Nozzle for continuous casting

Abstract

The invention provides a nozzle for continuous casting, which can alleviate stress concentration on a neck part and can restrain downward movement. Specifically, in the present invention, in a nozzle (1) for continuous casting comprising a nozzle body (2) made of a refractory having an inner hole (21) through which molten steel passes in the vertical direction, the nozzle body (2) comprises a flange part (22) at the upper end, and the flange part (22) comprises a tapered part (221) on the outer side surface, the tapered part (221) being inclined downward toward the inner hole (21) side. The lower surface includes a horizontal portion (222) extending in the horizontal direction from the lower end of the tapered portion (221) toward the inner hole (21) side. Furthermore, the nozzle (1) for continuous casting comprises a metal shell (3) covering the outer periphery of the flange part (22), the metal shell (3) comprises a horizontal plate part (31) facing the horizontal part (222) of the flange part (22) through the mortar (4) with a certain thickness, and the horizontal plate part (31) receives the pressing force from the lower part of the outside.

Description

Technical Field

[0001] The present invention relates to a nozzle for continuous casting for continuous casting of steel. Background Art

[0002] In a nozzle for continuous casting, due to losses caused by molten steel, blockage of the inner hole caused by adhesion and accumulation of inclusions in the molten steel such as non-metallic, i.e., alumina particles, durability limits, breakage, and breakage occur. For replacement, it is necessary to interrupt or end the continuous casting operation of steel. However, from the requirement of improving operation efficiency, as a method for achieving long-term injection, a device (for example, Patent Documents 1 and 2) has been introduced that can replace the continuous casting nozzle with a new continuous casting nozzle without interrupting the continuous casting operation of steel.

[0003] The basic structure of a continuous casting nozzle applied to such a continuous casting nozzle replacement device can be roughly divided into two parts, namely: a cylindrical nozzle body part having a molten steel passage, i.e., an inner hole, in the vertical direction; and a flange part that contacts an upper part (upper nozzle part) to support the nozzle body part against gravity and push it upward, and is supported from below by a support of the continuous casting nozzle replacement device, and the cross-sectional area is enlarged in the horizontal direction, and the boundary part where the cross-sectional area is enlarged is called a neck.

[0004] It is known that the neck is a stress concentration part in the structure, and cracks may occur due to the action of thermal stress and mechanical stress. Cracks in the neck become a problem for the service life of the immersion nozzle and the quality of steel. Since molten steel flows in the inner hole of the continuous casting nozzle, the pressure level in the inner hole space tends to be negative pressure. As a result, air is sucked in from the cracks in the neck, causing oxidation of the carbon component constituting the refractory, and as a result, there is a possibility of steel leakage, and there is also a possibility of steel being contaminated with oxygen.

[0005] Therefore, conventionally, from the viewpoint of alleviating the stress concentration on the neck as described above, for example, as disclosed in Patent Document 3, countermeasures such as forming the lower surface (support surface) of the flange part supported from below by the support of the continuous casting nozzle replacement device into an inclined conical surface have been taken.

[0006] However, in the case of a configuration in which the support surface is formed into a conical surface, for example, as pointed out in Patent Document 4, there is a problem that the continuous casting nozzle moves downward along the conical surface. On the contrary, Patent Document 4 proposes the following solution: a horizontal suspension part is formed on a metal shell fitted to the outer periphery of the nozzle body by an adhesive material such as mortar, and a metal ring is interposed in a triangular cross-sectional gap between the conical surface of the nozzle body and the suspension part of the metal shell.

[0007] However, according to the experiments conducted by the present inventors, it was found that even with the configuration of Patent Document 4, the continuous casting nozzle would still move downward. In addition, the above-mentioned problem of stress concentration on the neck and the problem of downward movement of the continuous casting nozzle are not limited to the continuous casting nozzle, especially the immersion nozzle, which is suitable for the continuous casting nozzle replacement device. For example, as pointed out in patent document 5, the problem may also occur in the continuous casting nozzle, such as the long nozzle, which is not suitable for the continuous casting nozzle replacement device.

[0008] Patent Literature Patent Document 1: Japanese Patent No. 2793039 Patent Document 2: Japanese Patent Publication No. 4-50100 Patent Document 3: Japanese Patent No. 5926230 Patent Document 4: Japanese Patent No. 4097795 Patent Document 5: Japanese Patent No. 2587873 Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a continuous casting nozzle which can alleviate stress concentration on the neck and suppress downward movement.

[0010] In order to solve the above-mentioned problems, the inventors first conducted a detailed study on the main reasons for the downward movement of the continuous casting nozzle. In this regard, although the thermal expansion of the metal shell (nozzle shell) and the support (support) is mainly regarded as the main reason for the downward movement in the above-mentioned patent documents 4 and 5, it is found through the experiments and studies of the inventors that, although it will be described in detail later, the buckling of the mortar between the nozzle body and the metal shell is a major main reason for the downward movement. Then, based on the analysis of the main reasons, the inventors further repeatedly conducted experiments and studies in order to realize a continuous casting nozzle that can take into account both the suppression of downward movement and the relaxation of stress concentration on the neck, and the results led to the present invention.

[0011] That is, according to one aspect of the present invention, the following continuous casting nozzle can be provided. A continuous casting nozzle, comprising a nozzle body made of refractory material and having an inner hole in the vertical direction for molten steel to pass through, characterized in that: The nozzle body includes a flange portion at the upper end, The flange portion includes a tapered portion on the outer side that is inclined downward toward the inner hole side, and includes a horizontal portion on the lower side that extends in the horizontal direction from the lower end of the tapered portion toward the inner hole side. further comprising a metal shell covering the outer periphery of the flange portion, The metal shell includes a horizontal plate portion that faces the horizontal portion of the flange portion through a certain thickness of mortar. The horizontal plate portion of the metal shell receives the pressing force from below outside.

[0012] The nozzle for continuous casting according to the present invention can relieve the stress concentration on the neck and can suppress the downward movement. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It shows a nozzle for continuous casting according to an embodiment of the present invention. (a) is a top view, and (b) is a cross-sectional view taken along the line A-A of (a). Figure 2 It is a partial perspective view of observing the upper part of the nozzle body of the nozzle for continuous casting from below Figure 1 of. Figure 3 It is Figure 1 a partial cross-sectional view of the upper part of the nozzle body of the nozzle for continuous casting of. Figure 4 It is a partial cross-sectional view of the upper part of the nozzle body of an existing nozzle for continuous casting. Figure 5 It is a top view of a nozzle for continuous casting according to another embodiment of the present invention. Figure 6 It is a model diagram for explaining the downward movement of the nozzle body caused by the buckling of the mortar. (a) is an example of the present invention, and (b) is a comparative example. Figure 7 It is a graph showing a calculation example of the stress generated in the neck of the nozzle body. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] Figure 1 It shows a nozzle for continuous casting according to an embodiment of the present invention. In the same figure, (a) is a top view, and (b) is a cross-sectional view taken along the line A-A of (a). Additionally, in the same figure (b), the lower part of the nozzle for continuous casting is omitted and only the upper part is shown. Furthermore, Figure 2 It is a partial perspective view of observing the upper part of the nozzle body of the nozzle for continuous casting from below Figure 1 of Figure 3 It is Figure 1 a partial cross-sectional view of the upper part of the nozzle body of the nozzle for continuous casting of.

[0015] Figure 1 The shown nozzle for continuous casting 1 is an immersion nozzle used for injecting molten steel from a tundish device into a mold during the continuous casting of steel, and is applied to the above-mentioned nozzle replacement device for continuous casting. The dipping nozzle 1 includes a nozzle body 2 made of refractory. The nozzle body 2 has a molten steel passage, i.e., an inner hole 21, in the vertical direction, and includes a flange portion 22 at the upper end. Although in the present embodiment, the flange portion 22 is composed of a lower flange portion 22a and an upper flange portion 22b, the lower flange portion 22a is integrally formed of the same refractory as the nozzle body 2, and the upper flange portion 22b is formed of a refractory different from the nozzle body 2, the entire flange portion 22 may also be integrally formed of the same refractory as the nozzle body 2. On the contrary, the entire flange portion 22 may also be formed of a refractory different from the nozzle body 2 and directly joined or joined to the nozzle body 2 through an adhesive. In short, the flange portion 22 includes a tapered portion 221 inclined downward in the direction toward the inner hole 21 on the outer side surface, and includes a horizontal portion 222 extending in the horizontal direction from the lower end of the tapered portion 221 toward the inner hole 21 on the lower surface.

[0016] The dipping nozzle 1 includes a metal shell 3 covering the outer periphery of the flange portion 22. Here, the outer periphery of the flange portion 22 refers to the general concept of the above-mentioned outer side surface and the lower surface. In the present embodiment, the metal shell 3 is arranged to cover the outer periphery of the flange portion 22 and a part of the outer periphery of the nozzle body 2 below it. In addition, although in the present embodiment, the upper end portion of the outer side surface on the outer periphery of the flange portion 22 is not covered by the metal shell 3 and is exposed, the entire outer periphery of the flange portion 22 may also be covered by the metal shell 3.

[0017] As Figure 1 (b) shows, the metal shell 3 includes a horizontal plate portion 31 facing the horizontal portion 222 of the flange portion 22 of the nozzle body 2 through a mortar 4 with a certain thickness. The dipping nozzle 1 receives the pressing force from the lower part outside through the horizontal plate portion 31. The pressing force from the lower part outside received by the horizontal plate portion 31 is transmitted to the horizontal portion 222 of the flange portion 22 through the mortar 4. Thereby, the dipping nozzle 1 can be pushed upward and brought into contact with the upper component (upper nozzle component).

[0018] In Figure 3 , it schematically shows an upward pressing force F (hereinafter only referred to as "force F") from the lower part outside acting on the horizontal portion 222 of the flange portion 22 of the nozzle body 2. As described above, since the horizontal portion 222 exists in such a way that it extends in the horizontal direction from the lower end of the tapered portion 221 toward the inner hole 21, compared with the nozzle body 2 of the existing dipping nozzle without a tapered portion shown in Figure 4 , the horizontal length L1 of the horizontal portion 222 on which the force F acts is shortened by the amount of the horizontal length L2 of the tapered portion 221. Therefore, the stress (moment force) caused by the force F acting on the neck 23 of the nozzle body 2 is also correspondingly reduced, thereby relieving the stress concentration on the neck 23.

[0019] Here, preferably, the horizontal length L1 of the horizontal portion 222 is in the range of 20% or more and 80% or less with respect to the total length L of this L1 and the horizontal length L2 of the tapered portion 221. When L1 exceeds 80% of L, it is difficult to significantly exhibit the above-described effect of alleviating the stress concentration on the neck portion 23. On the other hand, when L1 is less than 20% of L, the effect of suppressing the downward movement of the nozzle body 2 described later is significantly exhibited.

[0020] Next, particularly with reference to Figure 1 (a) and Figure 5 the definition (determination method) of L including L1 and L2 will be described. 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 the length on the straight line in the horizontal direction passing through the center 211 of the inner hole 21 and having the shortest length corresponding to L among the straight lines in the horizontal direction in the region where the force point portion P where the force F acts exists. For example, since the dipping nozzle 1 of the present embodiment is applied to the nozzle replacement device for continuous casting as described above, the force point portion P where the force F acts is as Figure 1 (a) schematically shown, and there are two symmetrically existing portions on the lower surface of the flange portion 22 having a substantially quadrilateral shape in plan view while sandwiching the inner hole 21. In this case, Figure 1 the straight line X1 shown in (a) is the above-described shortest straight line, and the total length of the horizontal length L1 of the horizontal portion 222 and the horizontal length L2 of the tapered portion 221 on this straight line X1 is L. On the other hand, in the case of a continuous casting nozzle such as a long nozzle that is not applied to the nozzle replacement device for continuous casting, the force point portion P where the force F acts is as Figure 5 schematically shown, and sometimes exists in a ring shape so as to surround the inner hole 21. In this case, Figure 5 the straight line X2 shown in is the above-described shortest straight line, and the total length of the horizontal length L1 of the horizontal portion 222 and the horizontal length L2 of the tapered portion 221 on this straight line X2 is L.

[0021] Thus, in the present invention, L including L1 and L2 is determined in the region where the force point portion P where the force F acts exists. From the viewpoint of stress concentration and the like, the length of L including L1 and L2 becomes a problem because of the region where the force point portion P exists. In addition, from the same viewpoint, the tapered portion 221 only needs to be formed in advance in the region corresponding to the region where the force point portion P exists. For example, in the dipping nozzle 1 of the present embodiment, as Figure 1(a) As shown, the tapered portions 221 are formed only on one pair of outer side surfaces corresponding to the region where the strong point portion P exists, and not formed on the other pair of outer side surfaces. Of course, the tapered portions can also be formed on the other pair of outer side surfaces.

[0022] As Figure 1 (b) As shown, in the dipping nozzle 1 of the present embodiment, mortar 4 is filled between the metal shell 3 and the tapered portion 221. The mortar 4 is integrated with the mortar 4 between the horizontal plate portion 31 of the metal shell 3 and the horizontal portion 222 due to the same material. Thus, by filling the mortar 4 between the metal shell 3 and the tapered portion 221, the outer periphery of the flange portion 22 can be stably covered without gaps by the metal shell 3. Additionally, an annular metal or ceramic component can be additionally disposed between the metal shell 3 and the tapered portion 221 instead of the mortar 4. However, from the viewpoints of workability and stability when covering the outer periphery of the flange portion 22 with the metal shell 3, it is preferred to fill the mortar 4 in the whole between the metal shell 3 and the outer periphery of the flange portion 22 as in the present embodiment. That is, by applying the mortar 4 to the outer periphery of the flange portion 22 and then installing the metal shell 3, the mortar 4 can be filled in the whole between the metal shell 3 and the outer periphery of the flange portion 22.

[0023] In addition, although in the metal shell 3 of the present embodiment, the portion opposite to the tapered portion 221 of the flange portion 22 is formed by extending the horizontal plate portion 31 opposite to the horizontal portion 222 of the flange portion 22 through a certain thickness of mortar 4 and formed into a horizontal plate shape, it can also be formed into a tapered shape in imitation of the tapered portion 221 of the flange portion 22 as shown in Figure 6 (a). Furthermore, although in the present embodiment, the tapered portion 221 is formed by a "plane", it is not limited thereto. For example, it can also be formed by a "curved surface" or a "stepped stepped surface". In short, in the present invention, the "tapered portion" only needs to be "inclined downward toward the inner hole side". In addition, the "tapered portion inclined downward toward the inner hole side" means that as long as the whole of its tapered portion is inclined downward toward the inner hole side. However, considering the ease of forming the tapered portion, etc., it is preferred that the tapered portion be formed by a "plane" as in the present embodiment.

[0024] Moreover, although in the present embodiment, the top view shape of the flange portion 22 is approximately quadrilateral, it can also be polygonal, elliptical or circular. And the top view shape of the nozzle body 2 other than the flange portion 22 is not limited to circular either. For example, it can also be rectangular or elliptical. Examples

[0025] First, the downward movement of the nozzle body caused by the buckling of the mortar will be described. For this purpose, in Figure 6The model diagrams are shown below. Figure (a) is an embodiment of the present invention, and Figure (b) is a comparative example. In the embodiment shown in Figure (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, and the total length L of L1 and L2 is 30 mm. In addition, the height H of the tapered portion 221 is 75 mm, and the thickness T of the mortar 4 between the horizontal portion 222 and the horizontal plate portion 31 is 2 mm. In this configuration, when a vertically downward force acts on the nozzle body 2 as a reaction force caused by contact with an upper component (upper nozzle component) not shown, the mortar 4 buckles and the nozzle body 2 moves downward. However, since the horizontal portion 222 exists in this embodiment, the downward movement of the nozzle body 2 converges within the thickness T of the mortar 4, that is, 2 mm. On the other hand, in the case of the comparative example shown in Figure (b), there is only the tapered portion 221 and no horizontal portion 222. Thus, since the vertical thickness of the mortar 4 is large on the tapered portion 221, the downward movement of the nozzle body 2 caused by the buckling of the mortar 4 becomes large. In this comparative example, it is calculated to be 5.4 mm, which is more than twice that of the embodiment. Although the problem of such buckling of the mortar has not been recognized in the past, it has been found through experiments and research by the inventors that such buckling of the mortar is a major cause of the downward movement of the nozzle body. Therefore, in the present invention, by providing the horizontal portion 222 together with the tapered portion 221, an effect of suppressing the downward movement of the nozzle body 2 can be obtained.

[0026] Next, the effect of suppressing stress concentration in the neck will be described. Figure 7 The following results are shown, that is, in Figure 3 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 is changed, and the stress generated in the neck 23 is calculated respectively. Here, when the ratio of the length L1 of the horizontal portion 222 is 100%, it corresponds to Figure 4 the nozzle body 2 of the existing dipping nozzle shown in Figure 7 The vertical axis "neck stress index" means an index with the stress generated in the neck 23 when the ratio of L1 is 100% as 100. From Figure 7 it can be seen that it is 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. That is, it is confirmed that by providing the tapered portion 221, an effect of suppressing stress concentration in the neck can be obtained. Symbol description

[0027] 1 - Immersion nozzle (nozzle for continuous casting); 2 - Nozzle body; 21 - Inner hole; 211 - Center of the inner hole; 22 - Flange part; 22a - Lower flange part; 22b - Upper flange part; 221 - Taper part; 222 - Horizontal part; 23 - Neck; 3 - Metal shell; 31 - Horizontal plate part; 4 - Mortar; P - Force point part.

Claims

1. A nozzle for continuous casting, comprising a nozzle body made of refractory material having an inner hole through which molten steel passes in the vertical direction, Characterized in that, The nozzle body includes a flange portion at the upper end, The flange portion includes a tapered portion on the outer side surface that inclines downward toward the inner hole side, and includes a horizontal portion on the lower surface that extends horizontally from the lower end of the tapered portion toward the inner hole side, It further includes a metal shell covering the outer periphery of the flange portion, The metal shell includes a horizontal plate portion that faces the horizontal portion of the flange portion through a certain thickness of mortar, The pressing force from below outside is received by the horizontal plate portion of the metal shell.

2. The nozzle for continuous casting according to claim 1, Characterized in that, The horizontal length of the horizontal portion is in the range of 20% or more and 80% or less with respect to the total horizontal length of the tapered portion and the horizontal portion.

3. The nozzle for continuous casting according to claim 1 or 2, Characterized in that, Mortar is filled between the metal shell and the tapered portion.

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