EP4691665A1

EP4691665A1 - Submerged nozzle

Info

Publication number: EP4691665A1
Application number: EP24192864.7A
Authority: EP
Inventors: Pavan Kumar Shivaram; Alexandre RESENDE; Pedro Domingos; Gernot Hackl; Yong Tang; Michael SILVAGGIO
Original assignee: Refractory Intellectual Property GmbH and Co KG
Current assignee: Refractory Intellectual Property GmbH and Co KG
Priority date: 2024-08-05
Filing date: 2024-08-05
Publication date: 2026-02-11
Also published as: WO2026032636A1

Abstract

Submerged nozzle (1) through which molten steel can be poured from a tundish into a mold, the submerged nozzle (1) comprising: a substantially tubular body (2), extending from a first end (3) to a second end (4); a passageway (5), extending through the tubular body (2) along a longitudinal axis (A) from the first end (3) towards the second end (4), the passageway (5) being defined by an inner wall (2i) of the tubular body (2), the passageway (5) having a passageway cross section (5a) normal to the longitudinal axis (A); at least one inlet port (6), opening into the passageway (5) at the first end (3); at least one pair of opposing outlet ports (8), opening into the passageway (5) in a region (7) adjacent to the second end (4), each outlet port (8) comprises an outlet port center (8a); an outlet port axis (8b) being defined as the connection between the outlet port centers (8a) of each opposing outlet port (8) of at least one pair of opposing outlet ports (8), wherein at least one pair of opposing outlet ports (8) are arranged such that the outlet port axis (8b) is orthogonal to the longitudinal axis (A); a transverse outlet port axis (8c) being defined as orthogonal to the outlet port axis (8b) and orthogonal to the longitudinal axis (A); and at least one first flow restrictor (10), preferably the at least one first flow restrictor (10) is a pair of opposing flow restrictors (10), the at least one first flow restrictor (10) protruding from the inner wall (2i) of the tubular body (2) into the passageway (5); wherein the at least one first flow restrictor (10) is positioned closer to the first end (3) than to the second end (4); wherein the at least one first flow restrictor (10) restricts the passageway cross-section (5a) at least in a direction of the transverse outlet port axis (8c) from the longitudinal axis (A) within the passageway cross-section (5a); and wherein the at least one first flow restrictor (10) does not restrict the passageway cross-section (5a) in any direction of the outlet port axis (8b) from the longitudinal axis (A) within the passageway cross-section (5a).

Description

The invention relates to a submerged nozzle, in particular a monotube (MT), through which molten steel can be poured from a tundish into a mold, and to a method for continuous casting of molten steel, using the submerged nozzle.
Submerged nozzles, such as submerged entry nozzles (SEN), monotubes (MT), or submerged entry shrouds (SES) are known, for example from EP 1 671 721 B1 or EP 3 488 949 A1 or EP 2 382 062 B1 . Such nozzles generally comprise a substantially tubular body extending from a first end to a second end, with a passageway (for example a bore), extending through the tubular body along a longitudinal axis from the first to the second end. In its use position in the continuous casting machine, the nozzle is arranged generally vertically, with the central longitudinal axis of the passageway extending vertically and with the first end of the tubular body positioned upside and the second end of the tubular body positioned downside. At least one inlet port at the first end is present, where molten metal can enter into the passageway, the inlet port opens into the passageway. A plurality of outlet ports, such as e.g. a pair of opposing outlet ports, is present, where molten metal can exit the passageway (and leave the submerged nozzle into a mold), the passageway opens into the outlet ports/the outlet ports open into the passageway in a region adjacent to the second end. In use, the nozzle is arranged generally vertical, with the first end above the second end.
A submerged nozzle is generally configured such that when molten steel is entering the submerged nozzle through the at least one inlet port, the molten steel is guided through the passageway by the inner wall to the at least one pair of outlet ports, where the steel exits the submerged nozzle. A submerged nozzle in the form of a monotube comprises a connection portion for connection to a slide gate system at the first end of the monotube.
One of the requirements in continuous steel casting is a high flow stability from the submerged nozzle into the mold. This means that during the whole casting sequence the flow velocities of the molten metal in the mold should be stable. Additionally, any asymmetrical flow patterns should be avoided (such as the so-called meniscus roll). The surface velocity of the steel in the mold should be as stable as possible. All these prerequisites reduce unwanted (non-metallic) inclusions into the steel, and thus enhance steel quality.
Especially an unsymmetrical flow within the passageway (e.g., a biased flow on one side of the passageway) of such a nozzle may lead to an asymmetric flow in the mold area and also to an asymmetric flow in the outlet ports. The resulting flow fluctuations may lead to areas within the passageway having a lower steel flow velocity which, in turn, may result in a buildup or freezing of steel and/or inclusions in the passageway, or to areas of increased steel flow velocities and, in turn, to increased wear. Therefore, a biased flow withing the passageway may lead to reduced durability and premature failure of a submerged nozzle during operation.
Accordingly, it is an object of this invention to provide a submerged nozzle and a method for continuous casting, where during pouring molten steel from a tundish into a mold, the flow stability is improved, especially in a way that a biased flow inside the passageway of such a nozzle is reduced or eliminated.
The object is achieved by a submerged nozzle through which molten steel can be poured from a tundish into a mold according to claim 1, and a method for continuous casting of molten steel according to claim 15. The advantages and refinements mentioned in connection with the method also apply analogously to the products / physical objects and vice versa.
In this application a submerged nozzle through which molten steel can be poured from a tundish into a mold comprises a substantially tubular body, that is a body of generally hollow cylindrical form, wherein there might be variation from a mathematical cylinder in the sense that, e.g., one or more flattened areas might be present. The substantially tubular body extends from a first end to a second end, wherein, in the use position of the submerged nozzle, the first end corresponds to its upper end and the second end corresponds to its lower end. Generally, the substantially tubular body might be elongated. A passageway extends through the tubular body along a longitudinal axis, which is the longitudinal axis of the substantially tubular body. The longitudinal axis is understood as an imaginary line extending from the first end to the second end in the center of the substantially tubular body. The passageway is an inner space / an opening, that is defined by an inner wall of the tubular body. The passageway has a passageway cross section which is to be understood as the cross section of the passageway (at any position between the first end and the second end) which is normal to the longitudinal axis. The passageway cross section will generally be restricted by the inner wall of the tubular body, in positions between the first end and the second end, where no flow restrictor is present and where no outlet port is present. The longitudinal axis (A) will generally be present in the center of the passageway cross section.
An inlet port is opening at the first end of the substantially tubular body into the passageway. A pair of opposing outlet ports is opening in a region adjacent to the second end of the substantially tubular body into the passageway, each outlet port comprises an outlet port center, which is the geometric center of the outlet port (that is the geometric center of the open area of the outlet port). The outlet port axis is understood as an imaginary line extending from one of the opposing outlet port centers to the other of the opposing outlet port centers, that is the outlet port axis is the connection between the outlet port centers of the respective opposing outlet port. The outlet port axis is orthogonal to the longitudinal axis (but does not necessarily intersect with the longitudinal axis (A), in which case the two axes represent skew lines and any two intersecting lines parallel to the outlet port axis and the longitudinal axis are orthogonal to each other). Both outlet ports might be symmetrically arranged, where each outlet port is tilted, e.g., downwards, with respect to the outlet port axis (this does not alter the fact that the outlet port axis and the longitudinal axis are orthogonal to each other). The transverse outlet port axis is understood as an imaginary line orthogonal to the outlet port axis and orthogonal to the longitudinal axis (A) (generally, the transverse outlet port axis intersects with the longitudinal axis, if this is not the case, any two intersecting lines parallel to the transverse outlet port axis and the longitudinal axis are orthogonal to each other). Additional outlet ports may be present, such as, e.g., a single additional outlet port at the second end.
Flow restrictors are understood to be parts that restrict the flow within the passageway. Flow restrictors can be any protrusions within the passageway, protruding from the inner wall of the tubular body into the passageway. Therefore, a flow restrictor protruding from the inner wall of the tubular body will restrict the passageway cross section at a certain position (height) between the first end and the second end. The restriction of a (specific) passageway cross section may happen in/along various directions from the longitudinal axis (A). A direction may be a direction of an axis, such as a transverse outlet port axis or an outlet port axis. Such a direction is to be understood as any direction of a line parallel to such an axis. A direction within a passageway cross section is thus a line within a specific passageway cross section, wherein this line is parallel to such an axis, e.g., parallel to the transverse outlet port axis or parallel to the outlet port axis. A direction generally starts from a certain object, thus, e.g., a direction from the longitudinal axis (A) within a passageway cross section starts at the longitudinal axis (A) within that passageway cross section (here the start of the direction is defined by the certain object being the longitudinal axis within the specific cross-section). Such a restriction of the (specific) passageway cross section from the longitudinal axis (A) is thus a restriction, which limits (reduces) the cross-section in this direction compared to the cross-section without this restriction.
As a flow restrictor protruding from the inner wall of the tubular body will restrict the passageway cross section in (along) certain directions from the longitudinal axis, such a flow restrictor might also not restrict the passageway cross-section in certain (other) directions from the longitudinal axis. The direction of a restriction or of a non-restriction in a specific passageway cross-section can be easily determined by comparing this specific passageway cross-section to another passageway cross-section below or above the respective flow restrictor. By such a comparison the (total) restriction (R) of a specific passageway cross-section can be determined as a percentage of the open area of the (specific) passageway cross-section containing the flow restrictor (A_restricted) and the open area of another passageway cross-section without a flow restrictor (A_unrestricted). Thus, such restriction (R) can be determined by the formula: R/% = 1 - A_restricted / A_unrestricted × 100.
Flow restrictors are positioned such that their upper surface lies within a certain restrictor range generally between the first and second end. The distance between the first end and the second end of the substantially tubular body defines the tubular body length.
An angle between two lines within this disclosure is to be understood as the smaller angle between the two lines, in case of skew lines, the smaller angle between any two intersecting lines parallel to the two lines.
The core idea of the invention is based on the finding, that by having at least one first flow restrictor, which restricts the passageway cross-section at least in (along) a direction of the transverse outlet port axis from the longitudinal axis within the passageway cross-section, and wherein the at least one first flow restrictor does not restrict the passageway cross-section in (along) any direction of the outlet port axis from the longitudinal axis within the passageway cross-section, it was found that the flow stability is improved due to a reduction of a biased flow.
In a first embodiment of the invention, the object is achieved by providing a submerged nozzle, preferably a monotube, through which molten steel can be poured from a tundish into a mold, the nozzle comprising:

a substantially tubular body, extending from a first end to a second end;
a passageway, extending through the tubular body along a longitudinal axis (A) from the first end towards the second end, the passageway being defined by an inner wall of the tubular body, the passageway comprising a passageway cross section normal to the longitudinal axis (A);
at least one inlet port, opening into the passageway at the first end;
at least one pair of opposing outlet ports, opening into the passageway in a region adjacent to the second end, each outlet port comprises an outlet port center;
an outlet port axis being defined as the connection between the outlet port centers of each opposing outlet port of at least one pair of opposing outlet ports, wherein at least one pair of opposing outlet ports are arranged such that the outlet port axis is orthogonal to the longitudinal axis (A);
a transverse outlet port axis being defined as orthogonal to the outlet port axis and orthogonal to the longitudinal axis (A);
and at least one first flow restrictor (preferably the at least one flow restrictor is a pair of opposing flow restrictors), the at least one first flow restrictor protruding from the inner wall of the tubular body into the passageway;
- wherein the at least one first flow restrictor is positioned closer to the first end than to the second end;
- wherein the at least one first flow restrictor restricts the passageway cross-section at least in a direction of the transverse outlet port axis from the longitudinal axis (A) within the passageway cross-section;
- and wherein the at least one first flow restrictor does not restrict the passageway cross-section in any direction of the outlet port axis from the longitudinal axis (A) within the passageway cross-section.

The placement of the at least one first flow restrictor according to this embodiment allows to center a potential biased flow, especially when the bias of the flow results from a partial opened slide gate valve above of the submerged nozzle or in any other situation, where the biased flow is constituted by the steel being biased on one side of the passageway on the symmetry plane of a submerged nozzle. Further, in that the at least one first flow restrictor does not restrict the passageway cross-section in any direction of the outlet port axis from the longitudinal axis (A), at least two "channels" for the flow are kept open, which seem to have a certain balancing effect and lead to a higher symmetry of the steel flow, as experimentally observed.
Preferably the at least one first flow restrictor restricts the passageway cross-section at least in a direction of the transverse outlet port axis from the longitudinal axis (A) within the passageway cross-section and in all directions deviating from the transverse outlet port axis from the longitudinal axis (A) within the passageway cross-section by at most (an angle (α) of) +/- 15° to +/- 70°, preferably by (an angle (α) of) +/- 20° to +/- 65°, more preferably by (an angle (α) of) +/- 30° to +/- 60°. This has shown that also certain deviations from a biased flow constituted by the steel being biased on one side of the passageway on the symmetry plane of a submerged nozzle can be stabilized, and, in consequence, an overall additional increased stability of the molten steel flow was observed.
Preferably, the at least one first flow restrictor comprises at least one pair of opposing first flow restrictors. This allows to center any biased flow constituted by the steel being biased on either side of the passageway on the symmetry plane of a submerged nozzle. Furthermore, this allows to center any biased flow when the bias of the flow results from a partial opened slide gate valve above the submerged nozzle, in any of the two possible orientations of the installed nozzle (i.e., when the nozzle is turned by 180° around the longitudinal axis) with respect to the slide gate mechanics.
Preferably, the at least one first flow restrictor comprises an upper surface with an upper surface normal, wherein the upper surface normal and the longitudinal axis form an angle (β₁) in the range of 0° to 45°, preferably 2° to 30°, more preferably 5° to 15°. The angle (β₁) is defined as the smaller angle between the upper surface normal and the longitudinal axis (A), in case of skew lines, the smaller angle between any two intersecting lines parallel to the upper surface normal and the longitudinal axis (A). Such angles of the upper surface normal help to center the flow.
Preferably, the at least one first flow restrictor is positioned such that the upper surface of the at least one first flow restrictor lies within a first restrictor region, the first restrictor region starting at a position of 4% of the tubular body length from the first end and ending at a position of 35% of the tubular body length from the first end to the second end, more preferably the first restrictor region starting at a position of 5% of the tubular body length from the first end to the second end and ending at a position of 25% of the tubular body length from the first end to the second end. Such a placement of the at least one first flow restrictor is highly efficient in reducing any biased flow constituted by the steel being biased on one side of the passageway on the symmetry plane of a submerged nozzle, also reducing any asymmetry due to a bouncing effect of the flow to the opposite side of the passageway.
Preferably, the at least one first flow restrictor restricts the passageway cross-section by 10% to 40%, preferably by 15% to 30%. Preferably, the pair of first flow restrictors restricts the passageway cross-section by 10% to 40%, preferably by 15% to 30%. Preferably, in sum all first flow restrictors of the at least one first flow restrictor restrict the passageway cross-section by 10% to 40%, preferably by 15% to 30%. This range shows a significant reduction in biased flow without inducing additional pressure disturbances.
Preferably, the at least one first flow restrictor has a first extension along the direction of the longitudinal axis (A) in the range of 1 % to 5% of the tubular body length.
Preferably, the submerged nozzle further comprises at least a second flow restrictor protruding from the inner wall of the tubular body into the passageway, wherein the at least one second flow restrictor is positioned closer to the second end than the first flow restrictor. The at least one second flow restrictor is able to further reduce any remaining bouncing effect induced by the at least one first flow restrictor. The inventors have found that such at least one second flow restrictor works only in combination with a first flow restrictor, as those second flow restrictors alone do not effectively reduce asymmetry in the flow.
Preferably, the at least one second flow restrictor restricts the passageway cross-section symmetrically with respect to the longitudinal axis (A), preferably the at least one second flow restrictor restricts the passageway cross-section axial symmetrically. This achieves a certain centering effect of the metal flow.
Preferably, the at least one second flow restrictor restricts the passageway symmetrically in at least four directions with respect to the longitudinal axis (A). This achieves an increased centering effect of the metal flow.
Preferably, the at least one second flow restrictor comprises at least one pair of opposing second flow restrictors, preferably, at least two pairs of opposing second flow restrictors. The inventors have found that one pair, and even more two pairs, of opposing second flow restrictors improve the stability of the flow even when fluctuations of the flow occur at the first end of the passageway.
Preferably, the at least one second flow restrictor comprises an upper surface with an upper surface normal, wherein the upper surface normal and the longitudinal axis form an angle (βz) in the range of 0° to 70°, preferably 15° to 60°, more preferably 25° to 50°. The angle (βz) is defined as the smaller angle between the upper surface normal and the longitudinal axis (A), in case of skew lines, the smaller angle between any two intersecting lines parallel to the upper surface normal and the longitudinal axis (A). Such angles of the upper surface normal help to center the flow.
Preferably, the at least one second flow restrictor has a second extension along the direction of the longitudinal axis (A) in the range of 10% to 30% of the tubular body length.
Preferably, in the at least one pair of opposing second flow restrictors, or in the at least two pairs of opposing second flow restrictors, each flow restrictor comprises an upper surface with an upper surface normal, wherein the upper surface normal and the longitudinal axis form angles (βz) in the range of 0° to 70°, preferably 15° to 60°, more preferably 25° to 50°, and wherein the surface normal and the longitudinal axis do not intersect. The angle (βz) is defined in this case of skew lines, as the smaller angle between any two intersecting lines parallel to the upper surface normal and the longitudinal axis (A). Such angles of the upper surface normal help to center the flow and additionally help to guide the flow around the restrictors or even into the channels.
Preferably, the at least one second flow restrictor is configured such that it does not restrict the passageway cross-section between each neighbouring second flow restrictors, such that at least two channels, preferably at least four channels, are formed between each neighbouring second flow restrictors. Preferably, the channels run along a direction of the longitudinal axis (A). The channels have the effect to avoid undesirable swirling motions that may occur after the streams collide with the first flow restrictor.
Preferably, the at least one second flow restrictor comprises at least one pair of opposing second flow restrictors, preferably at least two pairs of opposing second flow restrictors, such that at least two channels, preferably at least four channels, are formed between each neighbouring second flow restrictors.
Preferably, the channels run along a direction of the longitudinal axis (A), more preferably the channel have a channel extension along the direction of the longitudinal axis (A) in the range of 10% to 30% of the tubular body length. The channels have the effect to avoid undesirable swirling motions that may occur after the streams collide with, e.g., the first flow restrictor.
Preferably, at least one channel is formed at least in a direction of the outlet port axis from the longitudinal axis (A) within the passageway cross-section and preferably the channel runs along a direction of the longitudinal axis. The channels have the effect to avoid undesirable swirling motions that may occur after the streams collide with, e.g., the first flow restrictor, and they further collimate the flow.
Preferably, the channels are positioned rotationally symmetric around the longitudinal axis (A).
Preferably, the distance from the first end to the second end of the substantially tubular body defines a tubular body length, wherein the at least one second flow restrictor is positioned such that the upper surface of the at least one second flow restrictor lies within in a second restrictor region, the second restrictor region starting at a position of 10% of the tubular body length from the first end to the second end and ending at a position of 50% of the tubular body length from the first end to the second end, preferably the second restrictor region starting at a position of 12% of the tubular body length from the first end to the second end and ending at a position of 35% of the tubular body length from the first end to the second end. Such positions of the second flow restrictor have shown increased collimation of the flow.
Preferably, the at least one / each first flow restrictor comprises a lower surface. Preferably, the lower surface of the at least one / of each first flow restrictor and the upper surface of the at least one / of each second flow restrictor are spaced apart by 3% to 30% of the tubular body length.
Preferably, the at least one second flow restrictor restricts the passageway cross-section by 15% to 45%, preferably by 25% to 40%. Preferably, the pair of opposing second flow restrictors, or the at least two pairs of opposing second flow restrictors restricts the passageway cross-section in total by 15% to 45%, preferably by 25% to 40%. Preferably, in sum all second flow restrictors of the at least one second flow restrictor restrict the passageway cross-section by 15% to 45%, preferably by 25% to 40%. This range showed a significant reduction in biased flow without inducing additional pressure disturbances.
Preferably, the submerged nozzle further comprises at least one third flow restrictor protruding from the inner wall of the tubular body into the passageway, wherein the at least one third flow restrictor is positioned closer to the second end than the first flow restrictor and wherein preferably the at least one third flow restrictor is positioned closer to the second end than the at least one second flow restrictor. The at least one third flow restrictor detaches the flow from the walls of the submerged nozzle in the region above the outlet ports, promoting flow homogenization in the direction of the outlet port axis, so that a last fine tuning / centering of the flow occurs before the flow leaves through the outlet ports. This is particularly important when lower flow rates are adopted in the casting process, as this tends to increase the tendency of formation of stagnant and non-homogeneous flow regions in the passageway.
Preferably, the at least one third flow restrictor comprises at least one pair of opposing third flow restrictors. Preferably, the at least one third flow restrictor is one pair of opposing third flow restrictors. The pair of third flow restrictors will assure that the flow is symmetric, more specifically regarding the symmetry plane defined by the longitudinal axis and by the transverse outlet port axis. No localized high velocities over the ports are present.
Preferably, the at least one third flow restrictor restricts the passageway cross-section at least in a direction of the outlet port axis from the longitudinal axis (A) within the passageway cross-section. Preferably, the at least one third flow restrictor does not restrict the passageway cross-section in any direction of the transverse outlet port axis from the longitudinal axis (A) within the passageway cross-section. This even further enhances the homogeneity of the flow as described above.
Preferably, the at least one third flow restrictor restricts the passageway cross-section at least in a direction of the outlet port axis from the longitudinal axis (A) within the passageway cross-section and in all directions deviating from the outlet port axis from the longitudinal axis (A) within the passageway cross-section by at most an angle of +/- 15° to +/- 70°, preferably by +/- 20° to +/- 65°, more preferably by +/- 30° to +/- 60. These ranges showed an effective prevention of localized velocities disturbances over the ports.
Preferably, the at least one third flow restrictor restricts the passageway cross-section by 10% to 40%, preferably by 15% to 30%. Preferably, the pair of third flow restrictors restricts the passageway cross-section by 10% to 40%, preferably by 15% to 30%. Preferably, in sum all third flow restrictors of the at least one third flow restrictor restrict the passageway cross-section by 10% to 40%, preferably by 15% to 30%. This range showed a significant reduction in biased flow without inducing additional pressure disturbances as also described above.
Preferably, the at least one third flow restrictor has a third extension along the direction of the longitudinal axis (A) in the range of 1 % to 5% of the tubular body length.
Preferably, the distance from the first end to the second end of the substantially tubular body defines a tubular body length, and wherein the at least one third flow restrictor is positioned such that the upper surface of the at least one third flow restrictor lies within a third restrictor region, the third restrictor region starting at a position of 30% of the tubular body length from the first end to the second end and ending at a position of 85% of the tubular body length from the first end to the second end, preferably the third restrictor region starting at a position of 40% of the tubular body length from the first end to the second end and ending at a position of 70% of the tubular body length from the first end to the second end. By positioning the at least one third flow restrictor in this region of the tubular body length a particular high degree of homogenization of the flow in the direction of the outlet port axis was found.
Preferably, the at least one / each second flow restrictor comprises a lower surface. Preferably, the lower surface of the at least one / of each second flow restrictor and the upper surface of the at least one / of each third flow restrictor are spaced apart by 3% to 30% of the tubular body length.
Preferably, the at least one third flow restrictor comprises an upper surface with an upper surface normal, wherein the upper surface normal and the longitudinal axis form an angle (β₃) in the range of 0° to 45°, preferably 2° to 30°, more preferably 5° to 15°. The angle (β₃) is defined as the smaller angle between the upper surface normal and the longitudinal axis (A), in case of skew lines, the smaller angle between any two intersecting lines parallel to the upper surface normal and the longitudinal axis (A). Such angles of the upper surface normal help to smoothen and center the flow.
Preferably, the submerged nozzle comprises a set of flow restrictors, the set of flow restrictors consists of:

one first flow restrictor or one pair of opposing first flow restrictors;
one second flow restrictor or one pair of opposing second flow restrictors or two pairs of opposing second flow restrictors, the one second flow restrictor or the one pair of opposing second flow restrictors or the two pairs of opposing second flow restrictors is/are positioned closer to the second end than the one first flow restrictor or the one pair of opposing first flow restrictors;
one third flow restrictor or one pair of opposing third flow restrictors, the at least one third flow restrictor is positioned closer to the second end than the one first flow restrictor or the one pair of opposing first flow restrictors and wherein preferably the one third flow restrictor or the one pair of opposing third flow restrictors is positioned closer to the second end than the one second flow restrictor or the one pair of opposing second flow restrictors or the two pairs of opposing second flow restrictors.

Preferably, the one first flow restrictor or one pair of opposing first flow restrictors is/are positioned such that the upper surface(s) of the one first flow restrictor or one pair of opposing first flow restrictors lies/lie within a first restrictor region, the first restrictor region starting at a position of 4% of the tubular body length from the first end to a second end and ending at a position of 35% of the tubular body length from the first end to a second end, preferably the first restrictor region starting at a position of 5% of the tubular body length from the first end to a second end and ending at a position of 25% of the tubular body length from the first end to a second end, and whereas the lower surface(s) of the one first flow restrictor or one pair of opposing first flow restrictors and the upper surface(s) of the one second flow restrictor or one pair of opposing second flow restrictors or two pairs of opposing second flow restrictors are spaced apart by 3% to 30% of the tubular body length, and whereas the lower surface(s) of the one second flow restrictor or one pair of opposing second flow restrictors or two pairs of opposing second flow restrictors and the upper surface(s) of the one third flow restrictor or one pair of opposing third flow restrictors are spaced apart by 3% to 30% of the tubular body length.
Preferably, the submerged nozzle comprises a set of flow restrictors, the set of flow restrictors consists of:

one first flow restrictor or one pair of opposing first flow restrictors,
- wherein the at least one first flow restrictor restricts the passageway cross-section at least in a direction of the transverse outlet port axis from the longitudinal axis (A) within the passageway cross-section;
- and wherein the at least one first flow restrictor does not restrict the passageway cross-section in any direction of the outlet port axis from the longitudinal axis (A) within the passageway cross-section,
- wherein the at least one first flow restrictor is positioned such that the upper surface of the at least one first flow restrictor lies within a first restrictor region, the first restrictor region starting at a position of 4% of the tubular body length from the first end to a second end and ending at a position of 35% of the tubular body length from the first end to a second end, preferably the first restrictor region starting at a position of 5% of the tubular body length from the first end to a second end and ending at a position of 25% of the tubular body length from the first end to a second end;
one second flow restrictor or one pair of opposing second flow restrictors or two pairs of opposing second flow restrictors,
- wherein the one second flow restrictor or the one pair of opposing second flow restrictors or the two pairs of opposing second flow restrictors is/are positioned closer to the second end than the at least one first flow restrictor;
- wherein with one pair of opposing second flow two channels (12), and wherein with two pairs of opposing second flow restrictors four channels are formed between each neighbouring second flow restrictors;
- wherein the one second flow restrictor or the one pair of opposing second flow restrictors or the two pairs of opposing second flow restrictors is/are positioned such that the upper surface of each second flow restrictor lies within second restrictor region, the second restrictor region starting at a position of 10% of the tubular body length from the first end to a second end and ending at a position of 50% of the tubular body length from the first end to a second end, preferably the second restrictor region starting at a position of 12% of the tubular body length from the first end to a second end and ending at a position of 35% of the tubular body length from the first end to a second end
one third flow restrictor or one pair of opposing third flow restrictors,
- wherein the at least one third flow restrictor is positioned closer to the second end than the at least one first flow restrictor and wherein preferably the at least one third flow restrictor is positioned closer to the second end than the at least one second flow restrictor,
- wherein the at least one third flow restrictor restricts the passageway cross-section at least in a direction of the outlet port axis from the longitudinal axis (A) within the passageway cross-section;
- and wherein the at least one third flow restrictor does not restrict the passageway cross-section in any direction of the transverse outlet port axis from the longitudinal axis (A) within the passageway cross-section,
- wherein the at least one third flow restrictor is positioned such that the upper surface of the at least one third flow restrictor lies within a third restrictor region, the at least one third restrictor region starting at a position of 30% of the tubular body length from the first end to a second end and ending at a position of 85% of the tubular body length from the first end to a second end, preferably the third restrictor region starting at a position of 40% of the tubular body length from the first end to a second end and ending at a position of 70% of the tubular body length from the first end to a second end.

A preferred submerged nozzle, such as a monotube, through which molten steel can be poured from a tundish into a mold, comprises:

a substantially tubular body, extending from a first end to a second end;
a passageway, extending through the tubular body along a longitudinal axis (A) from the first end towards the second end, the passageway being defined by an inner wall of the tubular body, the passageway comprising a passageway cross section normal to the longitudinal axis (A);
at least one inlet port, opening into the passageway at the first end;
a pair of opposing outlet ports, opening into the passageway in a region adjacent to the second end, each outlet port comprising an outlet port center;
an outlet port axis being defined as the connection between the outlet port centers of each opposing outlet port of the pair of opposing outlet ports, wherein the opposing outlet ports are arranged such that the outlet port axis is orthogonal to the longitudinal axis (A);
a transverse outlet port axis being defined as orthogonal to the outlet port axis and orthogonal to the longitudinal axis (A);
a set of flow restrictors, each flow restrictor in the set of flow restrictors protruding from the inner wall of the tubular body into the passageway, the set of flow restrictors consists of:
- one first flow restrictor or one pair of opposing first flow restrictors,
  - wherein the at least one first flow restrictor restricts the passageway cross-section at least in a direction of the transverse outlet port axis from the longitudinal axis (A) within the passageway cross-section;
  - and wherein the at least one first flow restrictor does not restrict the passageway cross-section in any direction of the outlet port axis from the longitudinal axis (A) within the passageway cross-section,
  - wherein the at least one first flow restrictor is positioned such that the upper surface of the at least one first flow restrictor lies within a first restrictor region, the first restrictor region starting at a position of 4% of the tubular body length from the first end to a second end and ending at a position of 35% of the tubular body length from the first end to a second end, preferably the first restrictor region starting at a position of 5% of the tubular body length from the first end to a second end and ending at a position of 25% of the tubular body length from the first end to a second end;
- one second flow restrictor or one pair of opposing second flow restrictors or two pairs of opposing second flow restrictors,
  - wherein the one second flow restrictor or the one pair of opposing second flow restrictors or the two pairs of opposing second flow restrictors is/are positioned closer to the second end than the at least one first flow restrictor;
  - wherein with one pair of opposing second flow two channels, and wherein with two pairs of opposing second flow restrictors four channels are formed between each neighbouring second flow restrictors;
  - wherein the one second flow restrictor or the one pair of opposing second flow restrictors or the two pairs of opposing second flow restrictors is/are positioned such that the upper surface of each second flow restrictor lies within second restrictor region, the second restrictor region starting at a position of 10% of the tubular body length from the first end to a second end and ending at a position of 50% of the tubular body length from the first end to a second end, preferably the second restrictor region starting at a position of 12% of the tubular body length from the first end to a second end and ending at a position of 35% of the tubular body length from the first end to a second end;
- one third flow restrictor or one pair of opposing third flow restrictors,
  - wherein the at least one third flow restrictor is positioned closer to the second end than the at least one first flow restrictor and wherein preferably the at least one third flow restrictor is positioned closer to the second end than the at least one second flow restrictor,
  - wherein the at least one third flow restrictor restricts the passageway cross-section at least in a direction of the outlet port axis from the longitudinal axis (A) within the passageway cross-section;
  - and wherein the at least one third flow restrictor does not restrict the passageway cross-section in any direction of the transverse outlet port axis from the longitudinal axis (A) within the passageway cross-section,
  - wherein the at least one third flow restrictor is positioned such that the upper surface of the at least one third flow restrictor lies within a third restrictor region, the at least one third restrictor region starting at a position of 30% of the tubular body length from the first end to a second end and ending at a position of 85% of the tubular body length from the first end to a second end, preferably the third restrictor region starting at a position of 40% of the tubular body length from the first end to a second end and ending at a position of 70% of the tubular body length from the first end to a second end.

Preferably the submerged nozzle is a monotube which preferably comprises a connection portion for connection to a slide gate system at the first end of the monotube.
In a second embodiment the object is achieved by a method for continuous casting of molten steel, using a submerged nozzle according to the first embodiment. The method allows the production of steel with a high quality, due to the stability of the metal flow resulting in reduced amounts of inclusions.
Further characteristics of the invention result from the claims, the figures and the following figure description.
All features of the invention can be combined individually or in combination.
Exemplary embodiments of the invention are explained in more detail by means of illustrations:

Fig. 1 shows a first schematic cross-section (front view) of a schematic submerged nozzle (monotube) with a set of flow restrictors.
Fig. 2 shows a second schematic cross-section (side view) of a schematic submerged nozzle (monotube) with a set of flow restrictors.
Fig. 3 shows a schematic passageway cross-section without a flow restrictor.
Fig. 4 shows a schematic passageway cross-section with one first flow restrictor.
Fig. 5 shows a schematic passageway cross-section with two first flow restrictors.
Fig. 6 shows a schematic passageway cross-section with two first flow restrictors.
Fig. 7 shows a schematic passageway cross-section with one first flow restrictor.
Fig. 8 shows a schematic passageway cross-section with two second flow restrictors.
Fig. 9 shows a schematic passageway cross-section with two second flow restrictors.
Fig. 10 shows a schematic passageway cross-section with four second flow restrictors.
Fig. 11 shows a schematic passageway cross-section with two third flow restrictors.
Fig. 12 shows a flow pattern simulation in a submerged nozzle without any flow restrictor.
Fig. 13 shows a flow pattern simulation in a submerged nozzle with one first flow restrictor.
Fig. 14 shows a flow pattern simulation in a submerged nozzle with two first flow restrictors and with four second flow restrictors.
Fig. 15 shows a flow pattern simulation in a submerged nozzle with two first flow restrictors, with four second flow restrictors and with two third flow restrictors.

Fig. 1 and Fig. 2 show cross-sections of a front and side-view of a submerged nozzle 1, which in this example is a monotube 1a in its use position. The submerged nozzle 1 comprises a substantially tubular body 2 extending from a first end 3 (upper end) to a second end 4 (lower end), the substantially tubular body 2 is made of a carbon bonded refractory material. At the first end 3 (upper end) the monotube 1a comprises a plate like part as a connection portion for connection to a slide gate system (not shown). The submerged nozzle 1 further comprises a passageway 5, which extends through the tubular body 2, along a longitudinal axis A from the first end 3 to the second end 4. The passageway 5 is defined by an inner wall 2i of the tubular body 2, the passageway 5 comprises a passageway cross section 5a normal to the longitudinal axis A. The passageway 5 of this example is in the form of a circular cylinder, with its axis coinciding with the longitudinal axis A of the submerged nozzle 2, wherein the circular cylinder is capped on opposing sides, as shown in Fig. 3, where an unrestricted passageway cross-section 5a is shown. At the first end 3 the inlet port 6 opens into the passageway 5. In a region 7 adjacent to the second end 4 a pair (=two) of opposing outlet ports 8 open into the passageway 5. The outlet ports 8 are openings in the form of a rounded square in the wall of the tubular body 2. The outlet ports 8 are symmetrically arranged with respect to the longitudinal axis A, each outlet port 8 comprises an outlet port center 8a, which is the geometric center of the outlet port 8. An outlet port axis 8b is defined as the connection between the outlet port centers 8a of each opposing outlet port 8 of the at least one pair of opposing outlet ports 8. The outlet port axis 8b in Fig. 1 and Fig. 2 is orthogonal to the longitudinal axis A and intersects with the longitudinal axis A. A transverse outlet port axis 8c is defined as being oriented orthogonal to the outlet port axis 8b and orthogonal to the longitudinal axis A. The submerged nozzle 1 comprises a set of flow restrictors 10, 11, 13, consisting of one first flow restrictor 10, a pair of second flow restrictors 11 and a pair of third flow restrictors 13. The one first flow restrictor 10 is protruding from the inner wall 2i of the tubular body 2 into the passageway 5 and restricts the passageway cross-section 5a at least in a direction of the transverse outlet port axis 8c from the longitudinal axis A within the passageway cross-section 5a, as shown in Fig. 7.
The one first flow restrictor 10 restricts the passageway cross-section 5a at least in a direction of the transverse outlet port axis 8c from the longitudinal axis A within the passageway cross-section 5a and in all directions deviating from the transverse outlet port axis 8c from the longitudinal axis A within the passageway cross-section 5a by an angle α of +/- 45° in this example. Alternatively, also smaller deviations might be used, such as, e.g., by +/- 15°, preferably by +/- 20°, more preferably by +/- 30°, as schematically shown by the angle α in Fig. 4, or also larger deviations might be used, such as, e.g., +/- 60°, +/- 65°, or even +/-70°, such as, e.g., schematically shown in Fig. 5, Fig. 6 and Fig. 7.
Additionally, the at least one first flow restrictor 10 might comprise at least one pair of opposing first flow restrictors 10, as shown schematically in Fig. 5 and Fig. 6.
In this example, the distance from the first end 3 to the second end 4 of the substantially tubular body 2 defines the tubular body length 2a, and the one first flow restrictor 10 is positioned such that the upper surface 10u of the first flow restrictor 10 lies within a first restrictor region 10r at a position of the upper surface 11u of 12% of the tubular body length 2a from the first end 3 to a second end 4.
Here, the one first flow restrictor 10 has a first extension 10e along the direction of the longitudinal axis (A) of 4% of the tubular body length 2a.
Here, the one first flow restrictor 10 restricts the passageway cross-section 5a by 27%, which means that the remaining open cross-section (e.g., as shown in Fig. 7) - the open area - is 73% of the unrestricted cross section (e.g., as shown in Fig. 3).
The submerged nozzle 1 shown in Fig. 1 and 2 further comprises a pair of second flow restrictors 11 protruding from the inner wall 2i of the tubular body 2 into the passageway 5, wherein the pair of second flow restrictors 11 is positioned closer to the second end 4 (that is lower in its use position) than the one first flow restrictor 10.
The pair of second flow restrictors 11 restrict the passageway cross-section 5a symmetrically with respect to the longitudinal axis A, here they restrict the passageway cross-section 5a axial symmetrically. The respective passageway cross-section 5a is schematically shown in Fig. 8 and 9.
Alternatively, the at least one second flow restrictor 11 may consist of two pairs of opposing second flow restrictors 11 which restrict the passageway 5 symmetrically in at least four directions with respect to the longitudinal axis A, such as shown in Fig. 10.
Each first flow restrictor 10 in Fig. 1 and 2 comprise an upper surface 10u with an upper surface normal 10n, wherein the upper surface normal 10n and the longitudinal axis A form an angle β₁ of 15°.
Each second flow restrictor 11 in Fig. 1 and 2 comprise an upper surface 11u with an upper surface normal 11n, wherein the upper surface normal 11n and the longitudinal axis A form an angle β₂ of 50°.
Each third flow restrictor 13 in Fig. 1 and 2 comprise an upper surface 13u with an upper surface normal 13n, wherein the upper surface normal 13n and the longitudinal axis A form an angle β₃ of 15°.
The pair of second flow restrictors 11 is configured such that it does not restrict the passageway cross-section 5a between each neighbouring second flow restrictors 11, such that at least two channels 12 are formed. This is also shown schematically in Fig. 8 and 9.
Alternatively, when two pairs of flow restrictors 11 are used, then four channels 12 are formed between each neighbouring second flow restrictors 11, as depicted in Fig. 10.
In the examples of Fig. 8, 9 and 10, two channels 12 are formed in a direction of the outlet port axis 8b from the longitudinal axis A within the passageway cross-section 5a. These examples also show channels 12 that are positioned rotationally symmetric around the longitudinal axis A.
In the example of Fig. 1 and 2, the distance from the first end 3 to the second end 4 of the substantially tubular body 2 defines a tubular body length 2a, wherein the at least one second flow restrictor 11 is positioned such that the upper surface 11u of the second flow restrictor 11 lies within a second restrictor region 11r at a position of the upper surface 11u of 32% of the tubular body length 2a from the first end 3 to a second end 4. Here, the lower surface 10l of the one first flow restrictor 10 and the upper surface 11u of each second flow restrictor 11 are spaced apart by 16% of the tubular body length 2a.
Here, the at least one second flow restrictor 11 has a second extension 11e along the direction of the longitudinal axis (A) of 18% of the tubular body length 2a. The at least one second flow restrictor 11 restricts the passageway cross-section 5a by 30%.
Fig. 1 and 2 further show one pair of opposing third flow restrictors 13 protruding from the inner wall 2i of the tubular body 2 into the passageway 5, wherein the one pair of opposing third flow restrictors 13 is positioned closer to the second end 4 than the first flow restrictor 10 and closer to the second end 4 (that is lower in its use position) than the second flow restrictor 11.
The pair of third flow restrictors 13 restricts the passageway cross-section 5a in (both) direction of the outlet port axis 8b from the longitudinal axis A within the passageway cross-section 5a and does not restrict the passageway cross-section 5a in both directions of the transverse outlet port axis 8c from the longitudinal axis A within the passageway cross-section 5a, as shown in Fig. 11.
In this example, both third flow restrictors 13 restrict the passageway cross-section 5a at least in a direction of the outlet port axis 8b from the longitudinal axis A within the passageway cross-section 5a and in all directions deviating from the outlet port axis 8b from the longitudinal axis A within the passageway cross-section 5a by +/- 45°.
Here the distance from the first end 3 to the second end 4 of the substantially tubular body 2 defines a tubular body length 2a, wherein the one pair of third flow restrictors 13 is positioned such that the upper surface 13u of each third flow restrictor 13 lies within a third restrictor region 13r at a position of the upper surface 13u of 69% (in an alternative embodiment at 55% and at 60% - not shown in the figures) of the tubular body length 2a from the first end 3 to a second end 4.
The one pair of third flow restrictors 13 has a third extension 13e along the direction of the longitudinal axis (A) of 4% of the tubular body length 2a. Here, the lower surface 11l of each second flow restrictor 11 and the upper surface 13u of each third flow restrictor 13 are spaced apart by 19% of the tubular body length 2a. The one pair of third flow restrictors 13 restricts the passageway cross-section 5a by 25%.
The example shown in Fig. 1 and 2 shows a submerged nozzle 1 that comprises a set of flow restrictors 10, 11, 13, the set of flow restrictors 10, 11, 13 consists of:

one first flow restrictor 10;
one pair of opposing second flow restrictors 11;
one pair of opposing third flow restrictors 13.

Fig. 3 shows a passageway cross-section 5a without any flow restrictor, e.g., this cross-section 5a might be taken from a submerged nozzle 1 of Fig. 1 and 2 in a region without any flow restrictors 10, 11, 13.
Fig. 4 shows a passageway cross-section 5a with one first flow restrictor 10, which restricts the passageway cross-section 5a in a direction of the transverse outlet port axis 8c from the longitudinal axis A within the passageway cross-section 5a and in all directions deviating from the transverse outlet port axis 8c from the longitudinal axis A within the passageway cross-section 5a by +/- 45° (shown by angles α).
Fig. 5 shows a passageway cross-section 5a with one opposing pair of first flow restrictors 10, wherein the pair of first flow restrictors 10 restricts the passageway cross-section 5a by 20% (so each of the first flow restrictors 10 restrict the passageway cross-section 5a by 10%).
Fig. 6 shows a passageway cross-section 5a with one opposing pair of first flow restrictors 10, wherein the pair of first flow restrictors 10 restricts the passageway cross-section 5a by 40% (so each of the first flow restrictors 10 restrict the passageway cross-section 5a by 20%).
Fig. 7 shows a passageway cross-section 5a with one (single) first flow restrictor 10, wherein the one first flow restrictors 10 restrict the passageway cross-section 5a by 22% (so the single first flow restrictor 10 restricts the passageway cross-section 5a by 22%).
Fig. 8 shows a passageway cross-section 5a with one pair of second flow restrictors 11, wherein the pair of second flow restrictors 11 restrict the passageway cross-section 5a by 22% (so each of the second flow restrictors 11 restricts the passageway cross-section 5a by 11%).
Fig. 9 shows a passageway cross-section 5a with one pair of second flow restrictors 11, wherein the pair of second flow restrictors 11 restrict the passageway cross-section 5a by 28% (so each of the second flow restrictors 11 restricts the passageway cross-section 5a by 14%).
Fig. 10 shows a passageway cross-section 5a with two pairs of (i.e., a total of four) second flow restrictors 11, wherein the two pairs of second flow restrictors 11 restrict the passageway cross-section 5a by 30% (so each of the second flow restrictors 11 restricts the passageway cross-section 5a by 7,5%). Between each of the neighboring second flow restrictors 11 a channel 12 is formed, such that in total four channels 12 are present.
Fig. 11 shows a passageway cross-section 5a with one pair of third flow restrictors 13, wherein the pair of third flow restrictors 13 restrict the passageway cross-section 5a by 20% (so each of the third flow restrictors 13 restricts the passageway cross-section 5a by 10%).
Fig. 12 shows a flow pattern simulation in a submerged nozzle 1 without any flow restrictor in the passageway 5 as a comparative example. Fig. 12 shows a cross-sectional view, the cross-section is taken along the plane containing the longitudinal axis A and the transverse outlet port axis 8c. In the simulation results shown in Fig. 12 to Fig. 15, the bias of the flow results from a partial opened slide gate valve above of the submerged nozzle, but of course it could result from any other situation, where the biased flow is constituted by the steel being biased on one side of the passageway on the symmetry plane of a submerged nozzle containing the longitudinal axis and the transverse outlet port axis. Fig. 12 shows that the partial restriction of the channel due to the slide gate system results in a flow bias towards one direction of the transverse outlet port axis 8c. If the passageway 5 does not provide any (deflecting or restricting) feature to correct such a bias, the biased flow will reach the opposing outlet ports 8 and the mold in a non-homogeneous way. An asymmetric flow at the bottom the passageway 5 / near the opposing outlet ports 8 will, among other deviations from the ideal stable and symmetric double-roll flow pattern, result in asymmetric flow in the slab casting mold, potentially resulting in uneven shell solidification, too low or too high meniscus activity in some areas or direct impingement of the jet at the wide face. Such deviations might lead to defects such as cracks, slivers and breakouts.
Fig. 13 shows a flow pattern simulation in a submerged nozzle 1 with one first flow restrictor 10. Fig. 13 shows a cross-sectional view, the cross-section is taken along the plane containing the longitudinal axis A and the transverse outlet port axis 8c. Here, the flow collides with one of the first flow deflectors 10 and is directed towards the center of the passageway 5. The first flow restrictor 10 is positioned such that the upper surface 10u lies at a position of 6% of the tubular body length 2a from the first end 3 to a second end 4 and has a first extension 10e along the direction of the longitudinal axis (A) of 4% of the tubular body length 2a. The first flow restrictor 10 restricts the passageway cross-section 5a by 25%. Here the initial biased flow is dispersed and homogenized in the passageway 5 by the left first flow restrictor 10 in Fig. 13. Overall, Fig. 13 shows a reduced asymmetric flow at the bottom the passageway 5 / near the opposing outlet ports 8 especially with respect to any asymmetry along a direction of the transverse port axis 8c.
Fig. 14 shows a flow pattern simulation in a submerged nozzle 1 with two (i.e., a pair of) first flow restrictors 10 and with four (i.e., two pairs of) second flow restrictors 11. Fig. 14a shows a cross-sectional view taken along the plane containing the longitudinal axis A and the transverse outlet port axis 8c, Fig. 14b shows a cross-sectional view taken along the plane containing the longitudinal axis A and the outlet port axis 8b.
The two first flow restrictors 10 are positioned such that their upper surfaces 10u are located at a position of 7% of the tubular body length 2a from the first end 3 to a second end 4 and have a first extension 10e along the direction of the longitudinal axis (A) of 2% of the tubular body length 2a. In total, the first flow restrictors 10 restrict the passageway cross-section 5a by 27%.
The four second flow restrictors 11 are positioned such that their upper surfaces 11u are located at 13% of the tubular body length 2a from the first end 3 to a second end 4 and have a second extension 11e along the direction of the longitudinal axis (A) of 18% of the tubular body length 2a. Here, the lower surface 10l of each first flow restrictor 10 and the upper surface 11u of each second flow restrictor 11 are spaced apart by 4% of the tubular body length 2a. In total the second flow restrictors 11 restrict the passageway cross-section 5a by 33%.
As generally a design of a submerged nozzle 1 is adopted and used for a wide range of throughputs, it was found that it is important to further improve the centering effect of the flow in the passageway 5. Therefore, additionally to the example of Fig. 13, two pairs of opposing second flow restrictors 11 (yielding in total four second flow restrictors 11) are added in the passageway 5. Also, four channels 12 are formed between each neighbouring second flow restrictors 11. Such channels 12 have the effect of straightening the flow and directing it more vertically after successive changes of direction. Without such vertical channels, certain flow patterns show an increased risk of having undesirable velocity components perpendicular to the main casting channel axis. Such velocity components might cause flow swirling inside the main channel, which increase the risk of asymmetry between the outlet ports 8 and overall instability of the jet flowing through the outlet ports 8 and into the mold. Always one first flow restrictor 10 of the pair of opposing first flow restrictors 10 is used for improving the flow, as it is not always possible to completely ensure the correct orientation of the submerged nozzle 1 in plant operation, and it is much preferable to have a design that is "orientation-agnostic", i.e., effective in both possible orientations. Nevertheless, at least a small additional improvement of the flow is achieved with the pair of first flow restrictors 10. Overall, Fig. 14 shows a reduced asymmetric flow at the bottom of the passageway 5 near the opposing outlet ports 8 and further reduces unwanted swirling flow patterns.
Fig. 15 shows a flow pattern simulation in a submerged nozzle 10 with two first flow restrictors 10, four second flow restrictors 11 and with two third flow restrictors 13. Fig. 15a shows a cross-sectional view taken along the plane containing the longitudinal axis A and the transverse outlet port axis 8c, Fig. 15b shows a cross-sectional view taken along the plane containing the longitudinal axis A and the outlet port axis 8b.
The first flow restrictors 10 are positioned such that their upper surfaces 10u are located at a position of 11% of the tubular body length 2a from the first end 3 to a second end 4 and have a first extension 10e along the direction of the longitudinal axis A of 2% of the tubular body length 2a. In total, the first flow restrictors 10 restrict the passageway cross-section 5a by 23%.
The second flow restrictors 11 are positioned such that their upper surfaces 11u are located at a position of 21% of the tubular body length 2a from the first end 3 to a second end 4 and have a second extension 11e along the direction of the longitudinal axis A of 19% of the tubular body length 2a. Here, the lower surface 10l of each first flow restrictor 10 and the upper surface 11u of each second flow restrictor 11 are spaced apart by 8% of the tubular body length 2a. The channels 12 have a channel extension (12e) along the direction of the longitudinal axis A of 19% of the tubular body length 2a. In total the second flow restrictors 11 restrict the passageway cross-section 5a by 25%.
The third flow restrictors 13 are positioned such that their upper surfaces 13u are located at a position of 46% of the tubular body length 2a from the first end 3 to a second end 4 and have a third extension 13e along the direction of the longitudinal axis A of 2% of the tubular body length 2a. Here, the lower surface 11l of each second flow restrictor 11 and the upper surface 13u of each third flow restrictor 13 are spaced apart by 6% of the tubular body length 2a. In total the third flow restrictors 13 restrict the passageway cross-section 5a by 19%.
The effect of the third flow restrictors 13 is to further equalize the flow between the opposing outlet ports 8, in the direction of the outlet port axis 8b. While the two first flow restrictors 10 are aimed to center the flow with respect to the bias in a direction of the transverse port axis 8c, the two third flow restrictors 13 have a collateral effect of directing the flow to ensure that the flow will be symmetric also in the plane that passes through the outlet port axis 8b and longitudinal axis A, and, in combination with the two first flow restrictors 10 and the four second flow restrictors 11, ensure a highly symmetric and homogeneous flow distribution into the mold. In Fig. 15 each second flow restrictors 11 of the two pairs of opposing second flow restrictors 11 comprises an upper surface 11u with an upper surface normal 11n, wherein the upper surface normal 11n and the longitudinal axis A form an angle β₂ of 45°, which has shown to increase the centering effect significantly.

List of reference numerals and factors:

1: Submerged nozzle
1a: Monotube
2: Tubular body
2a: Tubular body length
2i: Inner wall of tubular body (2)
3: First end
4: Second end
5: Passageway
5a: Passageway cross section
6: Inlet port
7: Region adjacent to second end (4)
8: Opposing outlet port
8a: Outlet port center
8b: Outlet port axis
8c: Transverse outlet port axis
10: First flow restrictor
10e: First extension
10u: Upper surface of the first flow restrictor (10)
10l: Lower surface of the first flow restrictor (10)
10n: Upper surface normal of the upper surface of the first flow restrictor (10)
10r: First restrictor region
11: Second flow restrictor
11e: Second extension
11u: Upper surface of the second flow restrictor (11)
11l: Lower surface of the second flow restrictor (11)
11n: Upper surface normal of the upper surface of the second flow restrictor (11)
11r: Second restrictor region
12: Channel
12e: Channel extension
13: Third flow restrictor
13e: Third extension
13u: Upper surface of the third flow restrictor (13)
13n: Upper surface normal of the upper surface of the third flow restrictor (13)
13r: Third restrictor region
A: Longitudinal axis of tubular body (2)
α: Angle within the passageway cross-section (5a) starting from the transverse outlet port axis (8c)
β1: Angle between the surface normal 10n of the upper surface 10u of the first flow restrictor (10) and the longitudinal axis (A)
β2: Angle between the surface normal 11n of the upper surface 11u of the second flow restrictor (11) and the longitudinal axis (A)
β3: Angle between the surface normal 13n of the upper surface 13u of the third flow restrictor (13) and the longitudinal axis (A)

Claims

Submerged nozzle (1) through which molten steel can be poured from a tundish into a mold, the submerged nozzle (1) comprising:
1.1. a substantially tubular body (2), extending from a first end (3) to a second end (4);

1.2. a passageway (5), extending through the tubular body (2) along a longitudinal axis (A) from the first end (3) towards the second end (4), the passageway (5) being defined by an inner wall (2i) of the tubular body (2), the passageway (5) having a passageway cross section (5a) normal to the longitudinal axis (A);

1.3. at least one inlet port (6), opening into the passageway (5) at the first end (3);

1.4. at least one pair of opposing outlet ports (8), opening into the passageway (5) in a region (7) adjacent to the second end (4), each outlet port (8) comprises an outlet port center (8a);

1.5. an outlet port axis (8b) being defined as the connection between the outlet port centers (8a) of each opposing outlet port (8) of at least one pair of opposing outlet ports (8), wherein at least one pair of opposing outlet ports (8) are arranged such that the outlet port axis (8b) is orthogonal to the longitudinal axis (A);

1.6. a transverse outlet port axis (8c) being defined as orthogonal to the outlet port axis (8b) and orthogonal to the longitudinal axis (A);

1.7. and at least one first flow restrictor (10), preferably the at least one first flow restrictor (10) is a pair of opposing flow restrictors (10), the at least one first flow restrictor (10) protruding from the inner wall (2i) of the tubular body (2) into the passageway (5);
1.7.1. wherein the at least one first flow restrictor (10) is positioned closer to the first end (3) than to the second end (4);

1.7.2. wherein the at least one first flow restrictor (10) restricts the passageway cross-section (5a) at least in a direction of the transverse outlet port axis (8c) from the longitudinal axis (A) within the passageway cross-section (5a);

1.7.3. and wherein the at least one first flow restrictor (10) does not restrict the passageway cross-section (5a) in any direction of the outlet port axis (8b) from the longitudinal axis (A) within the passageway cross-section (5a).
Submerged nozzle (1) according to claim 1, wherein the at least one first flow restrictor (10) restricts the passageway cross-section (5a) at least in a direction of the transverse outlet port axis (8c) from the longitudinal axis (A) within the passageway cross-section (5a) and in all directions deviating from the transverse outlet port axis (8c) from the longitudinal axis (A) within the passageway cross-section (5a) by at most an angle α of +/- 15° to +/-70°, preferably by +/- 20° to +/- 65°, more preferably by +/- 30° to +/- 60°.
Submerged nozzle (1) according to claim 1 or 2, wherein the at least one first flow restrictor (10) comprises at least one pair of opposing first flow restrictors (10).
Submerged nozzle (1) according to any of claims 1 to 3, wherein the distance between the first end (3) and the second end (4) of the substantially tubular body (2) defines the tubular body length (2a), and wherein the at least one first flow restrictor (10) is positioned such that the upper surface (10u) of the at least one first flow restrictor (10) lies within a first restrictor region (10r), the first restrictor region (10r) starting at a position of 4% of the tubular body length (2a) from the first end (3) to the second end (4) and ending at a position of 35% of the tubular body length (2a) from the first end (3) to the second end (4), preferably the first restrictor region (10r) starting at a position of 5% of the tubular body length (2a) from the first end (3) to the second end (4) and ending at a position of 25% of the tubular body length (2a) from the first end (3) to the second end (4).
Submerged nozzle (1) according to any of claims 1 to 4, wherein the at least one first flow restrictor (10) restricts, preferably wherein the pair of first flow restrictors (10) restricts, the passageway cross-section (5a) by 10% to 40%, preferably 15% to 30%.
Submerged nozzle (1) according to any of claims 1 to 5, further comprising at least one second flow restrictor (11) protruding from the inner wall (2i) of the tubular body (2) into the passageway (5), wherein the at least one second flow restrictor (11) is positioned closer to the second end (4) than the at least one first flow restrictor (10).
Submerged nozzle (1) according to claim 6, wherein the at least one second flow restrictor (11) comprises an upper surface (11u) with an upper surface normal (11n), wherein the upper surface normal (11n) and the longitudinal axis (A) form an angle (βz) in the range of 0° to 70°, preferably 15° to 60°, more preferably 25° to 50°.
Submerged nozzle (1) according to any of claims 6 to 7, wherein the at least one second flow restrictor (11) restricts the passageway cross-section (5a) symmetrically with respect to the longitudinal axis (A), preferably the at least one second flow restrictor (11) restricts the passageway cross-section (5a) axially symmetrically.
Submerged nozzle (1) according to any of claims 6 to 8, wherein the at least one second flow restrictor (11) comprises at least one pair of opposing second flow restrictors (11), preferably, at least two pairs of opposing second flow restrictors (11).
Submerged nozzle (1) according to any of claims 6 to 8, wherein the at least one second flow restrictor (11) comprises at least one pair of opposing second flow restrictors (11), preferably at least two pairs of opposing second flow restrictors (11), such that at least two channels (12), preferably at least four channels (12), are formed between each neighbouring second flow restrictors (11).
Submerged nozzle (1) according to claim 10, wherein at least one channel (12) is formed at least in a direction of the outlet port axis (8b) from the longitudinal axis (A) within the passageway cross-section (5a).
Submerged nozzle (1) according to any of claims 6 to 11, wherein the distance from the first end (3) to the second end (4) of the substantially tubular body (2) defines a tubular body length (2a), wherein the at least one second flow restrictor (11) is positioned such that the upper surface (11u) of the at least one second flow restrictor (11) lies within a second restrictor region (11r), the second restrictor region (11r) starting at a position of 10% of the tubular body length (2a) from the first end (3) to a second end (4) and ending at a position of 50% of the tubular body length (2a) from the first end (3) to the second end (4), preferably the second restrictor region (11r) starting at a position of 12% of the tubular body length (2a) from the first end (3) to the second end (4) and ending at a position of 35% of the tubular body length (2a) from the first end (3) to the second end (4).
Submerged nozzle (1) according to any of claims 1 to 12, further comprising at least one third flow restrictor (13) protruding from the inner wall (2i) of the tubular body (2) into the passageway (5), wherein the at least one third flow restrictor (13) is positioned closer to the second end (4) than the at least one first flow restrictor (10) and wherein preferably the at least one third flow restrictor (13) is positioned closer to the second end (4) than the at least one second flow restrictor (11).
Submerged nozzle (1) according to claim 13,
14.1. wherein the at least one third flow restrictor (13) restricts the passageway cross-section (5a) at least in a direction of the outlet port axis (8b) from the longitudinal axis (A) within the passageway cross-section (5a);

14.2. and wherein the at least one third flow restrictor (13) does not restrict the passageway cross-section (5a) in any direction of the transverse outlet port axis (8c) from the longitudinal axis (A) within the passageway cross-section (5a);

14.3. wherein preferably the at least one third flow restrictor (13) restricts the passageway cross-section (5a) at least in a direction of the outlet port axis (8b) from the longitudinal axis (A) within the passageway cross-section (5a) and in all directions deviating from the outlet port axis (8b) from the longitudinal axis (A) within the passageway cross-section (5a) by at most +/- 15° to +/- 70°, preferably by +/- 20° to +/- 65°, more preferably by +/-30° to +/- 60°;

14.4. wherein preferably the distance from the first end (3) to the second end (4) of the substantially tubular body (2) defines a tubular body length (2a), and wherein the at least one third flow restrictor (13) is positioned such that the upper surface (13u) of the at least one third flow restrictor (13) lies within a third restrictor region (13r), the at least one third restrictor region (13r) starting at a position of 30% of the tubular body length (2a) from the first end (3) to the second end (4) and ending at a position of 85% of the tubular body length (2a) from the first end (3) to the second end (4), preferably the third restrictor region (13r) starting at a position of 40% of the tubular body length (2a) from the first end (3) to the second end (4) and ending at a position of 70% of the tubular body length (2a) from the first end (3) to the second end (4).
A method for continuous casting of molten steel, using a submerged nozzle (1) according to any of claims 1 to 14.