MXPA05009852A

MXPA05009852A - Submerged entry nozzle with dynamic stabilization.

Info

Publication number: MXPA05009852A
Application number: MXPA05009852A
Authority: MX
Inventors: Dong Xu
Original assignee: Vesuvius Crucible Co
Priority date: 2003-03-17
Filing date: 2004-03-09
Publication date: 2005-12-06
Also published as: AU2004221863A1; KR20050113230A; ES2267057T3; DE602004001980T2; US20060169728A1; CN1761543A; RU2005130062A; EP1603697A1; CN100346909C; AU2004221863B2; ATE336319T1; WO2004082871A1; DE602004001980D1; JP2006520694A; RU2331496C2; ZA200507285B; BRPI0408340A; CA2519050A1; EP1603697B1; UA85179C2

Abstract

The present invention relates to a pour tube for casting molten metal. The pour tube is adapted to reduce turbulence and mold disturbances, thereby producing a more stable, uniform outflow. The pour tube includes an exit port with at least one tongue to provide at least two slots on either side of the tongue. The slots generate counter-rotating flows, which result in a more diffusive and more homogeneous outflow. Advantageously, such an outflow can reduce detrimental asymmetry and alumina clogging in the pour tube.

Description

SUBMERGED INLET NOZZLE WITH DYNAMIC STABILIZATION FIELD OF THE INVENTION This invention relates generally to a refractory article and, more particularly, to a refractory casting tube for use in the transfer of molten metal in a continuous casting operation.

BACKGROUND OF THE INVENTION In the continuous casting of metal, in particular steel, a stream of molten metal is typically transferred via a refractory pouring tube from a first metallurgical container into a second metallurgical container or mold. Such tubes are commonly referred to as nozzles or dowels and have a bore adapted to transfer molten metal. The emptying tubes include submerged connected nozzles (SEN) or submerged connected droplets (SES), which discharge the molten metal below the liquid surface of a receiving container or mold. Liquid metal is discharged from the downstream end of the auger through one or more output ports. An important function of a drain tube is to discharge the molten metal evenly and stably without interruption or disruption. A uniform discharge facilitates the processing and can improve the quality of the finished product. A second important function of a pouring tube is to establish appropriate dynamic conditions within the liquid metal in the receiving container or mold to facilitate further processing. Producing appropriate dynamic conditions may require the discharge tube to have a plurality of outlet ports that are arranged to cause the stream of molten metal to be directed in one or more directions as it is discharged from the tube. Factors that can interrupt uniform and stable discharge include both physical and dynamic conditions that result in an asymmetric flow behavior of molten metal in the borehole and output ports. The asymmetries in the distribution of metal flow velocity and laminar currents can result from, for example, (a) an inefficient design of holes and ports, (b) the presence of upflow control devices, and ( c) uneven accumulation of clogging material inside the hole and ports. Even in the absence of these factors, the turbulent flow in the borehole can still cause the development of dynamic flow asymmetries. For example, while flowing through a borehole, a stream of molten metal can develop a higher fluid velocity near the centerline of the borehole than along the sides of the borehole, or a lower velocity on one side of the line central compared to the opposite side, or a higher fluid velocity outside the center line. Such varied speeds can cause pulsations and excessive turbulence when leaving the hole, which complicates processing and decreases the quality of the finished product. Sealing devices, such as plug rods or sliding gate valves, can partially block the entrance to the borehole and cause the current of molten metal to enter the borehole away from the center line. The current may flow preferentially down one side of the borehole and exit asymmetrically or unevenly from the pouring tube, causing excessive variation and turbulence in a mold. The pulsation, variation, turbulence and asymmetry of the discharged flow are aggravated by the provisions of the port that cause the current to rotate before being discharged from the tube. Asymmetries in the flow of current approaching an exit port can induce an unstable and swirling turn of the flow turned as it is discharged through the ports, which causes instability of the discharge direction, instability of the induced flow pattern inside the receiving container and undesirable dynamic conditions in the receiving container. Non-metallic precipitates or accumulations can also clog or restrict the borehole to interrupt the stable discharge of molten metal from the tube. In the molten steel, precipitates and non-metallic accumulations consist mainly of alumina and other impurities with high melting point. Alumina deposits can lead to restrictions and clogging that can substantially stop or prevent the uniform and stable flow of liquid steel. The asymmetric non-uniform metal flow can carry to the presence of preferential sites for obstruction deposits and may further exacerbate the non-uniformity of the flow. The tubes can be unblocked using an oxygen lance; however, the lanceado interrupts the process of casting, reduces the life of the refractory and decreases the efficiency of casting and the quality of the steel produced. The total or substantial blocking of borehole by precipitates decreases the expected life of the drain tube and is very expensive and time consuming for steel producers. Attempts by the prior art to improve flow include both chemical and mechanical means. For example, flow can be improved by reducing alumina precipitation and subsequent obstruction. The prior art has injected gas to pressurize the emptying tube and reduce the obstruction by alumina. Unfortunately, gas injection requires large volumes of gas, complicated refractory designs and is not always an effective solution. The gas can also dissolve or get trapped inside a metal, causing problems in the quality of the metal including porosity defects or small holes in the steel. Alternatively or in combination with the gas injection, the prior art has aligned the borehole with refractory compositions claiming to resist alumina accumulation. The compositions include refractories of low melting point, such as eutectics of CaO-MgO-Al203, calcium zirconate and calcium silicide, which break off as alumina deposits on the surface. These compositions have to crack to high temperature and, during casting, can dehydrate and dissipate. For these reasons, its useful life is limited. Other surface compositions which claim to inhibit the deposition of alumina include refractories containing SiAION-graphite, metal diborides, boron nitride, aluminum nitride and carbon-free compositions. Such refractories can be expensive, impractical and manufacturing can be both risky and time-consuming. Mechanical designs for improving flow include U.S. Patent No. 5,785,880 to Heaslip et al., Which teaches a pour tube having a diffusion geometry that uniformly supplies a stream of molten metal to a mold. Alternative designs include EP 0 765 702 B1, which describes a perforated obstacle within the hole that deflects the current from a preferred path. Both references attempt to control the introduction of molten metal into a mold by mechanically manipulating the molten metal stream. None describe the obstruction by alumina or the reduction of obstruction by alumina. The background technique also includes designs that claim improved flow by reducing the deposition of alumina in the borehole. These designs include drain tubes with both tapered and stepped holes. U.S. Patent No. 4,566,614 to Frykendahl teaches an inert gas injection nozzle having a conical bore which is intended to reduce "pulsations" in the gas flow. It is said that the more uniform gas flow inside the hole reduces the obstruction. The designs "Staggered" include drain tubes that have discontinuous changes in borehole diameter. Stepped designs also include casting tubes that have a spiral hole. JP Kokai 61-72361 illustrates the stepped pouring tubes and describes a pouring tube having a bore with at least one convex or concave section which generates a turbulent flow in the molten metal. The turbulent flow, in contrast to the laminar flow, is described as reducing the obstruction by alumina. U.S. Patent No. 5,328,064 to Nanbo et al. teaches a hole having a plurality of concave sections separated by steps having a constant diameter, d. Each section has a diameter greater than d and preferably the diameters of the sections decrease along the flow direction. The steps are described as turbulence generators that reduce the obstruction by alumina. US 6425505 to Heaslip teaches a drain tube comprising a plurality of fluidly connected sections that improve the flow of molten metal through the hole. The sections reduce the asymmetric flow of the molten metal stream and the likelihood of precipitates clogging the borehole. Each section comprises a convergent portion and a divergent portion. The converging portion deflects the current to the center of the hole, while the divergent portion diffuses the current. The combination of convergent and divergent elements produces a more symmetrical flow in the emptying tube.

Attempts in the prior art to control the flow of molten metal within the bore have done little to control the unstable flow from the outlet ports of the pouring tube. The output ports induce unstable flow patterns in the output current. The non-constant flow of the emptying tube into a mold can increase the turbulence and swell of the meniscus. Such a flow can also cause the outflow stream to fluctuate in the mold and to bypass the flow pattern in the mold. In addition, unstable outflow can cause alumina clogging in the lower regions of the drain pipe including the downhole part of the pipe and the lower corners of the ports. The obstruction will typically impart an asymmetric outflow from the drain tube. There is a continuing need for a refractory casting tube that produces a stable outflow and reduces meniscus turbulence, swell, symmetric flow patterns and alumina clogging. Ideally, said tube would also improve the flow of molten metal within a casting mold and improve the properties of cast metal.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a pour tube for use in the casting of molten metal. The discharge tube includes at least one outlet port and, in relation to the prior art, provides a more stable and uniform output flow of molten metal through and from the output port. The improved outflow reduces turbulence and meniscus swell, reduces clogging by alumina and promotes symmetrical outflow. These benefits can result in a better finished product. In a broader aspect, the article comprises a discharge tube having an outlet port shape that reduces flow instability, thus producing a more stable outflow. In this way, it reduces the unsteady back and forth flow pattern that is common in outflow currents from a drainage tube. This flow pattern is described as at least partly responsible for instabilities in mold flow and poor quality castings. In one aspect, the invention includes an outlet port that stabilizes and controls the rotation or rotation of the flow as it passes through an outlet port and discharges into the mold. The large scale rotation with which the circumference of the rotation flow approaches the width or height of an exit port is opposite and thereby reduces. The unstable and uncontrolled turn to large scale of the discharge flow is considered to cause more swell and instability of the flow pattern generated in the mold or receiving container. The outlet port includes a plurality of grooves that produce consistent counter-rotation flows in the molten metal and which oppose large-scale flow rotation in a single large-scale flow direction that ranges from one direction to the other. opposite. Stable counter-rotation flows within the outflow from the tube they provide a more diffuse, homogeneous and less turbulent discharge of molten metal and thereby provide a more consistent flow pattern in the receiving container. The outflow of a pour tube can form a portion of a top flow loop within a mold. The upper circulation loop is close to the upper surface of the mold and affects, for example, the swell of the upper surface and the turbulence of the meniscus. The outflow from an outlet port of the present invention can direct more molten metal to the surface of the mold without causing excessive turbulence of the meniscus or fluctuation in the level of the mold. You can also improve the thermal distribution inside! mold. The pattern of the overall flow within the mold becomes more stable. In one modality, the port Outlet includes a tongue on its descending edge. The tab and the falling edge define slots in the lower corners of the exit port. The presence of these grooves opposes the large-scale rotation of the discharge flow and promotes the formation of small-scale counter-rotation flows within the outlet flow of the tube. An outlet port comprising a tongue alters the pressure and flow characteristics within an outlet port and within the outlet region of the drain tube, so that the obstruction by alumina and the asymmetric flow are reduced. In a second embodiment, the exit port includes a tongue on its upper edge. The tongue and the upper edge define slots in the upper corners of the exit port. The presence of these grooves opposes the large-scale flow turn within the outflow. Large-scale rotation is not desired since such turns are inherently unstable and generally exhibit an occasional change of direction, which offers an inconsistent discharge direction and unstable dynamic behavior in the discharge flow and consequently in the mold. In a third embodiment, the exit port includes tabs on the ascending and descending edges of the port. An outlet port comprising both ascending and descending tabs promotes the formation of stable counter-rotation flows within the outflow with excellent symmetry and small, controlled scale. Other details, objects and advantages of the invention will be apparent from the following description of a current preferred method for practicing the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a three-dimensional view of a first embodiment of a pouring tube of the present invention. Figure 2 shows a view of a first embodiment of a pouring tube of the present invention from a view perpendicular to an exit port.

Figure 3 shows a view in a pouring tube of the prior art from a view perpendicular to an exit port and the Unstable Incidental flow pattern. Figure 4 shows a view of a first embodiment of a drain tube of the present invention that includes a counter-rotation flow pattern. Figure 5 shows a view of a first embodiment of a pouring tube of the present invention that defines the design parameters of a tongue. Figure 6 shows a sectional view of a first embodiment of a drainage tube of the present invention transversely sectioned defining the angles of unloading grooves and tongue. Figure 7 shows a view of a second embodiment of a pouring tube of the present invention from a view perpendicular to an exit port. Figure 8 shows a view of a second embodiment of a pouring tube of the present invention from a view perpendicular to an exit port including a counter-rotation flow pattern. Figure 9 shows a view of a third embodiment of a pouring tube of the present invention from a view perpendicular to an exit port.

DETAILED DESCRIPTION OF THE INVENTION The invention comprises a pour tube for use in the continuous casting of molten metal. The drain tube comprises a bore connected fluidly to at least one outlet port. "Emptying tube" means cranks, nozzles and other refractory parts for directing a stream of molten metal, including for example, submerged inlet nozzles and nozzles. The invention is particularly suitable for pouring tubes having an outlet port adapted to supply molten metal below the metal surface in a receiving container such as a mold. Figures 1 and 2 show alternative perspectives of a pouring tube. The drain tube 1 comprises an inlet 11 and an outlet port 12 fluidly connected by a bore 13. The drain tube 1 allows a stream of molten metal to pass from an upward end to the inlet 1 through the orifice and into an outlet. descending end at the exit port 12. The exit port 12 is defined by the perimeter of an orifice extending through the discharge tube 1 from its outer surface to its bore 13. The perimeter of the exit port 12 comprises a descending flow surface 21. The perimeter of the exit port may have any convenient general shape, including without restriction, ovoid, polygonal or any combination of these. Conveniently, the general shape of the exit port is substantially rectangular. In one embodiment, the exit port 12 is defined by the descending surface 21, an ascending surface 22, and lateral surfaces 23 connecting the descending and ascending surfaces. At least one tab 24 extends from the descending surface 21 or rising surface 22. The tab 24, descending surface 21 and lateral surfaces 23 define a plurality of slot-shaped openings 25. Figure 3 shows a draining tube 2 of the prior art with an inlet 11 and outlet ports 12. During the casting of molten metal, at least a portion of the kinetic energy of a falling stream 31 of molten metal is translated into a rotation output flow 32 having a angular impulse. The remaining kinetic energy causes the current to exit the output port as a high-speed jet. The output stream of rotation 32 is shown rotating counterclockwise as observed, but the direction of. Flow outflow from a pouring tube of the prior art is unstable and will show an occasional change of direction. Depending on the degree of asymmetry of the pulse distribution within the downstream 31, the scale of rotation in the outflow can be as large as the width, and the height, or the diameter of the outlet port. The unstable large-scale rotation within the outflow and the high velocity jet produced by the pouring tubes of the prior art generate turbulence, surface swell, flow pattern instability and lack of thermal homogeneity inside the mold. To further complicate these issues, the rotation flow 32 causes flow separation within the outlet port 12. Flow separation is associated with alumina clogging, which can block the outflow from the outlet port. The combination of a high-velocity jet and a large-scale flow of rotation produce an unstable output flow that can oscillate and fluctuate within the mold. The departure ports of the prior art do not correct these deficiencies. In contrast, the outlet port 12 of the present invention, as shown in FIG. 4, again directs the downflow 31 of the molten metal at least partially through the slots 25. The slots translate at least a portion of the kinetic energy of the downward current 31 within at least two counter-rotation flows 41 and thus opposing the formation of an individual large-scale turning loop within the output flow. The angular impulses of the counter-rotation flows 41 are substantially canceled so that the output flow from the output port 12 has little or no net angular momentum. Simultaneously, the kinetic energy and consequently the velocity of the discharged flow are substantially reduced since the flow of the discharged flow is distributed more evenly through the outlet port 12. The counter-rotation flows 41 allow the substantial reduction of the flow velocity of the flow. output and large-scale rotation, the formation of vortices or eddies in the outflow are inhibited. The outflow is more diffusive and can be directed more close to the surface without causing waves or surface turbulence. An output stream plus general diffuser a better thermal distribution in a mold. Additionally, the flow separation at the exit port 12 and the associated alumina clogging are reduced. The flow instabilities inherent in alumina clogging can be substantially avoided. A tongue must be large enough to define grooves capable of inducing counter-rotation flow in the outflow. Referring to Figure 5 the tab 24 has a width (w1) and a height (h1) 52. In relation to the width (W) 53 and the height (H) 54 of the exit port 12, the width 51 of the tongue will typically be at least one eighth the width of the exit port 53. The height 52 of the tongue will commonly be at least about one eighth of the height 54 of the exit port 12. Obviously, increasing the dimensions of the tongue can reduce the total discharge area of the outlet port, thereby reducing the possible output flow from the drain tube, whereby the tongue will be as small as possible to produce the counter-rotation flows. Casting conditions, including the grade of molten metal, casting temperature, mold geometry, flow volume with no outlet, size of drain tube and exit port size, will affect all dimensions of the tab. Referring to Figure 6, the tongue and its associated slots are designed to rotate the discharge flow to a desired angle. The longitudinal axis 61 of the hole 13 is aligned with the general direction of the descending metal flow through the hole. The perpendicular axis 63 is at a right angle to the longitudinal axis 61 and generally passes centrally through an outlet port. The surface of the tab away from the edge is defined as the extended surface 64 and is disposed at an angle i relative to the perpendicular axis 63. The descending surface 65 of a slot is disposed at an angle < ¾ to the perpendicular axis 63. The angles ai and ct2 can be chosen for discharge flow rotation portions towards the desired discharge angles. As those skilled in the art know, the desired discharge angles will depend on the casting conditions, such as the degree of molten metal, casting temperature, mold geometry, outflow volume, casting tube size and size of casting. exit port. The angles -? and 2 are typically on the scale of -45 to +45 degrees. Figure 7 shows a second embodiment of a pour tube of the present invention. The drain tube 1 comprises an inlet 11 and an outlet port 12 fluidly connected by a past flow bore 13. The drain tube 1 is adapted to convey a stream of molten metal from an upward end in the inlet 11, through of the auger, and thus a descending end comprising the exit port 2. The exit port 2 is defined by an ascending surface 22, a descending surface 21 and lateral surfaces 23 connecting the descending and ascending surfaces. The port of departure can have any convenient general form, including, without restriction, ovoid, polygonal or any combination of these. Conveniently, the general shape of the exit port is substantially rectangular. At least one tongue 24 extends downwardly from the rising surface 22. The tongue 24, rising surface 22 and side surfaces 23 define a plurality of slot-shaped openings 25. An outlet port 12 of the present invention, as shown in Fig. 1, again directs the downstream 31 of molten metal at least partially through the slots 25. In opposing the formation of an individual large-scale turning loop within the discharge flow, the slots 25 they transfer at least a portion of the kinetic energy of the rotation flows 32 into counter-rotation flows 41. The angular impulses of the counter-rotation flows 41 substantially reduce the angular impulse of the outflow from the exit port 12. The turns to Large scale, vortices or eddies in the outflow are inhibited and the outflow is more symmetrical, more diffusive and can be directed more closely to the sup upper surface of the mold or receiving container without excessive swell or turbulence on the surface. Additionally, the flow separation at the outlet port 12, flow instabilities inherent in alumina clogging, can be substantially avoided, and the associated alumina clogging can be reduced.

Figure 9 shows a third embodiment of a pour tube of the present invention. The drain tube 1 comprises an inlet 1 and an outlet port 12 fluidly connected by a past flow bore 13. The drain tube is adapted to convey a stream of molten metal from an upward end in the inlet 1 through the borehole and a descending end comprising the exit port 12. The exit port 12 is defined by an ascending surface 22, a descending surface 21 and lateral surfaces 23 connecting the descending and ascending surfaces. The port of departure may be of any convenient general form, including without restriction, ovoid, polygonal or any combination thereof. Conveniently, the general shape of the exit port is substantially rectangular. At least one lower tab 91 extends upwardly from the downward surface 21 and at least one upper tab 92 extends downwardly from the upward surface 22. The bottom tab 91, the upper tab 92, the descending surface 21, the rising surface 22 and the lateral surfaces 23 define a plurality of slot-shaped openings 25. The molten metal that is discharged from the emptying tube 1 passes at least partially through of the slots 25 with formation of small scale counter-rotation flows and very high stability. Obviously numerous modifications and variations of the present invention are possible. Conveniently, the present invention can be combined with borehole geometries of the art antecedent such as, for example, holes that include discontinuities or "steps", or holes that include frustoconical sections. Therefore, it should be understood that within the scope of the following claims, the invention may be put into practice in a manner other than that specifically described.

Claims

twenty NOVELTY OF THE INVENTION CLAIMS

1. - A pouring tube 1 for use in casting a stream of molten metal from an ascending position to a downward apposition, and the pouring tube comprises an inner surface defining a bore 13 and an outer surface having at least one an outlet port 12 defined at least partially by an edge and fluidly connected to the borehole, the outlet port is characterized by at least one tab 24 extending from an edge, with which at least two grooves are created. at the port of departure.

2. - The discharge tube according to claim 1, further characterized in that the outlet port includes a falling edge 21 and the tongue extending upwardly -from the falling edge.

3. - The discharge tube according to claim 1, further characterized in that the outlet port includes an upward edge 22 and the tongue extending downwardly from the rising edge.

4. - The drain tube according to claim 1, further characterized in that the outlet port includes an upper tab 92 extending downwardly from an upper edge 22, and twenty-one a lower tongue 91, extending upwardly from a falling edge 21.

5. The draining tube according to any of claims 1-4, further characterized in that the draining tube includes a longitudinal axis 71 between the ascending and falling.

6. - The discharge tube according to claim 5, further characterized in that at least one tongue includes an extended surface 64, and the extended surface defines a tongue plane that intersects the longitudinal axis on an axis of -45 to + 45 degrees.

7. The draining tube according to any of claims 5 and 6, further characterized in that at least one edge includes an edge surface that defines an edge plane that intersects the longitudinal axis at an angle of -45 to + 45 degrees.

8. - The drain tube according to any of claims 5-7, further characterized in that the outlet port defines an exit plane substantially parallel to the longitudinal axis.

9. - The drain tube according to any of claims 1-8, further characterized in that the hole comprises a plurality of sections connected fluidly.

10. The draining tube according to claim 9, further characterized by having a discontinuity separating each section. 22

11. - The drain tube according to any of claims 9 and 10, further characterized in that the sections include at least one frusto-conical section.

12. - A method for casting a stream of molten metal using a drain pipe according to any of claims 1-11, wherein: a) a stream of metal flows through the hole; b) the current is directed towards the exit port; c) symmetric counter currents occur in the currents as the current passes through the output port.