Casting nozzle comprising flow deflectors

Abstract

A casting nozzle comprises an elongated body defined by an outer wall and comprising a bore defined by a bore wall and extending along a longitudinal axis, X1, from a bore inlet to a downstream bore end, said bore comprising two opposite side ports, each extending transversally to said longitudinal axis, X1, from an opening at the bore wall defining a port inlet adjacent to the downstream bore end, to an opening at the outer wall defining a port outlet which fluidly connects the bore with an outer atmosphere. Upstream from, and directly above each port inlet, one or two flow deflectors protrude out of the bore wall and extend from an upstream deflector end remote from the port inlet to a downstream deflector end close to the port inlet.

Claims

1. Casting nozzle comprising an elongated body defined by an outer wall and comprising a bore defined by a bore wall and extending along a longitudinal axis, X1, from a bore inlet to a downstream bore end, said bore comprising two opposite side ports, each extending transversally to said longitudinal axis, X1, from an opening at the bore wall defining a port inlet adjacent to the downstream bore end, to an opening at the outer wall defining a port outlet which fluidly connects the bore with a casting nozzle exterior, wherein, upstream from, and directly above each port inlet, a number of flow deflectors selected from the group consisting of one and two protrudes out of the bore wall and extends from an upstream deflector end remote from the port inlet to a downstream deflector end close to the port inlet, over a deflector height, Hd, measured parallel to the longitudinal axis, X1, and wherein an area of a cross-section normal to the longitudinal axis, X1, of each flow deflector increases continuously over at least 50% of the deflector height, Hd, in the direction extending from the upstream deflector end towards the downstream deflector end.

2. Casting nozzle according to claim 1, wherein the area of the cross-section normal to the longitudinal axis, X1, of each flow deflector is and remains in a geometry selected from the group consisting of triangular or trapezoidal over at least 50% of the deflector height, Hd.

3. Casting nozzle according to claim 1, wherein the area of the cross-section normal to the longitudinal axis, X1, of each deflector increases continuously from the upstream deflector end over at least 80% of the deflector height, Hd, and wherein said area is and remains triangular or trapezoidal over at least 80% of the deflector height, Hd.

4. Casting nozzle according to claim 1, wherein the downstream deflector end of each flow deflector is at a distance, h, from the port inlet, wherein h is measured along the longitudinal axis, X1, and has a value from and including 0 to and including H, wherein H is the maximum height of the corresponding port inlet measured along the bore wall parallel to the longitudinal axis, X1.

5. Casting nozzle according to claim 1, wherein each flow deflector comprises first and second lateral surfaces which are planar and have a triangular or trapezoidal perimeter, and form an angle, , with one another having a value from and including 70 to and including 160.

6. Casting nozzle according to claim 5, wherein: a middle plane, P1, is defined as a plane comprising the longitudinal axis, X1, and normal to a line passing by the centroids of the port inlets of the two opposite side ports, each of said first and second lateral surfaces comprises a free edge remote from the bore wall, and for any cut along a plane normal to the longitudinal axis, X1, intercepting a lateral wall of a flow deflector, a straight line originating at the free edge of, and extending normal to at least one of the first and second lateral surfaces of each flow deflector intercepts the middle plane, P1, in a section comprised between the longitudinal axis, X1, and an outer perimeter defined by the outer wall of the casting nozzle.

7. Casting nozzle according to claim 5, wherein each flow deflector comprises a central surface which is planar and has a triangular, rectangular, or trapezoidal perimeter, and which is flanked on either side by the first and second lateral surfaces, joining them at their respective free edges.

8. Casting nozzle according to claim 7, wherein in a cut along a plane, fin, normal to the planar central surface and parallel to the longitudinal axis, X1, the planar central surface forms an angle, , with a normal projection of the longitudinal axis, X1, on said plane, fin, wherein has a value from and including 1 to and including 15.

9. Casting nozzle according to claim 5, wherein the free edges of the first and second lateral surfaces join to form a rectilinear ridge.

10. Casting nozzle according to claim 9, wherein in a cut along a plane, fib, comprising said rectilinear ridge and bisecting the angle, , formed by the first and second lateral surfaces the rectilinear ridge forms an angle, , with a normal projection of the longitudinal axis, X1, on said plane, fib, wherein has a value from and including 1 to and including 15.

11. Casting nozzle according to claim 1, comprising two flow deflectors upstream from each port inlet.

12. Casting nozzle according to claim 5, wherein for any cut along a plane normal to the longitudinal axis, X1, intercepting the first and second lateral walls of a flow deflector, a first straight line originating at the free edge of, and extending normal to the first lateral surface of each flow deflector intercepts the middle plane, P1, in a section comprised between the longitudinal axis, X1, and the outer perimeter, and a second straight line originating at the free edge of, and extending normal to the second lateral surface of each flow deflector intercepts a central plane, P2, in a section comprised between the longitudinal axis, X1, and the outer perimeter, wherein the central plane, P2, includes the longitudinal axis, X1, and is normal to P1.

13. Casting nozzle according to claim 1, comprising a single flow deflector upstream from each port inlet.

14. Casting nozzle according to claim 5, wherein for any cut along a plane normal to the longitudinal axis, X1, intercepting the first and second lateral walls of a flow deflector, straight lines originating at the free edges of, and extending normal to the first and second lateral surfaces of each deflector intercept the middle plane, P1, in a first and second sections located on either sides of the longitudinal axis, X1, and disposed between the longitudinal axis, X1, and the outer perimeter.

15. Casting nozzle according to claim 1, further comprising two edge ports protruding out of the bore wall and extending upstream from the downstream bore end to above the level of the port inlet, the two edge ports facing each other and being located between the port inlets of the two side ports.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Various embodiments of the present invention are illustrated in the attached Figures:

(2) FIG. 1: schematically illustrates a continuous metal casting installation;

(3) FIG. 2: shows (a) a detail of FIG. 1, illustrating a casting nozzle coupled to a tundish and partially engaged in a mould, and (b) a perspective view of a casting nozzle;

(4) FIG. 3: graphically compares the flow rates, Q1 and Q2, between a first side port and the other for a conventional casting nozzle of the prior art (PA) and two embodiments of the present invention (INV1, INV2);

(5) FIG. 4: shows a first embodiment of a nozzle according to the present invention comprising two flow deflectors;

(6) FIG. 5: shows an alternative embodiment of a nozzle according to the present invention comprising two flow deflectors and two edge ports;

(7) FIG. 6: shows an alternative embodiment of a nozzle according to the present invention comprising four flow deflectors;

(8) FIG. 7: shows an alternative embodiment of a nozzle according to the present invention comprising four flow deflectors and two edge ports;

(9) FIG. 8: shows a perspective cut view of the casting nozzle of FIG. 6;

(10) FIG. 9: shows different embodiments of flow deflectors according to the present invention;

(11) FIG. 10: shows cut views along a plane normal to X1, of two embodiments, showing the cross-section of the flow deflectors;

(12) FIG. 11: shows a side cut view and three cuts along planes normal to the longitudinal axis, X1, including the flow deflectors in (a) a first and (b) a second embodiment of nozzles according to the present invention.

(13) The invention is not limited to the embodiments illustrated in the drawings. Accordingly, it should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting the scope of the claims.

DETAILED DESCRIPTION OF THE INVENTION

(14) The present invention concerns casting nozzles (1N) used, as can be seen in FIGS. 1 and 2, for transferring molten metal (200) from a tundish (10) into a mould (100). The casting nozzles of the present invention yield a more stable and homogeneous flow of molten metal into a mould, with a vertical level of the meniscus (200m) formed in the mould at the top of the molten metal which remains stable during the casting operation.

(15) A nozzle according to the present invention is of the type comprising an elongated body defined by an outer wall and comprising a bore (1) defined by a bore wall and extending along a longitudinal axis, X1, from a bore inlet (1u) to a downstream bore end (1d). The bore comprises two opposite side ports (2), each extending transversally to said longitudinal axis, X1, from an opening at the bore wall defining a port inlet (2u) adjacent to the downstream bore end (1d), to an opening at the outer wall defining a port outlet (2d) which fluidly connects the bore with an outer atmosphere. The outer atmosphere defines any atmosphere surrounding the outer wall of the casting nozzle at the level of the port outlets. In use during a casting operation, the outer atmosphere is formed by molten metal filling the casting mould up to above the level of the side ports (see FIG. 2(a)). A casting nozzle according to the present invention may comprise more than two opposite side ports. For example, it may comprise four side ports opposite two by two.

(16) The gist of the present invention consists of providing upstream from, and directly above each port inlet (2u), one or two flow deflectors (3), which protrude out of the bore wall and extend from an upstream deflector end remote from the port inlet to a downstream deflector end close to the port inlet, over a deflector height, Hd, measured parallel to the longitudinal axis, X1. The expression directly above means herein that there is no protrusion or recess between the downstream deflector end of a flow deflector and the corresponding port inlet. The downstream deflector end is advantageously contiguous to the corresponding port inlet.

(17) The area of a cross-section normal to the longitudinal axis, X1, of each flow deflector increases continuously over at least 50% of the deflector height, Hd, in the direction extending from the upstream deflector end towards the downstream deflector end. Advantageously it increases continuously over at least 80%, advantageously over at least 90% of Hd. Advantageously it increases continuously over 100% of the deflector height, Hd, as illustrated in FIG. 9(a) to (c). In FIG. 9(a)&(b), the cross-sectional area increases linearly over the whole height, Hd, of the flow deflector, whilst in FIG. 9(c), the cross-sectional area increases continuously, but not linearly. FIG. 9(c) illustrates an embodiment wherein at one point located at a distance greater than 50% of Hd from the upstream deflector end, the cross-section decreases until the downstream deflector end. Whenever used, the terms upstream and downstream are defined with respect to a flow from the bore inlet (1u) towards the port outlets (2d).

(18) The cross-section of a flow deflector along a plane normal to the longitudinal axis is advantageously and advantageously remains triangular or trapezoidal over at least 50%, advantageously over at least 80%, advantageously at least over 90% of the deflector height, Hd. In a particular embodiment, said cross-section is and remains triangular or trapezoidal over the whole height (=100%), Hd, of the flow deflector, as illustrated in FIGS. 4 to 9 and 11. Flow deflectors as illustrated in FIG. 9 have a nose-like geometry, with a first and second non-parallel lateral surfaces (3R, 3L) joining either to one another to form a ridge as illustrated in FIG. 9(b)&(c), or at two opposite sides of a central surface (3C) forming an edge, as shown in FIG. 9(a). The central surface (3C) can be planar as depicted in FIG. 9(a), or can be curved as shown in FIG. 9(c).

(19) The downstream deflector end of a flow deflector must be located directly above (or upstream from) the corresponding port inlet. In a particular embodiment, the downstream deflector end is contiguous to said port inlet, forming a lip of the port inlet, as shown, e.g., in FIGS. 4 to 8. The downstream deflector end can also be located directly above the corresponding port inlet at a distance, h, from the port inlet, wherein, as illustrated in FIG. 11(b), the distance, h, is measured along the longitudinal axis, X1, and has a value from and including 0 to and including H, advantageously from and including 0 to and including H/2, wherein H is the maximum height of the corresponding port inlet measured along the bore wall parallel to the longitudinal axis, X1. If the downstream deflector end of a flow deflector is located at a distance, h>H, the effect of the flow deflectors discussed below of stabilizing the molten metal flow before exiting the bore through the side ports (2) is decreased. A low value of the distance, h, is therefore advantageous, with a particular value of h having a value from and including 0 to and including 30 mm, particularly from and including 0 to and including 15 mm; and more particularly, h=0, defining a downstream deflector end which is contiguous to the corresponding port inlet.

(20) As Illustrated in FIGS. 8 and 10, a middle plane, P1, can be defined as a plane comprising the longitudinal axis, X1, and normal to a line passing by the centroids of the port inlets of the two opposite side ports (2). A central plane, P2, can be defined as a plane including the longitudinal axis, X1, and the centroids of each of the port inlets, P1, is therefore normal to P2 and intercept at the longitudinal axis, X1.

(21) As mentioned supra, the flow deflectors have a nose like geometry with first and second lateral surfaces (3L, 3R). In a particular embodiment, said first and second lateral surfaces are substantially planar, forming a triangular or a quadrilateral perimeter with at least two opposite non-parallel edges, advantageously a trapezoidal perimeter. The first and second lateral surfaces converge towards one another from the bore wall, forming an angle, , with one another from and including 70 to and including 160 (cf. FIG. 9).

(22) Each of said first and second lateral planar surfaces comprises a free edge remote from the bore wall. The two lateral surfaces may meet at their respective free edges to form a ridge (3RL) which, as illustrated in FIG. 9b), can be rectilinear or, at least, can comprise a rectilinear section as shown in FIG. 9c). Such flow deflector has a triangular cross-section normal to X1 and is referred to as triangular flow deflector in reference with the cross-section thereof. Alternatively, the lateral surfaces can be separated by a central surface (3C) which can be planar (cf. FIG. 9(a)) or can comprise a planar portion (cf. FIG. 9c)), and has a triangular, rectangular, or trapezoidal perimeter. The central surface is flanked on either side by the first and second lateral surfaces (3R, 3L), joining them at their respective free edges, as shown in FIG. 9(a)&(c). Such flow deflector has a trapezoidal cross-section normal to X1 and is referred to as trapezoidal flow deflector in reference with the cross-section thereof. If the central surface is curved as depicted in FIG. 9c), the cross-section normal to X1 can be referred to as quasi-trapezoidal, and such flow deflector can be referred to as quasi-trapezoidal flow deflector.

(23) As shown in FIG. 9(b)&(c), the rectilinear ridge or a rectilinear ridge section of a triangular flow deflector is not parallel to the bore wall and forms a slope defined by an angle, , from and including 1 to and including 15, advantageously from and including 2 to and including 8, wherein is measured between said rectilinear ridge and a normal projection of the longitudinal axis, X1, on a plane, b, including said rectilinear ridge (section) and bisecting the angle, , formed by the first and second lateral surfaces (3R, 3L). The angle defines the slope of a nose like triangular flow deflector.

(24) Similarly and as shown in FIG. 9(a), the slope of the planar central surface (3C) or planar central surface portion of a trapezoidal flow deflector is not parallel to the bore wall and forms a slope defined by an angle, , from and including 1 to and including 15, advantageously from and including 2 to and including 8, wherein is measured between said planar central surface (portion) and a normal projection of the longitudinal axis, X1, on a plane, fin, normal to the planar central surface (3C) and parallel to the longitudinal axis, X1. The angle defines the slope of a nose like trapezoidal flow deflector.

(25) As shown in FIG. 10, it is advantageous that for any cut along a plane normal to the longitudinal axis, X1, intercepting a lateral wall of a flow deflector, a straight line originating at the free edge of, and extending normal to at least one of the first and second lateral surfaces of each flow deflector intercepts the middle plane, P1, in a section disposed between the longitudinal axis, X1, and an outer perimeter defined by the outer wall of the casting nozzle.

(26) In a particular embodiment, the casting nozzle comprises a single flow deflector (4) upstream from and advantageously contiguous to each port inlet (2u), as illustrated in FIGS. 4, 5, 10(a), and 11(a). In this embodiment illustrated in FIG. 10(a), the straight lines originating at the free edge of, and extending normal to the first and second lateral surfaces of each flow deflector intercept the middle plane, P1, in a first and second sections located on either sides of the longitudinal axis, X1, and disposed between the longitudinal axis, X1, and the outer perimeter.

(27) With this configuration, the flow is deflected towards the bore wall, pushed along the walls of the side ports, thus preventing the formation of secondary flows. In particular, the flow deflected towards the side wall of the port is split evenly between the two side ports (2), thus removing any bias flow behaviour inside the bore.

(28) In an alternative embodiment, the casting nozzle comprises two flow deflectors (4) upstream from each port inlet (2u) and advantageously contiguous thereto, as illustrated in FIGS. 6 to 8, 10(b), and 11(b). In this embodiment illustrated in FIG. 10(b), a first straight line originating at the free edge of, and extending normal to the first lateral surface of each flow deflector intercepts the middle plane, P1, in a section disposed between the longitudinal axis, X1, and the outer perimeter, and a second straight line originating at the free edge of, and extending normal to the second lateral surface of each flow deflector intercepts the central plane, P2, in a section disposed between the longitudinal axis, X1, and the outer perimeter.

(29) Like in the embodiment comprising a single flow deflector above each side port discussed supra, the flow deflected towards the bore wall by the first lateral surface prevents the formation of bias flow. Bias flow formation is also reduced by centering the flow towards the central plane, P2, by means of the second lateral surface. Bias flow formation is a problem commonly encountered when using large nozzle bores even in presence of an edge port. The flow deflected towards the central plane, P2, by the second lateral surface also yields a better jet stability, with reduced vertical fluctuations of the side port exiting jets. The deflection of the flow towards the central plane, P2, also guides the gas bubbles to be entrained by the side port exiting jets.

(30) The enhancement of the flow control out of the side ports by the flow deflectors (3) is demonstrated in FIG. 3, plotting the flow rates, Q1 (white columns) and Q2 (shaded columns), out of a first side port and a second side port, respectively, measured on three different casting nozzles each having a bore with a circular cross section: (a) a casting nozzle according to the prior art, devoid of any flow deflector, (b) a casting nozzle according to the present invention (INV1) comprising a single flow deflector above each side port, and (c) a casting nozzle according to the present invention (INV2) comprising two flow deflector above each side port. The relative flow difference, Q.sub.1-2=|Q1Q2|/MIN (Q1, Q2), between the first and second flow ports is also plotted (black circles) for each nozzle. It can be seen that the flow rate difference, Q.sub.1-2, between the first and second flow ports of a prior art casting nozzle (a) reaches 6.2%, with a flow rate, Q2, out of the second side port which is 20 dm.sup.3/min higher than the flow rate, Q1, out of the first side port. Such asymmetry in the flow behaviour out of a casting nozzle into a mould can be a source of inhomogeneity in the final slab thus formed.

(31) By contrast, the presence of one or two deflectors (b, c) above each side port reduces the difference between Q1 and Q2 to practically zero, yielding a symmetrical flow out of the casting nozzle into a mould. As discussed above, vertical flow fluctuations are substantially reduced by deflecting part of the flow towards the central plane, P2, which is shown by the lower standard deviation measured on casting nozzles comprising two flow deflectors above each side port.

(32) In order to promote the flow deflection, it is advantageous that the upstream deflector end (3u) of the flow deflectors have a non-zero cross-sectional area normal to the longitudinal axis, X1. Referring to FIG. 9, though the upstream deflector end (3u) could be formed at the summit, S, forming a zero cross-sectional area normal to X1, it is advantageous that the upstream deflector end forms downstream from said summit, S, a surface against which the incoming metal flow impacts. The upstream deflector end (3u) can form a surface normal to X1 as illustrated in FIG. 9(a), but it can also form a slope descending downstream from the bore wall to the central edge (3C) or ridge (3RL) of the flow deflector, as shown in FIG. 9(c). A cross-sectional area normal to X1 of the upstream deflector end advantageously protrudes out of the bore wall by a distance of 1 to 10 mm, advantageously of 2 to 6 mm, advantageously of 41 mm, measured normal to the bore wall. Such dimensions are several times larger than the boundary layers forming at the bore wall. FIG. 11 shows in the cut A-A examples of upstream deflector ends (3u) having a non-zero cross-sectional area.

(33) In a particular embodiment, a casting nozzle further comprises two edge ports (5) protruding out of the bore wall and extending upstream from the downstream bore end (2d) to above the level of the port inlet (2u), the two edge ports facing each other and being located between the port inlets (2u) of the two side ports. It is advantageous that the edge ports (5) be symmetrical with respect to the middle plane, P1, as illustrated in FIGS. 5 and 7. Edge ports are traditionally used for stabilizing the flow out of a casting nozzle. Edge ports alone, however, cannot reduce substantially bias flow formation, in particular for casting nozzles having a large size bore. They also have a nose-like geometry with two lateral edge surfaces forming an angle from and including 70 to and including 160. The lateral edges may meet to form a ridge, or they can be separated by a planar central plane of triangular, rectangular or trapezoidal geometry. Edge ports may extend from the bore end (1u) (i.e., the bottom floor of the bore) up along the longitudinal axis, X1, above the level of the bore inlets.

(34) The effect of edge ports (5) is enhanced by the presence of flow deflectors (3) as non-linear flow paths are formed as the metal melt bounces successively against a lateral surface of a flow deflector and on a lateral edge surface of an edge port, before exiting through a side port. This increases the local pressure in the liquid melt, thus further reducing turbulence and bias flows exiting the ports.

(35) The bore end (1d) or bore floor can be substantially planar and normal to the longitudinal axis, as shown in FIGS. 4, 5, and 11(a). It may be flush and continuous with a bottom floor of the side ports (2). In an alternative embodiment, the bore end (1d) comprises two bore end portions meeting at an apex forming a ridge comprised within the middle plane, P1, and sloping downwards towards the side ports, as illustrated in FIGS. 6, 7, and 11(b). Again the bottom floors of the side ports are advantageously flush and continuous (parallel to) with the bore end portions to ensure a smooth and quasi-laminar flow out of the side ports.

(36) A casting nozzle according to the present invention is advantageous over prior art casting nozzles in that the flow out of the first and second side ports is balanced, with an equal flow rate, Q1, Q2, out of the first and second side ports, and fluctuates substantially less in time, yielding beams having a greater homogeneity and reproducibility.

(37) TABLE-US-00001 Ref Description 1 Bore 1d bore end 1N casting nozzle 1u bore inlet 2 side port 2d side port outlet 2u side port inlet 3 flow deflector 3C central surface of a flow deflector 3d downstream end surface of a flow deflector 3L second lateral surface of a flow deflector 3R first lateral surface of a flow deflector 3RL ridge formed by joining first and second surfaces 3u upstream end surface of a flow deflector 5 edge port 7 Stopper 10 Tundish 11 Ladle 100 Mould 111 ladle shroud nozzle 200 molten metal 200m metal meniscus Hd Height of flow deflector measured parallel to X1 X1 Longitudinal axis P1 Middle plane including X1 and normal to P2 P2 Central plane including X1 and centroids of port inlets (2u) b plane bisecting the angle, a, formed by planar first and second surfaces n plane normal to a planar central surface angle formed by planar first and second surfaces angle formed by projections of central surface and X1 onto plane n angle formed by ridge and projection of X1 onto plane b