JP7712562B2 - Submerged Entry Nozzle - Google Patents

Description

The present invention relates to a submerged nozzle that is attached to a slide valve that controls the flow rate of molten steel by adjusting the opening size through the sliding movement of a sliding plate.

In a continuous steel casting process using an immersion nozzle, when flow control is performed using a sliding plate to adjust the amount of molten steel supplied from the tundish to the mold, drift inevitably occurs in the flow inside the immersion nozzle. In particular, when the sliding direction of the sliding plate is in the thickness direction of the mold and differs by 90 degrees from the direction of the discharge hole of the immersion nozzle in a plan view, the discharge conditions differ significantly between one end and the other end in the horizontal direction of one discharge hole, causing an imbalance in the discharge conditions. This imbalance causes the flow conditions of the meniscus to become uneven in the sliding direction of the sliding plate, which is thought to be a factor in increased fluctuations in the molten steel surface and uneven solidification of the molten steel.

Conventional techniques for suppressing drift in flow control using a slide valve include, for example, the techniques shown in the following patent documents 1 to 3.

Japanese Utility Model Application Publication No. 4-6351 JP 2005-297022 A Japanese Patent Application Publication No. 11-57955

The submerged nozzle described in Patent Document 1 has multiple steps on its inner wall surface. The submerged nozzle described in Patent Document 2 has multiple protruding structures on its inner wall surface.

However, the above-mentioned configuration of providing a step or convex structure on the inner wall surface of the submerged nozzle may be physically difficult to apply to a submerged nozzle for blooms and other applications that have a small inner tube diameter. Furthermore, if alumina clogging of the inner tube of the submerged nozzle is significant, such a configuration may become filled in and no longer be effective.

The submerged nozzle described in Patent Document 3 has a discharge hole with a discharge hole angle in the opposite direction to the deviation of the nozzle discharge flow caused by the deviation of the molten steel flow in the flow rate adjustment section of the slide valve, but there are cases where an extreme deviation in the mold thickness direction occurs temporarily.

The present invention was made in consideration of the above-mentioned circumstances, and its purpose is to provide an immersion nozzle that can be applied to immersion nozzles with small inner tube diameters, and that can suppress the occurrence of drift of molten steel within the nozzle while also suppressing drift within the mold.

The feature of the submerged entry nozzle according to the present invention is that the submerged entry nozzle is provided in a slide valve which controls the flow rate of molten steel by adjusting the opening amount by the sliding movement of a sliding plate, and
The nozzle body has a substantially cylindrical shape, and a pair of discharge holes are arranged opposite each other on a side surface near the bottom of the nozzle body, the vertical length of one end of the discharge holes in the circumferential direction of the side surface is longer than the vertical length of the other end, and the shapes of the pair of discharge holes have mirror symmetry with respect to each other, with a plane that includes the axis of the nozzle body and is parallel to the sliding direction of the sliding plate as the mirror plane.

As in this configuration, by setting the vertical length of one end of the discharge hole in the horizontal direction longer than the vertical length of the other end, and by having a pair of discharge holes with such a shape have mirror symmetry, it is possible to suppress the occurrence of drift of molten steel in the nozzle while also suppressing the occurrence of drift of molten steel in the mold, particularly the occurrence of weaving at the meniscus.

Therefore, according to the present invention, there is no need to provide a step or a convex structure on the inner wall surface of the submerged nozzle, and it can be applied to submerged nozzles with small inner tube diameters.

In the submerged nozzle according to the present invention, it is preferable that the ratio of the vertical length of the discharge hole at one end to the vertical length of the discharge hole at the other end is greater than 0.5 and less than 0.9.

This configuration makes it possible to prevent thermal stress from concentrating on the side with the shorter vertical length, thereby preventing cracks from occurring on that side.

In the submerged nozzle according to the present invention, it is preferable that the height of the upper end of the one end of the discharge hole is the same as the height of the upper end of the other end.

This configuration allows the molten steel to flow more easily from the upper part of the discharge hole, and alumina and other substances are less likely to adhere to the upper part, making it even less likely that the molten steel will drift.

In the submerged nozzle according to the present invention, it is preferable that one end side and the other end side of the discharge hole are provided in this order along the direction in which the opening amount increases in the sliding direction of the sliding plate.

FIG. 2 is a vertical cross-sectional view of a submerged nozzle. FIG. 2 is a cross-sectional plan view of a submerged nozzle.

An embodiment of the submerged nozzle according to the present invention will be described with reference to the drawings.

In a typical continuous casting facility, molten steel S from a ladle (not shown) is supplied into a mold 4 via a tundish T. The molten steel S is then injected into the mold 4 from the tundish T through an immersion nozzle 1 while the flow rate of the molten steel S is adjusted by the opening of a slide valve 3 provided in the middle, as shown in FIG. 1.

The slide valve 3 in this embodiment is a three-layer slide valve, and is configured to adjust the opening amount by the lateral sliding movement of the intermediate plate 30 (an example of a sliding plate) to control the flow rate of molten steel S.

As shown in FIG. 2, the mold 4 has opposing short-side steel plates 40 and opposing long-side steel plates 41. The intermediate plate 30 of the slide valve 3 is configured to move in a direction along the short-side steel plates 40, and each of the pair of discharge holes 2 of the submerged nozzle 1 is arranged to open toward the side of the short-side steel plates 40.

The submerged nozzle 1 in this embodiment has a nozzle body 10 having a substantially cylindrical shape, and a pair of discharge holes 2 are arranged opposite each other on the side surface near the bottom of the nozzle body 10. The shapes of the pair of discharge holes 2 have mirror symmetry with each other with respect to a mirror plane M that includes the axis A of the nozzle body 10 and is parallel to the sliding direction D of the intermediate plate 30.

As shown in FIG. 1, the shape of the discharge hole 2 is set such that the vertical length (HL) of one end side 20 of the discharge hole 2 in the circumferential direction of the side surface of the nozzle body 10 is longer than the vertical length (HS) of the other end side 21. In this embodiment, the one end side 20 and the other end side 21 of the discharge hole 2 are provided in this order along the direction in which the opening amount increases in the sliding direction D of the intermediate plate 30 (the one end side 20 is on the left side of the paper in FIG. 1, and the other end side 21 is on the right side), but this configuration is not limited to this.

It is preferable that the ratio of the vertical length of one end side 20 of the discharge hole 2 to the vertical length of the other end side 21 is greater than 0.5 and less than 0.9.

In this embodiment, the height of the upper end of one end side 20 of the discharge hole 2 is the same as the height of the upper end of the other end side 21. That is, the shape of the discharge hole 2 in this embodiment is approximately trapezoidal, the upper side of the discharge hole 2 is horizontal, and the lower side of the discharge hole 2 is inclined.

The shape of the discharge holes 2 is not limited to the above-mentioned embodiment, but may be asymmetric when viewed from the outside, and the pair of discharge holes 2 may have mirror symmetry with each other.

Basically, the vertical length of one end of the discharge hole 2 means the vertical length of the endmost part of the one end, and the vertical length of the other end of the discharge hole 2 means the vertical length of the endmost part of the other end. However, in order to suppress the concentration of thermal stress, the corners of the discharge hole 2 may be processed to have a roundness that does not affect the flow of molten steel. In this case, the vertical length of one end of the discharge hole 2 and the vertical length of the other end of the discharge hole 2 mean the length in virtual dimensions that do not assume such roundness. For example, if the endmost part of one end is a straight part extending in the vertical direction, the vertical length of one end of the discharge hole 2 means the length obtained by adding the vertical length of the rounded part connected to the straight part to the vertical length of the straight part. Similarly, for the other end, if the most extreme part of the other end is a straight part extending vertically, the vertical length of the other end of the discharge hole 2 means the vertical length of the rounded part connected to the straight part plus the vertical length of the straight part.

Other embodiments
1. In the above embodiment, an example was shown in which the submerged entry nozzle according to the present invention was applied to a three-layer slide valve, but the present invention is not limited to this configuration, and the submerged entry nozzle according to the present invention may also be applied to a two-layer slide valve.

Although the present invention has been described above with reference to the drawings, the present invention is not limited to the configurations shown in the drawings, and can be implemented in various forms without departing from the spirit and scope of the present invention.

The submerged nozzle according to the present invention can be suitably used, for example, in continuous steel casting equipment.

1: Submerged nozzle 10: Nozzle body 2: Discharge hole 20: One end side 21: Other end side 3: Slide valve 30: Intermediate plate (an example of a sliding plate)
4: Mold 40: Short side steel plate 41: Long side steel plate A: Axis center of nozzle body M: Mirror surface T: Tundish S: Molten steel D: Slide direction

Claims (3)

In a submerged entry nozzle provided in a slide valve which controls the flow rate of molten steel by adjusting the opening amount through the sliding movement of a sliding plate,
a nozzle body having a substantially cylindrical shape, a pair of discharge holes disposed opposite each other on a side surface near a bottom of the nozzle body, a vertical length of one end of the discharge holes in the circumferential direction of the side surface is longer than a vertical length of the other end of the discharge holes, and shapes of the pair of discharge holes have mirror symmetry with each other with a plane that includes an axis of the nozzle body and is parallel to the sliding direction of the sliding plate as a mirror plane,
a discharge hole having one end and another end arranged in this order along a direction in which an opening amount increases in a sliding direction of the sliding plate . The submerged nozzle according to claim 1, characterized in that the ratio of the vertical length of the one end of the discharge hole to the vertical length of the other end is greater than 0.5 and less than 0.9. The submerged nozzle according to claim 1, characterized in that the height of the upper end of the one end of the discharge hole is the same as the height of the upper end of the other end.