JP7427138B2 - immersion nozzle - Google Patents

Description

The present invention relates to a submerged nozzle used when continuously casting thin slabs.

Direct connection between continuous casting and hot rolling of the resulting slab has attracted attention as a result of the so-called direct connection, which eliminates the slab heating process and saves energy. is oriented. When casting a thin slab (for example, 200 mm or less in thickness), it is necessary to flatten the mold, so it is necessary to flatten the immersion nozzle as well (for example, Patent Document 1).

Japanese Patent Application Publication No. 08-039208

Skinning is particularly likely to be a problem when casting thin slabs. This is because thin slabs have a large aspect ratio of the molten steel surface area, so the surface temperature decreases more easily than ordinary slabs, and the wider the cross-sectional area of the nozzle in the immersion section, the more heat is removed by the nozzle, so the temperature is lower. This is due to the fact that it tends to decrease.

According to the immersion nozzle described in Patent Document 1, it is possible to prevent bare metal buildup occurring between the immersion nozzle and the mold wall and skinning of the molten metal surface that occurs near the short sides of the wide mold, and to prevent the molten metal from forming in the vicinity of the short sides of the wide mold. This can prevent the occurrence of suction phenomena and re-dissolution of coagulated shells. However, the immersion nozzle described in Patent Document 1 cannot be said to be sufficient in suppressing skinning at the meniscus portion.

Therefore, there is a need to realize a submerged nozzle that can suppress the skinning of the meniscus in continuous thin slab casting.

The immersion nozzle according to the present invention includes a flow path and an opening, and is provided with a first portion, a connection portion, and a second portion in order from the proximal end, wherein the first portion includes the The cross-sectional shape of the flow path is circular, in the second portion, the cross-sectional shape of the flow path is rectangular, and in the connection portion, the flow path has a shape that is similar to that of the flow path in the first portion. It has a shape that continuously connects the flow path of the second part, and in the second part, the ratio a/b of the length a of the long side and the length b of the short side of the rectangle is 3 or more. 7 or less, the cross-sectional area S ₂ of the flow path in the second portion is larger than the cross-sectional area S ₁ of the flow path in the first portion, and the opening portion has two first openings and two a second opening, and the first opening has one opening on each of two side surfaces corresponding to the two short sides of the second portion, and One side is open across one of the two side surfaces and the bottom surface, which is the top surface of the second part, and the other of the two second openings is between the two side surfaces. It is open across the other side surface and the bottom surface, and has an opening area S ₃ on the side surface of the first opening, an opening area S 4 on the side surface of the second opening, and an opening area S ₄ on the side surface of the second opening and the bottom surface. The opening area S5 _is characterized by satisfying the following equations (1) and (2) .
S ₄ <S ₅ (1)
(S ₄ +S ₅ )/S ₃ ≧1.5 (2)

When the immersion nozzle having the above configuration is used in continuous thin slab casting, skinning of the meniscus portion can be suppressed. The discharge flow discharged from the nozzle hits the short side of the mold and is separated into an upward flow and a downward flow. Here, if the upward flow is too strong, powder is likely to be engulfed, and if the downward flow is too strong, inclusions, bubbles, etc. are difficult to float. According to the above configuration, the balance between the upward flow and the downward flow can be optimized, and excessive meniscus flow can be suppressed.

Hereinafter, preferred embodiments of the present invention will be described. However, the scope of the present invention is not limited to the preferred embodiments described below.

In one aspect of the immersion nozzle according to the present invention, it is preferable that an opening area S ₃ on the side surface of the first opening is smaller than an opening area S ₆ on the flow path side.

According to this configuration, generation of suction flow at the first opening can be suppressed.

In one aspect of the immersion nozzle according to the present invention, the maximum width is preferably 300 mm or less.

According to this configuration, the workability when replacing the immersion nozzle using the quick replacement device is improved. As a result, the nozzle can be quickly replaced during casting, which can meet the increasing needs for casting high-grade steel grades that require strict casting conditions in continuous thin slab casting.

Further features and advantages of the invention will become clearer from the following description of exemplary and non-limiting embodiments, written with reference to the drawings.

FIG. 2 is a front sectional view of a nozzle according to an embodiment. FIG. 2 is a side cross-sectional view (cross-sectional view taken along line II-II in FIG. 1) of the nozzle according to the embodiment. FIG. 2 is a cross-sectional view (a cross-sectional view taken along the line III-III in FIG. 1) of a first portion of the nozzle according to the embodiment. FIG. 2 is a cross-sectional view (a cross-sectional view taken along the line IV-IV in FIG. 1) of a second portion of the nozzle according to the embodiment. FIG. 3 is a side view of a second portion of the nozzle according to the embodiment. FIG. 3 is a bottom view of the second portion of the nozzle according to the embodiment.

Embodiments of the immersion nozzle according to the present invention will be described with reference to the drawings. Below, an example in which the immersion nozzle according to the present invention is applied to a immersion nozzle 1 (hereinafter simply referred to as nozzle 1) used for continuous casting of slabs having a mold thickness of 200 mm or less will be described.

[Overall configuration of immersion nozzle]
The nozzle 1 is a cylindrical member made of a fireproof material. A flow path for circulating molten steel is formed inside, and an opening 5 is provided at the tip. The nozzle 1 is provided with a first part 2, a connecting part 3, and a second part 4 in order from the base end, and each part has a different shape (FIGS. 1 and 2). The nozzle 1 is connected to upstream equipment (stopper, sliding nozzle, etc., not shown) at the first portion 2, and molten steel flowing from the upstream equipment flows through the flow path. Further, the second portion 4 is provided with an opening 5 (a first opening 51 and a second opening 52), and molten steel flows out from the opening 5 into a mold (not shown).

The type of refractory material constituting the nozzle 1 is not particularly limited, and any refractory material conventionally used in this field can be used. Such fire-resistant materials include alumina-graphite, magnesia-graphite, spinel-graphite, zirconia-graphite, calcium zirconate-graphite, high alumina, alumina-silica, silica, zircon, and spinel. Examples include. Additionally, zone lining may be applied as appropriate.

When referring to directions in the following description, the arrangement shown in FIG. 1 is used as a reference. That is, when referring to the vertical direction, the proximal side (first part 2 side) is referred to as upper (upper, upper, upper side, upstream, etc.), and the distal end side (second part 4 side) is referred to as lower (lower, lower, etc.). (lower side, downstream, etc.).

Further, when referring to a cross section of a flow path, unless otherwise specified, it refers to a cross section in a direction perpendicular to the vertical direction defined above (a direction perpendicular to the plane of the paper in FIG. 1), and this cross section is referred to as a cross section. Note that when the nozzle 1 is used, the molten steel flows from the upper side defined above to the lower side, so the cross section defined above is also a cross section in the flow direction of the molten steel.

[Structure of the first part]
The first portion 2 is the main portion on the base end side of the nozzle 1. In the first portion 2, the cross-sectional shape of the channel 21 is circular (FIGS. 1 to 3). Note that the term "circular" here is not limited to a circle in a mathematical sense, but may be any shape that can be treated as a substantially circular shape. Therefore, there may be deviations (tolerances, etc.) from the mathematical circular shape that may occur when realizing a circular shape as an industrial product. In this embodiment, the cross-sectional area S ₁ of the flow path 21 is 6000 mm ² .

[Composition of the second part]
The second portion 4 is the main portion on the tip side of the nozzle 1. In the second portion 4, the cross-sectional shape of the flow path 41 is rectangular (FIGS. 1, 2, and 4). Note that the rectangle referred to here is not limited to a rectangle in a mathematical sense, but may be any shape that can be substantially treated as a rectangle. Therefore, it may be subjected to deformations (such as chamfering) that are normally applied when realizing a rectangular shape as an industrial product, or it may be deviated from a mathematical rectangle (such as tolerances).

In this embodiment, the cross-sectional area S ₂ of the flow path 41 is 10000 mm ² . Therefore, the cross-sectional area S ₂ of the flow path 41 is larger than the cross-sectional area S ₁ of the flow path 21 . In this way, by making the cross-sectional area of the downstream region (flow path 41) larger than the cross-sectional area of the upstream region (flow path 21), the flow velocity of molten steel discharged from the opening 5 is reduced. This provides an upward flow within the mold and suppresses excessive meniscus flow.

In this embodiment, in the cross-sectional shape of the flow path 41, the length a of the long side 42 of the rectangle is 200 mm, and the length b of the short side 43 is 50 mm (FIG. 4). Therefore, the ratio a/b between the two is 4.0. Note that the shape of the rectangle is not limited to the above numerical values, and may be changed within a range where the ratio a/b is 3 or more and 7 or less. When changing the ratio a/b, both the length a of the long side 42 and the length of the short side 43 of the rectangle can be changed, but the length b of the short side 43 is regulated by the length of the short side of the mold. Therefore, the length a of the long side 42 generally has a higher degree of freedom.

When the ratio a/b is 3 or more and 7 or less, the molten steel flow is difficult to separate from the wall surface of the flow path 41, and an appropriate flow can be obtained. On the other hand, if the ratio a/b is less than 3, the length a of the long side 42 becomes too small, making it difficult to secure the inner tube cross-sectional area necessary for casting. Further, when the ratio a/b exceeds 7, the length a of the long side 42 becomes excessive, and the weight of the nozzle 1 tends to increase, which may increase the load on the operator and equipment handling the nozzle 1. Moreover, when the ratio a/b exceeds 7, the deformation of the flow path 31 in the long side direction in the connecting portion 3 becomes steep, which may induce separation of the molten steel flow from the flow path wall surface.

Corresponding to the rectangular cross-sectional shape of the flow path 41, the cross-sectional shape of the substantial portion (refractory material portion) of the second portion 4 is also rectangular, and therefore the second portion 4 is formed into a bottomed prismatic shape. has been done. The width W of the surface corresponding to the long side 42 of the rectangle is 270 mm, and this width is the maximum width of the nozzle 1. As described above, it is preferable that the maximum width W of the nozzle 1 is less than 300 mm, since this improves the workability when replacing the nozzle 1 using a quick replacement device. This is because if the maximum width W of the nozzle 1 is less than 300 mm, it is easy to secure room inside the mold for replacing the nozzle 1 due to the dimensions of the nozzle 1 and the mold.

[Opening configuration]
In the second portion 4, a first opening 51 is opened in the side surface 44 corresponding to the short side 43 of the rectangle (FIGS. 1 and 5). Two first openings 51 are provided, and the two first openings 51 (51A, 51B) are connected to the two side surfaces 44 (44A, 44B) corresponding to the two short sides 43 (43A, 43B), respectively. They are opened one by one. Since the first opening 51 is open to the side surface 44, the molten steel flow can be discharged toward the short side of the mold. This can generate an upward flow within the mold to promote heat supply to the meniscus.

Further, two second openings 52 are opened across the side surface 44 and the bottom surface 45, which is the surface at the end in the longitudinal direction of the second portion 4 (FIGS. 1, 5, and 6). Of the two second openings 52, one second opening 52A is open across the side surface 44A (one side surface) and the bottom surface 45, and the other second opening 52B is open across the side surface 44B (the other side surface). It is open across the bottom surface 45. By opening the second opening 52 in the manner described above, the molten steel flow can be discharged downward into the mold, and the molten steel flow within the mold can be appropriately distributed.

In this embodiment, the opening area S ₃ (area of the first opening 51 shown in FIG. 5) on the side surface 44 of the first opening 51 is 2700 mm ² . Further, the opening area S ₄ (area of the second opening 52 shown in FIG. 5) at the side surface 44 of the second opening 52 is 2000 mm ² , and the opening area S ₅ (the area of the second opening 52 shown in FIG. 6) at the bottom surface 45 is 2000 mm 2 . The area of the second opening 52) is 5000 ^mm2 . From the above opening area, the following equations (1) and (2) hold true.
S ₄ <S ₅ (1)
(S ₄ +S ₅ )/S ₃ ≧1.5 (2)

By providing the first opening 51 and the second opening 52 with an opening area that satisfies equations (1) and (2), the balance between upward flow and downward flow is optimized, and excessive meniscus flow is prevented. It can be suppressed. Note that the opening area S ₃ of the first opening 51 and the opening areas S ₄ and S ₅ of the second opening 52 are not limited to the above values, and may be changed as long as formulas (1) and (2) are satisfied. It is possible.

Further, in this embodiment, the opening area S ₆ of the first opening 51 on the flow path 41 side is 4000 mm ² . Therefore, the opening area S ₃ on the side surface 44 of the first opening 51 is smaller than the opening area S ₆ on the flow path 41 side.

By configuring that the opening area S ₆ of the first opening 51 on the flow path 41 side is larger than the opening area S ₃ of the side surface 44 or that both are equal, the cross-sectional area of the flow path toward the exit in the flow direction of molten steel is As the molten steel flow gradually decreases, the molten steel flow is rectified. This suppresses the generation of suction flow in the upper part of the first opening 51, and facilitates smooth discharge of molten steel from the entire first opening 51.

[Configuration of connection part]
The connecting portion 3 is a portion that continuously connects the first portion 2 and the second portion 4 (FIGS. 1 and 2). In the connecting portion 3, a flow path 31 is provided that continuously connects the flow path 21 of the first portion 2 having a circular cross-sectional shape and the flow path 41 of the second portion 4 having a rectangular cross-sectional shape. There is. Therefore, the cross-sectional shape of the flow path 31 is circular at the upper end 32 and rectangular at the lower end 33.

[Other embodiments]
Finally, other embodiments of the immersion nozzle according to the present invention will be described. Note that the configurations disclosed in each of the embodiments below can be applied in combination with the configurations disclosed in other embodiments as long as no contradiction occurs.

In the above embodiment, the opening areas S ₃ , S ₄ , S ₅ , and S ₆ related to the opening 5 (the first opening 51 and the second opening 52) satisfy equations (1) and (2). The explanation has been given by taking as an example a configuration in which the conditions are satisfied and S ₃ is smaller than S ₆ . However, the immersion nozzle according to the present invention may not satisfy one or both of formula (1) and formula (2), and _S3 may be larger than _S6 .

In the above embodiment, the maximum width W of the nozzle 1 is 270 mm and is less than 300 mm. However, the maximum width of the submerged nozzle according to the invention may be 300 mm or more.

Regarding other configurations, it should be understood that the embodiments disclosed in this specification are illustrative in all respects, and the scope of the present invention is not limited thereby. Those skilled in the art will easily understand that modifications can be made as appropriate without departing from the spirit of the present invention. Therefore, other embodiments that are modified without departing from the spirit of the present invention are naturally included within the scope of the present invention.

In the following, the present invention will be further explained by showing examples. However, the present invention is not limited to the following examples.

〔Test method〕
Nozzles with various dimensional conditions were designed, and computational fluid dynamics calculations were performed on the mode of the discharged molten steel flow using fluid analysis software "PHOENICS" manufactured by CHAM-Japan. The dimensional conditions of each example and comparative example are as described in Tables 1 to 3 below. Based on the calculation results, a flow velocity contour diagram was output. The following parameters were applied to the calculation.
・Number of calculation cells: Approximately 500,000 (varies depending on model)
・Fluid: Molten steel (1560℃, density 7.08g/cm ³ )
・Casting speed: 4t/min
・Mold size: 1200mm x 150mm

[Evaluation of meniscus flow velocity]
For each example and comparative example, the meniscus flow velocity was determined based on the output flow velocity contour diagram. Evaluation was made in three stages, A to C, depending on the value of the meniscus flow rate.
A: The meniscus flow velocity is 10 cm/sec or more and 25 cm/sec or less.
B: Meniscus flow velocity is more than 25 cm/sec and less than 35 cm/sec.
C: Meniscus flow velocity is less than 10 cm/sec or more than 35 cm/sec.

[Separation of molten steel flow]
For each example and comparative example, the outputted flow velocity contour diagram was visually checked to identify the presence or absence of separation of the molten steel flow in the second portion 4, and the quality (A or C) was determined.
A: A molten steel flow is formed along the wall surface in the entire second portion 4.
C: Separation of the molten steel flow is observed in the second portion 4.

[Suction flow at first opening]
For each of the Examples and Comparative Examples, the outputted flow velocity contour diagrams were visually confirmed to identify the presence or absence and degree of suction flow in the first opening 51. Evaluation was made on a three-grade scale from A to C depending on the observed condition.
A: Molten steel flow is discharged from the first opening 51 without stagnation.
B: Stagnation of the molten steel flow is observed near the first opening 51.
C: Suction flow flowing into the first opening 51 is observed.

〔result〕
Table 1 shows the dimensional conditions and evaluation results for each example and comparative example. Examples 1 to 6 in which the ratio a/b was in the range of 3 or more and 7 or less were evaluated as A for peeling of molten steel flow. On the other hand, in Comparative Example 1 in which the ratio a/b was 8.0, the evaluation of peeling of the molten steel flow was C. Furthermore, in Examples 1 to 6 where S ₂ was greater than S ₁ , the meniscus flow rate was within the appropriate range (rating A or B). On the other hand, in Comparative Example 2 in which S ₂ was smaller than S ₁ , the meniscus flow rate was not within the preferable range (rating C).

In addition, in Examples 3 to 6 where S ₃ , S ₄ and S ₅ satisfy formula (2), the meniscus flow velocity was in a more suitable range compared to Examples 1 and 2 which did not satisfy formula (2). . Further _, in Examples 5 _{and 6 where S 3 is smaller than S 6 , the suction of} the first opening It showed more favorable results regarding the flow.

The present invention can be used, for example, in a submerged nozzle for continuous casting of thin slabs.

1 : Immersion nozzle 2 : First part 21 : Channel 3 : Connection part 31 : Channel 32 : Upper end of the connecting part 33 : Lower end of the connecting part 4 : Second part 41 : Channel 42 : Long side 43 : Short side 44 : Side surface 45 : Bottom surface 5 : Opening part 51 : First opening part 52 : Second opening part

Claims (3)

An immersion nozzle comprising a flow path and an opening, and in which a first part, a connecting part, and a second part are provided in order from the proximal end,
In the first portion, the cross-sectional shape of the flow path is circular;
In the second portion, the cross-sectional shape of the flow path is rectangular;
In the connection portion, the flow path has a shape that continuously connects the flow path of the first portion and the flow path of the second portion,
In the second portion, the ratio a/b of the length a of the long side and the length b of the short side of the rectangle is 3 or more and 7 or less,
A cross-sectional area _S2 of the flow path in the second portion is larger than a cross-sectional area _S1 of the flow path in the first portion,
The openings include two first openings and two second openings,
The first openings are opened one each on two side surfaces corresponding to the two short sides of the second portion,
One of the two second openings is open across one of the two side surfaces and a bottom surface that is a top surface of the second portion,
The other of the two second openings is open across the other of the two side surfaces and the bottom surface,
The opening area S ₃ on the side surface of the first opening , the opening area S ₄ on the side surface and the opening area S ₅ on the bottom surface of the second opening are calculated by the following equations (1) and (2). Filling immersion nozzle.
S ₄ <S ₅ (1)
(S ₄ +S ₅ )/S ₃ ≧1.5 (2) The immersion nozzle according to claim 1, wherein an opening area _S3 on the side surface of the first opening is smaller than an opening area _S6 on the flow path side. The immersion nozzle according to claim 1 or 2, wherein the maximum width is 300 mm or less.

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