JP4266312B2 - Nozzle for continuous casting of steel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nozzle for continuous casting of steel, and more particularly to a nozzle for continuous casting of steel characterized by preventing drift and blockage.
[0002]
[Prior art]
As nozzles for continuous casting of steel, immersion nozzles, long nozzles, tundish nozzles, semi-immersion nozzles and the like are known.
As an example of a continuous casting nozzle for steel, an “immersion nozzle” will be described as an example. The purpose of this immersion nozzle is to seal between the tundish mold and prevent reoxidation of the molten steel, and to discharge the immersion nozzle. The purpose is to control the flow of molten steel from the holes and supply the molten steel uniformly into the mold to stabilize the operation and improve the quality of the slab.
[0003]
When supplying molten steel into the mold through the immersion nozzle, there are a stopper method and a slide plate method as the flow rate control method.
In particular, in the slide plate method, one of the plates with two or three holes is slid and the flow rate is adjusted by the opening of the holes. The drift is likely to occur in the immersion nozzle. When uneven flow occurs in the immersion nozzle, the discharge flow rate from each discharge hole becomes non-uniform, and uneven flow occurs in the mold and the slab quality deteriorates. Therefore, in order to improve the quality of the slab, it is important to prevent the drift in the immersion nozzle.
[0004]
As a technique for preventing the drift in the immersion nozzle, there is a method for improving the shape of the inner hole portion. For example, “Immersion nozzle provided with a plurality of step portions in the molten steel flow hole (Patent Document 1: Japanese Utility Model Publication No. 7-23091)”, “Provided with a throttle part in the molten metal introduction part, from the throttle part to the discharge hole Immersion nozzle with a flow rate relaxation part (Patent Document 2: Japanese Patent No. 3050101) "," The inner surface of the nozzle hole is provided with four or more peaks in the direction of the molten metal in the direction of the molten metal. The soot is a continuous casting immersion nozzle having a crest-to-crest interval of 4 to 25 cm and a crest to trough depth of 0.3 to 2 cm (Patent Document 3: Japanese Patent Application Laid-Open No. H6-269913) "Providing an annular projection" has been proposed.
[0005]
Further, “Casting nozzle provided with spiral grooves or protrusions on the inner wall (Patent Document 4: Japanese Patent Laid-Open No. 57-130745)”, “Immersion preferably provided with double or triple helix on the inner wall “Providing a helical projection” such as “Nozzle (Patent Document 5: Japanese Patent Laid-Open No. 11-47896)” has been proposed. Furthermore, a “nozzle having a hemispherical uneven portion formed on the surface of the molten metal flow passage (Patent Document 6: Japanese Patent Laid-Open No. 62-89566)” has also been proposed.
[0006]
[Patent Document 1]
Japanese Utility Model Publication No. 7-23091 (Claims 1 to 4)
[Patent Document 2]
Japanese Patent No. 3050101 (Claims 1 to 10)
[Patent Document 3]
JP-A-6-269913 (Claim 1)
[Patent Document 4]
JP-A-57-130745 (Claims)
[Patent Document 5]
Japanese Patent Laid-Open No. 11-47896 (Claims 1 to 6)
[Patent Document 6]
JP-A-62-89566 (Claims)
[0007]
[Problems to be solved by the invention]
In the prior art focusing on the shape of the nozzle inner hole portion, it is possible to expect a certain degree of effect of partially generating turbulent flow and preventing drift of molten steel flow.
However, when casting Al killed steel or the like, depending on the method of disposing the protrusion, a non-metallic inclusion mainly composed of alumina (in the gap between the protrusion and the protrusion disposed in the molten steel flow hole of the immersion nozzle ( Hereinafter, in this specification, there is a problem that the deposit is simply deposited. If alumina adheres and fills the space between the protrusions, the effect of disposing the protrusions disappears, and the effect of preventing drift is lost.At the same time, the effective cross-sectional area of the inner hole part is reduced. Throughput (amount of molten steel that passes through per unit time) cannot be secured, and there is a drawback that the operation becomes impossible.
[0008]
The present invention has been made in view of the above-mentioned drawbacks and problems of the prior art, and its object is to prevent “diffuse flow of molten steel from the nozzle to the discharge hole” caused by the flow rate control. Furthermore, another object of the present invention is to provide a steel continuous casting nozzle capable of suppressing alumina from adhering particularly between the projections of the nozzle inner hole.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, i.e., to suppress the drift of the nozzle bore and to prevent the adhesion of alumina, the casting nozzle according to the present invention comprises:
“A plurality of independent protrusions having a height H of 2 to 15 mm, which are discontinuous in both the parallel and perpendicular directions to the molten steel flow direction, are arranged in the molten steel flow hole of the steel casting nozzle. In the casting nozzle formed,
The maximum base length L of the protrusion on the surface perpendicular to the molten steel distribution direction is (πD / 2) −10 mm or less [D: inner diameter (diameter) of nozzle (mm)], and relative to the molten steel distribution direction. A nozzle for continuous casting of steel, wherein the distance E between the bases of the protrusions in the parallel direction is at least 20 mm or more. "
Is the gist.
[0010]
And, as described above, by setting the “maximum base length L of the protrusion on the surface perpendicular to the molten steel flow direction (lateral direction) to be (πD / 2) −10 mm or less”, the nozzle bore The effect of generating turbulence can be promoted. Furthermore, by setting “the distance E between the base portions of the protrusions in the direction parallel to the flowing direction of the molten steel (longitudinal direction) is at least 20 mm or more”, the stagnation portion immediately below the protrusion portions is eliminated, and the alumina between the protrusions is eliminated. Can be prevented.
As a result, according to the casting nozzle according to the present invention, it is possible to suppress the drift of the nozzle inner hole and the alumina blockage during the operation of the actual machine, which can contribute to the stable operation and the improvement of the slab quality.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the casting nozzle according to the present invention will be described, but prior to that, the present invention will be described in more detail, including the effects provided by the present invention.
[0012]
As described above, the casting nozzle according to the present invention has a protrusion (having a plurality of independent protrusions) having a height H of 2 to 15 mm in the molten steel flow hole of the casting nozzle, as described above, in order to prevent drift without blocking. ) Is specified in the vertical direction (lateral direction) and the parallel direction (longitudinal direction) with respect to the molten steel flow direction.
[0013]
On the surface perpendicular to the flowing direction of the molten steel (lateral direction), the maximum base length L of the protrusion is “(πD / 2) −10 mm or less”. This is because, for example, when two protrusions are disposed facing a surface (lateral direction) perpendicular to the molten steel flow direction, there is a gap of at least 10 mm between the two protrusions. However, this is because it generates more turbulent flow and brings out a rectifying effect, and is preferably “(πD / 2) −20 mm or less”.
In other words, the annular protrusion is less likely to exhibit the effect of generating turbulent flow, and it is important that the protrusion is a discontinuous protrusion on a plane (lateral direction) perpendicular to the molten steel flow direction.
[0014]
Next, in a direction (longitudinal direction) parallel to the molten steel flow direction, the interval E between the bases of the protrusions is at least 20 mm or more, that is, the shortest part is 20 mm or more.
The distance E between the protrusions in the direction parallel to the flowing direction of the molten steel (longitudinal direction) is within the range where the height H of the protrusions is up to 15 mm. Therefore, alumina does not adhere between the protrusions. The interval E between the protrusions in the direction parallel to the molten steel flow direction is preferably 25 mm or more, and more preferably 30 mm or more.
[0015]
In the casting nozzle according to the present invention, as described above, on the assumption that the molten steel flow hole of the casting nozzle is provided with protrusions (independent protrusions) having a height H of 2 to 15 mm. To do. When the height H of the protrusions disposed in the inner hole of the nozzle is less than 2 mm, the rectifying effect is poor, and in order to ensure throughput, the height of the protrusions is preferably 15 mm or less.
[0016]
Here, the present invention will be described in more detail by comparing the prior art cited in the section of “Prior Art” with the present invention.
“Technology for preventing the drift of molten steel from the nozzle to the discharge hole generated by the flow rate control” related to the present invention is described in the above-mentioned Patent Document 1 (Japanese Utility Model Publication No. 7-23091). An immersion nozzle provided with a plurality of step portions is disclosed. Patent Document 2 (Japanese Patent No. 3050101) mentioned above describes that “a submerged nozzle provided with a throttle part in a molten metal introduction part and having a flow rate reducing part between the throttle part and the discharge hole”, and Patent Document 3 (Japanese Patent Application Laid-Open No. 6-269913) discloses that “a corrugated trough having an arcuate cross-section is provided on the inner surface of the nozzle hole in a direction in which the molten metal flows. An immersion nozzle for continuous casting in which the distance from the mountain is 4 to 25 cm and the depth from the mountain to the valley is 0.3 to 2 cm is disclosed. However, in these prior arts, since they are annular projections, the effect of scattering the molten steel flowing down the inner pipe of the nozzle to the left and right cannot be expected, and as a result, complete drift prevention cannot be expected.
[0017]
The above-mentioned patent document 4: Japanese Patent Laid-Open No. 57-130745 discloses “a casting nozzle provided with a spiral groove or protrusion on the inner wall”, and the above-mentioned patent document 5: Japanese Patent Laid-Open No. 11-47896. The publication discloses "a submerged nozzle provided with an inner wall, preferably a double or triple helix". Similarly to the above-described annular protrusion, such a spiral protrusion cannot be expected to scatter the molten steel flowing down the nozzle inner pipe to the left and right, and as a result, it cannot be expected to prevent complete drift.
[0018]
Japanese Patent Application Laid-Open No. 62-89566 discloses a “nozzle having a hemispherical uneven portion formed on the surface of a molten metal flow passage”. This is because the concave / convex radius is R = 2 to 9 mm, and the ratio of the concave / convex portion to the entire flow passage area in the refractory is preferably about 7 to 40%. And a plurality of convex portions formed alternately.
However, there is no specific description about the interval between the protrusions, and if the interval between the protrusions is narrow, it is considered that a stagnation portion occurs here and alumina adheres.
[0019]
In other words, in the prior art, in the case where the molten steel flow hole of the steel casting nozzle is provided with a protrusion having a height of 2 to 15 mm, and the molten steel flowing down the nozzle molten steel flow hole is rectified, By setting the maximum base length L of the protrusion on the surface perpendicular to the flowing direction of the molten steel (lateral direction) to “(πD / 2) −10 mm or less”, the molten steel colliding with the protrusion is scattered in a complicated manner. The knowledge of the present invention that “turbulent flow can be generated and rectified as a whole can be obtained” has not been obtained.
Furthermore, in order to prevent alumina from adhering between the protrusions, the present invention has ensured that the distance between the protrusions in the direction parallel to the molten steel flow direction (longitudinal direction) is 20 mm or more as an absolute value even in the shortest part. There is novelty.
[0020]
Next, an embodiment of the present invention will be described. In the casting nozzle according to the present invention, the shape of the protrusion may be a polyhedron shape, a streamlined shape or a hemispherical shape.
Moreover, in this invention, it is preferable to arrange | position 6 or more protrusion parts in the molten steel flow hole part of the nozzle for casting. If the number of protrusions is 5 or less, the effect of rectifying the molten steel flowing down the molten steel flow hole cannot be expected, and drift is likely to occur.
[0021]
The protrusion in the present invention can be disposed on the entire surface or a part of the molten steel flow hole of the casting nozzle, and is not limited to the portion to be disposed. Is preferred.
Further, in the present invention, examples of the casting nozzle in which the protrusion is disposed include an immersion nozzle, a long nozzle, a tundish upper / lower nozzle, a semi-immersion nozzle, a ladle upper / lower nozzle, and the like, all of which are included in the present invention. However, among these, it is particularly preferable to apply to the “immersion nozzle for continuous casting of steel”.
[0022]
【Example】
EXAMPLES Hereinafter, although the Example of this invention is given with a comparative example and this invention is demonstrated concretely, this invention is not limited by the following Examples 1-3.
[0023]
(Example 1, Comparative Examples 1 and 2: see FIG. 1)
Example 1 and Comparative Examples 1 and 2 corresponding thereto will be described with reference to FIG. In addition, FIG. 1 is the figure divided vertically in the direction parallel to a molten steel distribution direction.
An acrylic projection nozzle (1) with an inner diameter of φ80 mm is provided with an elliptical protrusion (2) having a height H = 10 mm and a maximum base length L = 30 mm in a direction perpendicular to the flowing direction of the molten steel (lateral direction). A water model experiment was conducted.
In Example 1, the distance E between the protrusion and the base of the protrusion in the direction parallel to the molten steel flow direction (longitudinal direction) is 20 mm. On the other hand, Comparative Example 1 is a straight nozzle that does not have a protrusion (2), and Comparative Example 2 is a protrusion with an interval E = 10 mm (outside the range specified by the present invention) (as in Example 1, H = 10 mm, L = 30 mm with an elliptical protrusion (2)) provided.
[0024]
Throughput: Equivalent to 5 steel · T / min. As a result of visually confirming the flow of water in the inner hole portion, it was confirmed that in Example 1, water flowed directly under the protruding portion and there was no stagnation portion. In Example 2, water did not flow immediately below the protrusion, and a stagnation portion was present.
[0025]
Subsequently, the maximum throughput of Example 1 and Comparative Examples 1 and 2 was measured. This is done by fully opening the slide valve attached to the top of the immersion nozzle and adjusting the flow rate adjustment valve in the vicinity of the pump that circulates the water so that the water level in the mold rises to a predetermined height (from the upper end of the discharge hole). The flow rate at this time was measured with a float type flow meter.
[0026]
As a result, the comparative example 1 of the straight nozzle flowed up to the maximum throughput: 1200 L / min, whereas the comparative example 2 flowed only 850 L / min.
On the other hand, in Example 1, 1150 L / min and the influence which arrange | positioned the projection part were recognized slightly, but it was able to stay to such an extent that there was no influence on operation of an actual machine. This is because Example 1 had H = 20 mm and the necessary interval was secured, so that water flowed directly under the protrusions and throughput could be secured, whereas Comparative Example 2 had H = 10 mm. Therefore, it is considered that water did not flow directly under the protrusion, that is, the inner hole itself was in the same state as when the diameter was reduced overall. As in Comparative Example 2, if the fluid does not flow directly under the protrusion, it becomes a stagnation part, and it is considered that alumina adheres to the actual machine.
[0027]
(Example 2, comparative example 3: see FIG. 2)
Example 2 and Comparative Example 3 corresponding thereto will be described with reference to FIGS. FIG. 2 is a view showing another example in which protrusions are arranged in the molten steel flow hole, in which (A) shows Example 2 and (C) shows a water model experiment for Example 2. It is the figure which showed the result. Moreover, (B) shows Comparative Example 3 corresponding to Example 2, and (D) is a diagram showing the results of a water model experiment for Comparative Example 3.
[0028]
A water model experiment was conducted by arranging a protrusion (2) having a height of 7 mm and a maximum base length of 60 mm on an acrylic immersion nozzle (1) having an inner diameter of 70 mm.
In Example 2, as shown in FIG. 2A, six protrusions (2) are arranged. On the other hand, in Comparative Example 3, as shown in FIG. 2B, four protrusions (2) are arranged. 2A and 2B are diagrams showing a state in which the nozzle is vertically divided in half.
[0029]
The water model experiment will be described with reference to (C) and (D) of FIG. 2. The experimental condition is that the slide plate (3) is a three-plate type, and the middle plate slides parallel to the long side of the mold. The flow rate was controlled to achieve a throughput equivalent to 4 steel T / min. In addition, air was blown at 5 L / min from the upper nozzle (3) installed immediately above the slide plate (3) so that the flow of water in the mold was easy to observe.
The result of Example 2 is shown in FIG. 2C, and the result of Comparative Example 3 is shown in FIG. 2C and 2D simply illustrate the flow of water (7) (discharge flow (6)) in the mold (5) discharged from the discharge holes.
[0030]
In Example 2 in which six protrusions (2) were arranged, the flow of water (7) in the mold (5) (discharge flow (6)) was almost even and stable, whereas the protrusion (2) In Comparative Example 3 in which only four parts (2) are arranged, it can be seen that the right discharge flow (6) is deeper than the left side, and the drift cannot be solved. From this fact, it can be said that the number of protrusions (2) is preferably 6 or more.
[0031]
(Example 3, comparative example 4: see FIG. 3)
In Example 3 and Comparative Example 4 corresponding thereto, the maximum base portion length L on the surface perpendicular to the molten steel flow direction of the protrusions disposed in the molten steel flow hole portion was examined. This will be described based on FIG. 3 (a cross-sectional view taken along a plane perpendicular to the flowing direction of molten steel). (For the symbols “H, W, E” described below, see FIG. 1 above)
A projection part (2) having a height W = 30 mm in a direction parallel to the flowing direction of the molten steel (longitudinal direction) W = 30 mm is placed on an acrylic immersion nozzle (1) having an inner diameter of φ80 mm at an interval of E = 30 mm. The water model experiment was conducted by blowing 10 air from the upper nozzle at a flow rate of 5 L / min.
[0032]
As shown in FIG. 3, since there are two protrusions (2) per cross section and there are five steps at intervals of E = 30 mm, the total number is ten, but 90 ° for each step. They were arranged shifted in the circumferential direction.
In Example 3, the experiment was performed with a in FIG. 3 (the interval between the bases of the protrusions in the direction perpendicular to the molten steel flow direction) being 10 mm, and in Comparative Example 4, a = 5 mm.
[0033]
As a result of observing the flow of water in the part a, in Comparative Example 4, bubbles were accumulated and water was not flowing, whereas in Example 3, bubbles were not accumulated and water was flowing smoothly. It was. As for the fluid rectifying effect due to the arrangement of the projecting portion (2), as in the case of the second embodiment, in the third embodiment, as shown in FIG. On the other hand, in Comparative Example 4, the left and right flows were non-uniform as shown in FIG.
From the above fact, the maximum base portion length L on the plane perpendicular to the molten steel flow direction of the protrusions disposed in the molten steel flow hole is (πD / 2) −10 mm or less, the rectifying effect and the alumina. It can be said that it is more preferable from the viewpoint of adhesion prevention.
[0034]
【The invention's effect】
As described in detail above, the casting nozzle according to the present invention has a structure in which alumina adheres and accumulates between the protruding portions when the protruding portions are disposed in the molten steel flow hole of the casting nozzle, and the rectifying effect of the protruding portions is obtained. In order to prevent the reduction, the maximum base portion length L of the protrusion on the plane perpendicular to the molten steel distribution direction is set to (πD / 2) −10 mm or less, and the protrusions in the direction parallel to the molten steel distribution direction It is characterized in that 20 mm or more is secured even at the shortest part. Thereby, the rectification effect by arrangement | positioning of a projection part can be maintained reliably until completion | finish of casting, and it can contribute to the stabilization of operation and improvement of the slab quality of steel.
[Brief description of the drawings]
FIG. 1 is a view showing an example (Example 1) in which protrusions are disposed in a molten steel flow hole, and is a view that is vertically divided in a direction parallel to the molten steel flow direction.
FIG. 2 is a view showing another example in which protrusions are arranged in the molten steel flow hole, in which (A) shows Example 2 and (C) shows the results of a water model experiment for Example 2. FIG. Moreover, (B) shows Comparative Example 3 corresponding to Example 2, and (D) is a diagram showing the results of a water model experiment for Comparative Example 3.
FIG. 3 is a view showing another example (Example 3) in which protrusions are arranged in the molten steel flow hole, and is a cross-sectional view in a direction perpendicular to the molten steel flow direction.
[Explanation of symbols]
(1) Immersion nozzle
(2) Protrusion
(3) Upper nozzle
(4) Slide plate
(5) Mold
(6) Discharge flow
(7) Water H Projection height W Base length L of the projection in a direction parallel to the molten steel flow direction (longitudinal direction) L of the projection on the surface perpendicular to the molten steel flow direction (lateral direction) Maximum base length E Spacing between bases of protrusions in a direction (longitudinal direction) parallel to the flow direction of molten steel Spacing between bases of protrusions in a direction (lateral direction) perpendicular to the flow direction of molten steel

Claims (3)

Disposed in the molten steel flow hole of the steel casting nozzle is a plurality of independent protrusions that are discontinuous in both directions parallel and perpendicular to the molten steel flow direction and have a height H of 2 to 15 mm. In the casting nozzle,
The maximum base length L of the protrusion on the surface perpendicular to the molten steel distribution direction is (πD / 2) −10 mm or less [D: inner diameter (diameter) of nozzle (mm)], and relative to the molten steel distribution direction. A nozzle for continuous casting of steel, wherein the distance E between the bases of the protrusions in the parallel direction is at least 20 mm or more. 6. The continuous casting nozzle for steel according to claim 1, wherein six or more protrusions are disposed in the molten steel flow hole. The nozzle for continuous casting of steel according to claim 1 or 2, wherein the nozzle for casting is an immersion nozzle for continuous casting of steel.

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