous casting method characterized by injecting molten steel.

(7) The electromagnetic stirring in the mold for swirling the molten steel in the mold in a direction perpendicular to the drawing direction in the same direction as the swirling flow or in the opposite direction is performed. The continuous casting method as described.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The continuous casting immersion nozzle of the present invention will be described in detail with reference to the drawings. In the continuous casting immersion nozzle of the present invention, molten steel flowing from the flow control device,
The center part of the arc-shaped inner peripheral wall of the continuous casting immersion nozzle is removed and guided by being inclined with respect to the longitudinal direction of the arc-shaped inner peripheral wall, and a function of imparting a swirling flow along the arc-shaped inner peripheral wall to molten steel is provided. And

FIGS. 1A and 1B are schematic views illustrating an example of a continuous casting immersion nozzle according to the present invention. FIG. 1A is a sectional view thereof, and FIG. 1B is a cross-sectional view taken along line AA. FIG. FIG.
As shown in FIG. 1, the continuous casting immersion nozzle 11 of the present invention (hereinafter, also referred to as a first immersion nozzle) is provided with a first nozzle 14 connected to a flow control device 13 at the bottom of the tundish 12 in order to realize the above function. And a second nozzle 16 for injecting molten steel flowing from the first nozzle 14 into the mold 15.
The first nozzle 14 has a bent portion 17 downstream of the flow control device 11, and is bent obliquely downward. This bent portion 17
The nozzle tip 18 subsequent to the second nozzle 16 is rotated so that the molten steel from the nozzle tip 18 turns along the arcuate inner peripheral wall 20 of the upper part 19 of the second nozzle 16.
Then, the central portion of the arc-shaped inner peripheral wall is removed, and the connection is made inclining with respect to the longitudinal direction of the arc-shaped inner peripheral wall. The inclination angle is 10 degrees or more and 90 degrees or less with respect to the longitudinal direction.

From the tundish 12 to the flow controller 13
Is injected into the first nozzle 14 through the bent portion 17.
And flows into the second nozzle 16 from the nozzle tip 18. The molten steel flowing into the second nozzle 16 becomes a flow 21 swirling along the conical inner peripheral wall 20 and is injected into the mold 15.

The swirling flow generates a flow 22 of molten steel toward the inner wall of the mold, and the molten steel collides with the inner wall of the mold to form an upward flow 24 toward the mold surface 23 of the mold. Due to the formation of the upward flow, molten steel having a high temperature is supplied to the molten metal surface, and the molten metal surface temperature can be maintained high. Further, a shearing force due to the swirling of the molten steel acts on the inner wall of the second nozzle, and the adhesion of inclusions to the inner wall is suppressed. Further, as described above, since the flow 22 of the molten steel toward the inner wall of the mold is formed, the discharge flow velocity of the molten steel downward is reduced, and the penetration depth of inclusions is reduced. The problem of the reoxidation of the molten steel at the connection between the first nozzle and the second nozzle can be solved by making the inert gas such as Ar gas slightly higher than the atmospheric pressure.

Next, another immersion nozzle for continuous casting according to the present invention will be described. In another continuous casting immersion nozzle of the present invention, the molten steel flowing from the flow control device is directed from the central portion of the arc-shaped inner peripheral wall of the continuous casting immersion nozzle to the arc-shaped inner peripheral wall, in the circumferential direction. It is characterized by having a function of imparting a swirling flow along the arc-shaped inner peripheral wall to molten steel by inclining and guiding.

FIGS. 2A and 2B are schematic views illustrating another example of a continuous casting immersion nozzle according to the present invention. FIG. 2A is a sectional view of the nozzle, and FIG. FIG. FIG.
As shown in FIG.
(Hereinafter, also referred to as a second immersion nozzle) is provided with a flow control device 13 at the bottom of the tundish 12 to realize the above function.
And a second nozzle 16 for injecting the molten steel flowing from the first nozzle 14 into the mold 15. The first nozzle 14 includes a single hole 34 having a bottom 33 extending downward from an upper portion 32 thereof, and a plurality of nozzle outlet holes 37 in a side wall 36 of the lower portion 35. The lower portion 35 is located at the center of the arc-shaped inner peripheral wall 20 of the second nozzle 16, and the nozzle 35 is formed so that molten steel from the nozzle outlet hole 37 turns along the arc-shaped inner peripheral wall 20 of the upper portion 19 of the second nozzle 16. Exit hole 37
Are provided to be inclined in the circumferential direction of the arc-shaped inner peripheral wall 20. The inclination of the nozzle outlet hole is such that the intersection angle between the center line of the nozzle outlet hole and the arc-shaped inner peripheral wall is 30 to 85 degrees in the circumferential direction and 10 to 90 degrees in the longitudinal direction.

From the tundish 12 to the flow controller 13
The molten steel injected into the first nozzle 14 through the nozzle flows into the second nozzle 16 from the nozzle outlet hole 37 and flows into the arc-shaped inner peripheral wall 20.
A stream 21 swirling along is injected into the mold 15.

Therefore, the molten steel injected into the mold becomes a swirling flow, and has the same operational effects as those described for the first immersion nozzle 11 shown in FIG. A reduction in the depth of inclusion penetration in the mold is obtained.

According to a preferred embodiment of the present invention, the tapered portion is provided with a tapered portion which is reduced downward following the arc-shaped inner peripheral wall and a straight portion which is directed downwardly following the tapered portion. Specifically, as shown in FIG. 1 or FIG. 2, the second nozzle 16 of the first immersion nozzle 11 or the second nozzle 16 of the second immersion nozzle 31 follows the arc-shaped inner peripheral wall 20 and goes downward. Tapered portion 38 which is reduced by
And a straight portion 39 directed downward,
The swirling of the molten steel by the second nozzle 16 is promoted and maintained, and the molten steel having a strong swirling flow can be injected into the mold 15.

FIG. 3 is a schematic view illustrating another example of another continuous casting immersion nozzle of the present invention. FIG. 3 (a) is a longitudinal sectional view and FIG. 3 (b) is a perspective view of a plug. FIG. 2C is a cross-sectional view of a main part of the plug. As shown in FIG. 3, another continuous immersion nozzle 41 for continuous casting of the present invention (hereinafter also referred to as a third immersion nozzle) is connected to the flow control device 13 at the bottom of the tundish 12 to realize the above function. Mold 15
And a plug 43 mounted on the nozzle base 42 for injecting molten steel. The nozzle base 42 has a through hole 45 at the center thereof, which extends downward from the upper portion 44. The plug 43 is mounted in the through hole 45 and has a single hole 34 with a bottom 33 at the center of the plug,
The outer diameter is reduced at the lower portion 46 of the plug, and the reduced lower portion 4 is formed.
6 is provided with a plurality of penetrating lateral holes 48 in the side wall 47. The horizontal hole is provided so as to be inclined in the circumferential direction of the arc-shaped inner peripheral wall 20 so that the molten steel flowing out of the horizontal hole 48 turns along the arc-shaped inner peripheral wall 20 of the nozzle base portion 42. The inclination is such that the intersection angle between the center line of the lateral hole 48 and the arc-shaped inner peripheral wall 20 is 30 degrees or more and 85 degrees or less in the circumferential direction, and 10 degrees or more and 90 degrees or less in the longitudinal direction. The through hole 45 of the nozzle base portion 42 has a straight shape as shown in FIG.
From the viewpoint of easy attachment of the plug, the inside diameter of the plug attachment site or the through hole above it may be enlarged.

From the tundish 12 to the flow controller 13
The molten steel that has been injected into the nozzle base 42 through the nozzle hole 42 flows out of the lateral hole 48 of the plug 43 and turns along the arc-shaped inner peripheral wall, and is injected into the mold 15.

Accordingly, the molten steel injected into the mold has a swirling flow, and the same operational effects as those described above, namely, the suppression of the decrease in the temperature of the molten metal, the suppression of the adhesion of inclusions, and the reduction of the depth of inclusion penetration into the mold. can get.

Next, another immersion nozzle for continuous casting according to the present invention will be described. According to still another immersion nozzle for continuous casting of the present invention, a plug having a plurality of twisted passages from above to below is provided inside the immersion nozzle for continuous casting.

FIGS. 4A and 4B are schematic views for explaining another example of a continuous casting immersion nozzle of the present invention. FIG. 4A is a sectional view thereof, and FIG. It is a perspective view of a plug.

As shown in FIG. 4, another immersion nozzle 51 for continuous casting according to the present invention (hereinafter also referred to as a fourth immersion model) is provided with a tundish 1 in order to realize the above function.
It has a nozzle base portion 42 connected to the two-bottom flow control device 13 for injecting molten steel into the mold 15 and a plug 43 attached to the nozzle base portion 42. The nozzle base portion 42 includes:
At the center thereof, there is provided a through hole 45 extending downward from the upper portion 44. The plug 43 has a plurality of passages 52 mounted in the through holes 45 and twisting downward from above the plug. In FIG. 4, the passage 52 is provided inside the plug 43.
Is shown, but it may be provided on the side surface of the plug 43. The angle of the twist is preferably in the range of 5 to 45 degrees.

The through hole 45 of the nozzle base 42
May be a straight shape as shown in FIG. 4, but from the viewpoint of easy attachment of the plug, the inside diameter of the attachment portion of the plug or the through hole above it may be enlarged.

From the tundish 12 to the flow controller 13
The molten steel flowing into the nozzle base portion 42 through the
Is given by passing through the passage 52 of the mold 1
5 is injected.

Therefore, the molten steel injected into the mold becomes a swirling flow, and the same operation and effect as described above, that is, the suppression of the decrease in the temperature of the molten metal, the suppression of the adhesion of the inclusions, and the reduction of the penetration depth of the inclusions in the mold. can get.

Next, the reason why the lowermost portion of the immersion nozzle is divergent toward the discharge port in a preferred embodiment of the present invention will be described with reference to the first immersion nozzle of FIG. 1 as an example. As shown in FIG. 1, the inner surface 26 of the lowermost portion 25 of the second nozzle 16 is divergent toward the discharge port 27. The molten steel that has turned into a swirling flow at the upper part of the second nozzle is injected into the mold 15 along the diverging inner surface 26 by centrifugal force, and a swirling flow that goes obliquely downward is formed. As a result, the downward discharge flow rate decreases, and a stronger upward flow in the mold surface direction in the mold is generated, and the effect of suppressing the decrease in the mold surface temperature and reducing the depth of inclusion inclusions in the mold is increased.

Next, a preferred embodiment of the continuous casting method of the present invention will be described. FIG. 5 is a schematic view for explaining an example of the continuous casting method of the present invention, in which the immersion nozzle shown in FIG. 1 is used. FIG. 5 (a) is a longitudinal sectional view, and FIG. -A
FIG. 3 is a cross-sectional view taken along a line arrow.

As shown in FIG. 5, the molten steel injected from the tundish 12 through the flow control device 13 into the first nozzle 14 flows into the second nozzle 16 and swirls along the arc-shaped inner peripheral wall 20. And injected into the mold 15.
At this time, electromagnetic stirring for rotating the molten steel in the mold in a plane perpendicular to the drawing direction is performed by the electromagnetic stirring device 56.

By the way, conventionally, the electromagnetic stirring in the mold has a purpose of increasing the equiaxed crystal ratio in addition to compensating for the temperature drop of the molten metal surface, so that the electromagnetic stirring in the mold may not be stopped in some cases. When the electromagnetic stirring in the mold is performed, a depression of the molten metal surface occurs at the center of the mold, which may cause a quality defect of the slab. In this case, as shown in FIG. 5, by giving a swirl by electromagnetic stirring in the opposite direction to the swirl flow formed by the immersion nozzle, the swirl flow 57 is formed and the depression of the molten metal surface can be suppressed. . On the other hand, under casting conditions in which cast slab defects due to depressions in the molten metal surface are not particularly problematic, turning the immersion nozzle and the rotation by electromagnetic stirring in the same direction can further suppress a decrease in temperature at the molten metal surface. Note that, even when another immersion nozzle of the present invention is used, the same method as described above can be performed, and the same effect can be obtained.

[0049]

(Embodiment 1) Example A of the present invention having the basic configuration shown in FIG. 1 and the main specifications shown in Table 1; Example B of the present invention having the basic configuration shown in FIG. 2 and the main specifications shown in Table 2; Four types of immersion nozzles for continuous casting according to the present invention, namely, Example C of the present invention having the main specifications shown in Table 3 in the configuration and Example D of the present invention having the main specifications shown in Table 4 having the basic configuration shown in FIG. For comparison, as a conventional example, a single-hole straight continuous immersion nozzle having a basic configuration shown in FIG. 5 and having a total length of 700 mm and an inner diameter of 60 mm was also manufactured.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

(Example 2) Example A of the present invention shown in Example 1
Using ＤD and the conventional continuous immersion nozzle for continuous casting, cast pieces of round billets were cast under the casting conditions shown in Table 5.

[0055]

[Table 5]

After measuring the temperature of the molten metal surface in the mold and casting a total weight of 300 tons, the state of inclusions inclusions on the inner surface of the immersion nozzle was investigated. In addition, samples were cut out from the cast slab at a pitch of 30 mm in the depth direction, the inclusion distribution on the cross section of the slab was measured by a slime extraction test, and the penetration depth of the inclusions was investigated.

Table 6 shows the results. Here, the inclusion adhesion index is a relative value when the thickness of the inclusions of Conventional Example 1 is set to 1.0, and the difference in the surface temperature is a value obtained by subtracting the liquidus temperature of the cast steel type from the surface temperature. Further, the inclusion penetration depth is a relative value with the inclusion penetration depth of Conventional Example 1 being 1.0.

[0058]

[Table 6]

As shown in Table 6, the thickness of the inclusions of Examples 1 to 4 of the present invention was reduced to about 20 to 30% of that of the conventional example, and the surface temperature was about 6 to 10 ° C. higher than that of Conventional Example 1. In addition, the depth of inclusion penetration has been improved to about half that of Conventional Example 1.

(Example 3) Example B of the present invention shown in Example 1
The casting was performed by using an immersion nozzle for continuous casting, and performing electromagnetic stirring in the mold. The frequency of electromagnetic stirring is 5Hz
, The applied current value was 200 A, and in Example 5 of the present invention, the applied direction was the direction opposite to the rotation of the molten steel in the immersion nozzle in the horizontal plane. In Example 6 of the present invention, the direction was the same as the rotation inside the immersion nozzle. The casting conditions other than the electromagnetic stirring are the same as in Table 5.

The state of depression of the molten metal surface and the temperature of the molten metal surface during casting were investigated, and the results were compared with those with and without electromagnetic stirring using the above-described conventional immersion nozzle. The conditions of the electromagnetic stirring are the same as described above. Table 7 shows the casting results. Here, the depression index of the molten metal surface is a relative value of the maximum depression depth when the maximum depression depth of Conventional Example 3 is set to 1.0.

[0062]

[Table 7]

As shown in Table 7, in Example 5 of the present invention, the electromagnetic stirring and the swirling by the immersion nozzle were set in opposite directions,
The depression depth of the molten metal surface was significantly reduced as compared with Conventional Example 3. On the other hand, in Example 6 of the present invention, the molten metal surface temperature was significantly higher than in Conventional Examples 2 and 3 by using the electromagnetic stirring and the swirling by the immersion nozzle in the same direction.

[0064]

According to the present invention, in continuous casting of steel, nozzle clogging caused by inclusion of inclusions in the immersion nozzle is prevented, and the temperature of molten steel in the mold is prevented from lowering on the molten metal surface. By reducing the flow rate of molten steel from the immersion nozzle and reducing the depth of inclusion penetration, stable continuous operation can be achieved, and it becomes possible to produce a slab without defects.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating an example of a continuous casting nozzle according to the present invention. FIG. 1 (a) is a sectional view thereof, and FIG.
FIG. 2 is a cross-sectional view taken along line A of FIG.

FIGS. 2A and 2B are schematic views illustrating an example of another continuous immersion nozzle for continuous casting according to the present invention. FIG. 2A is a cross-sectional view thereof, and FIG.
1 is a cross-sectional view taken along line AA.

3A and 3B are schematic views illustrating another example of another continuous immersion nozzle for continuous casting according to the present invention. FIG. 3A is a longitudinal sectional view, FIG. 3B is a perspective view of a plug, and FIG. (C) is a transverse sectional view of a main part of the plug.

FIGS. 4A and 4B are schematic views illustrating still another example of an immersion nozzle for continuous casting according to the present invention. FIG. 4A is a cross-sectional view thereof, and FIG. 4B is a perspective view of a plug mounted therein. FIG.

FIG. 5 is a schematic view illustrating an example of the continuous casting method of the present invention, in which the immersion nozzle shown in FIG. 1 is used. FIG. 5 (a) is a longitudinal sectional view, and FIG. FIG. 2 is a cross-sectional view taken along line A of FIG.

FIG. 6 is a schematic diagram showing pouring by a single-hole straight nozzle.

FIG. 7 is a schematic diagram showing stirring of molten steel by an electromagnetic stirring device.

[Explanation of symbols]

11 Immersion nozzle for continuous casting of the present invention (first immersion nozzle) 12, 61 Tundish 13, 62 Flow control device 14 First nozzle 15, 65 Mold 16 Second nozzle 17 Bent portion 18 Nozzle tip 19, 32, 44 Upper part 20 Arc-shaped inner peripheral wall 21 Swirling flow 22 Flow of molten steel toward the mold inner wall 23, 70 Hot surface 24 Ascending flow 25 Bottom part 26 Inner surface 27 Discharge port 31 Another immersion nozzle for continuous casting of the present invention (second immersion nozzle) 33 Bottom 34 Single Hole 35, 46 Lower 36, 47 Side Wall 37 Nozzle Exit Hole 38 Tapered Portion 39 Straight Portion 41 Another Continuous Dipping Nozzle for Continuous Casting (Third Dipping Nozzle) 42 Nozzle Base 43 Plug 45 Through hole 48 Lateral hole 51 Another dipping nozzle for continuous casting of the present invention (fourth dipping nozzle) 52 Passage 56, 69 Electromagnetic stirrer 57,66 swirling flow 63 single-hole straight nozzle 64 Chuyuryu 67 unmelted mold powder 68 melt mold powder

Claims (7)

[Claims] 1. A continuous casting immersion nozzle connected to a tundish bottom downstream of a flow control device for injecting molten steel into a mold, wherein the molten steel flowing from the flow control device is immersed in the continuous casting. A continuity characterized by having a function of removing a central portion of the arc-shaped inner peripheral wall of the nozzle, guiding the nozzle by inclining with respect to the longitudinal direction of the arc-shaped inner peripheral wall, and applying a swirling flow along the arc-shaped inner peripheral wall to the molten steel. Immersion nozzle for casting. 2. A continuous casting immersion nozzle connected downstream of a flow control device at a tundish bottom for injecting molten steel into a mold, wherein the molten steel flowing from the flow control device is immersed in the continuous casting. The nozzle has a function to guide it from the central part of the arc-shaped inner peripheral wall toward the arc-shaped inner peripheral wall by inclining in the circumferential direction of the arc-shaped inner peripheral wall, and to impart a swirling flow along the arc-shaped inner peripheral wall to the molten steel. An immersion nozzle for continuous casting characterized by the following. 3. The apparatus according to claim 1, further comprising: a tapered portion that decreases downward following the arc-shaped inner peripheral wall, and a straight portion that extends downward following the tapered portion. Immersion nozzle for continuous casting. 4. A continuous casting immersion nozzle connected to the tundish bottom downstream of a flow control device for injecting molten steel into a mold, wherein the continuous casting immersion nozzle is provided with an inside extending downward from above. An immersion nozzle for continuous casting, comprising a plug having a plurality of twisted passages. 5. The continuous casting immersion nozzle according to claim 1, wherein a lowermost portion of the continuous casting immersion nozzle is divergent toward a discharge port. 6. Using a continuous casting immersion nozzle according to any one of claims 1 to 5, injecting molten steel into a mold while applying a swirling flow to the molten steel in the continuous casting immersion nozzle. Characteristic continuous casting method. 7. The continuous electromagnetic stirring according to claim 6, wherein in the plane perpendicular to the drawing direction, in-mold electromagnetic stirring for swirling molten steel in the mold in the same direction as or in the opposite direction to the swirling flow is performed. Casting method.