Title of Invention

A CASTING NOZZLE FOR FLOWING LIQUID METAL THERETHROUGH AND A METHOD FOR FLOWING LIQUID METAL THROUGH SAID CASTING NOZZLE

Abstract

The invention relates to a casting nozzle for flowing liquid metal therethrough, comprising: an elongated bore having an entry port and at least one exit port; and a baffle positioned proximate to the exit port to divide the flow of liquid metal exiting the exit port into at least two separate streams. The invention relates to a method for flowing liquid metal through a casting nozzle, comprising the steps of: flowing liquid metal through an elongated bore having an entrance port and at least one exit port; dividing the flow of liquid metal into two outer streams and a central stream; deflecting the two outer streams in substantially opposite directions; dividing the central stream into two inner streams; and deflecting the two inner streams in substantially the same direction in which the two outer streams are defleted.

Full Text

The present invention relates to a casting or submerged entry nozzle and more particularly to a casting or submerged entry nozzle that improves the flow behavior associated with the introduction of liquid metal into a mold through a casting nozzle. Description of the Related Art In the continuous casting of steel (e.g. slabs) having, for example, thicknesses of 50 to 60 mm and widths of 975 to 1625 mm, there is often employed a casting or submerged entry nozzle. The casting nozzle contains liquid steel as it flows into a mold and introduces the liquid metal into the mold in a submerged manner. The casting nozzle is commonly a pipe with a single entrance on one end and one or two exits located at or near the other end. The inner bore of the casting nozzle between the entrance region and the exit region is often simply a cylindrical axially symmetric pipe section. The casting nozzle has typical outlet dimensions of 25 to 40 mm widths and 150 to 250 mm lengths. The exit region of the nozzle may simply be an open end of the pipe section. The nozzle may also incorporate two oppositely directed outlet ports in the sidewall of the nozzle where the end of the pipe is closed. The oppositely directed outlet ports deflect molten steel streams at apparent angles between 10-90° relative to the vertical. The nozzle entrance is connected to the source of a liquid I metal. The source of liquid metal in the continuou casting process is called a tundish. The purposes of using a casting nozzle are: (1) to carry liquid metal from the tundish int the mold without exposing the liquid meta; to air; (2) to evenly distribute the liquid metal ii the mold so that heat extraction an solidified shell formation are uniform; an (3) to deliver the liquid metal to the mold ii a quiescent and smooth manner, withoul excessive turbulence particularly at thE meniscus, so as to allow good lubrication, and minimize the potential for surface defect formation. The rate of flow of liquid metal from th€ tundish into the casting nozzle may be controlled ir various ways • Two of the more common methods of controlling the flow rate are: (1) with a stopper rod, and (2) with a slide gate valve. In either instance, the nozzle must mate with the tundish stopper rod or tundish slide gate and the inner bore of the casting nozzle in the entrance region of the nozzle is generally cylindrical and may be radiused or tapered. Heretofore, prior art casting nozzles accomplish the aforementioned first purpose if they are properly submerged within the liquid steel in the mold and maintain their physical integrity. Prior art nozzles, however, do not entirely accomplish the aforementioned second and third purposes. For example, FIGS. 19 and 2 0 illustrate a typical design of a two-ported prior art casting nozzle with a closed end. This nozzle attempts to divide the exit flow into two opposing outlet streams. The first problem with this type of nozzle is the acceleration of the flow within the bore and the formation of powerful outlets which do no1 fully utilize the available area of the exit ports. ThE second problem is jet oscillation and unstable mold flo patterns due to the sudden redirection of the flow in th€ lower region of the nozzle. These problems do not alLo even flow distribution in the mold and cause excessive turbulence. FIG. 20 illustrates an alternative design of c two-ported prior art casting nozzle with a pointed flov divider end. The pointed divider attempts to improve exit jet stability. However, this design experiences the same problems as those encountered with the design of FIG. 18. In both cases, the inertial force of the liquid meta] travelling along the bore towards the exit port region of the nozzle can be so great that it cannot be deflected tc fill the exit ports without flow separation at the top of the ports. Thus, the exit jets are unstable, produce oscillation and are turbulent. Moreover, the apparent deflection angles are not achieved. The actual deflection angles are appreciably less. Furthermore, the flow profiles in the outlet ports are highly non-uniform with low flow velocity at the upper portion of the ports and high flow velocity adjacent the lower portion of the ports. These nozzles produce a relatively large standing wave in the meniscus or surface of the molten steel, which is covered with a mold flux or mold powder for the purpose of lubrication. These nozzles further produce oscillation in the standing wave wherein the meniscus adjacent one mold end alternately rises and falls and the meniscus adjacent the other mold end alternately falls and rises. Prior art nozzles also generate intermittent surface vortices. All of these effects tend to cause entrainment of mold flux in the body of the steel slab, reducing its quality. Oscillation of the standing wave causes unsteady heat transfer through the mold at or near the meniscus. This effect deleteriously affects the uniformity of steel shell formation, mold powder, lubrication, and causes stress ir, the mold copper. These effects become more and more severe as the casting rate increases; and consequently it becomes necessary to limit the casting rate to produce steel of a desired quality. Referring now to FIG. 17, there is shown a nozzle 3 0 similar to that described in Europear. Application 0403808. As is known to the art, molten steel flows from a tundish through a valve or stopper rod intc a circular inlet pipe section 3 0b. Nozzle 3 0 comprises a circular-to-rectangular main transition 34. The nozzle further includes a flat-plateflow divider 32 which directs the two streams at apparent plus and minus 90° angles relative to the vertical. However, in practice the deflection angles are only plus and minus 45°. Furthermore, the flow velocity in outlet ports 46 and 48 is not uniform. Adjacent the right diverging side wall 34C of transition 34 the flow velocity from port 48 is relatively low as indicated by vector 627. Maximum flow velocity from port 48 occurs very near flow divider 3 2 as indicated by vector 622. Due to friction, the flow velocity adjacent divider 32 is slightly less, as indicated by vector 621. The non-uniform flow from outlet port 48 results in turbulence. Furthermore, the flow from ports 46 and 48 exhibit a low frequency oscillation of plus and minus 20° with a period of from 2 0 to 60 seconds. At port 46 the maximum flow velocity is indicated by vector 602 which corresponds to vector 622 from port 48. Vector 602 oscillates between two extremes, one of which is vector 602a, displaced by 65° from the vertical and the other of which is vector 602b, displaced by 25° from the vertical. As shown in FIG. 17a, the flows from ports 4' and 48 tend to remain 90° relative to one another so that when the output from port 46 is represented by vecto: 602a, which is deflected by 65° from the vertical, the output from port 48 is represented by vector 622a which it deflected by 25° from the vertical. At one extreme o: oscillation shown in FIG. 17a, the meniscus Ml at the lefthand end of mold 54 is considerably raised while the meniscus M2 at the right mold end is only slightly raised. The effect has been shown greatly exaggerated for purposes of clarity. Generally, the lowest level of the meniscus occurs adjacent nozzle 30. At a casting rate of thre tons per minute, the meniscus generally exhibits standinc waves of 18 to 30 mm in height. At the extreme o1 oscillation shown, there is a clockwise circulation CI oi large magnitude and low depth in the left mold end and counterclockwise circulation C2 of lesser magnitude anc greater depth in the right mold end. As shown in FIGS. 17a and 17b, adjacent nozzle 30 there is a mold bulge region B where the width of the mold is increased to accommodate the nozzle, which has typical refractory wall thicknesses of 19mm. At the extreme of oscillation shown in FIG. 17a, there is a large surface flow Fl from lefttoright into the bulge regior in front of and behind nozzle 30. There is also a smal3 surface flow F2 from righttoleft toward the bulge region. Intermittent surface vortices V occur in the meniscus in the mold bulge region adjacent the right side of nozzle 30. The highly nonuniform velocity distribution at ports 46 and 48, the large standing waves in the meniscus, the oscillation in the standing waves, and the surf ace vortices all tend to cause entrainment of mold powder or mold flux with a decrease in the quality of the cast steel. In addition, steel shell formation is unsteady and nonuniform, lubrication is detrimentally affected, and stress within mold copper at or near the meniscus is generated. All of these effects are aggravated at higher casting rates. Such prior art nozzles require that the casting rate be reduced. Referring again to FIG. 17, the flow divider may alternately comprise an obtuse triangular wedge 32c having a leading edge included angle of 156°, the sides of which are disposed at angles of 12° from the horizontal, as shown in a first German Application DE 3709188, which provides apparent deflection angles of plus and minus 78°. However, the actual deflection angles are again approximately plus and minus 45°; and the nozzle exhibits the same disadvantages as before. Referring now to FIG. 18, nozzle 30 is similar to that shown in a second German Application DE 4142447 wherein the apparent deflection angles are said to range between 10 and 22 °. The flow from the inlet pipe 3 0b enters the main transition 34 which is shown as having apparent deflection angles of plus and minus 20° as defined by its diverging side walls 34c and 34f and by triangular flow divider 32. If flow divider 32 were omitted, an equipotential of the resulting flow adjacent outlet ports 46 and 48 is indicated at 50. Equipotential 50 has zero curvature in the central region adjacent the axis S of pipe 30b and exhibits maximum curvature at its orthogonal intersection with the right and left sides 34c and 34f of the nozzle. The bulk of the flow in the center exhibits negligible deflection; and only flow adjacent the sides exhibits a deflection'of plus and minus 20°. In the absence of a flow divider, the mean deflections at ports 4 6 and 48 would be less than 1/4 and perhaps 1/5 or 2 0% of the apparent deflection of plus and minus 20°. Neglecting wall friction for the moment, 64a is a combined vector and streamline representing the flow adjacent the left side 34f of the nozzle and 66a is a combined vector and streamline representing the flow adjacent the right side 34c of the nozzle. The initial point and direction of the streamline correspond to the initial point and direction of the vector; and the length of the streamline corresponds to the length of the vector. Streamlines 64a and 66a of course disappear into the turbulence between the liquid in the mold and the liquid issuing from nozzle 30. If a short flow divider 32 is inserted, it acts substantially as a truncated body in two dimensional flow. The vectorstreamlines 64 and 66 adjacent the body are of higher velocity than the vector streamlines 64a and 66a. Streamlines 64 and 66 of course disappear into the low pressure wake downstream of flow divider 32. This low pressure waJce turns the flow adj acent divider 3 2 downwardly. The latter German application shows the triangular divider 3 2 to be only 21% of the length of main transition 34. This is not sufficient to achieve anywhere near the apparent deflections, which would require a much longer triangular divider with corresponding increase in length of the main transition 34. Without sufficient lateral deflection, the molten steel tends to plunge into the mold. This increases the amplitude of the standing wave, not by an increase in height of the meniscus at the mold ends, but by an increase in the depression of the meniscus in that portion of the bulge in front of and behind the nozzle where flow therefrom entrains liquid from such portion of the bulge and produces negative pressures. The prior art nozzles attempt to deflect the streams by positive pressures between the streams, as provided by a flow divider. Due to vagaries in manufacture of the nozzle, the lack of the provision of deceleration or diffusion of the flow upstream of flow division and to low frequency oscillation in the flows emanating from ports 46 and 48, the center streamline of the flow will not generally strike the point of triangular flow divider 32 of FIG. 18. Instead, the stagnation point generally lies on one side or the other of divider 32. For example, if the stagnation point is on the left side of divider 3 2 then there occurs a laminar separation of flow on the right side of divider 32. The separation "bubble" decreases the angular deflection of flow on the right side of divider 32 and introduces further turbulence in the flow from port 48. SUMMARY OF THE INVENTION Accordingly, it is an object of our invention to provide a casting nozzle that improves the flow behavior associated with the introduction of liquid metal into a mold through a casting nozzle. Another object is to provide a casting noz zle wherein the inertial force of the liquid metal flowing through the nozzle is divided and better controlled by dividing the flow into separate and independent streams within the bore of the nozzle in a multiple stage fashion, A further object is to provide a casting nozzle that results in the alleviation of flow separation, and therefore the reduction of turbulence, stabilization of exit jets, and the achievement of a desired deflectior angle for the independent streams. It is also an object to provide a castinc nozzle to diffuse or decelerate the flow of liquid meta] travelling therethrough and therefore reduce the inertia] force of the flow so as to stabilize the exit jets froi the nozzle. It is anoQier object to provide a casting nozzl wherein deflection of the streams is accomplished in parf by negative pressures applied to the outer portions of thi streams, as by curved terminal bending sections, to rende: the velocity distribution in the outlet ports more uniform. A further object is to provide a casting nozzle having a main transition from circular crosssection containing a flow of axial symmetry, to an elongated crosssection with a thickness which is less than the diameter of the circular crosssection and a width which is greater than the diameter of the circular crosssection containing a flow of planar symmetry with generally uniform velocity distribution throughout the transition neglecting wall friction. A still further object is to provide a casting nozzle having a hexagonal crosssection of the main transition to increase the efficiency of flow deflections within the main transition. A still further object is to provide a casting nozzle having diffusion between the inlet pipe and the outlet ports to decrease the velocity of flow from the ports and reduce turbulence. A still further object is to provide a casting nozzle having diffusion or deceleration of the flow within the main transition of crosssection to decrease the velocity of the flow from the ports and improve the steadiness of velocity and uniformity of velocity of streamlines at the ports. A still further object is to provide a casting nozzle having a flow divider provided with a rounded leading edge to permit variation in stagnation point without flow separation. A still further object is to provide a casting nozzle which more effectively utilizes the available space within a bulged or crownshaped mold and promotes an improved flow pattern therein. A still further object is to provide a casting nozzle having a bore with a multifaceted interior geometry which provides greater internal crosssectional area for the bore near a central axis of the casting nozzle than at the edges. A still further object is to provide a casting nozzle which achieves a wide useful range of operational flow throughputs without degrading flow characteristics. A still further object is to provide a casting nozzle with baffles which proportion the flow divided between outer streams and a central stream so that the effective discharge angle of the outer streams exiting upper exit ports varies based on the throughput of liquid metal through the casting nozzle. A still further object is to provide a casting nozzle with baffles which proportion the flow divided between outer streams and a central stream so that the effective discharge angle of the outer streams exitinc upper exit ports increases as the throughput of liquid metal through the casting nozzle increases. It has been found that the above and othei objects of the present invention are attained in a method and apparatus for flowing liquid metal through a castinc nozzle includes an elongated bore having at least one entry port, at least one upper exit port, and at least one lower exit port. A baffle is positioned proximate to the upper exit port to divide the flow of liquid metal through the bore into at least one outer stream and a centra] stream, the outer stream flowing through the upper exit port and the central stream flowing past the baffle anc toward the lower exit port. The baffle is adapted tc allocate the proportion of liquid metal divided betweei the outer stream and the central stream so that the effective discharge angle of the outer stream exitinc through the upper exit port varies based on the flowe throughput of liquid metal through the casting nozzle. Preferably, the effective discharge angle of the outer streams increases as flow throughput increases. In a preferred embodiment, the baffles are adapted so that about 1545%, most preferably 2540%, of the total flow of liquid through the casting nozzle is allocated to the outer streams and about 5585%, most preferably 6075%, of the total flow of liquid through the nozzle is allocated to the central stream. In a preferred embodiment, the theoretical discharge angle of the upper exits ports is about 025°, and most preferably about 710°, downward from the horizontal. The casting nozzle may also include a central axis and at least one entry port and at least one exit port, the bore of the casting nozzle including an enlarged portion to provide the bore with greater crosssectional area near the central axis than near the edges of the bore. In a preferred embodiment, the enlarged portion comprises at least two bending facets, each of which extends from a point on a plane which is substantially parallel to and intersects the central axis, toward c lower edge of the bore. In a preferred embodiment, the bending facets include a top edge and a central edge, anc at least two of the top edges are adjacent to each othei to form a pinnac 1 e pointing generally toward the entr} port. Preferably, the central edge of each bending facet is more distant from a lengthwise horizontal axis of the casting nozzle than the top edge of the bending facel within a horizontal crosssection. It has been found that the above and othei objects of the presfent invention axe attained in a metho and apparatus for flowing liquid metal through a castin nozzle that includes an elongated bore having an entr; port and at least two exit ports. A first baffle i positioned proximate to one exit port and a second baffle is positioned proximate to the other exit port. The baffles divide the flow of liquid metal into two outer streams and a central stream, and deflect the two outer streams in substantially opposite directions. A flow divider positioned downstream of the baffles divides the central stream into two inner streams, and cooperates with the baffles to deflect the two inner streams in substantially the same direction in which the two outer streams are deflected. Preferably, the outer and inner streams recombine before or after the streams exit at least one of the exit ports. In a preferred embodiment, the baffles deflect the outer streams at an angle of deflection of approximately 209 0° from the vertical. Preferably, the baffles deflect the outer streams at an angle of approximately 30° from the vertical. In a preferred embodiment, the baffles deflect the two inner streams in a different direction from the direction in which the two outer streams are deflected. Preferably, the baffles deflect the two outer streams at an angle of approximately 45° from the vertical and deflect the two inner streams at an angle of approximately 3 0° from the vertical. Other features and objects of our invention will become apparent from the following description of the invention which refers to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form part of the instant specification and which are to be read ir conjunction therewith and in which like reference numerals are used to indicate like parts in the various views: FIG. 1 is an axial sectional view looking rearwardly taken along the line 11 of FIG. 2 of a first casting nozzle having a hexagonal smallangle diverging main transition with diffusion, and moderate terminal bending. FIG. la is a fragmentary crosssection looking rearwardly of a preferred flow divider having a rounded leading edge. Fig. lb is an alternate axial sectional view taiken along the line lblb of FIG. 2b of an alternate embodiment of a casting nozzle, having a main transition with deceleration and diffusion, and deflection of the outlet flows. FIG. 2 is an axial sectional view looking to the right taken along the line 22 of FIG. 1. FIG. 2a is an axial sectional view taken along the line 2a2a of FIG. lb. FIG. 3 is a crosssection taken in the plane 33 of FIGS. 1 and 2, looking downwardly. FIG. 3a is a crosssection taken in the plane 3a3a of FIGS, lb and 2a. FIG. 4 is a crosssection taken in the plane 44 of FIGS. 1 and 2, looking downwardly. FIG. 4a is a crosssection taken in the plane 4a4a of FIGS, lb and 2a. FIG. 5 is a crosssection taken in the plane 55 of FIGS. 1 and 2, looking downwardly. FIG. 5a is a crosssection taken in the plane 5a5a of FIGS, lb and 2a. .JIG. 6 is a crosssection taken in the plane 66 of FIGS. 1 and 2, looking downwardly. FIG. 6a is an alternative crosssection taken in the plane 66 of FIGS. 1 and 2, looking downwardly. FIG, 6b is a crosssection taken in the plane 6 6 of FIGS. 13 and 14 and of FIGS. 15 and 16, looking downwardly. FIG. 6c is a crosssection taken in the 6a6a of FIGS, lb and 2a. FIG. 7 is an axial sectional view looking rearwardly of a second casting noz zle having a constant area roundtorectangular transition, a hexagonal small angle diverging main transition with diffusion, and moderate terminal bending. FIG. 8 is an axial sectional view looking to the right of the nozzle of FIG. 7. FIG. 9 is an axial sectional view looking rearwardly of a third casting nozzle having a roundto square transition with moderate diffusion, a hexagonal mediumangle diverging main transition with constant flow area, and low terminal bending. FIG. 10 is an axial sectional view looking to the right of the nozzle of FIG. 9. FIG. 11 is an axial sectional view looking rearwardly of a fourth casting nozzle providing roundto square and squaretorectangular transitions of high total diffusion, a hexagonal highangle diverging main transition with decreasing flow area, and no terminal bending. FIG. 12 is an axial sectional view looking to the right of the nozzle of FIG. 11. Fig. 13 is an axial sectional view looking rearwardly of a fifth casting nozzle similar to that of FIG. 1 but having a rectangular main transition. FIG. 14 is an axial sectional view looking to the right of the nozzle of FIG. 13. FIG. 15 is an axial sectional view looking rearwardly of a sixth casting nozzle having a rectangular smallangle diverging main transition with diffusion, minor flow deflection within the main transition, and higl terminal bending, FIG. 16 is .an axial, sectional view looking tc the right of the. nozzle of FIG. 15. FIG. 17 is an axial sectional view lookinc rearwardly of a prior art nozzle. FIG. 17a is a sectional view, lookinc rearwardly, showing the mold flow patterns produced by th€ nozzle of FIG. 17. FIG. 17b is a crosssection in the curvilinear plane of the meniscus, looking downwardly, and showing the surface flow patterns produced by the nozzle of FIG. 17. FIG. 18 is an axial sectional view lookinc rearwardly of a further prior art nozzle. FIG. 19 is an axial sectional view of another prior art nozzle. FIG. 20 is a partial side sectional view of the prior art nozzle of FIG. 19. FIG. 21 is an axial sectional view of another prior art nozzle. FIG. 22 is top plan view on arrow A of the prior art nozzle of FIG 21. FIG. 23 shows an axial sectional view of an alternative embodiment of a casting nozzle of the present invention. FIG. 24 shows a crosssectional view of FIG. 23 taken across line AA of FIG. 23. FIG. 25 shows a crosssectional view of FIG. 23 taken across line BB of FIG. 23. FIG. 26 shows a partial side axial sectional view of the casting nozzle of FIG. 23. FIG. 27 shows a side axial sectional view of the casting nozzle of FIG. 23. FIG. 28 shows an axial sectional view of an alternative embodiment of a casting nozzle of the present invention. FIG. 29 shows a side axial sectional view of the casting nozzle of FIG'. 28. Fig. 30 shows an axial sectional view of an alternative embodiment of a casting nozzle of the present invention. Fig. 30A shows a crosssectional view of Fig. 30 taken across line AA of Fig. 30. Fig. 30B shows a crosssectional view of Fig. 30 taken across line BB of Fig. 30. Fig. 30C shows a crosssectional view of Fig. 30 taken across line CC of Fig. 30. Fig. 30D shows a crosssectional view of Fig. 30 taken across line DD of Fig. 30. Fig. 30EE is a partial plan view of an exit port of the casting nozzle of Fig. 30 looking along arrow EE. Fig. 31 shows a side axial sectional view of the casting nozzle of Fig. 30. Fig. 3 2 shows an axial sectional view of an . alternative embodiment of a casting nozzle of the present invention. Fig. 32A shows a crosssectional view of Fig. 32 taken across line AA of Fig. 32. Fig. 32B shows a crosssectional view of Fig. 32 taken across line BB of Fig. 32. Fig. 32C shows a crosssectional view of Fig. 32 taken across line CC of Fig. 32. Fig. 32D shows a crosssectional view of Fig. 3 2 taken across line DD of Fig. 32. Fig. 32E shows a crosssectional view of Fig. 32 taken across line EE of Fig. 32. Fig. 33 shows a side axial sectional view of the casting nozzle of Fig. 32. Fig 34A shows an axial sectional view of the casting nozzle of Fig 32 and illustrates the effective discharge angles of exit jets at low throughput flow. Fig 34B shows an axial sectional view of the casting nozzle of Fig. 32 and illustrates the effective discharge angles of exit jets at medium throughput flow. Fig. 34C shows an axial sectional view of the casting nozzle of Fig. 32 and illustrates the effective discharge angles of exit jets at high throughput flow. Fig. 3 5 shows an axial sectional view of an alternative embodiment of a casting nozzle of the present invention. Fig. 35A shows a crosssectional view of Fig. 35 taken across line AA of Fig. 35. Fig. 35B shows a crosssectional view of Fig. 35 taken across line BB of Fig. 35. Fig. 35C shows a crosssectional view of Fig. 35 taken across line CC of Fig. 35. Fig. 35D shows a crosssectional view of Fig. 35 taken across line DD of Fig. 35. Fig. 35E shows a crosssectional view of Fig. 35 taken across line EE of Fig. 35. Fig. 35QQ is a partial plan view of an upper exit port of the casting nozzle of Fig. 35 looking along arrow QQ. Fig. 3 5RR is a partial plan view of a lower exit port of the casting nozzle of Fig. 35 looking along arrow RR. Fig. 36 shows a side axial sectional view of the casting nozzle of Fig. 35. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. lb and 2a, the casting nozzle is indicated generally by the reference numeral 30. The upper end of the nozzle includes an entry nozzle 30a terminating in a circular pipe or bore 30b which extends downwardly, as shown in FIGS, lb and 2a, The axis of pipe section 30b is considered as the axis S of the nozzle. Pipe section 3 0b terminates at the plane 3a3a which, as can be seen from FIG. 3a, is of circular crosssection. The flow then enters the main transition indicated generally by the reference numeral 34 and preferably having four walls 34a through 34d. Side walls 34a and 34b each diverge at an angle from the vertical. Front walls 34c and 34d converge with rear walls 34a and 34b. It should be realized by those skilled in the art that the transition area 34 can be of any shape or crosssectional area of planar symmetry and need not be limited to a shape having the number of walls (four of six walls) or cross sectional areas set forth herein just so long as the transition area 34 changes from a generally round cross sectional area to a generally elongated crosssectional area of planar symmetry, see FIGS. 3a, 4a, 5a, 6c. For a conical twodimensional diffuser, it is customary to limit the included angle of the cone to approximately 8° to avoid undue pressure loss due to incipient separation of flow. Correspondingly, for a one dimensional rectangular diffuser, wherein one pair of opposed walls are parallel, the other pair of opposed walls should diverge at an included angle of not more than 16°; that is, plus 8° from the axis for one wall and minus 8° from the axis for the opposite wall. For example, in the diffusing main transition 34 of FIG. lb, a 2.65° mean convergence of the front walls and a 5.2° divergence of side walls yields.an equivalent onedimensional,divergence of the side walls of 10.4 5.3 = 5.1°, approximately, which is less than the 8° limit. FIGS. 4a, 5a and 6c are crosssections taken ir the respective planes 4a4a, 5a5a and 6c6c of FIGS. Ik and 2a, which are respectively disposed below plane 3a3a. FIG. 4a shows four salient corners of large radius; FIG. 5a shows four salient corners of medium radius; and FIG. 6c shows four salient corners of small radius. The flow divider 32 is disposed below the transition and there is thus created two axis 35 and 37. The included angle of the flow divider is generally equivalent to the divergence angle of the exit walls 38 and 3 9. The area in plane 3a3a is greater than the area of the two angled exits 35 and 37; and the flow from exits 35 and 37 has a lesser velocity than the flow in circular pipe section 30b. This reduction in the mean velocity of flow reduces turbulence occasioned by liquid from the nozzle entering the mold. The total deflection is the sum of that produced within main transition 34 and that provided by the divergence of the exit walls 38 and 39. It has been found that a total deflection angle of approximately 30° is nearly optimum for the continuous casting of thin steel slabs having widths in the range from 975 to 1625 mm or 38 to 64 inches, and thicknesses in the range of 50 to 6 0 mm. The optimum deflection angle is dependent on the width of the slab and to some extent upon the length, width and depth of the mold bulge B. Typically the bulge may have a length of 800 to 1100 mm, a width of 150 to 200 mm and a depth of 700 to 800 mm. Referring now to FIGS. 1 and 2, an alternative casting nozzle is indicated generally by the reference numeral 30. The upper end of the nozzle includes an entry nozzle 30a terminating in a circular pipe 30b of 76 mm inside diameter which extends downwardly, as shown in FIGS. 1 and 2. The axis of pipe section 30b is considered as the axis S of the nozzle. Pipe section 30b terminates at the plane 33 which, as can be seen from FIG. 3, is of circular crosssection and has an area of 4536 mm2. The flow then enters the main transition indicated generally by the reference numeral 34 and preferably having six walls 34a through 3 4f. Side walls 34c and 34f each diverge at an angle, preferably an angle of 10° from the vertical. Front walls 34d and 34e are disposed at small angles relative to one another as are rear walls 3 4a and 34b. This is explained in detail subsequently. Front walls 34d and 34e converge with rear walls 34a and 34b, each at a mean angle of roughly 3.8° from the vertical. For a conical twodimensional diffuser, it is customary to limit the included angle of the cone to approximately 8° to avoid undue pressure loss due to incipient separation of flow. Correspondingly, for a one dimensional rectangular diffuser, wherein one pair of opposed walls are parallel, the other pair of opposed walls should diverge at an included angle of not more than 16°; that is, plus 8° from the axis for one wall and minus 8° from the axis for the opposite wall. In the diffusing main transition 3 4 of FIG. 1, the 3.8° mean convergence of the front and rear walls yields an equivalent one dimensional divergence of the side walls of 10 3.8 = 6.2°, approximately, which is less than the 8° limit. FIGS. 4, 5 and 6 are crosssections taken in the respective planes 44, 55 and 66 of FIGS. 1 and 2, which are respectively disposed 100, 2 00 and 351.6 mm below plane 33. The included angle between front walls 34e and 34d is somewhat less than 180° as is the included angle between rear walls 34a and 34b. FIG. 4 shows four salient corners of large radius; FIG. 5 shows four salient corners of medium radius; and FIG". 6 shows four salient corners of small radius. The intersection of rear walls 34a and 3 4b may be provided with a filet or radius, as may the intersection of front walls 3 4d and 3 4e. The length of the flow passage is 111.3 mm in FIG. 4, 146.5 mm in FIG. 5, and 200 mm in FIG. 6. Alternatively, as shown in FIG. 6a, the cross section in plane 66 may have four salient corners oi substantially zero radius. The front walls 34e and 34c and the rear walls 34a and 34b along their lines of intersection extend downwardly 17.6 mm below plane 66 tc the tip 32a of flow divider 32. There is thus created twc exits 35 and 37 respectively disposed at plus and minus 10° angles relative to the horizontal. Assuming that transition 34 has sharp salient corners in plane 66, as shown in FIG. 6a, each of the angled exits would b€ rectangular, having a slant length of 101.5 mm and a width of 28.4 mm, yielding a total area of 5776 mm2. The ratio of the area in plane 33 to the area of the two angled exits 35 and 37 is TT/4 = .785; and the flow from exits 35 and 37 has 78.5% of the velocity ir circular pipe section 30b. This reduction in the mear velocity of flow reduces turbulence occasioned by liquid from the nozzle entering the mold. The flow from exits 3 = and 37 enters respective curved rectangular pipe sections 38 and 40. It will subsequently be shown that the flow ir main transition 34 is substantially divided into twc streams with higher fluid velocities adjacent side walls 34c and 34f and lower velocities adjacent the axis. This implies a bending of the flow in two opposite directions in main transition 34 approaching plus and minus 10°. The curved rectangular pipes 38 and 40 bend the flows through further angles of 20°. The curved sections terminate at lines 39 and 41. Downstream are respective straight rectangular pipe sections 42 and 44 which nearly equalize the velocity distribution issuing from the bending sections 3 8 and 40. Ports 4 6 and 4 8 are the exits of respective straightsections 42 and 44. It is desirable that the inner walls 38a and 40a of respective bendinc sections 3 8 and 4 0 have an appreciable radius of curvature, preferably not much less than half that of outer walls 38b and 40b. The inner walls 38a and 40a ma have a radius of 100 mm; and outer walls 38b and 40b wouL have a radius of 201.5 mm. Walls 38b and 40b are define by flow divider 3 2 which has a sharp leading edge with a: included angle of 20°. Divider 32 also defines walls 42: and 44b of the straight rectangular sections 42 and 44. It will be understood that adjacent inner wall 38a and 40a there is a low pressure and hence hig velocity whereas adjacent outer walls 38b and 40b there is a high pressure and hence low velocity. It is to be note that this velocity profile in curved sections 38 and 40 is opposite to that of the prior art nozzles of FIGS. 17 am 18. Straight sections 42 and 44 permit the highvelocit; lowpressure flow adjacent inner walls 3 8a and 40a o bending sections 38 and 40 a reasonable distance alon walls 42a and 44a within which to diffuse to lowe: velocity and higher pressure. The total deflection is plus and minus 3 0 comprising 10° produced within main transition 34 and 20 provided by the curved pipe sections 38 and 40. It ha; been found that this total deflection angle is nearl; optimum for the continuous casting of steel slabs havin widths in the range from 975 to 1625 mm or 38 to 6 inches. The optimum deflection angle is dependent on the width of the slab and to some extent upon the length width and depth of the mold bulge B. Typically the bulgi may have a length of 800 to 1100 mm, a width of 150 to 20i mm and a depth of 700 to 800 mm. Of course it will by understood that where the section in plane 66 is as show in FIG. 6, pipe sections 38, 40, 42 and 44 would no longe: be perfectly rectangular but would be only generally so It will be further appreciated that in FIG. 6, side wall: 34c and 34f may be substantially semicircular with n straight portion. The intersection of rear walls 34a an 34b has been shown as being very sharp, as along a line to improve the clarity of the drawings. In FIG. 2, 340k and 340d represent the intersection of side wall 34c with respective front and rear walls 3 4b and 34d, assuming square salient corners as in FIG. 6a. However, due tc rounding of the four salient corners upstream of plane 6 6, lines 340b and 340d disappear. Rear walls 34a and 34k are oppositely twisted relative to one another, the twist being zero in plane 33 and the twist being nearly maximuit in plane 66. Front walls 34d and 34e are similarly twisted. Walls 38a and 42a and walls 40a and 44a may be considered as flared extensions of corresponding side walls 34f and 34c of the main transition 34. Referring now to FIG, la, there is shown on ar enlarged scale a flow divider 32 provided with a roundec leading edge. Curved walls 38b and 40b are each provided with a radius reduced by 5 mm, for example, from 201.5 tc 196.5 mm. This produces, in the example, a thickness oi over 10mm within which to fashion a rounded leading edge of sufficient radius of curvature to accommodate the desired range of stagnation points without producing laminar separation. The tip 32b of divider 3 2 may hi semielliptical, with vertical semimajor axis. Preferably tip 32b has the contour of an airfoil such, foi example, as an NACA 0024 symmetrical wing section ahead ol the 30% chord position of maximum thickness, Correspondingly, the width of exits 3 5 and 37 may b increased by 1.5 mm to 29.9 mm to maintain an exit area ol 5776 mm2. Referring now to FIGS. 7 and 8, the uppe: portion of the circular pipe section 30b of the nozzle has been shown broken away. At plane 33 the section is circular. Plane "1616 is 50mm below plane 33. the crosssection is rectangular, 76 mm long and 59.7 mm wid so that the total area is again 4536 mm2. The circularto rectangular transition 52 between planes 33 and 1616 ca: be relatively short because no diffusion of flow occurs. Transition 52 is connected to a 25 mm height of rectangular pipe 54, terminating at plane 1717, to stabilize the flow from transition 52 before entering the diffusing main transition 34, which is now entirely rectangular. The main transition 34 again has a height of 351.6 mm between planes 1717 and 66 where the cross section may be perfectly hexagonal, as shown in FIG. 6a. The side walls 34c and 34f diverge at an angle of 10° from the vertical, and the front walls and rear walls converge at a mean angle, in this case, of approximately 2.6° from the vertical. The equivalent onedimensional diffuser wall angle is now 10 2.6 = 7.4°, approximately, which is still less than the generally used 8° maximum. The rectangular pipe section 54 may be omitted, if desired, sc that transition 52 is directly coupled to main transitior. 34. In plane 66 the length is again 200 mm and the widtfc adjacent wal 1 s 34c and 34f is again 28.4 mm. At the centerline of the nozzle the width is somewhat greater. The crosssections in planes 44 and 55 are similar tc those shown in FIGS. 4 and 5 except that the four salieni corners are sharp instead of rounded. The rear walls 3 4c and 34b and the front walls 34d and 34e intersect alone lines which meet the tip 32a of flow divider 32 at a poin 17.6 mm below plane 66. Angled rectangular exits 3 5 an 3 7 again each have a slant length of 101.5 mm and a widtl of 28.4 mm yielding a total exit area of 5776 mm2. Th twisting of front wall 34b and rear wall 34d is clear1 seen in FIG. 8. In FIGS. 7 and 8, as in FIGS. 1 and 2, the flow from exits 3 5 and 37 of transition 34 pass throug respective rectangular turning sections 38 and 40, wher the respective flows are turned through an additional 2 0 relative to the vertical, and then through respectiv straight rectangular equalizing sections 42 and 44. Th flows from sections 42 and 44 again have total deflections of plus and minus 30° from the vertical. The leading edge of flow divider 32 again has an included angle of 20°. Again it is preferable that the flow divider 32 has a rounded leading edge and a tip (32b) which is semi elliptical or of airfoil contour as in FIG. la. Referring now to FIGS. 9 and 10, between planes 33 and 1919 is a circulartosquare transition 56 with diffusion. The area in plane 1919 is 76= » 5776mm2. The distance between planes 33 and 1919 is 7 5 mm; which is equivalent to a conical diffuser where the wall makes ar angle of 3.5° to the axis and the total included angle between walls is 7.0°. Side walls 34c and 3 4f of transition 34 each diverge at an angle of 20° from the vertical while rear walls 34a34b and front walls 34d34e converge in such a manner as to provide a pair ol rectangular exit ports 35 and 37 disposed at 20° angles relative to the horizontal. Plane 2020 lies 156.6 mi below plane 1919. In this plane the length between walls 34c and 34f is 190 mm. The lines of intersection of the rear walls 34a34b and of the front walls 34d34e extenc 34.6 mm below plane 2020 to the tip 32a of divider 32. The two angled rectangular exit ports 35 and 37 each hav a slant length of 101.1 mm and a width of 28.6 mm yieldinc an exit area of 5776 mm2 which is the same as the entrance area of the transition in plane 1919. There is no nei diffusion within transition 34. At exits 35 and 37 ar disposed rectangular turning sections 38 and 40 which, ii this case, deflect each of the flows only through a; additional 10°. The leading edge of flow divider 32 ha an included angle of 40°. Turning sections 38 and 40 ar followed by respective straight rectangular sections 4 and 44. Again, the inner walls 38a and 40a of sections 3 and 40 may have a radius of 100 mm which is nearly half o the 201.1 mm radius of the outer walls 38b and 40b. Th total deflection is again plus and minus 30°. Preferably flow divider 3 2 is provided with a rounded leading edge and a tip (3 2b) which is semielliptical or of airfoil contour by reducing the radii of walls 38b and 40b and, if desired, correspondingly increasing the width of exits 3 5 and 37. Referring now to FIGS, 11 and 12, in plane 33 the crosssection is again circular; and in plane 1919 the crosssection is square. Between planes 33 and 1919 is a circulartosquare transition 56 with diffusion. Again, separation in the diffuser 56 is obviated by making the distance between planes 33 and 1919 75 mm. Again the area in plane 1919 is 762 = 5776 mm2. Between plane 1919 and plane 2121 is a onedimensional squareto rectangular diffuser. In plane 2121 the length is (4/7r)76= 96.8 mm and the width is 76 mm, yielding an area of 7354 mm2. The height of diffuser 58 is also 75 mm; and its side walls diverge at 7.5° angles from the vertical. In main transition 34, the divergence of each of side walls 34c and 34f is now 30° from the vertical. To ensure against flow separation with such large angles, transition 34 provides a favorable pressure gradient wherein the area of exit ports 35 and 37 is less than in the entrance plane 2121. In plane 2222, which lies 67.8 mm below plane 21 21, the length between walls 34c and 34f is 175 mm. Angled exit ports 35 and 37 each have a slant length of 101.0 mm and a width of 28.6 mm, yielding an exit area of 5776 mm2. The lines of intersection of rear walls 34a34b and front walls 34d34e extend 50.5 mm below plane 2222 to the tip 32a of divider 32. At the exits 35 and 37 of transition 34 are disposed two straight rectangular sections 42 and 44. Sections 42 and 44 are appreciably elongated to recover losses of deflection within transition 34. There are no intervening turning sections 38 and 40; and the deflection is again nearly plus and minus 30° as provided by main transition 34. Flow divider 32 is a triangular wedge having a leading edge included angle of 60°. Preferably divider 32 is provided with a rounded leading edge and a tip (32b) which is of semi elliptical or airfoil contour, by moving walls 42a and 42t outwardly and thus increasing the length of the base of divider 32. The pressure rise in diffuser 58 is, neglecting friction, equal to the pressure drop which occurs in main transition 34. By increasing the width of exits 35 and 37, the flow velocity can be further reduced while still achieving a favorable pressure gradient ir transition 34. In FIG. ll, 52 represents an equipotential oi flow near exits 35 and 37 of main transition 34. It wil] be noted that equipotential 52 extends orthogonally tc walls 34c and 34f, and here the curvature is 2ero. As equipotential 52 approaches the center of transition 34, the curvature becomes greater and greater and is maximui at the center of transition 34, corresponding to axis S, The hexagonal crosssection of the transition thus provides a turning of the flow streamlines withii transition 34 itself. It is believed the mean deflectior efficiency of a hexagonal main transition is more than 2/: and perhaps 3/4 or 75% of the apparent deflection produce by the side walls. In FIGS. 12 and 78 the 2.5° loss from 10° i] the main transition is almost fully recovered in the bending and straight sections. In FIGS. 910 the 5° los." from 20° in the main .transition is nearly recovered in the bending and straight sections. In FIGS. 1112 the 7.5 loss from 30° in the main transition is mostly recovere in the elongated straight sections. Referring now to FIGS. 13 and 14, there is show a variant of FIGS. 1 and 2 wherein the main transition 3 is provided with only four walls, the rear wall being 34a and the front wall being 34de. The crosssection in plane 66 may be generally rectangular as shown in FIG. 6b. Alternatively, the crosssection may have sharp corners of zero radius. Alternatively, the side walls 34c and 34f may be of semicircular crosssection with no straight portion, as shown in FIG. 17b. The crosssections in planes 44 and 55 are generally as shown in FIGS. 4 and 5 except, of course, rear walls 34a and 34b are collinear as well as front walls 34e and 34d. Exits 3 5 and 37 both lie in plane 66. The line 35a represents the angled entrance to turning section 38; and the line 37a represents the angled entrance to turning section 40. Flow divider 32 has a sharp leading edge with an included angle of 20°. The deflections of flow in the lefthand and righthand portions of transition 34 are perhaps 2 0% of the 10° angles of side walls 34c and 34f, or mean deflections of plus and minus 2°. The angled entrances 35a and 37a of turning sections 38 and 40 assume that the flow has been deflected 10° within transition 34. Turning sections 38 and 40 as well as the following straight sections 42 and 44 will recover most of the 8° loss of deflection within transition 34; but it is not to be expected that the deflections from ports 4 6 and 48 will be as great as plus and minus 30°. Divider 32 preferably has a rounded leading edge and a tip (32b) which is semi elliptical or of airfoil contour as in FIG. la. Referring now to FIGS. 15 and 16, there is shown a further nozzle similar to that shown in FIGS. 1 and 2. Transition 34 again has only four walls, the rear wall being 34ab and the front wall being 34de. The cross section in plane 66 may have rounded corners as shown in FIG. 6b or may alternatively be rectangular with sharp corners. The crosssections in planes 44 and 55 are generally as shown in FIGS. 4 and 5 except rear walls 34a 34b are collinear as are front walls 34d34e. Exits 35 and 37 both lie in plane 66. In this embodiment of the invention, the deflection angles at exits 3537 ars assumed to be 0°. Turning sections 38 and 40 each defied their respective flows through 30°. In this case, if flo divider 32 were to have a sharp leading edge, it would b in the nature of a cusp with an included angle of 0°, which construction would be impractical. Accordingly, walls 3 8b and 4 0b have a reduced radius so that the leading edge of the flow divider 32 is rounded and the tij (32b) is semielliptical or preferably of airfoil contour The total deflection is plus and minus 3 0° as providec solely by turning sections 38 and 40, Outlet ports 46 an 48 of straight sections 42 and 44 are disposed at an anglt from the horizontal of less than 30°, which is the floi deflection from the vertical. Walls 42a and 44a are appreciably longer tha: walls 42b and 44b. Since the pressure gradient adjacen walls 42a and 44a is unfavorable, a greater length i: provided for diffusion. The straight sections 42 and 4 of FIGS. 1516 may be used in FIGS. 12, 78, 910, an 1314. Such straight sections may also be used in FIGS 1112; but the benefit would not be as great. It will b noted that for the initial onethird of turning section; 38 and 40 walls 38a and 40a provide less apparen' deflection than corresponding side walls 34f and 34c However, downstream of this, flared walls 3 8a and 40a an flared walls 42a and 44a provide more apparent deflectio: than corresponding side walls 34f and 34c. In an initial design similar to FIGS 13 and 1 which was built and successfully tested, side walls 34 and 34f each had a divergence angle of 5.2° from th vertical; and rear wall 34ab and front wall 34de eac converged at an angle of 2.65° from the vertical. I plane 33, the flow crosssection was circular with diameter of 76 mm. In plane 44, the flow crosssectio was 95.5 mm long and 66.5 mm wide with radii of 28.5 mn for the four corners. In plane 55 the crosssection was 115 mm long and 57.5 mm wide with radii of 19 mm for the corners. In plane 66, which was disposed 150 mm, instead of 151.6 mm, below plane 55, the crosssection was 144 mn long and 43.5 mm wide with radii of 5 mm for the corners; and the flow area was 6243mm2. Turning sections 38 and 4C were omitted. Walls 42a and 44a of straight sections 4C and 42 intersected respective side walls 34f and 34c ir plane 66. Walls 42 and 44a again diverged at 30° fron the vertical and were extended downwardly 95 mm belo plane 66 to a seventh horizontal plane. The sharj leading edge of a triangular flow divider 32 having ar included angle of 60° (as in FIG. 11) was disposed in this seventh plane. The base of the divider extended 110 mn below the seventh plane. The outlet ports 4 6 and 48 each had a slant length of 110 mm. It was found that the tops of ports 4 6 and 4 8 should be submerged at least 150 mn below the meniscus. At a casting rate of 3.3 tons pei minute with a s lab width of 1384 mm, the height of standing waves was only 7 to 12 mm; no surface vortices formed in the meniscus; no oscillation was evident for mold widths less than 1200 mm; and for mold width greater than this, the resulting oscillation was minimal. It is believed that this minimal oscillation for large mole widths may result from flow separation on walls 42a anc 44a, because of the extremely abrupt terminal deflection, and because of flow separation downstream of the sharj leading edge of flow divider 32. In this initial design, the 2.65° convergence of the front and rear walls 34ab anc 34de was continued in the elongated straight sections 42 and 44. Thus these sections were not rectangular with f mm radius corners but were instead slightly trapezoidal, the top of outlet ports 46 and 48 had a width of 35 mm anc the bottom of outlet ports 46 and 48 had a width of 24.1 mm. We consider that a section which is slightly trapezoidal is generally rectangular. Referring now to FIGS. 2329, there is shown alternative embodiments of the present invention. These casting nozzles are similar to the casting nozzles of the present invention, but include baffles 100106 tc incorporate multiple stages of flow division into separate streams with independent deflection of these streams within the interior of the nozzle. It should be realized, however, by those skilled in the art that the baffles dc not have to be used with the nozzles of the present invention, but can be used with any of the known or prior art casting or submerged entry nozzles just so long as the baffles 100106 are used to incorporate multiple stages of flow division into separate streams with independent deflection of these streams within the interior of the nozzle. With respect to FIGS. 2327, there is shown a casting nozzle 30 of the present invention, e.g., a casting nozzle having a transition section 34 where there is a transition from axial symmetry to planar symmetry within this section so as to diffuse or decelerate the flow and therefore reduce the inertial force of the flow exiting the nozzle 30. After the metal flow proceeds along the transition section 34, it encounters baffles 100, 102 which are located within or inside the nozzle 30. Preferably, the baffles should be positioned so that the upper edges 101, 103 of the baffles 100, 102, respectively, are upstream of the exit ports 46, 48. The lower edges 105, 107 of the baffles 100, 102, respectively, may or may not be positioned upstream of the exit ports 46, 48, Although it is preferred that the lower edges 105, 107 aire positioned upstream of the exit ports 46, 48. The baffles 100, 102 function to diffuse the liquid metal flowing through the nozzle 3 0 in multiple stages. The baffles first divide the flow into three separate streams 108, 110 and 112. The streams 108, 112 are considered the outer streams and the stream 114 is considered a central stream. The baffles 100, 102 include upper faces 114, 116, respectively, and lower faces 118, 120, respectively. The baffles 100, 102 cause the twc outer streams 108, 112 to be independently deflected ir opposite directions by the upper faces 114, 116 of the baffles. The baffles 100, 102 should be constructed anc arranged to provide an angle of deflection of approximately 20 90°, preferably, 30°, from the vertical. The central stream 114 is diffused by the diverging lower faces 118, 120 of the baffles. The central stream 114 is subsequently divided by the flov divider 32 into two inner streams 122, 124 which are oppositely deflected at angles matching the angles that the outer streams 108, 112 are deflected, e.g., 20 90°, preferably 30°, from the vertical. Because the two inner streams 122, 12 4 are oppositely deflected at angles matching the angles that the outer streams 108, 112 are deflected, the outei streams 108, 112 are then recombined with the innei streams 122, 124, respectively, i.e., its matching stream, within the nozzle 30 before the streams of molten meta] exit the nozzle 3 0 and are released into a mold. The outer streams 108, 112 recombine with the inner streams 122, 124, respectively, within the nozzle 3C for an addition reason. The additional reason is that ii the lower edges 105, 107 of the baffles 100, 102, are upstream of the exit ports 46, 48, i.e., do not full] extend to the exit ports 46, 48, the QiAt&T streams 108, 112,are no iongfegsy being physicallyC separated from the inner streams 122, 124 before the streams exit the nozzle 30. FIGS. 2 829 show an alternative embodiment of the casting nozzle 30 of the present invention. In this embodiment, the upper edges 13 0, 132, but not the lower edges 126, 128, of the baffles 104, 106 are positioned upstream of the exit ports 46, 48. This completely separates the outer streams 108, 112 and the inner streams 122, 124 within the nozzle 30. Moreover, in this embodiment, the deflection angles of the outer streams 108, 112 and the inner streams 122, 124 do not match. As a result, the outer streams 108, 112 and the inner streams 122, 124 do not recombine within the nozzle 30. Preferably, the baffles 104, 106 and the flo divider 32 are constructed and arranged so that the outei streams 108, 112 are deflected about 45° from the vertical, and the inner streams 122, 124 are deflectec about 30° from the vertical. Depending on the desirec mold flow distribution, this embodiment allows independenl adjustment of the deflection angles of the outer and innea streams. Referring now to Figs. 3 0 and 31, there is showi another alternative embodiment of the present invention A bifurcated casting nozzle 140 is provided which has tw exit ports 146, 148 and is similar to other casting nozzl embodiments of the present invention. The casting nozzl 140 of Figs. 3 0 and 31, however, includes a faceted o: "diamondback" internal geometry giving the nozzle greate: internal crosssectional area at the central axis o: center line CL of the nozzle than at the edges of th nozzle. Near the Dottom or exit end of the trans it io section 134 of casting nozzle 140, two angled, adjacen edges 142 extend downward from the center of each of th interior broad faces of casting nozzle 140 toward the top of the exit ports 146 and 148. Edges 142 preferably fon a pinnacle 143 between sections BB and CC pointinc upwards towards entry port 141, and comprise the top edges of interior bending facets 144a and 144b. These bendinc facets 144a and 144b comprise the diamondback interna: geometry of nozzle 140. They converge at a central edge 143a and taper outward toward the exit ports 146, 148 frox central edge 143a. Top edges 142 preferably generally match the discharge angle of exit ports 146 and 148, thereby, promoting flow deflection or bending of the liquid metai flow to the theoretical discharge angle of exit ports 14( and 148. The discharge angle of exit ports 146 and 14 should be about 4580° downward from the horizontal. Preferably, the discharge angle should be about 60' downward from the horizontal. Matching the top edges 142 to the discharge angle of exit ports 146 and 148 minimizes flow separatioi at the top of the exit ports and minimizes separation froi the sidewall edges as the flow approaches the exit ports, Moreover, as most clearly seen in Figs. 30, 30C and 3 0D, bending facets 144a and 144b are more distant from lengthwise axis LA at a central edge 143a than at the toj edge 142 within the same horizontal crosssection. As result, greater internal crosssectional area is providec near the central axis of the casting nozzle than at the edges. As shown in Fig. 30EE, the diamondback interior geometry causes exit ports 146 and 148 to be wider at the bottom of the port than at the top, i.e., wider near flow divider 149, if present. As a result, the diamond back port configuration more naturally matches the dynamic pressure distribution of the flow within the nozzle 140 ij the region of the exit ports 14 6 and 148 and thereb; produces more stable exit jets. Referring now to Figs. 3234, there is shown another alternative embodiment of the present invention The casting nozzle 150 of Figs. 3234 is similar to other casting noz z le embodiments of the present invention. Casting nozzle 150, however, is configured to proportion the amount of flow that is distributed between upper and lower exit ports 153 and 155, respectively, and produce varying effective discharge angles of upper exit jets which exit upper exit ports 153 depending on the throughput flow of liquid metal through the casting nozzle 150. As shown in Figs. 32 and 33, casting nozzle 150 preferably incorporates multiple stages of flow division as described in the casting nozzle embodiments of the present invention set forth above. Casting nozzle 150 includes baffles 156 which, in conjunction with the lower faces 160a of sidewalls 160 and top faces 156a of baffles 156, define upper exit channels 152 which lead to upper exit ports 153. Casting nozzle 150 may optionally include a lower flow divider 158 positioned substantially along the center line CL of casting nozzle 150 and downstream of baffles 156 in the direction of flow through the nozzle. With lower flow divider 158, bottom faces 156b of baffles 156 and top faces 158a of lower flow divider 158 would then define lower exit channels 154 which lead to lower exit ports 155. Sidewalls 160, baffles 156 and flow divider 158 are preferably configured so that the theoretical discharge angle of the upper exit ports diverges from the theoretical discharge angle of the upper exit ports by at least about 15°. Preferably, sidewalls 160 and baffles 156 provide upper exit ports 153 having a theoretical discharge angle of about 025°, most preferably about 7 10°, downward from the horizontal. Baffles 156 and lower flow divider 158 preferably provide lower exit ports 15 having a theoretical discharge angle of about 4580°, mos preferably about 6070°, downward from the horizontal. If casting nozzle 150 does not include flo divider 158, casting nozzle 150 would then only includ one lower exit port 155, not shown, def ined by botto faces 156b of baffles 156. Lower exit port 155 would the have a theoretical discharge angle of about 4590°. Referring now to Figs. 3234, in practice baffles 156 initially divide the flow of liquid meta through the bore 151 into three separate streams: namely two outer streams and one central stream. The two oute streams are deflected by the upper exit ports 153 to th theoretical discharge angle of about 025° downward fro the horizontal and in opposite directions from the cente line CL. These outer streams are discharged from th upper exit ports 153 as upper exit jets into the mold. Meanwhile, the central stream proceeds downwar through bore 151 and between the baffles 156. Thi central stream is further divided by the lower flo divider 158 into two inner streams which are oppositel deflected from the center line CL of the nozzle 150 i accordance with the curvature of the bottom faces 156b o the baffles 156 and the top faces 158a of the lower flo divider 158. The curvature or shape of the top faces 156a o the baffles 156 or the shape of the baffles 156 themselve should be sufficient to guide the two outer streams to th theoretical discharge angle of the upper exit ports 153 o about 025° from the horizontal, although about 710° i preferred. Moreover, the configuration or shape o sidewall lower faces 160a and baffles 156 including th curvature or slope of the top faces 156a should t sufficient to keep substantially constant the cross sectional area of the upper exit channels 152 to uppej exit ports 153. The curvature or shape of the bottom faces 1561 of the baffles 156 and the top faces 153a of the flo divider 158 should be sufficient to guide the two inne: streams to the theoretical discharge angle of the lowei exit ports 155 of about 4580° downward from the horizontal, although about 6070° is preferred. This significantly diverges from the preferred theoretical discharge angle of about 710° of the upper exit port 153, The location of leading edges 156c of the baffles 156 in relation to the crosssection of the casting nozzle bore immediately above the leading edges 156c, e.g., Fig. 3 2E, determines the theoretical proportion of the flow which is divided between the outea streams and the central stream. Preferably, baffles 15 are located to produce a symmetric division of the flo (i.e. equivalent flow in each of the outer streams througi the upper exit ports 153) . Preferably, a larger proportion of the totai flow is allocated to the central stream than to the outei streams. In particular, it is advantageous to construd casting nozzle 150 and position the leading edges 156c ol baffles 156 in relation to the crosssection of the casting nozzle bore immediately above the leading edge 156c so that about 1545%, preferably about 2540%, of the total flow through the casting nozzle 150 is associatec with the two outer streams of the upper exit ports 153, and the remaining 5585%, preferably about 6075%, of the total flow is associated with the central stream which is discharged as the two inner streams through the lower exi ports 155 (or one central stream through lower exit por 155 if the casting nozzle 150 does not include lower floi divider 158) . Proportioning the flow between the uppe: and lower exit ports 153 and 155 so that the lower exi ports 155 have a larger proportion of flow than the uppe: exit ports 153, as described above, also causes the effective discharge angle of the flow exiting the uppe; exit ports 153 to be influenced by the total f lo1 throughput. Figs. 34A34C illustrate the variance in the effective discharge angle of the exit jets through the upper and lower exit ports as a function of f lo1 throughput Figs. 34A34C illustrate the ef f ect iv discharge angles of the exit jets at low, medium and hig] flow throughputs, respectively, through casting nozzL 150. For example, a low flow throughput would be les; than or about 1.5 to 2 tons/minute, a medium flo1 throughput about 23 tons/minute, and a high f lo1 throughput about 3 or more tons/minute. At low flow throughput as shown in Fig. 34A, the exit jets exiting the upper exit ports 153, represented b; arrows 162, are independent of the lower exit jets represented by arrows 164, and substantially achieve th> theoretical discharge angle of the upper exit ports 15 (preferably about 710° from the horizontal). As flow throughput increases as shown in Figs 3 4B and 3 4 C, the upper exit j ets 162 are drawn downwar towards the center line CL of the casting nozzle 150 b the higher momentum associated with the lower exit jet 164 exiting the lower exit ports 155. Thus, the effectiv discharge angle of the upper exit jets 162 increases fro: the theoretical discharge angle (a larger angle downwar from the horizontal) as flow throughput increases. Th effective discharge angles of the upper exit jets 162 als becomes less divergent from the discharge angle of th lower exit jets asthe flow throughput increases. As flow throughput increases as shown in Figs 3 4B and 3 4C, the lower exit j ets 164 exiting the lowe exit ports 155 also varies slightly. The lower exit jet 164 are drawn slightly upward away from the center line C of the casting nozzle 150. Thus, the effective discharge angle of the lower exit jets 164 slightly decreases froi the theoretical discharge angle (a smaller angle downwan from the horizontal) as flow throughput increases. It should be known that for purposes of the present invention, the exact values of the low, medium and high flow throughput are not of any particula: importance. It is only necessary that whatever the value: are, the effective discharge angle of the upper exit jet; increases from the theoretical discharge angle (a large: angle downward from the horizontal) as flow inpu' increases. The varying effective discharge angle of the upper exit jets 162 with rate of flow throughput is highl] beneficial. At low flow throughput, it is desirable t evenly deliver the hot incoming liquid metal to tht meniscus region of the liquid in the mold so as to promote proper heat transfer to the mold powder for propel lubrication. The shallow effective discharge angle of th( upper exit jets 162 at low flow throughput accomplishes this objective. In contrast, at higher flow throughput, the mixing energy delivered by the exit jets to the mole is much higher. Consequently, there is a substantially increased potential for excessive turbulence and/oi meniscus disturbance in the liquid within the mold. the steeper, or more downward, effective discharge angle ol the upper exit jets 162 at higher flow throughpui effectively reduces such turbulence or meniscus disturbance. Accordingly, the casting nozzle 150 of Figs, 3234 enhances the delivery and proper distribution o] liquid metal within? the mold across a substantial range oi flow throughputs through the casting nozzle 150. Referring now to Figs. 3 5 and 36, there is showi another alternative embodiment of the present invention The casting nozzle 170 shown in Figs. 35 and 36 combine features of casting nozzle 140 of Figs, 3031 and castin nozzle 150 of Figs. 3234. The multifaceted diamondback internal geometr; of casting nozzle 140 of Figs. 3031 is incorporated h casting nozzle 170 such that top edges 172 of bendin facets 174 are aligned with the theoretical discharge angle of lower exit ports 176, i.e., about 4580° downwarc from the horizontal, although about 6070° is preferred Thus, the bending facets 174 are provided generally in the vicinity of the central stream which flows between baffles 178. The diamondback internal geometry promotes smoother bending and splitting of the central stream ii the direction of the discharge angles of the lower exil ports 176 without separation of flow along bottom faces 178a of baffles 178. As shown in Fig. 35RR, the lowei exit port 17 6 is preferably widest toward the bottom thar at the top, i.e., wider near flow divider 180. As showr in Fig. 35QQ, the upper exit port 182 is preferably widest toward the top than at the bottom, i.e., widest near lowei faces 184a of sidewalls 184. Furthermore, as with casting nozzle 150 of Figs. 3234, the flow through casting nozzle 170 is preferably divided by baffles 178 into flow streams which are discharged through upper and lower exit ports 182 and 176, respectively, and the flow through casting nozzle 170 is preferably proportioned to vary the effective discharge angle of the streams exiting the upper exit ports based or flow throughput. The effective discharge angle of the upper exit ports 182 will vary in a manner similar to that of casting nozzle 150 as shotfn in Figs. 34A34C. However, as a result of the multifaceted diamondback internal geometry of casting nozzle 170, casting nozzle 170 produces smoother exit jets from the lower exit ports 176 at high flow throughput with less variance in effective discharge angle and more consistent control of the meniscus variation due to waving and turbulence in the mold as compared to casting nozzle 150. Moreover, the multifaceted diamondback internal geometry of casting nozzle 170 contributes to more efficient proportioning of a greater proportion of the flow out of the lower exit ports 176 than the upper exit ports 182. The diamondback internal geometry is preferably configured so that about 1545%, preferably about 2540%, of the total flow exits through the upper exit ports 182 while about 5585%, preferably about 60 75%, of the total flow exits through the lower exit ports 176, or single exit port 176 if casting nozzle 170 does not include a flow divider 180. It will be seen that we have accomplished at least some of the objects of our invention. By providing diffusion and deceleration of flow velocity between the inlet pipe and the outlet ports, the velocity of flow from the ports is reduced, velocity distribution along the length and width of the ports is rendered generally uniform, and standing wave oscillation in the mold is reduced. Deflection of the two oppositely directed streams is accomplished by providing a flow divider which is disposed below the transition from axial symmetry to planar symmetry. By diffusing and decelerating the flow in the transition, a total stream deflection of approximately plus and minus 30° from the vertical can be achieved while providing stable, uniform velocity outlet flows. In addition, deflection of the two oppositely directed streams can be accomplished in part by providing negative pressures at the outer portions of the streams. These negative pressures are produced in part by increasing the divergence angles of the side walls downstream of the main transition. Deflection can be provided by curved sections wherein the inner radius is an appreciable fraction of the outer radius. Deflection of flow within the main transition itself can be accomplished by providing the transition with a hexagonal crosssection having respective pairs of front and rear walls which intersect at included angles of less than 180°. The flow divider is provided with a rounded leading edge of sufficient radius of curvature to prevent vagaries in stagnation point due either to manufacture or to slight flow oscillation from producing a separation of flow at the leading edge which extends appreciably downstream. The casting nozzles of FIGS. 2 328 improve the flow behavior associated with the introduction of liquid metal into a mold via a casting nozzle. In prior art nozzles, the high inertial forces of the liquid metal flowing in the bore of the nozzle led to flow separation in the region of the exit ports causing high velocity, and unstable, turbulent, exit jets which do not achieve their apparent flow deflection angles. With the casting nozzles of FIGS. 2328, the inertial force is divided and better controlled by dividing the flow into separate and independent streams within the bore of the nozzle in a multiple stage fashion. This results in the alleviation of flow separation, and therefore the reduction of turbulence, stabilizes the exit jets, and achieves a desired deflection angle. Moreover, the casting noz zle of FIGS. 2829 provide the ability to achieve independent deflection angles of the outer and inner streams. These casting nozzles are particularly suited for casting processes where the molds of are of a confined geometry. In these cases, it is desirable to distribute the liquid metal in a more diffuse manner. With the casting nozzle of Figs. 3031, a multi faceted internal geometry is incorporated in which the bore of the nozzle has a greater thickness at the center line of the nozzle than at the edges, creating a diamond back internal geometry. As a result, more open area can be designed into the bore of the casting nozzle without increasing the external dimensions of the nozzle around the narrow face sidewall edges. Consequently, the nozzle provides improved flow deceleration, flow diffusion and flow stability within the interior bore of the nozzle, thereby improving the delivery of the liquid metal to the mold in a quiescent and smooth manner. Moreover, the diamondback geometry is particularly suited to a bulged or crownshaped mold geometry wherein the mold is thicker in the middle of the broad face and narrower at the narrow face sidewalls, because the casting nozzle better utilizes the available space within the mold to promote a proper flow pattern therein. With the multiport casting nozzle of Figs. 32 34, delivery of liquid metal to, and distribution of liquid metal within, the mold is improved across a wide useful range of total flow throughputs through the casting nozzle. By properly proportioning the amount of flow that is distributed between the upper and lower exit ports of the multiport casting nozzle, and by separating the theoretical discharge angle of the upper and lower ports by at least about 15°, the effective discharge angle of the upper exit ports will vary with an increase or decrease in casting nozzle throughput in a beneficial manner. The result of such variance is a smooth, quiescent meniscus in the mold with proper heat transfer to the mold powder at low flow throughputs, combined with the promotion of meniscus stability at high f lo throughputs. Therefore, a wider useful range of operational flow throughputs can be achieved without degradation of flow characteristics as compared to prior art casting nozzles. With the casting nozzle of Figs. 35 and 36, the effective discharge angle of the upper exit ports advantageously varies with flow throughput in a manner similar to that of the casting nozzle of Figs. 3234 and, in combination with a diamondback multifaceted internal geometry similar to that of the casting nozzle of Figs. 3031, the casting nozzle of Figs. 35 and 36 produces smooth exit jets from the lower exit ports at high flow throughput with less variance in effective discharge angle and more consistent control of meniscus variation in the mold. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features of subcombinations. This is contemplated by and is within the scope of our claims. It is therefore to be understood that our invention is not tc be limited to the specific details shown and described. We claim: 1. A casting nozzle for flowing liquid metal therethrough, comprising: an elongated bore having an entry port and at least one exit port; and a baffle positioned proximate to the exit port to divide the flow of liquid metal exiting the exit port into at least two separate streams. 2. The casting nozzle of claim 1, wherein the nozzle comprises; a second exit port; a second baffle positioned proximate to the entry port; and a flow divider positioned downstream of the baffles, wherein the baffles divide the flow of liquid metal into two outer streams and a central stream. 3. The casting nozzle of claim 2, wherein the baffles include upper faces and the upper faces deflect the outer streams in substantially opposite directions. 4. The coating nozzle of claim 3, wherein the baffles include substantially diverging lower faces, and the lower faces diffuse the central stream. 5. The casting nozzle of claim 4, wherein the flow divider divides the diffused central stream into two inner streams and the flow divider and the inner faces deflect the two inner streams in substantially the same direction in which the two outer streams are deflected. 6. The casting nozzle of claim 5, wherein the outer and inner streams recombine before the streams exit at least one of the exit ports. 7. The casting nozzle of claim 5, wherein the outer and inner streams recombine after the streams exit at least one of the exit ports. 8. The casting nozzle of claim 4, wherein the flow divider divides the diffused flow into two inner streams and the flow divider and the inner faces deflect the two inner streams in a different direction than the direction in which the two outer streams are deflected. 9. The casting nozzle of claim 3, wherein the upper faces deflect the outer streams at an angle of deflection of approximately 20-90 degrees from the vertical. 10. The casting nozzle of claim 9, wherein the upper faces deflect the outer stream at an angle of approximately 30 degrees from the vertical. 11. The casting nozzle of claim 2, wherein the bore includes a transition section in fluid communication with the baffles to substantially continuously change the nozzle's cross sectional symmetry from a generally axially symmetry to a generally planar symmetry. 12. A casting nozzle for flowing liquid metal therethrough comprising: an elongated bore having an entry port and at least two exit ports; a first baffle positioned proximate to the one exit port and a second baffle positioned proximate to the other exit port, wherein the baffles divide the flow of liquid metal into two outer streams and a central stream, and deflect the two outer streams in substantially opposite directions; and a flow divider positioned downstream of the baffles to divide the central stream into two inner streams, and to cooperate with the baffles to deflect the two inner streams in substantially the same direction in which the two outer streams are deflected. 13. The casting nozzle of claim 12, wherein the outer and inner streams recombine before the streams exit at least one of the exit ports. 14. The casting nozzle of claim 12, wherein the outer and inner streams recombine after the streams exit at least one of the exit ports. 15. The casting nozzle of claim 12, wherein the baffles deflect the two inner streams in a different direction from the direction in which the two outer streams are deflected. 16. The casting nozzle of claim 12, wherein the baffles deflect the outer streams at an angle of deflection of approximately 20-90 degrees from the vertical. 17. The casting nozzle of claim 13, wherein the baffles deflect the outer streams at an angle of approximately 30 degrees from the vertical. 18. The casting nozzle of claim 15, wherein the baffles deflect the two outer streams at an angle of approximately 45 degrees from the vertical, and deflect the two inner streams at an angle of approximately degrees from the vertical. 19. A casting nozzle for flowing liquid metal therethrough, comprising; an elongated entrance pipe section having a first cross-sectional flow area and a generally axial symmetry; a diffusing transition section in fluid communication with the pipe section, the transition section adapted and arranged to substantially continuously change the nozzle's cross-sectional flow area in the transition section from the first cross-sectional flow area to a generally elongated second cross-sectional flow area which is greater in cross-sectional flow area than the first cross-sectional flow area, and to substantially continuously change the nozzle's symmetry in the transition section from the generally axial symmetry to a generally planar symmetry; at least two exit ports in fluid communication with the transition section; a first baffle positioned proximate to the one exit port and a second baffle positioned proximate to the other exit port, wherein the baffles divide the flow of liquid metal from the transition section into two outer streams and a central stream, and deflect the two outer streams in substantially opposite directions; and a flow divider positioned downstream of, and in fluid communication with, the baffles to divide the central stream into two inner streams, and to cooperate with the baffles to deflect the two inner streams in substantially the same direction in which the two outer streams are deflected. 20. A method for flowing liquid metal through a casting nozzle comprising the steps of: flowing liquid metal through an elongated bore having an entrance port and at least one exit port; dividing the flow of liquid metal into two outer .streams and a central stream; deflecting the two outer streams in substantially opposite directions; dividing the central stream into two inner streams; and deflecting the two inner streams in substantially the same direction in which the two outer streams are deflected. 21. The method of claim 20, comprising the step of recombining the outer and inner streams before the streams exit the at least one exit port. 22. The method of claim 20, comprising the step of recombining the outer and inner streams after the streams exit the at least one exit port. 23. The method of claim 20, wherein the two inner streams are deflected in a different direction from the direction in which the two outer streams are deflected. 24. The method of claim 20, comprising the step of deflecting the outer streams at an angle of deflection of approximately 20-90 degrees from the vertical. 25. The method of claim 24, comprising the step of deflecting the outer { streams at an angle of approximately 30 degrees from the vertical. 26. The method of claim 23, comprising the step of deflecting the two outer streams at an angle of approximately 45 degrees from the vertical, and deflecting the two inner streams at an angle of approximately 30 degrees from the vertical

Documents:

1614-che-2005 abstract-duplicate.pdf

1614-CHE-2005 CLAIMS GRANTED.pdf

1614-che-2005 claims-duplicate.pdf

1614-CHE-2005 CORRESPONDENCE OTHERS.pdf

1614-CHE-2005 CORRESPONDENCE PO.pdf

1614-che-2005 description (complete)-duplicate.pdf

1614-che-2005 drawings-duplicate.pdf

1614-CHE-2005 FORM 2.pdf

1614-CHE-2005 FORM 3.pdf

1614-che-2005 form-18.pdf

1614-che-2005 form-3.pdf

1614-CHE-2005 PETITIONS.pdf

1614-CHE-2005 POWER OF ATTORNEY.pdf

1614-che-2005-abstract.pdf

1614-che-2005-claims.pdf

1614-che-2005-correspondnece-others.pdf

1614-che-2005-correspondnece-po.pdf

1614-che-2005-description(complete).pdf

1614-che-2005-drawings.pdf

1614-che-2005-form 1.pdf

1614-che-2005-form 18.pdf

1614-che-2005-form 3.pdf

1614-che-2005-form 5.pdf