Tundish cover

Abstract

A thermal insulation cover for covering an opening in a tundish and forming a sealed closure thereabout according to this invention comprises a pair of cover members adapted to be positioned in covering relation over the opening, and means for locking the cover members together and ensuring that respective abutment faces of the covers are spaced apart by a predetermined amount. The locking means comprises first and second brackets mounted respectively on the cover members, an elongated lock bar mounted for movement relative to the brackets, the lock bar having a stop member at its rearward end to abut the first bracket to limit movement of the bar and position a recess at its forward end relative to the second bracket, and a lock member mountable in the recess to abut the second bracket to prevent retrograde movement of the bar. Complete thermal sealing is ensured by a first thermal seal member being compressed between the lower surfaces of the respective cover members and the top of the tundish, and a second thermal seal member being compressed between the abutment faces of the cover members.

Description

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a sealed tundish for use in the continuous casting of molten steel and more particularly to an insulating cover for covering the opening of a tundish and an improved tundish closure for such use.

[0004] 2. Description of Related Art

[0005] The adverse effects of atmospheric oxygen and nitrogen contacting molten steel in a pouring or casting operation are well known, and numerous patents have issued on apparatus and devices for shielding the molten metal from the atmosphere to prevent oxygen and nitrogen pickup during such operations. In a continuous casting operation, it is conventional for molten steel to be transported from the converter to the caster in a ladle where it is supported on a turret for movement into position above a tundish having its pouring outlet, or outlets, directly above the open top of the caster mold, or molds.

[0006] Molten steel in the ladle is dispensed through an outlet in the ladle bottom under control of a slide valve. A refractory shroud tube attached to the slide valve extends through an opening in the tundish cover to a point beneath the surface of the pool of metal in the tundish during casting. From the tundish the metal flows through one or more bottom outlets under control of stopper valves, again through a refractory tube or tubes extending below the level of the molten metal the caster mold.

[0007] Thus, the molten metal is shielded from the atmosphere in its flow path from the ladle into the tundish and from the tundish into the mold. In the tundish, however, and particularly during the initial filling of a newly lined tundish, contact with the atmosphere can result in substantial pickup and oxidation of the molten steel.

[0008] Accordingly, attempts have been made to purge atmosphere containing free oxygen and nitrogen from the interior of as tundish by injecting an inert gas into the tundish. However, because of the size and weight of the tundish cover used in modern casters, the number and size of openings required in the conventional tundish cover, and the fact that the tundish cover is oftentimes in two or more sections, such attempts to purge the tundish have required an excessive amount of inert gas and have not been entirely successful.

[0009] In a continuous casting process, the tundish cover, due to its weight, would typically be left in place once installed. The tundish cover typically has several openings therethrough for the pouring of steel from the ladle or to accommodate the insertion and manipulation of the stopper rods employed to control the flow rate from the tundish. The openings in the tundish cover are necessarily larger than the shroud or stopper rod to be inserted therethrough. As such, introducing a sufficient amount of purge gas into the tundish can be a problem.

[0010] Further, the greatest heat loss occurs through the central opening in the top of the tundish. A sealed closure or cover that is not cumbersome and enables its deployment is desirable. Additionally, a multi-piece cover would enable replacement of one of the cover parts and its sealing capabilities deteriorate in use.

[0011] A method of continuous casting using a sealed tundish is disclosed in U.S. Pat. No. 5,645,121, issued Jul. 8, 1997 to Barnes. The continuous seal is formed between a rigid one-piece cover and the tundish top wall by a plurality of self-supporting sealing boards of refractory fiber material placed in side-by-side relation on the open top of the tundish and form a continuous seal underlying the cover.

[0012] A pre-formed rigid one-piece multi-layered thermal insulating heat conservation cover adapted to be placed over and have a raised central portion thereof fitted into the opening of a hot liquid metal transfer car is disclosed in U.S. Pat. No. 5,643,529, issued Jul. 1, 1997 to Scriven, the disclosure of which is specifically incorporated herein by reference. The cover materials are adapted to dissolve into the molten metal if the metal is poured directly onto the cover. The dissolved materials do not contaminate the metal in the transfer car and the cover is replaced. This may be undesirable in certain continuous casting operations for a variety of reasons, including the downtime needed to replace the cover, the costs associated with the cover, and an ongoing need to keep a supply of covers in inventory.

SUMMARY OF THE INVENTION

[0013] Accordingly, objects of this invention are provision of a two-piece cover adapted for placement about the top of an upwardly open tundish which facilitates easy and safe positioning, is capable of providing the airtight seal associated with a one-piece cover, ensures heat retention within the tundish when installed, and is provided with a simple arrangement for interlocking the two cover parts in a sealed relation.

[0014] Advantageously, the two-part cover enhances ease of installation and minimization of heavy equipment moving apparatus.

[0015] A thermal insulation cover for covering an opening in a tundish and forming a sealed closure thereabout according to this invention comprises:

[0016] a first and a second cover member, each said cover member including a pair of opposed upper and lower surfaces and an outer periphery, said outer periphery comprising a sidewall and an abutment face, said lower surfaces being adapted to be positioned in covering relation over said opening and said abutment faces being adapted to be positioned in juxtaposition with one another when said surfaces are covering said opening, and

[0017] interlocking means associated with said sidewalls for locking the cover members together.

[0018] The interlocking means comprise a first channel or bracket fixedly secured to the sidewall of the first cover member, a second channel or bracket fixedly secured to the sidewall of the second cover member, an elongated lock bar having a forward end portion for receiving a lock member and a rearward end portion in the form of a stop member. The lock bar is associated with the first bracket for slidable movement thereto from a first position disconnected from the second bracket and to a second position whereat the stop member engages the first bracket to prevent further movement of the lock bar, the lock bar thereat being disposed at least in part within and having its forward end portion disposed outwardly from the second bracket to receive the lock member.

[0019] The lock member engages the second bracket to prevent retrograde movement of the lock bar and thus prevents the cover members from separating from one another.

[0020] Preferably, the cover members would include a respective pair of second sidewalls, and the second sidewalls would be provided with the above described interlocking means.

[0021] The lock member is in the form of a generally rectangularly shaped block and the forward end portion of the lock bar is cut-out to form a rectangular shaped recess for receiving the lock member. A threaded fastener is utilized to fixedly secure the block to the lock bar.

[0022] The stop member comprises a leg which extends perpendicularly from the lock member to engage the first channel means.

[0023] Complete thermal sealing is ensured by a first thermal seal member being compressed between the lower surfaces of the respective cover members and the top extensions of the vertical sidewalls of the tundish, and a second thermal seal member being compressed between the abutment faces of the cover members.

[0024] For a more complete understanding of the present invention, reference is made to the following detailed description and accompanying drawings. In the drawings, like reference characters refer to like parts throughout the several views in which:

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a top plan view of an interlocked two part cover providing an improved seal for a continuous caster tundish;

[0026] FIG. 2 is schematic view in section of a continuous caster operation showing the two cover parts in sealing relation with the tundish, taken along lines 2-2 of FIG. 1;

[0027] FIG. 3 is a section view of the tundish cover taken along line 3-3 of FIG, 1; and

[0028] FIGS. 4-7 are partial schematic views showing the steps taken in obtaining a locked sealed relation between the two cover parts.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0029] Referring now to FIGS. 1-4, there is depicted therein a thermal insulating cover 10 in accordance with the present invention for covering and sealing the opening of a tundish 12. The tundish 12 is used in continuous steel casting operation with molten steel 13 being supplied from a ladle 14 through a conventional slide gate 16 and shroud tube 18 into the sealed inner chamber 20 of the tundish.

[0030] The tundish, illustrated schematically in FIG. 2, comprises a refractory lined vessel 22 of generally rectangular shape having a bottom wall 24 with a pair of pouring openings 25 therein, and sidewalls 28 vertically extending upwardly from the bottom wall to form a closable open top. A pair of pouring tubes 26 project downwardly from the bottom wall 24 to convey molten metal via respective slide gates 16 into caster molds 27 therebelow.

[0031] In addition, a pair of interior skimmer or splash walls 29 are provided within the tundish. One or more inlets 79 are provided in the sidewalls 28 to permit argon or some other suitable gas to be admitted to purge oxygen-containing atmosphere from the interior of the tundish.

[0032] The cover 10 is removably supported on the upward extension of the sidewalls 28 and disposed in substantially closing relation over the open top to prevent thermal heat loss from the molten metal contained within the tundish.

[0033] According to the present invention, the cover or lid 10 is formed by a pair of cover members 30 and 32, each being of like shape and construction. The cover members are generally rectangular in form and include, respectively, a pair of generally parallel sidewalls 34 and 36, an endwall 38 and 40, and an abutment face 42 and 44. The cover members are approximately of equal size and cover about one-half of the tundish opening, and the respective abutment faces 42 and 44 are adapted to be brought into juxtaposition with one another when the cover members are positioned into covering relation with the opening

[0034] The cover members 30 and 32 are multilayered and rigid in construction to enable their being moved into and from covering relation with the tundish. Each cover comprises an upper sheet 48 which defines an upper surface 48a of the cover member exposed to the air, a lower sheet 50 which defines a lower surface 50a of the cover member exposed to the molten steel, and a middle sheet or end bar 52 sandwiched between the upper and lower sheets 48 and 50 to provide support.

[0035] The upper and middle sheets 48 and 52 are formed of a metal, such as steel, and preferably similar to the metal from which the tundish is formed. These materials are conventional and will not be described further.

[0036] The lower sheet 52 is formed of a refractory material, such as a castable low cement or porous brick. Similarly, this material is conventional and will not be described further.

[0037] To inhibit heat from escaping or air and nitrogen from entering the chamber 20, a thermal seal is provided between the two cover members 30 and 32 and around the tundish. A first seal member 54 is interposed between the lower surface 50a of the cover members and the upward ends of the vertical walls 28 of the tundish 12 and compressed into sealing relation. A second seal member 56 is disposed between the respective abutment faces 42 and 44 of the two cover members and compressed into sealing relation when the cover members are positioned about the opening.

[0038] Preferably, the seal members 54 and 56 are comprised of a thermal insulator, such as a non-metallic ceramic material. In a preferred embodiment, the seal members comprise a mixture of a commercially available ceramic called CERROWOOL, which is available from Premier Refractories, and silica sand. Details of the seal construction and formation are provided in the above U.S. Pat. No. 5,643,529 to Scriven incorporated herein by reference.

[0039] Preferably, the cover 10 comprises means for removably securing or interlocking the two cover members together. In this regard, an elongated U-shaped channel member or bracket 58 is fixedly secured to each sidewall 36 of the cover member 32, each bracket extending along its respective sidewall in generally parallel relation to the upper and lower surfaces 48a and 50a of the cover member. The channel member 58 includes a mating endface 58a, an abutment endface 58b and a passageway 58c extending between the end faces 58a and 58b.

[0040] A channel or bracket 60 is fixedly secured to each sidewall 34 of the cover member. As shown, the bracket 60 comprises a pair of elongated planar plates that are disposed in parallel, vertically spaced relation to one another and to the upper and lower surfaces 48a and 50a. The plates 60 include a mating endface 60a, an abutment endface 60b, and define a passageway 60c extending between the endfaces 60a and 60b.

[0041] As mounted to their respective sidewalls 34 and 36, the respective passageways 60c and 58c of the plate members 60 and bracket 58 are axially aligned with one another.

[0042] An elongated generally planar lock bar 62 is adapted to slide within the passageway 60c formed between a respective pair of plates 60 in the cover member 30 and pass into and partially through the passageway 58c defined by the channel member 58 in the cover member 32. The lock bar 62 includes a generally rectangular cut-out locking recess 64 adjacent its forward end 62a and a leg or stop member 66 extending perpendicularly adjacent its rearward end 62b. The locking recess 64 includes a pair of opposed vertical walls 64a and 64b and a horizontal base 64c.

[0043] The leg 66 includes a vertically disposed abutment face 66a adapted to bear against an abutment endface 60b on one of the plates 60. The leg limits movement of the lock bar 62 relative to the plates 60 and the channel member 58 and positions the locking recess 64 adjacent to the abutment endface 58b and outwardly of the passageway 58c of the U-shaped channel 58.

[0044] A generally rectangular lock member 68, shown in the form of a generally rectangular block, is adapted to be removably connected to the locking recess 64. The lock member 68 includes a pair of first walls 68a and 68b adapted to be disposed vertically, and upper and lower walls 68c and 68d adapted to be disposed horizontally. The lock member 68 is adapted to be seated in the locking recess 64 in such manner that the walls 68a and 68b are in juxtaposition with the respective walls 64a and 64b of the locking recess 64 and the lower wall 68d is seated against the recess wall 64c.

[0045] Preferably, the lock member 68 is secured in the recess such as by means of a bolt, pin or other suitable securement or fastener member. As shown, a bore 68e extends between the upper and lower walls 68c and 68d and a threaded fastener 70 extends through the bore for securement to the lock bar. Further, if appropriately dimensioned, and if the mating sidewalls 68a and 68b of the block and sidewalls 64a and 64b of the recess were suitably tapered, a frictional securement could be provided.

[0046] Importantly, the abutment face 68a of the lock member 68 engages the rear abutment endface 58b of the channel member 58 to prevent retrograde movement and disconnection of the lock bar 62 from the channel 58c. The leg or stop member 66, in cooperation with the lock member 68, prevents retrograde movement of the cover member 30 oppositely from the cover member 32. Importantly, so interlocked, the seal between the abutment faces 42 and 44 of the cover members 30 and 32 is maintained.

[0047] The cover 10, by virtue of the sheet material employed, is rigid and relatively inflexible. This rigidity gives improved handling and ensures blockage of the tundish opening. Although the cover can be formed to any configuration, what is important is that the cover be rigid and be configured to block the opening to prevent heat loss by sealing the thermal energy within the tundish. Additionally, heat loss from the tundish occurs when the tundish is empty. If the cover is in place over the tundish when it is empty, this also preserves heat.

[0048] The cover members 30 and 32 are provided with openings or holes to permit various apparatus to gain access to the interior of the tundish and enhance the casting process. Typically, these openings would be larger than the cross-section of the apparatus that are to project therethrough during the casting operation to avoid interference with the insertion and/or manipulation of the respective apparatus as required during casting.

[0049] According to a preferred embodiment of this invention, the cover 32 has a tear drop shaped opening 72 for receiving the shroud tube 18. The cover member 30 has a pair of circular openings 74 and 76 to permit the insertion of slag removal rods or gas lances or for receiving stopper rods (not shown) and an opening 78 to receive a temperature probe (not shown). permit argon or some other suitable gas to be admitted to purge oxygen-containing atmosphere from the interior of the tundish The stopper rods control flow through to the pouring tubes 26 via the outlets 25.

[0050] Each of these openings 72, 74, 76 and 78 are provided with a breakable cover or mini-cap “C” to ensure that oxygen does not enter the tundish or that heat escapes from the tundish. Preferably, the mini-cap “C” is suitably configured and sized to cover its respective opening and comprises a sheet of a thermal insulator, such as a non-metallic ceramic material. These materials are commercially available and known to those skilled in the art. In use, the shroud 18 or the stopper rods would penetrate through the ceramic caps and the material thereof would form a seal therearound.

[0051] With respect to the pour opening 72, it is contemplated that an interior ledge be formed therearound to form a recessed vacuum seal. A cap off thermal insulator, such as a ceramic fiber board is, then, formed to the configuration of the opening and is seated on the ledge.

[0052] To assist in the placement and removal of the cover members 30 and 32 from the tundish 12, hooks and positioning brackets are disposed along the sidewalls 34 and 36. As shown in FIG. 1, each sidewall 34 and 36 is provided with a hook 82 and a positioning bracket 82.

[0053] Turning to FIGS. 3-7, the steps of providing a sealed closure are illustrated. The cover members 30 and 32 are placed in covering relation over the tundish opening with their respective abutment endfaces 42 and 44 and the endfaces 60a and 58a of the brackets 60 and 58 in juxtaposition with one another and the seal member 56 positioned in the separation between the covers. The lock bar 62 is slidably disposed relative to the cover member 30 and moved in a first direction spaced from and disconnected from the cover member 32 and into the passageway 58c of the U-shaped channel 58. Continued movement of the lock bar 62 is prevented when the abutment face 66c of the leg 66 engages the endface 60b of the plate 60, whereupon the locking recess 64 is placed in juxtaposition with the endface 58b of the U-shaped channel 58. The lock member 68 is secured to the 64.

[0054] Importantly, the locking arrangement ensures that a proper gap between the cover members and thus compression of the seal member 56 is achieved. According to a preferred embodiment, a tundish cover 10 comprised a pair of cover members 30 and 32 each approximately 98 inches by 71 inches, about 7½ inches thick, and interlocked to compress the seal and provide a seal gap of approximately 0.375 inches.

[0055] By virtue of the mini-caps and the pour opening cover, there is maintained a substantially near zero atmosphere within the Tundish.

[0056] Although various embodiments of the invention have been disclosed for illustrative purposes, it is to be understood that variations and modifications can be made by one skilled in the art without departing from the spirit of the invention. For example, the locking arrangement could be modified wherein a single plate 60 would be provided on the cover member 30, and the leg 66 would extend downwardly from the lock bar 62. As such, the leg 66 would still engage the bracket 60, and position the locking recess 64 in juxtaposition with the U-shaped channel 58.

Claims

1. A thermal insulation cover for covering an opening in a tundish and forming a sealed closure thereabout comprising: a first and a second cover member, each said cover member including a pair of opposed upper and lower surfaces and an outer periphery, said outer periphery comprising a sidewall and an abutment face, said lower surfaces being adapted to be positioned in covering relation over said opening and said abutment faces being adapted to be positioned in juxtaposition with one another when said surfaces are covering said opening, and interlocking means associated with and extending outwardly from said sidewalls for locking the cover members together.

2. The thermal insulation cover as claimed in claim 1 wherein said interlocking means comprises: a first bracket fixedly secured to one of said sidewalls, a second bracket fixedly secured to the other of said sidewalls, a lock bar having a rearward end portion in the form of a stop member and a forward end portion, said lock bar associated with said first bracket for movement from a first position disconnected from said second bracket and to a second position whereby said stop member is engaging the first bracket to prevent further movement of the lock bar, and a lock member removably mounted to the forward end portion of the lock bar, the lock member engaging the second bracket to prevent retrograde movement of the lock bar.

3. The thermal insulation cover as claimed in claim 2 wherein the cover members comprise a first and a second sidewall, each respective pair of first and second sidewalls being provided with a like interlocking means.

4. The thermal insulation cover as claimed in claim 2 wherein the forward end portion of the lock bar is cut-out to form a recess for receiving the lock member.

5. The thermal insulation cover as claimed in claim 4 wherein the lock member comprises a rectangular block

6. The thermal insulation cover as claimed in claim 5 wherein a threaded bolt is utilized to fixedly secure the lock member to the lock bar.

7. The thermal insulation cover as claimed in claim 6 wherein the stop member comprises a leg which extends perpendicularly from the lock member to engage the first channel.

8. The thermal insulation cover as claimed in claim 1 further comprising sealing means for ensuring a thermal seal between the cover members and the tundish, the sealing means comprising a first thermal seal member compressed between the lower surface of the cover members and the walls of the tundish, and a second thermal seal member compressed between the abutment faces of the cover members.

9. The thermal insulation cover as claimed in claim 2 wherein said first bracket comprises an elongated plate having first and second ends, said second bracket comprises a generally U-shaped channel having first and second ends and a passageway extending between its ends, the first ends of said brackets being disposed in juxtaposition with one another, said lock bar comprises an elongated plate having a rearward end portion in the form of a stop member and a forward end portion, said stop member engaging the second end of said first bracket and said forward end portion being in juxtaposition with the second end of said second bracket when said lock bar is in said second position, and said lock member comprises a block having an endface abutting the second end of said second bracket when the lock bar is in said second position.

10. The thermal insulation cover as claimed in claim 9 wherein the forward end portion of said lock bar includes a rectangularly shaped recess, and said stop member comprises a rectangularly shaped block fittable within said recess to prevent retrograde movement of the lock bar.

11. The thermal insulation cover as claimed in claim 1 wherein each said cover member having a metallic upper sheet forming an outer shell exposed to the air, a non-metallic lower sheet, and a middle sheet interposed between the upper and lower sheets, the non-metallic lower sheet comprising a fused woven blend of ceramic fiber and silica sand.

12. A sealed tundish for use in a continuous steel casting, comprising: an upwardly open molten metal receiving vessel having substantially vertically standing walls and a bottom wall, a two part cover sized to cover the vessel opening, and means for locking the two cover parts together in sealed relation.