IMPACT PAD FOR A REFRACTORY ARTESA WITH DOWNPADS IN THE BACKGROUND This invention describes the handling of molten metal, especially steel. In particular, the invention describes an impact pad for a refractory tundish with bottom dies, that is to say an article formed of a refractory material to be placed on the floor of a refractory tundish with dips in the bottom to receive an inlet stream. of molten metal poured into the refractory trough with nozzles at the bottom of a pouring cauldron. The invention has a particular utility in the continuous melting of steel. International Patent Application No. WO 96/14951 (FOSECO) discloses an impact pad for a refractory tundish with bottom dies comprising a body of refractory material capable of withstanding contact with molten steel in a refractory tundish with buzos in the background. The body of the impact pad comprises a base having an impact surface, an outer side wall extending upward from the impact surface, and an upper surface connected to the side wall and defining a hole therein. The upper surface has an inner annular portion substantially parallel to the impact surface, and there is a substantially straight angular corner between the side wall and the impact surface, and also between the side wall and the inner annular portion of the top surface. This impact pad provides an increased residence time of the molten steel in the refractory tundish with buts at the bottom, which is important to ensure that the unwanted inclusions have sufficient time to float to the surface of the steel and to be removed. International Patent Application No. WO 97/37799 (FOSECO) discloses an impact pad for a refractory tundish with bottom dies comprising a body of refractory material capable of supporting the contact of molten steel in a refractory tundish with dips in the background. The body of the impact pad comprises a base having an impact surface for the molten steel, an outer side wall extending upward from the impact surface and extending around the base to completely enclose it. A portion of the annular body connected to the side wall provides an upper surface substantially parallel to the impact surface and defines an orifice into which the molten steel can be poured, the lower surface of the annular body portion and the inner face of the side wall defining a recess having a slanted cut portion extending continuously around and above the impact surface. A portion of the upper surface is at a lower level than the surplus of the upper part and the gap below the portion of the upper surface is of a smaller cross section than the rest of the gap.
This impact pad is particularly useful for improving the flow characteristics in the refractory troughs with elongated bottom nozzles in which the molten steel is poured into the refractory tundish with bottom nozzles at one end of the refractory tundish
with buzzes in the bottom and the or each outlet for the steel is at the opposite end of the refractory trough with buzzes in the bottom. The impact pad is oriented in such a way that the lower level portion of the end wall is adjacent to the end wall near the end wall.
The incoming stream of molten steel, so that the steel bouncing off the pad preferably flows towards this end wall. This has the effect of significantly reducing the surface turbulence created in the tundish
fe_M_fi? __. J i .. «J .... ^ td: refractory with buzzes in the bottom, and that in general improves the flow patterns, which result in the production of desander steel. It will be appreciated that the process of designing a new impact pad for a refractory trough with buzzers at the bottom which knows the particular pre-determined criteria is extremely complex, since it changes an aspect of the design of an impact pad in general it has unforeseen ramifications on the dynamics of the flow of the refractory trough system with buoys in the total bottom. The present inventors have identified a need for a new impact pad for a refractory tundish with bottom dies which causes the molten metal to bounce off the impact surface to be generally symmetrically directed around the longitudinal axis of the refractory tundish with buzos in the background. This is particularly important, for example, for refractory tundishes with buts on the bottom in which the or each outlet is located on the longitudinal axis of the refractory tundish with buzzers at the bottom, or where two or more outlets are arranged symmetrically around this axis. Furthermore, it is common for the incoming streams of the molten metal ("the pouring kettle stream") to be "off-center", ie not located on the longitudinal axis of the refractory tundish with bottom nozzles. This commonly occurs because the casing of the pouring cauldron (the tube through which incoming metal flows from the pouring cauldron inside the refractory tundish with bottom buts) normally moves together with a guillotine gate valve which controls the flow of the metal of the laundry cauldron, and since the valve is frequently only partially open in order to limit the rate of flow, the casing of the laundry cauldron is often off-center with respect to the refractory tundish with buoys in the bottom. According to a first aspect of the present invention, there is provided an impact pad for a refractory pan with buoys in the bottom formed of refractory material, the impact pad comprises a base having an impact surface which in use faces towards up to receive the molten metal poured on the impact pad, and a wall extending upwards from the base around at least a portion of the periphery of the impact surface, the wall including a projection projecting on a peripheral region of the impact surface, the projection that includes a plurality of profusions which are also projected on the impact surface than on the rest of the projection. The wall preferably extends around the total periphery of the impact surface, completely enclosing the impact surface. According to a second aspect, the invention provides a refractory pan with buoys in the bottom containing an impact pad according to the first aspect of the invention. The refractory pan with buoys at the bottom is preferably enlarged in shape (ie in the plan view), preferably has outlets near each longitudinal end, and in use the incoming streams of molten metal, and therefore the impact pad, preferably are located substantially in the longitudinal center of the refractory tundish with buts in the bottom. The refractory pan with buoys at the bottom preferably includes at least one lady that extends transversely in its width between the impact pad and an outlet. The upper surface of the brim preferably has a central portion (i.e. a central part with respect to the longitudinal axis of the refractory tundish with bottom skirts) which is lower than
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the peripheral portions on each side of this. This generally helps to direct the flow of the molten metal in the direction of the longitudinal axis of the refractory tundish with buts in the bottom. The inventors of the present invention have found that the provision of a plurality of profusions which project more on the impact surface than on the rest of the peripheral wall projection generally causes the molten metal to bounce off the impact surface to be directed substantially in the direction of the center of the impact pad. This generally has the effect of causing a substantially symmetrical flow of the molten metal out of the impact pad, even if the metal flowing within the pad on the impact surface is "off center", i.e. separating a distance from the center of the pad. pad. Such a substantially symmetrical flow out of the impact pad generally causes a symmetrical flow throughout the refractory tundish with buts at the bottom, resulting in the reduction of the so-called "dead zones" where the proportion of molten metal flow is relatively low (causing a poor supply of fresh metal and the possibility of solidification of the metal) and in general improves the consistency of the residence time in the refractory tundish with bottom drums experienced by the molten metal. The impact surface of the pad preferably has at least two corners (e.g., four corners) on which a respective profusion is projected. Advantageously, at least one (and preferably all) of the corners may be formed at the convergence of the substantially straight sides of the impact surface. More preferably, the impact surface can be substantially polygonal, more preferably substantially quadrangular, especially rectangular or square. A profusion is preferably projected onto each corner of a polygonal impact surface. Additionally or alternatively, at least one profusion (preferably two or more profusions) may extend along at least most of the length of a respective side of the impact surface, and may equally extend along substantially the length total of a respective side of the impact surface. In some of the preferred embodiments, the distance or distance between the projection extends between the two
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Profusions projected onto the impact surface are substantially uniform along at least the greater part of their length. The projection extending between the two profusions can advantageously be substantially straight along at least the greater part of its length. Additionally or alternatively, however, for one or more of the projection (s) extending between the two profusions, the distance by which the projection projects over the impact surface may be substantially non-uniform along at least most of its length, for example one or more of the projection (s) extending between two profusions may be curved in the plan view, for example such that the or each projection projects more on the impact surface in the center of its length than it does at each end, or alternatively such that it projects more at each end than it does at the center. It will be appreciated that the shape and size of the outgoing face between the profusions, and / or the shape and size of each profusion, can be varied according to each particular circumstance, for example, depending on the shape and / or size of the refractory tundish. with buzzes in the bottom, and / or the amount by which the incoming stream of molten metal is off-center, or according to any other user requirements. The maximum distance by which the or each profusion of the impact pad is projected onto the impact surface is preferably at least 110%, more preferably at least 120%, even more preferably at least 140%, especially at least 150% of the maximum distance by which the rest of the projection projects over the impact surface. The or each profusion of the impact pad is projected onto the impact surface by a maximum distance preferably of not more than 600%, more preferably not more than 500%, especially not more than 450% of the maximum distance per which the rest of the projection is projected on the impact surface. Advantageously, the height of the projection above the impact surface may not be uniform along its length. For embodiments of the invention having at least three profusions, the height of the projection extending between two of the profusions is preferably different from that of the projection extending between one of two profusions and another profusion, or between two others profusions Advantageously, at least one portion of the projection which is lower than that of the other portion of the projection may project a greater distance on the impact surface than does the other, the highest portion of the projection. It has been found that to cause the molten metal that bounces off the impact surface and hits the low protrusions to be re-directed back toward the center of the impact pad in general more energetically than the metal striking the ledge. highest. This in turn appears to help cause the metal to flow symmetrically away from the impact pad. (However, it is possible to construct a non-limitation on the interpretation of the invention of the postulated explanations established here of the functioning of its various aspects). In some preferred embodiments, the peripheral region of the impact surface comprises a channel that extends around at least a portion of a central region of the impact surface. For the embodiments in which the impact surface has corners, the channel is preferably wider at the corners than elsewhere. For example, the shape of the channel (in plan view) can substantially reflect that of the projection of the wall.
The invention will now be described, by way of example, with reference to the accompanying drawings, of which: Figure 1 shows, in an isometric projection, an impact pad for a refractory pan with buts in the bottom according to the invention; Figure 2 shows, in an isometric projection, a longitudinal cross-section of the impact pad for a refractory pan with buoys at the bottom shown in Figure 1; Figure 3 is a schematic representation of the asymmetric flow of the molten metal in a refractory pan with buts in the enlarged bottom of an off-center casing cover. Figure 4 is a schematic representation of the symmetrical flow of molten metal in a refractory pan with buts in the enlarged bottom of a decentered pouring kettle cover using an impact pad and novel ladies according to the invention; and Figure 5 shows a lady as shown schematically in Figure 4. Figure 1 shows an impact pad 1 for a refractory pan with buoys in the bottom according to the invention, comprising a base 3 having a surface 5 of impact which in use faces upwards to receive the molten metal poured onto the impact pad, and a wall 7 extending upwards from the base around the periphery of the impact surface, the wall includes a projection 9 projecting on a peripheral region 11 of an impact surface, the projection includes a plurality of profusions 13 which project more on the impact surface than on the rest of the projection. The impact pad 1 is rectangular in plan view, both the base 3 and the impact surface 5 are rectangular in shape. Each of the profusions 13 are located in one of the four corners of the pad. Along each of the longer sides of the rectangular pad, between the profusions 13, the projection 9a is relatively small, and is substantially straight and uniform. Along each of the shorter sides of the pad, between the profusions 13, the projection 9b is relatively long, and is curved in plan view. In addition, the projections 9b are at a level ba to above the impact surface than the projections 9a.
_ & _ _-k_. _j_ _, g > _-. ", _» _. < _. . i »-. . _. The peripheral region 11 of the impact surface comprises a channel, the shape of which substantially reflects that of the entire projection 9a, 9b, 13. Figure 2 shows a longitudinal cross-section of the impact pad of Figure 1. The extension of the projections 9b is clearly visible, as the depth of the channel 11. It is also clear that the shorter walls 7b are perpendicular to the impact surface 5, and the projections 9b are perpendicular to the walls 7b.The longer walls 7a are, however, inclined with the perpendicular, ie they are inclined outward from the impact surface to the projections 9a.Figure 3 is a schematic representation of the asymmetric flow of the molten metal in a refractory tundish with buts in the enlarged bottom of an unbalanced casting cauldron cover In each of the parts (a) - (c), the refractory trough with buzzes in the bottom is shown in a view in plan, with a stream of the pouring cauldron entering of molten metal represented by a circle in a longitudinal center of the refractory tundish with buoys in the bottom but offset in a transverse direction, ie closer to a longitudinal side wall of the refractory trough with buzzes in the background that of the other. The
. j. t jfcm refractory tundish with buzzers in the bottom also contains a pair of checkers 15 (containing holes to allow the flow of the molten metal) on both longitudinal sides of the refractory tundish with buzzes at the bottom, and outputs indicated by circles at each end of the refractory trough with buzzes in the background. The arrows indicate the flow patterns of the molten metal; In part (a), the initial flow patterns of the metal entering the refractory tundish with buts in the bottom are shown. (According to the practice of normal work, the refractory trough with buzzers at the bottom is then filled with molten metal that flows through it - the flow patterns show merely indicating the predominant flow paths at various distances from the tundish refractory with buzos in the background). Even at this early stage it can be observed that because the current of the casting cauldron is off-center, the flow is asymmetric with respect to the longitudinal axis of the refractory tundish with bottoms. In part (b), the molten metal has begun to flow through the checkers, and the asymmetry of the flow paths is even more apparent. In part (c), the molten metal has reached the exits. Indicated by the number 17 are the so-called "dead zones"
___ _______ where there is little or no molten metal flow during these stable state conditions. The presence of dead zones in a refractory tundish with buzzers in the bottom is a major problem, since the metal cools in these regions and can initiate solidification, also causes variations in the composition of the metal flowing out of the refractory tundish with buzzes in the background. Figure 4 shows how the flow paths of the molten metal are changed by the use of an impact pad 1 according to the invention. Also present in the refractory trough with nozzles at the bottom of Figure 4 are the ladies 19 located closer to the outsides than the ladies of Figure 3. These ladies have a central portion 21 of their upper surface which is lower than the peripheral portions 23 on either side of this. As in Figure 3, the stream of the pouring kettle entering from Figure 4 is once again off-center, but this time the presence of an impact pad according to the invention causes the flow paths of the molten metal to they leave the impact pad more symmetrical. By the time the molten metal has reached the outlets, the flow paths are substantially symmetrical, and no dead zones are present. Figure 5 shows a front view and cross-sectional view of a lady 19 (shown only 5 symmetrically in Figure 4). The lady has a bottom surface 25 and side surfaces 27 formed and sized to fit tightly in a refractory trough with buts at the bottom across its width. Its upper surface has a central portion 21 which is 0 lower than the peripheral portions 23 on each side thereof. This has the effect of grooving the molten metal flowing over the lady along an axial flow path generally in the refractory tundish with buts in the bottom. It is therefore, complementary to the impact pad 5, to cause a symmetrical and / or axial flow of molten metal in the refractory tundish with bottom dies. The lady also has a plurality of holes 29 extending therethrough, to allow the molten metal to flow through the lady in addition to the molten metal 0 which can flow over the lady. The orifices 29 are inclined upward in the direction of flow of the molten metal, so as to impart a flow path directed upwards to the target flowing through them.
í * < a &3t .- - -oriencies. The angle of inclination of the holes is preferably greater for the lower orifices and preferably decreases when rising above the brim. As indicated in the drawing, the lower holes preferably have an angle of inclination of 40 °, which is reduced to 30 ° and then to 20 ° respectively for the highest orifices. The dimensions shown are in millimeters.