Tundish with filter module

Abstract

A filter module (1) for a filter system of a tundish (10) comprises a filter unit (1f) provided with a channel (1c) extending from a channel inlet to a channel outlet. The filter system comprises a wall module (2) comprising a wall defining an opening (2o) extending from the floor (10f) over an opening height (h2). A bypass passage (2b) having a maximum width (t12) is defined between the wall module (2) and the filter module (1) such that the metal melt can only flow from the inlet portion to the outlet portion either through the channel of the filter unit (1f) or through the bypass passage (2b). The wall module comprises a wall ledge (2L) having a width (t2L). The filter module (1) further comprises a filter ledge (1L) having a width (t1L) and being offset in vertical direction relative to the wall ledge (2L) to form a baffle therewith.

Description

Technical Field

[0001] Embodiments of the present invention relate to an intermediate ladle for continuous molten metal casting, the intermediate ladle being provided with a filtering unit for removing solid impurities before the molten metal is poured into a mold or tool. Specifically, the present invention relates to an intermediate ladle including a filter module that provides two possible pathways for the molten metal to flow from an inlet portion to an outlet portion, the outlet portion including an intermediate ladle outlet for pouring the molten metal into a mold or tool. The molten metal must flow through the filtering unit or through a bypass passage designed to facilitate flow through the filtering unit. However, in the event of a blockage in the filtering unit, the flow can continue through the bypass passage. Background Technology

[0002] In continuous metal forming, molten metal is transferred from one metallurgical vessel to another, and then to a mold or tool. For example, a ladle filled with molten metal from a furnace is driven above a tundish to discharge the molten metal from the ladle into the tundish through a long gate. The molten metal can then be poured from the tundish outlet through a gating gate into a mold or tool to continuously form slabs, billets, beams, thin slabs, etc. Under gravity, the molten metal flows from the ladle into the tundish, and then from the tundish into the mold or tool.

[0003] Defects (such as inclusions and impurities) in cast metal parts are a concern. These defects primarily originate from debris and impurities present in the ladle, or from wear caused by impact and friction between the molten metal and the refractory material in the casting zone of the tundish. It is important to prevent such debris and impurities from reaching the tundish exit to reduce the number of defects in the cast metal parts.

[0004] To reduce the amount of debris and impurities reaching the tundish outlet, EP 3470149 proposes a baffle module extending across the entire width of the tundish cavity, dividing the cavity into an inlet section (defined as the portion of the tundish that receives molten metal from the ladle) and an outlet section (defined as the portion of the tundish cavity that includes the tundish outlet). The baffle module consists of two parallel walls vertically offset from each other: a first wall and a second wall. The first wall, adjacent to the inlet section, defines an opening between the bottom plate of the cavity and the free edge of the first wall. The second wall extends from the bottom plate to a height above the opening defined by the first wall. The molten metal flowing from the inlet section to the outlet section is redirected by the baffle module, causing most debris and other solids to be retained at the bottom of the second wall. However, as described in EP 3470149, the baffle module primarily traps the heaviest debris and other solids, which cannot follow the tortuous flow provided by the baffle. Lighter solids, on the other hand, remain suspended and pass through the baffle module to reach the tundish outlet. Given the high density of molten metal, solids tend to remain suspended, and the removal efficiency of this baffle module is unsatisfactory for many applications.

[0005] Filter modules extending across the entire width of the tundish cavity have also been proposed to separate the tundish cavity between the inlet and outlet portions. For example, KR 200303465 describes a tundish including a filter module extending across the entire cross-section of the tundish cavity. This filter module includes filter units defining channels through which molten metal in the inlet portion of the cavity must flow to reach the outlet portion, thereby removing most of the debris and impurities from the molten metal reaching the outlet portion. Using filter modules allows for a significant reduction in the amount of debris and impurities flowing out of the tundish and into the tool, but it also presents significant risks. In practice, over time, debris and other solids accumulate on the inlet side of the filter units, thereby significantly reducing the permeability of the filter units and increasing the pressure differential (ΔP) required to drive the molten metal through them. Consequently, the level of the molten metal in the cavity inlet portion rises relative to the level in the outlet portion until it reaches the top of the filter module to flow across the filter module instead of through the filter units. If the height of the filter module is close to the height of the tundish, there is a serious risk that molten metal may overflow from the tundish, causing terrible consequences.

[0006] To address the overflow problem in the event of filter unit blockage, KR 101853768 describes a filter system that combines the solutions proposed in EP 3470149 and KR 200303465 discussed above, namely, by introducing a filter module between the first and second walls of the baffle module in EP 3470149. This filter module is lower than the filter module described in KR 200303465, and its height is similar to the opening height defined by the first wall. The first wall serves to deflect a portion of the molten metal to flow across the filter module and defines a bypass passage between the filter module and the first wall. Thus, in the event of filter unit blockage, the molten metal can flow through the bypass passage, across the filter module and the second wall, and thus reach the tundish outlet, with some of the heaviest debris and other solids remaining at the edges of the filter module and the second wall. The problem with this solution is that even when the filter unit is not blocked, a significant portion of the molten metal flows through the bypass passage instead of the filter unit, thereby reducing the effectiveness of the filter system described in KR 101853768.

[0007] Accordingly, there is a need for an improved filtration system that overcomes the limitations of this field. Summary of the Invention

[0008] Embodiments of the present invention relate to a filtration system for effectively removing most debris and other solids present in molten metal flowing through the tundish from the inlet to the outlet, regardless of their density, while ensuring a high level of safety without the risk of molten metal overflowing the tundish edges due to filtration system malfunction. These and other advantages of the invention will be described in more detail in the following sections.

[0009] Embodiments of the present invention provide a tundish for continuous metal casting. In several different embodiments, the tundish (10) defines a cavity having a cavity height (h10) measured along a vertical axis (Z), a cavity length measured along a longitudinal axis (X), and a cavity width measured along a transverse axis (Y), wherein X⊥Y⊥Z. The cavity includes: an inlet portion (10i) configured to receive a flow of molten metal (20m) discharged from the outside of the tundish into the cavity by gravity; an outlet portion (10o) including an outlet (11o) configured to discharge the molten metal from the cavity into a mold; and a filtration system separating the inlet portion (10i) and the outlet portion (10o) across the entire cavity width. The filtration system includes a filter module (1) that extends over the entire width of the cavity and extends inside the cavity, wherein the filter module includes an inlet side facing the inlet portion (10i) of the intermediate package and extending from the bottom plate (10f) of the cavity to a top surface, the shortest distance from the top surface to the bottom plate along the vertical axis (Z) being equal to the minimum filter module height (h1), and wherein the filter module (1) includes a filter unit (1f) that extends along the vertical axis (Z) over the filter height (hf) and is provided with channels (1c) that extend from a channel inlet (i.e., an opening on the inlet side facing the inlet portion (10i) of the intermediate package) to a channel outlet (i.e., an opening on the outlet side of the filter module (1) facing the outlet portion and separated from the inlet side by a filtration depth (tf). The filtration system further includes a wall module (2) comprising a wall that extends across the entire width of the cavity and extends within the cavity, defining one or more openings (2o) distributed across the width of the wall and at an opening height (h2) measured from the base plate (10f) along the vertical axis (Z). The filter module (1) is arranged closer to the outlet (11o) than the wall module (2), and a bypass passage (2b) with a maximum width (t12) measured along the longitudinal axis (X) is defined between the wall module (2) and the filter module (1), such that the molten metal can flow only from the inlet portion through the one or more openings to the inlet side of the filter module (1), and from the one or more openings to the outlet portion via the channel flowing through the filter unit (1f) or the bypass passage (2b).The wall rung (2L) protrudes from the wall of the wall module (2) at a wall rung distance (d2L) from the bottom plate (10f) that does not exceed the minimum filter module height (h1) (i.e., d2L≤h1), and extends toward the inlet side of the filter module (1) without contacting the filter module (1). The wall rung (2L) has a width (t2L) measured along the longitudinal axis (X), where 20mm<t2L<t12. In addition, the filter rung (1L) protrudes from the inlet side of the filter module (1) at a filter rung distance (d1L) from the bottom plate (10f) that exceeds the opening height (h2) (i.e., d1L>h2), and is offset relative to the wall rung (2L) (i.e., d1L≠d2L). The filter rung extends toward the wall module (2) without contacting the wall module or the wall rung, and the filter rung (1L) has a width (t1L) measured along the longitudinal axis (X), where 20mm<t1L<t12.

[0010] In a plurality of different embodiments, the ratio (h2 / h1) of the opening height (h2) to the filter module height (h1) is comprised between 20% and 95% (0.2≤h2 / h1≤0.95), preferably between 40% and 80%.

[0011] In a plurality of different embodiments, the ratio ((t1L+t2L) / t12) of the sum of the widths (t1L, t2L) of the filter rung and the wall rung to the maximum width (t12) of the bypass passage is comprised between 20% and 150% (i.e., 0.2≤(t1L+t2L) / t12≤1.5), preferably between 30% and 120%, more preferably between 50% and 100%.

[0012] In a plurality of different embodiments, the wall module comprises a single opening extending from a lower boundary at a distance of 0 to 5% of the cavity height (h10) from the bottom plate to the lower edge of the wall, such that the opening height (h2) is defined as the distance between the bottom plate and the farthest point of the lower edge. Alternatively, in a second embodiment, the wall module comprises more than one opening, wherein the top opening is defined as the opening having the boundary farthest from the bottom plate, and the boundary farthest from the bottom plate is spaced apart from the bottom plate by the opening height (h2).

[0013] In a plurality of different embodiments, the opening height (h2) may be related to the cavity height (h10), and the ratio (h2 / h10) of the opening height (h2) to the cavity height (h10) is comprised between 10% and 60% (0.1≤h2 / h10≤0.6), preferably between 40% and 60%.

[0014] In a number of different embodiments, the tortuosity of the bypass passage can be characterized very simply by defining a straight line extending through the bypass passage between the bottom plate of the inlet portion and the outlet portion, which straight line does not exist (since the straight line cannot reach the bottom plate or pass through the bypass passage without adjoining the refractory element), or forms an angle (θ) with the vertical axis (Z), which angle does not exceed 70°, preferably does not exceed 60°, and more preferably does not exceed 45°.

[0015] In a number of different embodiments, the filter rung (1L) is "higher than" the wall rung (2L). In other words, the filter rung distance (d1L) may be greater than the wall rung distance (d2L) (i.e., d1L>d2L). Alternatively, the filter rung (1L) may be "lower than" the wall rung (2L). In other words, the filter rung distance (d1L) may be less than the wall rung distance (d2L) (i.e., d1L<d2L). However, the filter rungs are not flush with the wall rungs, i.e., the filter rung distance (d1L) is not equal to the wall rung distance (d2L) (i.e., d1L≠d2L).

[0016] In a number of different embodiments, the wall module (2) may comprise more than one wall rung (2L), which are parallel to each other, never in contact with each other, and distributed over the height of the wall module (2). Similarly, the filter module (1) may comprise more than one filter rung (1L), which are parallel to each other, never in contact with each other, and distributed over the height of the filter module (1). The one or more wall rungs and / or filter rungs collectively define additional baffles in the bypass passage.

[0017] In a number of different embodiments, each baffle is defined at least by a wall rung and a filter rung, wherein the bypass passage reverses the flow direction component along the longitudinal axis (X) of the molten metal flowing from the inlet portion to the outlet portion of the cavity.

[0018] In at least one embodiment, the lower boundary of the filter unit may be at a small distance (hd) from the bottom plate of the cavity, which small distance is comprised between 0 and 10 cm (i.e., 0≤hd≤10 cm), and preferably between 2 and 5 cm. The upper boundary of the filter unit may be at a distance (hf+hd) from the bottom plate, such that the ratio of said distance ((hf+hd)) to the opening height (h2) ((hf+hd) / h2) is comprised between 0.7 and 1.2 (i.e., 70%≤(hf+hd) / h2≤120%), and preferably between 80% and 100%.

[0019] In at least one embodiment, the wall rung (2L) protrudes from a partial width of the wall; in some embodiments, the wall rung (2L) protrudes from the entire width of the wall.

[0020] In at least one embodiment, the filter crossbar (1L) protrudes from a portion of the width of the inlet side of the filter module (1); in some embodiments, the filter crossbar (1L) protrudes from the entire width of the inlet side of the filter module (1). Attached Figure Description

[0021] The following detailed descriptions of the various methods, processes, compositions, and articles disclosed are taken with reference to the accompanying drawings, in which:

[0022] Figure 1 A side sectional view of a metallurgical facility including an intermediate ladle, according to at least one embodiment of the subject matter of this disclosure, is shown.

[0023] Figure 2 A top perspective view of the cavity of the intermediate package according to the present invention is shown.

[0024] Figures 3(a) to 3(d) Several different embodiments of the wall portion according to the present invention are shown.

[0025] Figures 4(a) to 4(f) Side sectional views of several different embodiments of the filtering system according to the present invention are shown.

[0026] Figures 5(a) and 5(b) show side sectional views illustrating various sizes of the filtration system according to the invention.

[0027] Figures 6(a) and 6(b) show side-view perspective views illustrating how the cavity height (h10) is measured.

[0028] Figures 7(a) and 7(b) show top perspective views of two alternative embodiments of an intermediate package including more than one intermediate package outlet. Detailed Implementation

[0029] In continuous metal forming processes, molten metal is transferred from one metallurgical vessel to another, or to a mold or tool. For example, as... Figure 1As shown, a ladle (5L) is filled with molten metal from a furnace (not shown) and is driven above a tundish (10) to discharge the molten metal from the ladle into the tundish via a long ladle nozzle (5s). The molten metal can then be poured from the tundish outlet (11o) through a pouring nozzle (15) into a mold or tool (25) to continuously form slabs, billets, beams, thin slabs, etc. Under gravity, the molten metal flows from the ladle into the tundish and then from the tundish into the mold or tool. The flow rate can be controlled by a sliding gate mechanism that is in fluid communication with the outlets of the ladle and the tundish. A ladle sliding gate mechanism (5g) can be used to control the flow rate leaving the ladle and even interrupt the flow at a sealed position. Similarly, a tundish sliding gate mechanism (not shown) can be used to control the flow rate leaving the tundish and interrupt the flow at a sealed position. Typically, the flow rate leaving the tundish is controlled by a plug (7) rather than a sliding gate mechanism.

[0030] Since the casting of metal into molds or tools is a continuous process, the tundish acts as a buffer, and the level (h20) of the molten metal in the tundish must be kept substantially constant throughout the casting operation. However, the level (h20) of the molten metal in the tundish drops when a new ladle filled with molten metal is replaced with an empty ladle. The flow rate out of the tundish is maintained substantially constant by (1) reducing the ladle replacement time and (2) controlling the orifice of the tundish outlet (11o) through a plug (7) or a sliding gate mechanism.

[0031] Defects (such as inclusions and impurities) in cast metal parts are a concern. One source of these defects is the presence of foreign matter in the molten metal (20m) in the tundish. Slag (20s) can also contribute to these defects. These defects primarily arise from debris and impurities present in the ladle, or from wear caused by impact and friction between the molten metal and the refractory material in the casting zone of the tundish. It is important to prevent such debris and impurities from reaching the tundish outlet to reduce the number of defects in the cast metal parts.

[0032] According to various embodiments of the subject matter of this disclosure, such as Figure 1As shown, a tundish (10) for continuous metal casting according to at least one embodiment of the invention defines a cavity having a cavity height (h10) measured along a vertical axis (Z), a cavity length measured along a longitudinal axis (X), and a cavity width measured along a transverse axis (Y), wherein X⊥Y⊥Z. The cavity includes an inlet portion (10i) configured to receive a flow of molten metal (20m) discharged from the outside of the tundish into the cavity by gravity. The cavity includes an outlet portion (10o) comprising a tundish outlet (11o) configured to discharge the molten metal from the cavity into a mold or tool (25). The cavity includes a filtration system that separates the inlet portion (10i) from the outlet portion (10o) across the entire width of the tundish. The filtration system includes a filter module (1) that extends across the entire width of the cavity and extends from the bottom plate (10f) of the cavity along a vertical axis (Z) to a top surface at a minimum filter module height (h1). The filter module includes an inlet side facing the inlet portion (10i) of the tundish. The filter module (1) includes a filter unit (1f) that extends along the vertical axis (Z) at a filter height (hf) and is provided with channels (1c) extending from a channel inlet (i.e., an opening at the inlet side) to a channel outlet (i.e., an opening at the outlet side of the filter module (1) facing the outlet and separated from the inlet side by a filtration depth (tf). The filtration system includes a wall module (2) that includes a wall that extends over the entire width of the cavity and along a vertical axis (Z) and defines one or more openings (2o) that are distributed over the width of the wall and at an opening height (h2) measured from the base plate (10f) along the vertical axis (Z).

[0033] The filter module (1) is arranged closer to the outlet (11o) than the wall module (2), and a bypass passage (2b) with a maximum width (t12) measured along the longitudinal axis (X) is defined between the wall module (2) and the filter module (1), such that the molten metal can only flow from the inlet portion through the one or more openings (2o) to the inlet side of the filter module (1), and flow from the one or more openings (2o) to the outlet portion through the channel flowing through the filter unit (1f) or the bypass passage (2b).

[0034] Cavity: The cavity has a cavity height (h10) measured along the vertical axis (Z), a cavity length measured along the longitudinal axis (X), and a cavity width measured along the transverse axis (Y), where X⊥Y⊥Z. The cavity is defined by a base plate (10f) and surrounded by an outer wall. As shown in Figures 6(a) and 6(b), the cavity height (h10) corresponds to the liquid level filling the cavity, measured from the base plate (10f), above which fluid flows out of the cavity through the edge (without a cover closing the cavity). In other words, the cavity height is the minimum height of the outer wall measured from the base plate to the top of the outer wall. If an overflow port (10s) is provided in the middle, the cavity height (h10) is the separation distance between the base plate (10f) and the bottom of the overflow port (see Figure 6(b)).

[0035] Molten metal from a ladle (5L) is gravity-poured into the receiving section of the tundish cavity, thus feeding the tundish. To protect the pouring flow from atmospheric contamination, the ladle is typically equipped with a long ladle nozzle (5s). To prevent the pouring flow from perforating the bottom plate of the cavity upon impact, an impact pad (9) (or impact box) is usually placed in the impact zone where the pouring flow impacts the bottom plate. A tundish is typically fed by a single ladle (5L) at a time. However, this disclosure is applicable to multi-ladle feeding systems.

[0036] As shown in Figures 7(a) and 7(b), the cavity may include more than one tundish outlet (11o) supplied by the ladle (5L). In any case, there is always at least one metal feed area associated with one or more tundish outlets (11o), each metal feed area defining a metal flow path extending between the receiving portion (shown in the figures as the location of the box or impact pad (9)) and the tundish outlet (11o). According to the invention, it is sufficient that all flow paths be intercepted by at least one filtration system, as defined in more detail below. In the case of more than one tundish outlet (11o), more than one filtration system may be required to meet this requirement.

[0037] like Figure 1 , Figures 4(a) to 4(f) As shown in Figures 5(a) and 5(b), in steady mode, i.e., when the ladle is currently discharging fresh molten metal into the tundish, the cavity is filled with a substantially constant molten metal (20m) level (h20). Only during the period when an empty ladle (5L) is replaced with a new ladle is the tundish not fed fresh molten metal, and the molten metal level (h20) in the tundish decreases over time as casting continues. The constant flow rate out of the tundish outlet is controlled by a plug (7) or a sliding gate mechanism (not shown) at the tundish outlet (11o) based on pressure reduction.

[0038] The liquid level (h20) of the molten metal (20m) must not exceed the cavity height (h10) (i.e., h20<h10), so as to prevent the molten metal from flowing over the edge or through the overflow port (10s) and out of the tundish. In the stable mode, the liquid level (h20) of the molten metal may be comprised between 75% and 90% of the cavity height (h10). An excessively high liquid level will unduly increase the risk of overflow, while an excessively low liquid level will increase the cost of an oversized tundish.

[0039] Filtration system: The filtration system divides the cavity into an inlet portion (10i) and an outlet portion (10o). The inlet portion (10i) comprises the region into which fresh metal is poured from the ladle (5L) into the tundish cavity. The outlet portion (10o) comprises the tundish outlet (11o). Molten metal is poured into the inlet portion and must flow through the filtration system to exit from the tundish outlet (11o) into the mold or tool (25). The filtration system comprises a wall module (2) and a filter module (1), the filter module comprising a filter unit (1f) provided with channels (1c) extending from channel inlets (i.e., openings at the inlet side of the filter module (1) facing the inlet portion (10i)) to channel outlets (i.e., openings at the outlet side facing the outlet portion (10o)).

[0040] The molten metal (20m) has only two options, that is, to flow through the filter unit via the channels (1c) of the filter unit (1f), or to pass through the bypass passage (2b) defined between the filter module (1) and the wall module (2).

[0041] Various embodiments of the presently disclosed subject matter relate to designing the filtration system such that in the stable mode, more than 50% of the molten metal flowing through the filtration system flows through the channels of the filter unit (1f). As with any filtration system, the filter unit (1f) used in the tundish (10) will be clogged by debris and solids trapped upstream of the filter unit. One way to measure the clogging degree of the filter unit is to monitor the evolution over time of the pressure drop (ΔP=(Pu-Pd)) upstream (Pu) relative to downstream (Pd) of the filter unit. As the clogging degree increases, the pressure drop increases relative to the nominal pressure drop (ΔP0). In the present invention, it is preferred that for a pressure drop up to twice the nominal pressure drop (i.e., for ΔP / ΔP0≤2), more than 50%, preferably more than 60%, more preferably more than 75% of the molten metal flows through the filter unit (1f). Conversely, it is preferred that less than 50%, preferably less than 40%, more preferably less than 25% of the flow passes through the bypass passage (2b).

[0042] The filtration system disclosed herein allows for the interception of large amounts of debris or other solids present in the molten metal before it is discharged into the mold or tool (25). Simultaneously, in the event of excessive blockage of the filter unit (1f) resulting in a high pressure drop across the filter unit, the molten metal can flow through the bypass passage (2b) to the outlet section (10o). This prevents the molten metal from clogging the inlet section (10i), which would cause the molten metal level to rise dangerously close to or above the cavity height (h10) in the inlet section, resulting in the catastrophic consequence of molten metal overflowing from the tundish.

[0043] Unlike the system described in KR 101853768 discussed above, the filtration system of this disclosure does not require a weir located downstream of the filter module (1) between the filter module (1) and the intermediate package outlet (11o). The design of the filtration system of this disclosure will be further detailed.

[0044] Wall Module (2): The wall module (2) is one of the two basic components of the filtration system of the present invention, which divides the cavity into an inlet portion (10i) and an outlet portion (10o). The wall module (2) is adjacent to the inlet portion (10i) and separated from the tundish outlet by the filter module (1). The wall module (2) includes a wall that extends across the entire width of the cavity and along a vertical axis (Z) to its upper edge. The wall defines one or more openings (2o) distributed across the width of the wall and at an opening height (h2) measured from the bottom plate (10f) along the vertical axis (Z). The upper edge of the wall is above the stable liquid level (h20) of the molten metal. The upper edge is generally positioned at a distance from the bottom plate (10f) that is between 90% and 100% of the cavity height (h10), preferably between 95% and 100% of h10. When the tundish has an overflow port (10s), the upper edge can extend above h10, preferably flush with the free edge of the tundish excluding the overflow port. This is especially true when the overflow port (10s) is located in the outlet portion (10o).

[0045] like Figures 3(a) to 3(d) As shown, the one or more openings (2o) can have various geometries. Figures 3(a) to 3(b)In the illustrated embodiment, a single opening (2o) extends from the base plate (10f) to the lower edge of the wall, which may be straight and parallel to the base plate (refer to FIG. 3(a)) or curved (refer to FIG. 3(b)). The opening height (h2) is the distance from the base plate to the farthest point of the lower edge. In a variant of this embodiment, the opening extends from a lower boundary (forming a step) at a distance from the base plate (10f) (up to 5% of the cavity height (h10)) to the lower edge of the wall. The opening height (h2) is defined as the separation distance between the base plate and the farthest point of the lower edge (i.e., ignoring the presence of the step). The presence of a step across the entire width of the cavity hinders the evacuation of all molten metal remaining in the tundish, thereby filling the inlet portion (10i) to the height of the step. The step may be provided with an evacuation channel to avoid this problem. In an alternative embodiment shown in FIG. 3(c), the wall may include more than one opening (2o). The top opening is defined as the opening with the boundary furthest from the base plate (10f). The opening height (h2) is defined as the separation distance between the boundary and the base plate. Figure 3(c) shows the same circular opening. It is clear that the multiple openings can have any geometry and size as needed.

[0046] For the molten metal to flow from the inlet section to the outlet section, it must pass through one or more openings in the wall. There is no alternative unless the level of the molten metal in the inlet section increases above the upper edge of the wall. The ratio of the opening height (h2) to the cavity height (h10) (h2 / h10) is preferably between 10% and 60% (i.e., 0.1 ≤ h2 / h10 ≤ 0.6), preferably between 15% and 50%, and more preferably between 20% and 40%. The opening height (h2) is important because, as Figure 1 (Dashed line) As shown, it forces the molten metal to bounce upwards toward the surface of the molten metal after impacting the impact pad (9), and its flow path is downwards. There are steps protruding from the base plate that can be used to trap the heaviest solids, but their presence is not necessary.

[0047] The wall module (2) also includes a wall crossbar (2L) that protrudes from the entire width of the wall at a distance (d2L) from the base plate (10f) and extends toward the inlet side of the filter module (1) without contacting it. The wall crossbar (2L) has a width (t2L) measured along the longitudinal axis (X). For a wall comprising a single opening with a straight upper edge, the wall crossbar can be flush with the upper edge such that the wall crossbar distance (d2L) equals the opening height (h2) (i.e., h2L = h2), for example, as Figure 1, Figure 3(a), Figure 4(a), Figure 4(b), Figure 4(e), and Figure 5(a). Alternatively, the wall rung (2L) can be spaced any distance (d2L) from the bottom plate, such that h2<d2L<80%h10, preferably d2L is less than 70% of h10. Embodiments in which the wall rungs are not flush with the upper edge of the top opening are shown in Figure 3(d), Figure 4(c), Figure 4(d), Figure 4(f) and Figure 5(b). In some embodiments, the wall rung (2L) protrudes from a partial width of the wall; in some embodiments, the wall rung (2L) protrudes from the entire width of the wall.

[0048] The wall module (2) may include more than one wall rung (2L) distributed over the height of the wall module (2), as shown in Figure 4(e). In various different embodiments, the more than one wall rungs are straight and extend parallel to each other and parallel to the bottom plate (10f). If not parallel to each other, the more than one wall rungs (2L) preferably do not contact each other. The wall rung distance (d2L) is the distance from the wall rung closest to the bottom plate (10f) to the bottom plate. In various different embodiments, the wall and the wall rungs (2L) are made of refractory material, preferably the same refractory material lines the peripheral wall and the bottom plate of the cavity.

[0049] Filter module: The filter module (1) extends over the entire width of the cavity, and extends from the bottom plate (10f) of the cavity along the vertical axis (Z) over a minimum filter module height (h1) to the top surface. The filter module is positioned adjacent to the outlet portion (10o) and includes an inlet side facing the inlet portion (10i) of the tundish. The filter module (1) comprises a filter unit (1f) provided with channels (1c) extending from channel inlets (i.e. openings at the inlet side) to channel outlets (i.e. openings at the outlet side of the filter module (1) facing the outlet portion and spaced from the inlet side by a filter depth (tf)). The filter unit (1f) preferably extends vertically below the top surface, such that the top surface is not part of the filter unit (1f). The filter unit (1f) may extend over any portion of the tundish width as required. The larger the area in the plane (Y, Z), the higher the volumetric throughput through a filter unit with a given permeability.

[0050] In at least one embodiment, the filter crossbar (1L) protrudes across the entire width of the inlet side of the filter module (1) at a distance (d1L) from the base plate (10f) exceeding the opening height (h2) (i.e., d1L>h2). The filter crossbar (1L) is offset relative to the wall crossbar (2L) (i.e., d1L≠d2L) such that they do not face each other at the same height. The filter crossbar (1L) extends toward the wall module (2) without contacting the wall module or the wall crossbar, and the filter crossbar (1L) has a width (t1L) measured along the longitudinal axis (X). In some embodiments, the filter crossbar (1L) protrudes from a portion of the width of the inlet side of the filter module (1); in some embodiments, the filter crossbar (1L) protrudes from the entire width of the inlet side of the filter module (1).

[0051] The filter module (1) may include more than one filter crossbar (1L) distributed along the height of the filter module (1), as shown in FIG4(f). In at least one embodiment, the more than one filter crossbar is straight and parallel to each other and extends parallel to the base plate (10f). If they are not parallel to each other, the more than one filter crossbar (1L) preferably does not contact each other and does not contact the wall crossbar (2L). The filter crossbar distance (d1L) is the distance from the filter crossbar closest to the base plate (10f) to the base plate.

[0052] In one embodiment, the distance (d1L) between the filter crossbars and the bottom plate is greater than the distance (d2L) between the wall crossbars (i.e., d1L>d2L). Figure 1 , Figures 4(a) to 4(c) This embodiment is illustrated in Figures 4(e), 5(a), and 5(b). In the alternative embodiment shown in Figures 4(d) and 4(f), the distance (d1L) between the filter crossbars and the bottom plate is less than the distance (d2L) between the wall crossbars (i.e., d1L). <d2L)。

[0053] The filter unit (1f) can be any type of filter unit known in the field of continuous metal casting. The function of the filter unit (1f) is to trap all debris and solids (= entrapment) upstream of the filter unit, while allowing molten metal to flow through the channels (1c) through the filter unit (= effluent) and from there to the tundish outlet (11o). These channels can be straight or tortuous; when tortuous, the dimensions (cross-section and length) of these channels help to define the permeability of the filter unit. The permeability of the filter unit depends on the requirements of the specific application, and technicians know how to optimize the characteristics of the filter unit (1f) accordingly.

[0054] The lower boundary of the filter unit (1f) can be separated from the bottom plate (10f) of the cavity by a small distance (hd), which is between 0 and 10 cm (i.e., 0 ≤ hd ≤ 10 cm), and preferably between 2 and 5 cm. Similarly, the upper boundary of the filter unit (1f) can be separated from the bottom plate (10f) by a certain distance (hf + hd), such that the ratio of said distance ((hf + hd)) to the opening height (h2) ((hf + hd) / h2) is between 0.7 and 1.2 (i.e., 70% ≤ (hf + hd) / h2 ≤ 120%), and preferably between 80% and 100%.

[0055] Bypass Path: The bypass path (2b) defined in the filtration system is the essence of this invention. This bypass path must ensure that casting can continue smoothly even if the filter unit (1f) is blocked, and at the same time, it cannot provide an easier flow path than through the filter unit (1f) so that, under steady conditions, at least 50% of the metal flow reaches the outlet portion (10o) of the tundish through the filter unit. To this end, the bypass path of this disclosure is designed to impose a first and second reversal of the direction of the velocity vector along the longitudinal direction (X) on the molten metal flow. This is achieved by a combination of a wall crossbar (2L) and a filter crossbar (1L), which baffle the path defined between the wall and the filter module (1).

[0056] Such as about Figure 1 , Figures 4(a) to 4(c)As discussed in Figures 4(e), 5(a), and 5(b), the wall crossbar (2L) can be lower than the filter crossbar (1L) (i.e., closer to the bottom plate (10f)). Thus, the portion of molten metal above the opening height (h2) from the bottom plate (10f) is blocked by the wall and redirected downwards (i.e., towards the opening (2o)), thereby changing direction towards the filter module (1) as it approaches the bottom plate (10f). The molten metal can flow upwards to directly behind the wall until it reaches the lower surface of the wall crossbar (2L). If the wall crossbar (2L) is flush with the opening (i.e., d2L = h2), the molten metal cannot flow upwards to directly behind the wall at all. Similarly, the portion of molten metal below the opening height (h2) from the bottom plate (10f) cannot flow upwards to directly behind the wall and is forced to flow towards the filter module (1). When the molten metal impacts the lower surface of the wall crossbar (2L), the flow is redirected toward the filter module (1). The filter section flows straight (parallel to the longitudinal axis (X)) or downward against the filter unit (1f). The bypass section flows upward against the inlet side of the filter module (1) until it impacts the lower surface of the filter crossbar (1L). This redirects the flow in the opposite direction of the velocity vector component (=X component) parallel to the longitudinal axis (X), causing the X component of the flow to return in the direction of the inlet section (10i). The flow impacts the wall, and the X component of the velocity vector reverses again, causing the flow to return in the direction of the outlet section (10o). As shown in FIG4(e), the wall module (2) may include a second wall crossbar above the wall crossbar (2L) to force the velocity vector toward a direction more parallel to the longitudinal axis (X). The filter unit may include additional filter crossbars to combine with corresponding additional wall crossbars as additional baffles to change the X component of the velocity vector.

[0057] As discussed with respect to Figures 4(d) and 4(f), the filter crossbar (1L) can alternatively be positioned below the wall crossbar (2L) (i.e., closer to the bottom plate (10f)). Thus, upon sensing resistance flowing through the filter unit (1f), a portion of the molten metal is redirected upwards and impacts the lower surface of the filter crossbar (1L). This redirects the flow in the opposite direction of the X component of the velocity vector, causing the X component of the flow to return in the direction of the inlet portion (10i). The flow then impacts the wall and is redirected upwards again until it impacts the lower surface of the wall crossbar (2L), thereby forcing it to change the direction of the X component of the velocity vector again in the direction of the outlet portion (10o). Therefore, the molten metal can continue to flow toward the outlet portion (10o) across the filter module (1) and downwards to the tundish outlet (11o). The filter unit may include additional filter crossbars to combine with corresponding additional wall crossbars as additional baffles to change the X component of the velocity vector.

[0058] Technicians can adjust the desired portion of molten metal forced through a given filter unit (1f) by changing the dimensions of the bypass passage (2b) to make it more or less tortuous and thus more or less easier to flow through compared to the filter unit. Relevant dimensions include, for example, the maximum width (t12) (where t12>0), the width of the filter crossbar (t1L), the width of the wall crossbar (t2L), the distance between the filter crossbars (d1L), the distance between the wall crossbars (d2L), the separation distance between the wall crossbars and the filter crossbars measured along the vertical axis (Z) (|d1L-d2L|), and so on.

[0059] According to at least one embodiment, the ratio of the sum of the widths (t1L, t2L) of the filter crossbars and the wall crossbars (1L, 2L) to the maximum width (t12) of the bypass passage (2b) ((t1L+t2L) / t12) is between 20% and 150% (i.e., 0.2≤(t1L+t2L) / t12≤1.5), preferably between 30% and 120%, and more preferably between 50% and 100%.

[0060] The portion flowing through the filter unit also depends on the opening height (h2) and the minimum filter module height (h1). According to at least one embodiment, the ratio (h2 / h1) of the opening height (h2) to the filter module height (h1) is between 20% and 95% (i.e., 0.2 ≤ h2 / h1 ≤ 0.95), preferably between 40% and 80%.

[0061] A simple way to characterize the tortuosity of the bypass path is to draw a straight line from the base plate (10f) in the inlet section through the bypass path (2b) to the outlet section. According to at least one embodiment, such a straight line does not exist because it cannot reach the base plate, as shown in Figures 4(b) and 4(d), or the line forms an angle (θ) with the vertical axis (Z) that does not exceed 70°, preferably not more than 60°, more preferably not more than 45°, and most preferably not more than 35°. This angle is illustrated in Figures 4(a) and 4(c).

[0062] The above conditions prevent the molten metal from finding a straight flow path from the bottom plate (where the molten metal bounces back after being discharged from the ladle (5L)) through the bypass passage (2b). If such a flow path were available, a significant portion of the molten metal would bypass the filter unit (1f) and instead flow through the bypass passage, which is clearly undesirable.

[0063] For example, for an intermediate package with a cavity height (h10) between 800 and 1800 mm, preferably between 1000 and 1300 mm, the opening height (h2) can be between 80 and 600 mm, preferably between 100 and 500 mm. The maximum width (t12) separating the wall from the filter module in the bypass passage (2b) can be between 60 and 800 mm, preferably between 80 and 600 mm. The distance (d1L) between the filter crossbar and the bottom plate can be between 80 and 650 mm, preferably between 100 and 620 mm, and the distance (d2L) between the wall crossbar and the bottom plate can be between 80 and 600 mm.

[0064] In several different embodiments, the wall crossbar width (t2L) and the filter crossbar width (t1L) may be between 20 and 200 mm; in some embodiments, the wall crossbar width (t2L) and the filter crossbar width (t1L) may be between 50 and 150 mm. In at least one embodiment, each of the wall crossbar width (t2L) and the filter crossbar width (t1L) has a minimum value of 20 mm. In at least one embodiment, each of the wall crossbar width (t2L) and the filter crossbar width (t1L) has a maximum value of 200 mm. However, in some embodiments, the wall crossbar width (t2L) and the filter crossbar width (t1L) may be adjusted or customized based on the size and dimensions of the intermediate package (10). However, in several different embodiments, each of the wall crossbar width (t2L) and the filter crossbar width (t1L) is a non-zero value; in other words, various embodiments of the subject matter of this disclosure include the presence of wall crossbars and filter crossbars regardless of their respective widths.

[0065] The advantage of the intermediate package disclosed herein is that most of the debris and other solids are removed from the molten metal (20m) before it is poured into the tool (25). When the filter unit (1f) is new or its channels are clean and free of solid debris, the filter unit is characterized by a pressure drop (ΔP) between the inlet and outlet sides of the filter unit equal to the nominal pressure drop (ΔP0). During use, debris and other solids trapped in the channels accumulate and partially and eventually completely block some or all of the channels. The pressure drop (ΔP) increases, making it more difficult for the molten metal to flow through the filter unit (1f). With an increase in pressure drop (ΔP), it is found that the molten metal flows more easily through the bypass passage (2b) than through the filter unit.

[0066] For example, when the filter unit (1f) is fully operational (e.g., ΔP / ΔP0 < 2), more than 50%, preferably more than 60%, more preferably more than 75%, and most preferably more than 85% of the molten metal flows through the filter unit (1f). The molten metal flowing from the inlet portion (10i) through the filtration system to the outlet portion (10o) flows through the filter unit (1f), and the remainder flows through the bypass passage (2b). However, in the case of significant blockage of the filter unit (i.e., when the pressure drop reaches a high value, e.g., ΔP / ΔP0 > 10), it is found that the molten metal is difficult to flow through the filter unit (1f) and flows out more easily through the bypass passage (2b). This reduces the risk of seeing the molten metal level (h20) rise to a dangerous level close to the cavity height (h10) in the inlet portion.

[0067] In addition to effectively and easily meeting the requirements of specific applications in a modular way, this solution is also very simple to implement, requiring only two simply designed modules: a wall module (2) and a filter module (1). This solution is therefore very economical and ensures continuity during metal casting.

[0068] A tundish (10) for continuous metal casting, the tundish defining a cavity having a cavity height (h10) measured along a vertical axis (Z), a cavity length measured along a longitudinal axis (X), and a cavity width measured along a transverse axis (Y), wherein X⊥Y⊥Z, and wherein the cavity includes: an inlet portion (10i) configured to receive a flow of molten metal (20m) discharged from the outside of the tundish into the cavity by gravity; an outlet portion (10o) including an outlet (11o) configured to discharge the molten metal from the cavity into a mold; and a filtration system separating the inlet portion (10i) from the outlet portion (10o) over the entire cavity width. The filtration system includes a filter module (1) that extends over the entire width of the cavity and extends inside the cavity, wherein the filter module includes an inlet side facing the inlet portion (10i) of the intermediate package and extending from the bottom plate (10f) of the cavity to a top surface, the shortest distance from the top surface to the bottom plate along the vertical axis (Z) being equal to the minimum filter module height (h1), and wherein the filter module (1) includes a filter unit (1f) that extends along the vertical axis (Z) over the filter height (hf) and is provided with channels (1c) that extend from a channel inlet (i.e., an opening on the inlet side facing the inlet portion (10i) of the intermediate package) to a channel outlet (i.e., an opening on the outlet side of the filter module (1) facing the outlet portion and separated from the inlet side by a filtration depth (tf). The filter system further includes a wall module (2) comprising a wall extending over the entire width of the cavity and extending within the cavity, defining one or more openings (2o) distributed across the width of the wall and at an opening height (h2) measured from the base plate (10f) along the vertical axis (Z). The filter module (1) is arranged closer to the outlet (11o) than the wall module (2), and a bypass passage (2b) with a maximum width (t12) measured along the longitudinal axis (X) is defined between the wall module (2) and the filter module (1), such that the molten metal can flow only from the inlet portion through the one or more openings to the inlet side of the filter module (1), and from the one or more openings to the outlet portion via a channel flowing through the filter unit (1f) or the bypass passage (2b), characterized in that...

[0069] a. The ratio (h2 / h1) of the opening height (h2) to the filter module height (h1) is between 20% and 95% (0.2 ≤ h2 / h1 ≤ 0.95), preferably between 40% and 80%.

[0070] b. The wall rung (2L) protrudes from the entire width of the wall at a wall rung distance (d2L) from the bottom plate (10f) that does not exceed the minimum filter module height (h1), that is, d2L≤h1, and extends toward the inlet side of the filter module (1) without contacting the filter module. The wall rung (2L) has a width (t2L) measured along the longitudinal axis (X), where 0<t2L<t12,

[0071] c. The filter rung (1L) protrudes from the entire width of the inlet side of the filter module (1) at a filter rung distance (d1L) from the bottom plate (10f) that exceeds the opening height (h2), that is, d1L>h2, and is offset relative to the wall rung (2L), that is, d1L≠d2L; and the filter rung extends toward the wall module (2) without contacting the wall module or the wall rung. The filter rung (1L) has a width (t1L) measured along the longitudinal axis (X), where 0<t1L<t12, and

[0072] d. The ratio of the sum of the widths (t1L, t2L) of the filter rung and the wall rung (1L, 2L) to the maximum width (t12) of the bypass passage (2b) ((t1L+t2L) / t12) is between 20% and 15%, that is, 0.2≤(t1L+t2L) / t12≤1.5, preferably between 30% and 120%, more preferably between 50% and 100%.

[0073] The foregoing description is presented merely for the purpose of clear understanding, and no unnecessary limitation shall be construed therefrom, as modifications within the scope of the present invention may be apparent to those of ordinary skill in the art.

[0074]

[0075]

Claims

1. A tundish (10) for continuous metal casting, the tundish defining a cavity, wherein, The cavity has a cavity height (h10) measured along the vertical axis (Z), a cavity length measured along the longitudinal axis (X), and a cavity width measured along the transverse axis (Y), wherein X⊥Y⊥Z, and wherein the cavity comprises: An inlet section (10i) is configured to receive a flow of molten metal (20m) discharged from the outside of the tundish into the cavity of the tundish by gravity; An outlet section (10o) includes an outlet (11o) configured to discharge the molten metal from the cavity into the mold; A filtration system that separates the inlet portion (10i) and the outlet portion (10o) across the entire cavity width, the filtration system comprising... A filter module (1) extends over the entire width of the cavity and extends within the cavity, wherein the filter module includes an inlet side extending toward the inlet portion (10i) of the intermediate package and from the bottom plate (10f) of the cavity to a top surface, the shortest distance from the top surface to the bottom plate along the vertical axis (Z) being equal to the minimum filter module height (h1), and wherein the filter module (1) includes a filter unit (1f) extending along the vertical axis (Z) over the filter height (hf) and provided with channels (1c) for these channels. From the channel entrance, that is, the opening on the entrance side of the entrance portion (10i) facing the intermediate package. Extending to the channel outlet, that is, the opening of the filter module (1) at the outlet side facing the outlet portion and separated from the inlet side by a filtration depth (tf); and A wall module (2) includes a wall that extends over the entire width of the cavity and extends within the cavity, defining one or more openings (2o) distributed over the width of the wall and at an opening height (h2) measured from the base plate (10f) along the vertical axis (Z). The filter module (1) is arranged closer to the outlet (11o) than the wall module (2), and a bypass passage (2b) with a maximum width (t12) measured along the longitudinal axis (X) is defined between the wall module (2) and the filter module (1), such that the molten metal can only flow from the inlet portion through the one or more openings to the inlet side of the filter module (1), and from the one or more openings to the outlet portion through the channel of the filter unit (1f) or the bypass passage (2b). Its features are, A wall crossbar (2L) protrudes from the wall of the wall module (2) at a distance (d2L) from the base plate (10f) not exceeding the minimum filter module height (h1), and extends toward the inlet side of the filter module (1) without contacting the filter module (1). The wall crossbar (2L) has a width (t2L) measured along the longitudinal axis (X), wherein the width (t2L) of the wall crossbar (2L) is greater than 20 mm and less than the maximum width (t12). A filter crossbar (1L) protrudes from the inlet side of the filter module (1) at a distance (d1L) from the base plate (10f) exceeding the opening height (h2) and is offset relative to the wall crossbar (2L). The filter crossbar (1L) extends toward the wall module (2) without contacting the wall module or the wall crossbar. The filter crossbar (1L) has a width (t1L) measured along the longitudinal axis (X), wherein the width (t1L) of the filter crossbar (1L) is greater than 20 mm and less than the maximum width (t12).

2. The intermediate package according to claim 1, wherein, The ratio of the opening height (h2) to the filter module height (h1) is between 20% and 95%.

3. The intermediate package according to claim 2, wherein, The ratio of the opening height (h2) to the filter module height (h1) is between 40% and 80%.

4. The intermediate package according to claim 1, wherein, The ratio of the sum of the width (t1L) of the filter crossbar (1L) and the width (t2L) of the wall crossbar (2L) to the maximum width (t12) of the bypass passage (2b) is between 20% and 150%.

5. The intermediate package according to claim 4, wherein, The ratio of the sum of the width (t1L) of the filter crossbar (1L) and the width (t2L) of the wall crossbar (2L) to the maximum width (t12) of the bypass passage (2b) is between 30% and 120%.

6. The intermediate package according to claim 5, wherein, The ratio of the sum of the width (t1L) of the filter crossbar (1L) and the width (t2L) of the wall crossbar (2L) to the maximum width (t12) of the bypass passage (2b) is between 50% and 100%.

7. The intermediate package according to claim 1, wherein, The wall module (2) includes a single opening (2o) extending from a lower boundary of 0% to 5% of the cavity height (h10) from the base plate (10f) to the lower edge of the wall, thereby defining the opening height (h2) as the distance between the base plate and the farthest point of the lower edge.

8. The intermediate package according to claim 1, wherein, The wall module (2) includes more than one opening (2o), wherein the top opening is defined as the opening having the boundary furthest from the base plate (10f), the boundary furthest from the base plate (10f) being separated from the base plate by the opening height (h2).

9. The intermediate package according to claim 1, wherein, The ratio of the opening height (h2) to the cavity height (h10) is between 10% and 60%.

10. The intermediate package according to claim 9, wherein, The ratio of the opening height (h2) to the cavity height (h10) is between 40% and 60%.

11. The intermediate package according to claim 1, wherein, A straight line extending through the bypass passage (2b) between the base plate (10f) of the inlet portion and the outlet portion. Does not exist, or An angle (Z) with the vertical axis (Z) θ The angle does not exceed 70°.

12. The intermediate package according to claim 11, wherein, The angle shall not exceed 60°.

13. The intermediate package according to claim 12, wherein, The angle shall not exceed 45°.

14. The intermediate package according to claim 1, wherein, The distance between the filter crossbars (d1L) is greater than the distance between the wall crossbars (d2L).

15. The intermediate package according to claim 1, wherein, The wall module (2) includes more than one wall crossbar (2L), which are parallel to each other, never in contact with each other, and distributed at the height of the wall module (2).

16. The intermediate package according to claim 1, wherein, The filter module (1) includes more than one filter crossbar (1L), which are parallel to each other, never touch each other, and are distributed at the height of the filter module (1).

17. The intermediate package according to claim 1, wherein, The bypass passage (2b) reverses the flow direction component along the longitudinal axis (X) of the molten metal flowing from the inlet portion (10i) of the cavity to the outlet portion (10o).

18. The intermediate package according to claim 1, wherein, The lower boundary of the filter unit (1f) is separated from the bottom plate (10f) of the cavity by a small distance (hd), the small distance being between 0 and 10 cm, and / or wherein, The distance between the upper boundary of the filter unit (1f) and the base plate (10f) is the sum of the filter height (hf) and the smaller distance (hd), such that the ratio of the distance to the opening height (h2) is between 0.7 and 1.

2.

19. The intermediate package according to claim 18, wherein, The smaller distance is defined as being between 2 and 5 cm; and / or The ratio of the distance between the upper boundary of the filter unit (1f) and the base plate (10f) to the opening height (h2) is between 80% and 100%.

20. The intermediate package according to claim 1, wherein, The wall crossbar (2L) protrudes from a portion of the width of the wall or the entire width of the wall.

21. The intermediate package according to claim 1, wherein, The filter crossbar (1L) protrudes from a portion of the width of the inlet side of the filter module (1) or the entire width of the inlet side of the filter module (1).

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