Immersion nozzle

Abstract

An immersion nozzle that is applicable to an immersion nozzle replacement apparatus satisfies both the suppression of occurrence of cracks in a neck portion thereof and the suppression of occurrence of sinking thereof. The immersion nozzle includes a bridging member bridging an inner peripheral surface of a metal case surrounding a flange portion and an outer peripheral surface of a nozzle body. The bridging member has one end fixed to the metal case and the other end engaged with a recess provided in the outer peripheral surface of the nozzle body. Further, in an area above an action point of an upward support force by a support device of the immersion nozzle replacement apparatus, the outer peripheral surface of the nozzle body is formed to have a shape extending in a vertical direction without dimensional change with respect to a central axis of an inner bore, except for the recess.

Description

TECHNICAL FIELD

[0001] The present invention relates to an immersion nozzle used when pouring molten steel from tundish equipment into a mold, in continuous casting of steel.BACKGROUND ART

[0002] An immersion nozzle is required to be replaced because of its durable limitation, cracks, or breakage, caused by wear damage due to molten steel, and clogging of an inner bore due to adhesion and accumulation of inclusions in molten steel, such as non-metallic alumina particles, and for the replacement, an operation of continuous casting of steel has to be interrupted or ended. However, from a viewpoint of demand for improving operational efficiency, it is necessary to realize long-time pouring. As a measure of this, an apparatus for replacing a used immersion nozzle with a new one without interrupting the operation of continuous casting of steel is introduced (e.g. Patent Documents 1 and 2).

[0003] A basic structure of an immersion nozzle applicable to such an immersion nozzle replacement apparatus may roughly comprise two components: a cylindrical-shaped nozzle body having an inner bore oriented in a vertical direction, as a molten steel passage path; and a flange portion whose cross-sectional area is enlarged in a horizontal direction and which is supported from therebelow by a support device of the immersion nozzle replacement apparatus in order to push the nozzle body upwardly against gravity to bring the nozzle body into contact with an above-located member (upper nozzle member), wherein a boundary portion in which the cross-sectional area of the flange portion is enlarged will hereinafter be referred to as a neck portion.

[0004] The neck portion is a stress concentration area in structure, and it is known that thermal stress and mechanical stress act thereon, possibly leading to occurrence of cracks. Such cracks in the neck portion become a problem for durable life of the immersion nozzle and the quality of steel. When molten steel flows through the inner bore of the immersion nozzle, the pressure level of an inner bore space tends toward a negative pressure. As a result, air is sucked from the cracks in the neck portion, and oxidizes a carbon component constituting a refractory material of the nozzle body, possibly resulting in causing leakage of steel and in contaminating steel with oxygen.

[0005] Therefore, the present inventors have disclosed, in Patent Document 3, an immersion nozzle comprising a nozzle body having a shape in which there is not any change in cross-sectional area which can be called as a neck portion.CITATION LISTPatent Document

[0006] Patent Document 1: JP2793039 B2

[0007] Patent Document 2: JP H04-050100B2

[0008] Patent Document 3: JP 6122393B2SUMMARY OF INVENTIONTechnical Problem

[0009] The present inventors conducted a test in which the immersion nozzle illustrated in FIG. 1 of Patent Document 3 was subjected to an actual casting operation. As a result, the problem of occurrence of cracks in the neck portion has been resolved, but it has been ascertained that there is a problem of sinking of the nozzle body as a new problem. If the sinking of the nozzle body occurs, a gap is formed in a joining region with the above-located member (upper nozzle member), and becomes a factor of deterioration in steel quality due to air aspiration, and a factor of wear loss of the refractory material. The gap also becomes a factor causing a big trouble which has an influence on casting operation due to leakage of steel.

[0010] Therefore, a technical problem to be solved by the present invention is to make it possible for an immersion nozzle applicable to an immersion nozzle replacement apparatus to satisfy both the suppression of occurrence of cracks in a neck portion thereof and the suppression of occurrence of sinking thereof.Solution to Technical Problem

[0011] According to one aspect of the present invention, there is provided an immersion nozzle which comprises: a nozzle body made of a refractory material and having an inner bore oriented in a vertical direction; and a flange portion made of a refractory material and formed in a flat plate shape, the flange portion being joined to an outer periphery of an upper end section of the nozzle body, directly or through an adhesive, in such a manner as to surround the outer periphery of the upper end section of the nozzle body and protrude in a horizontal direction, wherein respective outer peripheries of the flange portion and a portion of a lower section of the nozzle body below the flange portion are surrounded by a metal case, and respective upper edge faces of the nozzle body and the flange portion are in a same horizontal plane, wherein the immersion nozzle is installed such that both the upper edge faces of the nozzle body and the flange portion are joined to a lower edge face of an upper nozzle member located above the immersion nozzle through an operation of sliding the immersion nozzle in the horizontal direction with an underside of the flange portion supported by a support device; and wherein the immersion nozzle comprises a bridging member which bridges an inner peripheral surface of a portion of the metal case surrounding the flange portion and an outer peripheral surface of the nozzle body, the bridging member having one end fixed to the portion of the metal case and the other end engaged with a recess provided in the outer peripheral surface of the nozzle body, wherein in an area above an action point of an upward support force by the support device, the outer peripheral surface of the nozzle body extends in the vertical direction without dimensional change with respect to a central axis of the inner bore, except for the recess.Advantageous Effects of Invention

[0012] The present invention makes it possible for an immersion nozzle applicable to an immersion nozzle replacement apparatus to satisfy both the suppression of occurrence of cracks in a neck portion thereof and the suppression of occurrence of sinking thereof.BRIEF DESCRIPTION OF DRAWINGS

[0013] FIG. 1 is a longitudinal sectional view of an immersion nozzle according to one embodiment of the present invention.

[0014] FIG. 2 is a longitudinal sectional view of a relevant part of the immersion nozzle in FIG. 1 (sectional view taken along the line A-A in FIG. 1), wherein the immersion nozzle is in a usage state.

[0015] FIG. 3 is a plan view of the immersion nozzle in FIG. 1

[0016] FIG. 4 is a longitudinal sectional view of a conventional immersion nozzle.DESCRIPTION OF EMBODIMENTS

[0017] FIG. 1 is a longitudinal sectional view of an immersion nozzle according to one embodiment of the present invention. FIG. 2 is a longitudinal sectional view of a relevant part of the immersion nozzle in FIG. 1, wherein the immersion nozzle is in a usage state, and FIG. 3 is a plan view of the immersion nozzle of FIG. 1.

[0018] The immersion nozzle 10 comprises a nozzle body 11 and a flange portion 12. The nozzle body 11 is made of a refractory material (shaped refractory material), and formed to have an inner bore 11a oriented in a vertical direction, as a molten steel passage path. The nozzle body 11 also has discharge ports 11b located symmetrically in a lower end section thereof to discharge molten steel to a mold. The flange portion 12 is made of a refractory material different from that of the nozzle body 11 (in this embodiment, a castable refractory material). The flange portion 12 is formed in a flat plate shape. More specifically, it is joined to an outer periphery of an upper end section of the nozzle body 11 directly or through an adhesive, in such a manner as to surround the outer periphery of the upper end section of the nozzle body 11 and protrude in a horizontal direction. Respective upper edge faces of the nozzle body 11 and the flange portion 12 are in the same horizontal plane. Further, respective outer peripheries of the flange portion 12 and a portion of a lower section of the nozzle body 11 below the flange portion 12 are surrounded by a metal case 13. A joint material 14 (e.g., an unshaped refractory material such as mortar, or a fiber sheet) is interposed between the metal case 13 and the nozzle body 11.

[0019] Through an operation of sliding the immersion nozzle 10 in the horizontal direction with an underside of the flange portion 12 supported by a support device 20 of an immersion nozzle replacement apparatus, the immersion nozzle 10 is installed such that both the upper edge faces of the nozzle body 11 and the flange portion 12 are joined to a lower edge face of an upper nozzle member 30 located above the immersion nozzle 10, as shown in FIG. 2, and used. As used here, the term “sinking” of the immersion nozzle (nozzle body) means a phenomenon that the nozzle body 11 is displaced downwardly by a reaction force against an upward support force by the support device 20.

[0020] In the above basic configuration, as appearing in FIGS. 1 and 3, the immersion nozzle 10 comprises a bridging member 15 extending in the horizontal direction to bridge an inner peripheral surface of a portion 13A of the metal case 13 surrounding the flange portion 12 and an outer peripheral surface of the nozzle body 11. The bridging member 15 has one end fixed to the portion 13A of the metal case 13, and the other end engaged with a recess 11c provided in the outer peripheral surface of the nozzle body 11. By providing the bridging member 15 in this configuration, it becomes possible to suppress sinking of the nozzle body 11.

[0021] Further, in the present invention, with a view to suppressing the occurrence of cracks in a neck portion, in an area above an action point P of the upward support force by the support device 20 (in an area above the horizontal broken line in FIG. 2), the outer peripheral surface of the nozzle body 11 extends in the vertical direction without dimensional change with respect to a central axis C of the inner bore 11a, except for the recess 11c.

[0022] In this embodiment, as appearing in FIG. 3, the bridging member 15 is not arranged in a vertically-extending area where there is the action point P of the upward support force by the support device 20. By allowing the bridging member 15 not to be arranged in the vertically-extending area where there is the action point P, as just described, it becomes possible to avoid a situation where the upward support force acts directly on the bridging member 15, and the recess 11c in the outer peripheral surface of the nozzle body 11. This makes it possible to further suppress the occurrence of cracks in the neck portion.

[0023] In this embodiment, the bridging member 15 is provided in a number of two, wherein the two bridging members 15 are arranged with 2-fold rotational symmetry about the central axis C of the inner bore 11a serving as a rotation axis. By arranging the bridging members 15 with rotational symmetry about the central axis C of the inner bore 11a serving as a rotating shaft, as just described, it becomes possible to effectively suppress the sinking of the nozzle body 11.

[0024] In this embodiment, the bridging member 15 is a circular columnar-shaped pin, and the recess 11c provided in the outer peripheral surface of the nozzle body 11 has a circular shape, correspondingly to the bridging member 15. By forming the bridging member 15 and the recess 11c, respectively, into a circular columnar shape and a circular shape, as just described, stress becomes less likely to concentrate on the bridging member 15 and the recess 11c, and it becomes possible to further suppress the occurrence of cracks in the neck portion.

[0025] However, respective shapes of the bridging member 15 and the recess 11c are not limited to a circular columnar shape and a circular shape, but may be, for example, a shape which is extended circumferentially along the outer periphery of the nozzle body 11. On the other hand, since the recess 11c provided in the outer peripheral surface of the nozzle body 11 can become a stress concentration area in the nozzle body 11, the ratio of the circumferential length (perimeter) of the recess 11c (when the number of the recesses 11c is plural, the total circumferential length (total perimeter) of the recesses 11c) to the circumferential length (perimeter) of the nozzle body 11 is preferably 20% or less, more preferably 10% or less.

[0026] In this embodiment, a plan-view shape of the flange portion 12 is an octagonal shape, as appearing in FIG. 3, but may be a rectangular shape, a polygonal shape, an elliptical shape, or a circular shape. Similarly, a plan-view shape of the nozzle body 11 is not limited to a circular shape, but may be, e.g., a rectangle shape or an elliptical shape.

[0027] The immersion nozzle 10 of the present invention can be produced, e.g., in the following manner. First of all, as preparation for production, one end of the bridging member 15 is fixed to the metal case 13. More specifically, a through-hole for mounting one end of the bridging member 15 is provided in the metal case 13, and one end of the bridging member 15 is attached to the through-hole and fixed by welding or the like. Further, a recess 11c for engaging the other end of the bridging member 15 is provided in the outer peripheral surface of the nozzle body 11.

[0028] When the preparation for production has been completed, the metal case 13 is set around the nozzle body 11 such that the other end of the bridging member 15 is engaged with the recess 11c provided in the outer peripheral surface of the nozzle body 11. Then, a castable refractory material is filled between the nozzle body 11 and the metal case 13 to form the flange portion 12. In this process, respective upper edge faces of the nozzle body 11 and the flange portion 12 serving as a joining surface with the lower edge face of the upper nozzle member 30 are formed to protrude upwardly from an upper edge of the metal case 13. Then, the upper edge faces of the nozzle body 11 and the flange portion 12 are machined such that they form the same horizontal surface.

[0029] By forming the flange portion 12 using a castable refractory material, as just described, it becomes possible to install the bridging member 15 in the flange portion 12 without any gap. Further, since the castable refractory material is also filled in the recess 11c which engages the other end of the bridging member 15, during production, the other end of the bridging member 15 can be engaged with the recess 11c without any gap. This makes it possible to effectively suppress the occurrence of cracks in the neck portion and the occurrence of sinking of the immersion nozzle.

[0030] Although one embodiment of the present invention has been described above, it is to be understood that the present invention is not limited thereto. For example, although the flange portion 12 in this embodiment is formed using a castable refractory material, it may be formed using a shaped refractory material.

[0031] Further, with regard to the nozzle body 11, it has been simplistically illustrated as a single and integral structure for the sake of convenience. However, the present invention does not need to be limited to such a single and integral structure. For example, it is possible to employ a configuration in which a refractory material different from a refractory applied to a portion of the nozzle body 11 other than a specific section of the nozzle body 11, such as the vicinity of an outer peripheral section corresponding to a mold powder line, a part or the entirety of an inner bore surface, or a part or the entirety of the vicinity of the discharge port, is applied to the specific section of the nozzle body 11, and a configuration in which a gas pool or a gas introduction pathway is provided in a portion of the nozzle body 11 to inject gas into the inner bore.EXAMPLES

[0032] A test for checking the effect of suppressing the occurrence of sinking was performed for the immersion nozzle 10 illustrated in FIG. 1, which serves as an inventive example. The same test was also performed for the immersion nozzle 10′ illustrated in FIG. 4, which serves as a comparative example. The immersion nozzle 10′ is an immersion nozzle disclosed in FIG. 1 of the Patent Document 1, and the basic configuration thereof is the same as the immersion nozzle 10 according to the present invention. Thus, in the immersion nozzle 10′ illustrated in FIG. 4, the same element or component as that of the immersion nozzle 10 illustrated in FIG. 1 is designated by the same reference numeral. In the immersion nozzle 10 and the immersion nozzle 10′, the outer diameter of the nozzle body 11 is 150 mm, and the outer diameter of the flange portion 12 is 215 mm.

[0033] Further, in the immersion nozzle 10 illustrated in FIG. 1, the bridging member 15 is a circular columnar-shaped pin having an outer diameter of 12 mm, and the arrangement thereof is as shown in FIG. 3. In the immersion nozzle 10′ illustrated in FIG. 4, a support portion 13a is a circular columnar-shaped pin having an outer diameter of 12 mm, and this support portion 13a is provided in a number of three, wherein the three support portions 13a are arranged at equal intervals in the circumferential direction of the nozzle body 11.

[0034] The test was performed in the following manner.

[0035] The inner bore 11a was heated by a gas burner such that the temperature of the nozzle body 11 rose to 1000° C., and then only the nozzle body 11 was pressed from thereabove at a given pressure for 60 minutes. After completion of the pressing test, a difference in height level between the upper edge face of the nozzle body 11 and the upper edge face of the flange portion 12 was checked. In the evaluation for the presence or absence of the occurrence of sinking, a case where the difference was 0.05 mm or more was evaluated as having occurrence of sinking, and a case where the difference was less than 0.05 mm was evaluated as having no occurrence of sinking.

[0036] A result of the evaluation is shown in Table 1. As shown in Table 1, in the comparative example (immersion nozzle 10′), sinking occurred at a pressure (total pressure) of 20 kg. In contrast, in the inventive example (immersion nozzle 10), no sinking occurred even at a pressure (total pressure) of 700 kg. This shows that the inventive example (immersion nozzle 10) can efficiently suppress the sinking of the nozzle body 11.

[0037] This result also consists with a result of an actual casting operation test conducted by the present inventors. That is, as a result of the actual casting operation test, the sinking of the nozzle body 11 occurred in the comparative example (immersion nozzle 10′), but no sinking of the nozzle body 11 occurred in the inventive example (immersion nozzle 10).TABLE 1Pressure(totalComparative ExampleInventive Examplepressure / kg)(immersion nozzle 10′)(immersion nozzle 10)20With occurrence of sinkingWithout occurrence of sinking100—Without occurrence of sinking500—Without occurrence of sinking700—Without occurrence of sinking

[0038] As just described, there is the difference in the effect of suppressing the sinking of the nozzle body 11 between the comparative example (immersion nozzle 10′) and the inventive example (immersion nozzle 10). This is considered to be for the following reasons.

[0039] In the comparative example (immersion nozzle 10′), it is attempted to suppress the occurrence of sinking by the support portion 13a. However, since the support portion 13a is arranged below the flange portion 12, it is located at a relatively small distance to a mold as a heat source, and receives heat from the mold directly. Thus, a gap is generated around the support portion 13a due to expansion of the metal case 13, etc., and therefore the nozzle body 11 becomes more likely to sink by a distance corresponding to the gap.

[0040] In contrast, since the bridging member 15 in the inventive example (immersion nozzle 10) is arranged within the flange portion 12, the distance to the mold as the heat source becomes longer. Further, since the underside of the flange portion 12 is supported by the support device 20 of the immersion nozzle replacement apparatus, as illustrated in FIG. 2, the flange portion 12 is located inside the immersion nozzle replacement apparatus during casting operation. Therefore, the bridging member 15 becomes less likely to receive heat from the mold directly. For these reasons, in the inventive examples (immersion nozzle 10), a gap becomes less likely to be formed around the bridging member 15, and consequently, the sinking of the nozzle body 11 becomes less likely to occur. Further, since the flange portion 12 in the inventive example (immersion nozzle 10) is formed using a castable refractory material, the bridging member 15 can be installed in the flange portion 12 without any gap, and the other end of the bridging member 15 can be engaged with the recess 11c without any gap, as described above. This makes the sinking of the nozzle body 11 further less likely to occur.

[0041] On the other hand, with regard to the effect of suppressing the occurrence of cracks in the neck portion, since the recess 11c in the inventive example (immersion nozzle 10) can become a stress concentration area, there is a possibility that the effect slightly diminishes as compared with the comparative example (immersion nozzle 10′). However, through an actual casting operation test, the present inventors have confirmed that the problem of the occurrence of cracks in the neck portion is resolved by the inventive example (immersion nozzle 10).LIST OF REFERENCE SIGNS10, 10′: immersion nozzle

[0043] 11: nozzle body

[0044] 11a: inner bore

[0045] 11b: discharge port

[0046] 11c: recess

[0047] 12: flange portion

[0048] 13: metal case

[0049] 13A: portion of metal case surrounding flange portion

[0050] 13a: support portion (pin)

[0051] 14: joint material

[0052] 15: bridging member (pin)

[0053] 20: support device

[0054] 30: upper nozzle member

Claims

1. An immersion nozzle comprising:a nozzle body made of a refractory material and having an inner bore oriented in a vertical direction; anda flange portion made of a refractory material and formed in a flat plate shape, the flange portion being joined to an outer periphery of an upper end section of the nozzle body, directly or through an adhesive, in such a manner as to surround the outer periphery of the upper end section of the nozzle body and protrude in a horizontal direction,wherein respective outer peripheries of the flange portion and a portion of a lower section of the nozzle body below the flange portion are surrounded by a metal case, and respective upper edge faces of the nozzle body and the flange portion are in a same horizontal plane,wherein the immersion nozzle is installed such that both the upper edge faces of the nozzle body and the flange portion are joined to a lower edge face of an upper nozzle member located above the immersion nozzle through an operation of sliding the immersion nozzle in the horizontal direction with an underside of the flange portion supported by a support device; andwherein the immersion nozzle comprises a bridging member which bridges an inner peripheral surface of a portion of the metal case surrounding the flange portion and an outer peripheral surface of the nozzle body, the bridging member having one end fixed to the portion of the metal case and the other end engaged with a recess provided in the outer peripheral surface of the nozzle body,wherein in an area above an action point of an upward support force by the support device, the outer peripheral surface of the nozzle body extends in the vertical direction without dimensional change with respect to a central axis of the inner bore, except for the recess.

2. The immersion nozzle as claimed in claim 1, wherein the flange portion is made of a castable refractory material.

3. The immersion nozzle as claimed in claim 1 or 2, wherein the bridging member is not arranged in a vertically-extending area where there is the action point of the upward support force by the support device.

4. The immersion nozzle as claimed in claim 2, wherein the bridging member is not arranged in a vertically-extending area where there is the action point of the upward support force by the support device.

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