WO2024106221A1

WO2024106221A1 - Continuous casting nozzle

Info

Publication number: WO2024106221A1
Application number: PCT/JP2023/039579
Authority: WO
Inventors: 裕也内田; 卓也岡田; 貴宏黒田; 順也矢野; 覚藤井
Original assignee: 黒崎播磨株式会社
Priority date: 2022-11-14
Filing date: 2023-11-02
Publication date: 2024-05-23
Also published as: JP7461442B1; JP2024071220A

Abstract

The present invention provides a continuous casting nozzle with which it is possible to mitigate concentrations of stress in the neck part and inhibit slippage. The present invention is a continuous casting nozzle 1 including a nozzle body 2 made of a refractory material having, in the vertical direction, an internal hole 21 through which molten steel passes, wherein the nozzle body 2 includes a flange part 22 at the upper end, the flange part 22 including, on the outer side surface thereof, a tapered part 221 that inclines downwards towards the internal hole 21, and on the lower surface thereof, a horizontal part 222 that extends horizontally from the lower end of the tapered part 221 towards the internal hole 21. The continuous casting nozzle 1 further includes a metal case 3 covering the outer periphery of the flange part 22, the metal case 3 including a horizontal plate part 31 that faces the horizontal part 222 of the flange part 22 with mortar 4 of a given thickness interposed therebetween, a pressing force from an outer lower direction being received by the horizontal plate part 31.

Description

Continuous casting nozzle

The present invention relates to a continuous casting nozzle used in the continuous casting of steel.

In continuous casting nozzles, the continuous casting of steel must be interrupted or stopped in order to replace them due to wear caused by molten steel, wear limit caused by clogging of the inner hole due to adhesion and accumulation of inclusions in the molten steel, such as non-metallic alumina particles, cracking or breakage. However, in order to improve operational efficiency, a device has been introduced that can replace the continuous casting nozzle with a new one without interrupting the continuous casting of steel as a method of achieving long-term injection (for example, Patent Documents 1 and 2).

The basic structure of a continuous casting nozzle that is applied to such a continuous casting nozzle replacement device can be broadly divided into two parts: a cylindrical nozzle body with a vertical inner hole through which the molten steel passes, and a flange portion with a horizontally enlarged cross-sectional area that is supported from below by a support device of the continuous casting nozzle replacement device in order to support the nozzle body against gravity and push it upward to contact the upper member (upper nozzle member). The boundary portion where the cross-sectional area is enlarged is called the neck.

The neck is a structural stress concentration area and is known to be susceptible to cracks caused by thermal and mechanical stresses. Cracks in the neck are problematic for the service life of the submerged entry nozzle and for the quality of the steel. When molten steel flows through the inner bore of a continuous casting nozzle, the pressure level in the inner bore space becomes negative, which can cause air to be sucked in through the cracks in the neck, oxidizing the carbon components that make up the refractory and potentially resulting in steel leaks and contamination of the steel with oxygen.

In the past, in order to alleviate the above-mentioned stress concentration on the neck, measures such as making the underside (support surface) of the flange part supported from below by the support fixture of the continuous casting nozzle replacement device into a downwardly tapered surface have been taken, as disclosed in Patent Document 3, for example.

However, when the support surface is a tapered surface, there is a problem that the continuous casting nozzle slides downward along the tapered surface, as pointed out in Patent Document 4, for example. In response to this, Patent Document 4 proposes forming a horizontal suspension part on a metal case that is fitted to the outer periphery of the nozzle body with an adhesive such as mortar, and placing a metal ring in the gap with a triangular cross section between the tapered surface of the nozzle body and the suspension part of the metal case.

However, according to tests conducted by the present inventors, it was found that even with the configuration of Patent Document 4, the continuous casting nozzle still slipped downward.
The above-mentioned problems of stress concentration at the neck and of the continuous casting nozzle slipping down are not limited to continuous casting nozzles, particularly submerged nozzles, that are applied to a continuous casting nozzle replacement device. As pointed out in Patent Document 5, for example, these problems also occur in continuous casting nozzles that are not applied to a continuous casting nozzle replacement device, such as long nozzles.

Japanese Patent No. 2793039 Japanese Patent Publication No. 4-50100 Japanese Patent No. 5926230 Patent No. 4097795 Patent No. 2587873

The problem that this invention aims to solve is to provide a continuous casting nozzle that can reduce stress concentration on the neck and prevent slippage.

In solving the above problem, the inventors first conducted a detailed study on the causes of slippage of a continuous casting nozzle. In this regard, the above-mentioned Patent Documents 4 and 5 state that the cause of slippage is solely the thermal expansion of the metal case (nozzle case) and the support (holder), but the inventors' tests and studies, which will be described in detail later, revealed that the main cause of slippage is buckling of the mortar interposed between the nozzle body and the metal case. Based on this analysis of the causes, the inventors conducted further tests and studies to realize a continuous casting nozzle that can both suppress slippage and reduce stress concentration in the neck, and as a result, they came up with the present invention.

That is, according to one aspect of the present invention, there is provided the following continuous casting nozzle.
A continuous casting nozzle including a nozzle body made of a refractory material having an inner hole through which molten steel passes in a vertical direction,
The nozzle body includes a flange portion at an upper end,
the flange portion includes a tapered portion on an outer surface thereof that slopes downward toward the inner hole, and a horizontal portion on a lower surface thereof that extends horizontally from a lower end of the tapered portion toward the inner hole,
Further, a metal case is included which covers an outer periphery of the flange portion,
the metal case includes a horizontal plate portion facing the horizontal portion of the flange portion with a certain thickness of mortar interposed therebetween,
A continuous casting nozzle in which a pressing force from below is received by the horizontal plate portion of the metal case.

The continuous casting nozzle of the present invention can reduce stress concentration on the neck and prevent it from slipping down.

1A and 1B show a continuous casting nozzle according to an embodiment of the present invention, in which FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along the line A-A of FIG. FIG. 2 is a partial perspective view of an upper portion of the nozzle body of the continuous casting nozzle of FIG. 1 as viewed from below. FIG. 2 is a partial cross-sectional view of an upper portion of a nozzle body of the continuous casting nozzle of FIG. 1 . FIG. 2 is a partial cross-sectional view of an upper portion of a nozzle body of a conventional continuous casting nozzle. FIG. 4 is a plan view of a continuous casting nozzle according to another embodiment of the present invention. 1A and 1B are model diagrams for explaining the downward displacement of the nozzle body due to buckling of mortar, in which FIG. 1A is an embodiment of the present invention, and FIG. 6 is a graph showing a calculation example of stress generated in a neck portion of a nozzle body.

FIG. 1 shows a continuous casting nozzle according to one embodiment of the present invention, with FIG. 1(a) being a plan view and FIG. 1(b) being a cross-sectional view taken along the line A-A in FIG. 1(a). Note that FIG. 1(b) shows only the upper part of the continuous casting nozzle, with the lower part omitted. FIG. 2 is a partial perspective view of the upper part of the nozzle body of the continuous casting nozzle of FIG. 1, as seen from below, and FIG. 3 is a partial cross-sectional view of the upper part of the nozzle body of the continuous casting nozzle of FIG. 1.

The continuous casting nozzle 1 shown in FIG. 1 is a submerged nozzle used when injecting molten steel from a tundish facility into a mold in the continuous casting of steel, and is applied to the continuous casting nozzle exchange device described above.
The submerged nozzle 1 includes a nozzle body 2 made of a refractory material. The nozzle body 2 has an inner hole 21 in the vertical direction, which is a passageway for molten steel, and includes a flange portion 22 at an upper end. In this embodiment, the flange portion 22 includes a lower flange portion 22a integrally formed with the nozzle body 2 from the same refractory material as the nozzle body 2, and an upper flange portion 22b formed from a refractory material different from that of the nozzle body 2. However, the entire flange portion 22 may be integrally formed with the nozzle body 2 from the same refractory material as the nozzle body 2, or conversely, the entire flange portion 22 may be formed from a refractory material different from that of the nozzle body 2 and joined directly or via an adhesive to the nozzle body 2.
In any case, the flange portion 22 includes a tapered portion 221 on its outer surface that slopes downward toward the inner hole 21, and a horizontal portion 222 on its underside that extends horizontally from the lower end of the tapered portion 221 toward the inner hole 21.

The submerged nozzle 1 includes a metal case 3 that covers the outer periphery of the flange portion 22. Here, the outer periphery of the flange portion 22 is a general concept that refers to the outer surface and the lower surface described above. In this embodiment, the metal case 3 is arranged to cover the outer periphery of the flange portion 22 and the outer periphery of a portion of the nozzle body 2 below it. Note that in this embodiment, the upper end of the outer surface of the outer periphery of the flange portion 22 is exposed and not covered by the metal case 3, but the entire outer periphery of the flange portion 22 may be covered by the metal case 3.

As shown in FIG. 1(b), the metal case 3 includes a horizontal plate portion 31 that faces the horizontal portion 222 of the flange portion 22 via a certain thickness of mortar 4. The submerged nozzle 1 receives a pressing force from below at this horizontal plate portion 31. The pressing force from below received by this horizontal plate portion 31 is transmitted to the horizontal portion 222 of the flange portion 22 via the mortar 4. This causes the submerged nozzle 1 to be pushed upward and come into contact with the upper member (upper nozzle member).

Figure 3 conceptually shows an upward pressing force F (hereinafter simply referred to as "force F") acting from below on the horizontal portion 222 of the flange portion 22 of the nozzle body 2. As described above, the horizontal portion 222 is present so as to extend horizontally from the lower end of the tapered portion 221 toward the inner hole 21. Therefore, compared to the nozzle body 2 of a conventional immersion nozzle that does not have a tapered portion as shown in Figure 4, the horizontal length L1 of the horizontal portion 222 on which force F acts is shorter by the horizontal length L2 of the tapered portion 221. Therefore, the stress (moment force) due to force F acting on the neck portion 23 of the nozzle body 2 is also reduced by that amount, and stress concentration on the neck portion 23 is alleviated.

Here, it is preferable that the horizontal length L1 of the horizontal portion 222 is within a range of 20% to 80% of the total length L of L1 and the horizontal length L2 of the tapered portion 221. If L1 exceeds 80% of L, the effect of reducing the stress concentration on the neck portion 23 described above is unlikely to be noticeable. On the other hand, if L1 is less than 20% of L, the effect of suppressing the downward slippage of the nozzle body 2 described below is unlikely to be noticeable.

Next, the definition (determination method) of L including L1 and L2 will be described with particular reference to Figures 1(a) and 5. In the present invention, the total length L of the horizontal length L1 of the horizontal portion 222 and the horizontal length L2 of the tapered portion 221 is defined as the length on a horizontal line passing through the center 211 of the inner hole 21 in the region where the force point P on which the force F acts is located, which has the shortest length corresponding to L.
For example, since the submerged nozzle 1 of this embodiment is applied to the continuous casting nozzle replacing device as described above, there are two force points P where the force F acts, which are symmetrically opposed to each other across the inner hole 21 on the underside of the flange portion 22, which has a generally rectangular shape in plan view, as conceptually shown in Fig. 1(a). In such a case, the straight line X1 shown in Fig. 1(a) is the shortest straight line described above, and the total length L is the horizontal length L1 of the horizontal portion 222 on this straight line X1 and the horizontal length L2 of the tapered portion 221.
On the other hand, in the case of a continuous casting nozzle not applied to the continuous casting nozzle replacing device, such as a long nozzle, the force point P where the force F acts may exist in a ring shape surrounding the inner bore 21, as conceptually shown in Fig. 5. In such a case, the straight line X2 shown in Fig. 5 is the shortest straight line mentioned above, and the total length L is the horizontal length L1 of the horizontal portion 222 on this straight line X2 and the horizontal length L2 of the tapered portion 221.

In this way, in the present invention, L including L1 and L2 is determined in the region where the force point P on which the force F acts is present. The length of L including L1 and L2 is an issue from the standpoint of stress concentration and the like because it is the region where the force point P is present. From a similar standpoint, the tapered portion 221 may be formed in a region corresponding to the region where the force point P is present. For example, in the immersion nozzle 1 of this embodiment, as shown in FIG. 1(a) etc., the tapered portion 221 is formed only on one pair of outer surfaces corresponding to the region where the force point P is present, and no tapered portion is formed on the other pair of outer surfaces. Of course, a tapered portion may also be formed on the other pair of outer surfaces.

1(b), in the submerged nozzle 1 of this embodiment, mortar 4 is filled between the metal case 3 and the tapered portion 221. This mortar 4 is made of the same material as the mortar 4 interposed between the horizontal plate portion 31 and the horizontal portion 222 of the metal case 3 and is integrated with the metal case 3. In this way, by filling the space between the metal case 3 and the tapered portion 221 with mortar 4, the outer periphery of the flange portion 22 can be stably covered by the metal case 3 without any gaps. Note that, instead of mortar 4, a ring-shaped metal member or ceramic member may be separately disposed between the metal case 3 and the tapered portion 221. However, from the viewpoint of workability and stability when covering the outer periphery of the flange portion 22 with the metal case 3, it is preferable to fill the entire space between the metal case 3 and the outer periphery of the flange portion 22 with mortar 4 as in this embodiment. In other words, by applying mortar 4 to the outer periphery of the flange portion 22 and then attaching the metal case 3, the entire space between the metal case 3 and the outer periphery of the flange portion 22 can be filled with mortar 4.

In the metal case 3 of this embodiment, the portion facing the tapered portion 221 of the flange portion 22 is formed in a horizontal plate shape by extending the horizontal plate portion 31 that faces the horizontal portion 222 of the flange portion 22 via a certain thickness of mortar 4, but it may be formed in a tapered shape to follow the tapered portion 221 of the flange portion 22 as shown in Figure 6 (a) described later.
In addition, in this embodiment, the tapered portion 221 is formed by a "flat surface", but is not limited thereto, and may be formed by, for example, a "curved surface" or a "step-like step surface". In any case, in the present invention, the "tapered portion" may be one that "inclines downward toward the inner hole". In addition, the "tapered portion that slopes downward toward the inner hole" may be one that slopes downward toward the inner hole as a whole. However, in consideration of the ease of forming the tapered portion, it is preferable that the tapered portion be formed by a "flat surface" as in this embodiment.

In addition, in this embodiment, the flange portion 22 has a generally rectangular shape in plan view, but it can also be polygonal, elliptical, or circular. Furthermore, the shape of the nozzle body 2 excluding the flange portion 22 in plan view is not limited to a circle, and can also be, for example, rectangular or elliptical.

First, the downward slippage of the nozzle body due to buckling of the mortar will be described. FIG. 6 shows a model diagram for this purpose, with FIG. 6(a) being an embodiment of the present invention and FIG. 6(b) being a comparative example. In the embodiment shown in FIG. 6(a), the horizontal length L1 of the horizontal portion 222 is 10 mm, the horizontal length L2 of the tapered portion 221 is 20 mm, the total length L of L1 and L2 is 30 mm, the height H of the tapered portion 221 is 75 mm, and the thickness T of the mortar 4 interposed between the horizontal portion 222 and the horizontal plate portion 31 is 2 mm. In this form, when a vertically downward force acts on the nozzle body 2 as a reaction force due to contact with an upper member (upper nozzle member) not shown, the mortar 4 buckles and the nozzle body 2 slips downward. However, in this embodiment, since the horizontal portion 222 exists, the downward slippage of the nozzle body 2 is contained within the thickness T of the mortar 4, that is, 2 mm. On the other hand, in the comparative example shown in FIG. 6(b), only the tapered portion 221 does not exist and the horizontal portion 222 does not exist. In this case, since the vertical thickness of the mortar 4 is large at the tapered portion 221, the nozzle body 2 will shift downward due to buckling of the mortar 4 to a large extent, and in the case of this comparative example, the calculated downward shift is 5.4 mm, which is more than twice that of the embodiment.
Although the problem of mortar buckling was not recognized in the past, the inventors' tests and studies revealed that mortar buckling is a major factor in the downward slippage of the nozzle body. Therefore, in the present invention, by providing the horizontal portion 222 together with the tapered portion 221, the effect of suppressing the downward slippage of the nozzle body 2 can be obtained.

Next, the effect of suppressing stress concentration on the neck will be described. Figure 7 shows the results of calculating the stress generated in the neck 23 by changing the ratio of the length L1 of the horizontal portion 222 to the total horizontal length L of the tapered portion 221 and the horizontal portion 222 in Figure 3. Here, when the ratio of the length L1 of the horizontal portion 222 is 100%, it corresponds to the nozzle body 2 of the conventional submerged nozzle shown in Figure 4, and the vertical axis "neck stress index" in Figure 7 is an index in which the stress generated in the neck 23 when the ratio of L1 is 100% is set to 100. As is clear from Figure 7, it was confirmed that the lower the ratio of the length L1 of the horizontal portion 222, in other words, the higher the ratio of the length L2 of the tapered portion 221, the lower the stress generated in the neck 23. In other words, it was confirmed that the provision of the tapered portion 221 provides an effect of suppressing stress concentration on the neck.

1. Submerged nozzle (nozzle for continuous casting)
2 Nozzle body 21 Inner hole 211 Center of inner hole 22 Flange portion 22a Lower flange portion 22b Upper flange portion 221 Tapered portion 222 Horizontal portion 23 Neck portion 3 Metal case 31 Horizontal plate portion 4 Mortar P Point of force

Claims

A continuous casting nozzle including a nozzle body made of a refractory material having an inner hole through which molten steel passes in a vertical direction,
The nozzle body includes a flange portion at an upper end,
the flange portion includes a tapered portion on an outer surface thereof that slopes downward toward the inner hole, and a horizontal portion on a lower surface thereof that extends horizontally from a lower end of the tapered portion toward the inner hole,
Further, a metal case is included which covers an outer periphery of the flange portion,
the metal case includes a horizontal plate portion facing the horizontal portion of the flange portion with a certain thickness of mortar interposed therebetween,
A continuous casting nozzle in which a pressing force from below is received by the horizontal plate portion of the metal case.
The continuous casting nozzle according to claim 1, wherein the horizontal length of the horizontal portion is within a range of 20% to 80% of the total horizontal length of the tapered portion and the horizontal portion.
The continuous casting nozzle according to claim 1 or 2, wherein mortar is filled between the metal case and the tapered portion.