Casting nozzle

Abstract

This disclosure provides a casting nozzle in which a nozzle body is hardly damaged in a region where a metal case exists. Specifically, disclosed is a casting nozzle 1 wherein a nozzle body upper part 21, which is the upper part of a nozzle body 2, is surrounded by a metal case 3, the metal case 3 being provided with a slit 31 extending in the vertical direction.

Description

Casting Nozzle

[0001] The present invention relates to a casting nozzle used in continuous casting of molten steel.

[0002] In continuous casting of molten steel, when discharging molten steel from a molten steel ladle (ladle) to a tundish, a long nozzle as a casting nozzle is generally used to suppress oxidation of the molten steel and entrainment of slag present on the upper surface in the tundish into the molten steel. Further, in pouring molten steel from a tundish into a mold, an immersion nozzle as a casting nozzle is generally used. A general configuration of such a casting nozzle is such that the upper part of a nozzle body made of a refractory is surrounded by a metal case.

[0003] By the way, in the casting nozzle in which the upper part of the nozzle body is surrounded by the metal case as described above, there has been a problem that cracks, breakage, and the like (hereinafter collectively referred to as "damage") are likely to occur in the nozzle body in a region where the metal case is present. As a countermeasure against this problem, Patent Document 1 discloses a configuration in which a plurality of arc-shaped notches are formed at the lower end of the metal case. However, the stress relaxation effect obtained by the configuration of Patent Document 1 is only achieved at the locations where the arc-shaped notches are provided, and only has the effect of shifting the stress concentration position, so it is not sufficient as a measure for suppressing damage to the nozzle body in the region where the metal case is present as described above.

[0004] Japanese Patent No. 6813471

[0005] The problem to be solved by the present invention is to provide a casting nozzle in which damage to the nozzle body is less likely to occur in the region where the metal case is provided.

[0006] To devise a means to solve the above problem, the inventors first conducted a detailed analysis and examination of the cause (mechanism) of damage to the nozzle body in the region where the metal case is present. As a result, the mechanism was estimated to be as follows: When using a casting nozzle, that is, when hot, especially in the initial stages of heat absorption, the refractory material expands, but the temperature of the metal case has not risen. Therefore, until the temperature of the metal case rises and its thermal expansion is equal to or greater than that of the thermal expansion of the refractory material, the restraining force on the refractory material inside the region where the metal case is present increases. In other words, because the timing of the expansion of the refractory material due to heating from the inner bore side of the nozzle body, which is made of refractory material, and the expansion of the metal case are different, the refractory material in the region where the metal case is present, especially the boundary region with the metal case (hereinafter simply referred to as the "metal case boundary region"), has regions where it expands and a high restraining force is generated, and regions where it is not restrained, and a vector leading to shear is generated. That is, stress concentration occurs in the above metal case boundary region, and it was estimated that damage to the nozzle body occurs particularly in this metal case boundary region.

[0007] Therefore, the inventors of this invention, based on the technical idea that reducing the restraining force on the refractory material by the metal case, which is caused by the difference in the magnitude of thermal expansion between the metal case and the refractory material, and thereby reducing stress concentration in the metal case boundary region, would be effective in solving the above-mentioned problems, further investigated the specific configuration of the metal case and completed the present invention.

[0008] In other words, according to one aspect of the present invention, the following casting nozzle is provided: A casting nozzle in which the upper part of the nozzle body is surrounded by a metal case, wherein the metal case has a slit extending in the vertical direction, and the lower end of the slit is located above the lower end of the metal case.

[0009] According to the present invention, by forming slits in the metal case, the restraining force of the refractory material by the metal case can be reduced, thereby suppressing damage to the nozzle body in the area where the metal case is present.

[0010] A perspective view of the main part of a casting nozzle, which is one embodiment of the present invention. An enlarged front view of the metal case alone. A conceptual diagram showing various models for which simulations were performed. A conceptual diagram showing various models for which additional simulations were performed.

[0011] Figure 1 shows a perspective view of the main part of a casting nozzle, which is one embodiment of the present invention. The casting nozzle 1 shown in the figure has a nozzle body upper part 21, which is the upper part of a nozzle body 2 made of refractory material, surrounded by a metal case 3.

[0012] The metal case 3 has slits 31 that extend in the vertical direction. In this embodiment, the slits 31 are provided in multiple rows (specifically, two rows vertically) spaced apart in the vertical direction, and in multiple rows (specifically, three rows in the circumferential direction with two rows vertically) spaced apart in the circumferential direction. That is, in this embodiment, there are a total of six slits 31: two rows vertically and three rows in the circumferential direction.

[0013] In this embodiment, the configuration of the six slits 31 is substantially the same. Therefore, the configuration of the slits 31 will be explained with reference to the enlarged front view of the metal case 3 shown in Figure 2. In this embodiment, the lower end of the slit 31 branches in multiple directions (specifically, two directions), and the shape of the branched portion is an upwardly convex arc (hereinafter, this portion will be referred to as the "lower end arc-shaped portion" and will be denoted by reference numeral 31a). In this embodiment, the upper end of the slit 31 branches in multiple directions (specifically, two directions), and the shape of the branched portion is an downwardly convex arc (hereinafter, this portion will be referred to as the "upper end arc-shaped portion" and will be denoted by reference numeral 31b). In addition, in this embodiment, an arc-shaped notch 32 formed in the lower end of the metal case 2 is located below the lower end of the lower slit 31. Furthermore, in this embodiment, a circular hole 33 is provided between the upper and lower two slits 31, 31.

[0014] Referring again to Figure 1, in this embodiment, the upper part 21 of the nozzle body has a large diameter portion 21A at the upper end, a small diameter portion 21B at the lower end, and a neck portion 21C connecting the large diameter portion 21A and the small diameter portion 21B. Also, as shown in Figure 2, the metal case 3 has a large diameter portion 3A, a small diameter portion 3B, and a neck portion 3C corresponding to the large diameter portion 21A, the small diameter portion 21B, and the neck portion 21C of the upper part 21 of the nozzle body. In this embodiment, the six slits 31 are provided in the small diameter portion 3B. In this embodiment, the metal case 3 is provided so as to surround the entire circumference of the large diameter portion 21A of the upper part 21 of the nozzle body, but it can also be provided so as to surround the neck portion 21C and the small diameter portion 21B from below the large diameter portion 21A without surrounding the upper part of the large diameter portion 21A. In this case as well, the slits 31 can be provided in the small diameter portion 3B.

[0015] In the above configuration, the slit 31 is provided to interrupt the circumferential continuity of the metal case 3. That is, the presence of the slit 31 in the metal case 3 makes it easier for the metal case 3 to expand when stress is generated from the refractory material constituting the inner nozzle body upper part 21, causing the outer metal case 3 to expand due to its deformation or malleability. As a result, the restraining force on the refractory material (nozzle body upper part 21) by the metal case 3, caused by the difference in the magnitude of thermal expansion between the metal case 3 and the refractory material (nozzle body upper part 21), is reduced, and stress concentration in the metal case boundary region is reduced as described above. As a result, the occurrence of damage to the nozzle body 2 in the region where the metal case 3 is present can be suppressed.

[0016] Thus, in the present invention, the slits are provided to interrupt the circumferential continuity of the metal case, and from this viewpoint, there is no limit to the number of slits; for example, there may be one slit. However, in order to more effectively reduce the restraining force of the metal case on the refractory material (upper part of the nozzle body), it is preferable to provide multiple rows of slits spaced apart in the circumferential direction of the metal case. Furthermore, the shape of the slits does not need to be linear as shown in Figures 1 and 2, but may be curved, for example. The width of the slits is also not particularly limited; they may be zero width, i.e., tightly closed, or open to any width.

[0017] The length of the slit is not limited, but its lower end should be located above the lower end of the metal case, as shown in Figures 1 and 2. If the lower end of the slit extends to the lower end of the metal case, problems such as difficulty in maintaining the shape of the metal case will arise. On the other hand, the position of the upper end of the slit is not limited, but it is preferable that it be located at the small diameter portion 3B of the metal case 3, as shown in Figures 1 and 2. In other words, it is preferable to form the slit only in the small diameter portion of the metal case, from the viewpoint of ease of slit formation, etc. Furthermore, the slit may be provided in one upper and lower stage, but if the length of the slit becomes long, problems such as difficulty in maintaining the shape of the metal case may arise, and in such cases, multiple stages can be provided with spacing in the vertical direction, as shown in Figures 1 and 2.

[0018] The lower and upper ends of the slit are preferably branched in multiple directions, as shown in Figures 1 and 2, and it is even more preferable that the lower end has a lower arc-shaped portion 31a and the upper end has an upper arc-shaped portion 31b. By branching the lower and upper ends of the slit in multiple directions, the effect of reducing the restraining force of the refractory material by the metal case can be enhanced. Furthermore, by making the lower end of the slit an upwardly convex arc and the upper end of the slit an downwardly convex arc, the effect of reducing the restraining force of the refractory material by the metal case can be further enhanced.

[0019] Next, we will explain the simulations conducted to verify the effect of the slits. Figure 3 conceptually shows the various models used in the simulations. In the simulations, we used a model with a length of 84 mm (half the length of a cylinder) and a slit width of 2 mm, and determined the reaction force from the slit direction toward the center when a forced displacement was applied to expand the inside of the cylinder radially by 20 μm. The results are shown in Table 1. Of the models 1 to 6 shown in Figure 3, Model 1 is a conventional model without slits, Models 2 and 3 are models of the present invention with slits of different lengths, Model 4 is a model of the present invention with the lower end of the slit being an upwardly convex arc shape (lower end arc shape portion) and an arc shape notch provided at the lower end of the metal case, Model 5 is a model of the present invention in which the lower end arc shape portion of Model 4 has been removed, and Model 6 is a model of the present invention in which the arc shape notch of Model 4 has been removed. In Table 1, the continuous length refers to the continuous length of the metal case from the lower end of the slit to the lower end of the metal case. Note that in Model 1, there are no slits, so the continuous length is the length of the cylinder, 84 mm. Furthermore, in Table 1, the reaction force (index) is an index where the reaction force of Model 1, the conventional model, is set to 1.

[0020]

[0021] Table 1 shows that the reaction force is reduced by adding a slit, as can be seen from the comparison of models 1 to 3. Furthermore, the comparison of models 4 to 6 shows that the reaction force is further reduced by branching the lower end of the slit, and the reaction force is reduced even more when the branching of the lower end of the slit is combined with an arc-shaped notch, as in model 4.

[0022] Figure 4 conceptually shows various simulation models that were additionally performed to verify the influence of factors such as the branching width at the lower end of the slit. Table 2 shows the simulation results. Of the models 7 to 13 shown in Figure 4, model 7 is the present invention model in which the lower end of the slit is not branched, and models 8 to 13 are the present invention models in which the lower end of the slit is branched linearly with different widths. In Table 2, the branching width refers to the branching width at the lower end of the slit as described above. Other notations are the same as in Table 1.

[0023]

[0024] Table 2 shows that the reaction force decreases as the branching width increases. Also, the branching width at the lower end of the slit of Model 4 shown in Figure 3 is 31 mm, which is the same as Models 9 and 10 shown in Figure 3, but the reaction force in Model 4 is significantly reduced compared to Models 9 and 10. From this, it can be said that the shape of the branching part at the lower end of the slit is preferably an upwardly convex arc, and from this, it can be determined that the shape of the branching part at the upper end of the slit is preferably a downwardly convex arc.

[0025] 1 Casting nozzle 2 Nozzle body 21 Upper part of nozzle body 21A Large diameter section 21B Small diameter section 21C Neck section 3 Metal case 3A Large diameter section 3B Small diameter section 3C Neck section 31 Slit 31a Lower arc-shaped section 31b Upper arc-shaped section 32 Notch 33 Circular hole

Claims

1. A casting nozzle in which the upper part of the nozzle body is surrounded by a metal case, wherein the metal case has a slit extending in the vertical direction, and the lower end of the slit is located above the lower end of the metal case.

2. The casting nozzle according to claim 1, wherein the lower end of the slit is branched in multiple directions.

3. The casting nozzle according to claim 2, wherein the shape of the portion that branches in multiple directions at the lower end of the slit is an upwardly convex arc.

4. The casting nozzle according to claim 1, wherein the upper end of the slit is branched in multiple directions.

5. The casting nozzle according to claim 4, wherein the shape of the portion that branches in multiple directions at the upper end of the slit is a downwardly convex arc.

6. The casting nozzle according to any one of claims 1 to 5, wherein the slits are provided in multiple stages spaced apart in the vertical direction.

7. The casting nozzle according to any one of claims 1 to 5, wherein the slits are provided in multiple rows spaced apart in the circumferential direction.

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