GB2545664A - Improved tube changer - Google Patents

Abstract

A changer apparatus for changing a refractory component 302, 306 in a casting apparatus comprises a changing mechanism comprising an electric ram (305, figure 11) operable to move said component between a position offset from a path of a flow channel through which molten metal may pass 306 and a position lying in the path of the flow channel 302. The mechanism preferably comprises a channel (503, figure 5) and a pusher component (310, figure 3A). The ram may comprise a moveable piston (1100, figure 11) which extends from and retracts into an outer casing (1002), a drive mechanism and an electric motor. Also disclosed is a changer device for changing a refractory nozzle or a shroud tube 302, 306 under a tundish comprising a frame, a horizontally extending channel member (503, figure 5) for holding a plurality of nozzles or tubes simultaneously and a pusher (310, figure 3A) comprising an electric ram (305, figure 11) for moving a tube or nozzle between a holding position 306, an operating position 302 located under a liquid metal outlet and a removal position.

Description

IMPROVED TUBE CHANGER

Field of the Invention [0001] The present invention relates to tube changers, particularly although not exclusively tube changers for a tundish.

Background of the Invention [0002] In metal casting, metal is poured into a tundish, which is a broad open container with one or more apertures in the bottom through which molten metal passes into a mould or series of moulds. A tundish allows a reservoir of metal to continue to feed a casting machine whilst ladles are switched, thus acting as a buffer reservoir for hot metal as well as to control the flow during a continuous casting operation. Typically, a casting tundish is lined with refractory materials to enhance the life of the tundish and to be stable when in contact with the liquid metal being cast.

[0003] Referring to Figure 1 herein, there is illustrated schematically apparatus for conventional continuous casting method used for steel production. Molten metal is delivered from a ladle 1 into a tundish 2 via a ladle tube 3. The molten metal passes from the tundish 2 into a mould 4 via a tundish tube 5, from which a continuous slab of metal is cast, and passes into a series of rollers 6 which transport the continuous cast slab to a withdrawal unit 7 at the end of the series of rollers 6. The series of rollers 6 are typically arranged into a turning zone 8, in a gradual curved shape. The cast metal is still at high temperature in this turning zone and therefore flexible. As the metal approaches the withdrawal unit, the temperature reduces, and the metal slab 9 becomes relatively more solid and rigid.

[0004] A series of ladles 1 can be used alternately to fill the tundish 2, so that the casting of the metal slab is continuous, and needs only be interrupted by design, in the case of emergency, or for maintenance of the equipment for example.

[0005] Any stoppages of the continuous casting process result in production downtime, and the object of the continuous casting process is to keep the process running continuously for as long as possible without interruption.

[0006] Between the outlet of the tundish and the mould, the tundish shroud tube 5 guides the molten metal to a continuous casting mould or the like. The shroud tube between the tundish and the continuous casting mould is also conventionally known as a tundish tube.

[0007] Conventionally, the tundish tube is attached from beneath the tundish and is aligned with an upper nozzle fixed inside the tundish. The two are joined together end to end in close contact, while being constantly pressed against each other in the axial direction (upwards/downwards direction). The tundish tube is intended to shield molten steel flow from ambient air in order to prevent oxidation of molten metal. Any oxidation of the metal during casting will change the mechanical properties of the finished metal slab. The tundish tube also has the secondary function of preventing splashes of molten metal during transfer from the tundish to the continuous casting mould.

[0008] Some types of known tundish tube changers are capable of changing the tundish tube underneath the tundish without the need to raise the tundish from the mould.

[0009] Referring to figure 2 herein, there is illustrated schematically a known continuous casting apparatus comprising a ladle 200; a tundish 201; and a mould 202, in which molten metal is transferred from the ladle 200 to the tundish 201 via a hydraulically powered slide gate valve arrangement 204 and through a ladle shroud 205 into the tundish 201; molten metal from the tundish is transferred to the continuous casting mould 202 via a tundish tube 206 which can be changed by a horizontal sliding tundish tube changer 207 which is conventionally hydraulically or pneumatically operated.

[0010] As the tundish tube 206 is a consumable refractory item which becomes affected by chemical and mechanical action from molten metal, for example steel, and other agents, for this reason a regular replacement of the tundish tube is required.

[0011] US 8,778,258 B1 discloses a known tundish tube changer device of a horizontal sliding type for exchanging a tundish tube for use in a continuous casting plant. The tundish tube exchanging device uses a hydraulic cylinder to exchange a tundish tube extending between the underside of the tundish and a mould. The known tundish tube exchanging device has a pair of arms pressing and supporting the lower tube, and a mechanism for laterally sliding the lower tube in a horizontal direction. The tube sliding mechanism operates in a substantially horizontal plane and is hydraulically powered.

[0012] US 6,227,421 B1 describes a tundish for continuous casting in a steel mill and having a rotary type tundish tube changer. In this type of known tube changer, the tube changer comprises a chassis mounted on a tundish; refractory pieces which delimit a pouring channel for passage of steel from the tundish to a continuous mould, the refractory pieces comprising a fixed plate underneath a tundish; an upper refractory tundish tube; a chassis mounted in a fixed position under the plate; a rotatable assembly mounted on the chassis, the rotating member supporting a plate/tube assembly. The rotating assembly holds a lower tube, the lower end of which is located in the continuous casting mould. To change the tube, the rotating assembly rotates so that the lower tube is swung out of the continuous casting mould and replaced by an alternate lower tube held by another part of the rotor. The rotating assembly is pushed by means of an hydraulic jack cylinder attached to an articulated arm. The rotating member rotates over an arc of approximately 90 degrees so that alternate first and second tubes can be swung into and out of position in the casting mould.

[0013] Prior art tube changers for changing the tube at the base of tundish are operated either hydraulically or pneumatically. Problems with prior art hydraulic tube changers include firstly the bulk, the technical complexity and expense of the hydraulic control equipment and secondly the safety problem of having hydraulic oil leaks in contact with high temperature components. Oil leaks can enter the liquid steel and blow out steel which is dangerous.

[0014] Prior art pneumatic tube changers also require a significant amount of hardware and engineered parts including pumps, reservoirs, pneumatic couplings and the like and require regular maintenance.

[0015] WO 2015/067735 describes an example of a submerged nozzle for continuous casting of steel, where the nozzle comprises an elongate tubular member of a refractory material having an upper end which has a protruding annular lip which can be held within a nozzle changing equipment underneath a tundish.

Summary of the Invention [0016] One objective is to reduce the complexity and number of components required for changing consumable refractory components such as nozzles, shroud tubes or blanking / stopper plates in metal casting plants.

[0017] Another objective is to improve the safety of tundish outlet changers, and / or nozzle changers.

[0018] A further objective is to reduce downtime of the apparatus by reducing the maintenance requirement for known tundish outlet changers or nozzle changers.

[0019] A yet further objective is to improve reliability of a tundish outlet changer or nozzle changer.

[0020] According to a first aspect of the present invention, there is provided a changer apparatus for changing a refractory component in a casting apparatus, said changer apparatus comprising: a changing mechanism for moving a said refractory component between a first position in which said refractory component is located offset from a path of a flow channel through which molten metal may pass, and a second position in which said refractory component lies in said path of said flow channel; said changing mechanism characterised by comprising an electric ram operable to move a said refractory component between said first and second positions.

[0021] The invention includes a changer device for changing a refractory tundish tube under a tundish, said changer comprising; a frame adapted to be mounted under a said tundish; a horizontally extending channel member able to hold a plurality of said tubes simultaneously; a pusher for pushing said tundish tube along said channel. said pusher operable to push one or more said tundish tubes along said channel such that said tubes are pushed successively between a holding position in which a said tundish tube is held ready to be pushed into an operating position; said operating position, in which said tundish tube is positioned underneath a liquid metal outlet; and a removal position in which said tundish tube can be removed from said changer device; wherein said pusher comprises an electric ram operable to move said tundish tube between said positions.

[0022] Other aspects are as set out in the claims herein.

Brief Description of the Drawings [0023] For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which:

Figure 1 shows schematically a conventional continuous casting process;

Figure 2 shows a continuous casting apparatus having a prior art sliding gate valve and a prior art horizontal type tundish tube changing device;

Figure 3A herein shows schematically in cutaway view from one side, components of a first novel horizontal type sliding tundish outlet changer according to a first specific embodiment in a continuous casting position;

Figure 3B herein shows schematically the automatic tundish outlet changer of figure 3A in a closed position;

Figure 3C herein shows the automatic tundish outlet changer in an end of cast configuration, where a blank refractory closes off a flow of metal from a tundish;

Figure 3D herein shows the automatic outlet changer of figure 3A with a replacement shroud tube in a ready position, ready to replace a shroud tube currently in use;

Figure 3E herein shows the automatic outlet changer of figure 3A in a fire position in which a replacement shroud tube has been moved into a casting position, and a previously used shroud tube is moved to a removal position;

Figure 3F herein shows the automatic outlet changer of figure 3A operating with a second type of shroud tube having an upper flange extending to one side of the shroud tube in a ready position, ready to replace a shroud tube currently in use;

Figure 3G herein shows the automatic outlet changer in a fire position, in which a replacement shroud tube has been moved into a casting position, replacing a previously used worn tube;

Figure 3H shows the automatic outlet changer in a casting position, in which the second type of shroud tube having a flange is in place;

Figure 31 herein shows the automatic outlet changer in a blanking position at the end of the cast, in which the second type of shroud tube is moved off centre from the main tundish nozzle outlet, so that the flange portion of the second type tundish tube blanks off the end of the channel of the tundish nozzle;

Figure 4 shows in perspective view from one side, the first horizontal sliding tundish tube changer of figure 3 with an electric ram;

Figure 5 shows schematically in view from underneath, the first outlet changer of figures 3 and 4 loaded with two tundish tubes;

Figure 6 herein shows in perspective view, the first automatic outlet changer in an open state with two tundish tubes loaded into the tube changer;

Figure 7 shows in perspective view the first automatic outlet changer in a closed state in which the tube changer can be operated for changing a refractory tube;

Figure 8 shows the first automatic outlet changer in view from underneath, loaded with first and second refractory tubes, in a first operating position;

Figure 9 shows the first automatic outlet changer in view from underneath, loaded with first and second refractory tubes, in a second operating position;

Figure 10 shows schematically an electric ram component and a gate and latch assembly of the first automatic outlet changer in perspective view from the rear;

Figure 11 shows the electric ram component, gate and latch assembly, having an additional piston guard, in view from the front and one side;

Figure 12 herein shows the electric ram, gate and latch assembly of figures 10 and 11, with an additional lower guard around the ram;

Figure 13 herein shows the electric ram, gate and latch assembly with an upper and lower guard around the electric cylinder;

Figure 14 herein shows schematically in perspective view from above and one side a second automatic outlet changer mechanism for holding and changing a refractory tube under a tundish or a ladle, in a continuous casting operation, with an operating arm in a first open operating position;

Figure 15 herein shows schematically in perspective view from above and one side, the second automatic outlet changer of figure 14 showing a tube changing arm being operated to a second operating position to effect a tube change;

Figure 16 herein shows the second automatic outlet changer showing the tube changing arm in a third operating position, further extended for pushing a refractory tube out of an operating position;

Figure 17 herein shows schematically the second automatic outlet changer showing additional guard components around its electric ram, and additional electric cabling and shielding components;

Figure 18 herein shows schematically two types of known nozzle for use in the automatic outlet changer devices described herein;

Figure 19 herein shows schematically a tundish blanking plate which can be used in the automatic outlet changer devices described herein;

Figure 20A herein shows schematically in perspective view from above and one side, an example of a known shroud tube which can be used with the automatic outlet changers described herein; and

Figure 20B herein shows the shroud tube of figure 20A in view from above.

Detailed Description of the Embodiments [0024] There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the description.

[0025] In this specification, the terms electric cylinder and electro cylinder are used interchangeably to describe a ram device which performs a function equivalent to that performed by an hydraulic or pneumatic linear cylinder which operates to extend or contract along a line of action. Such devices may also be termed linear actuators. The term cylinder is not restricted to a circular cylinder, but may include cylinders having a square or rectangular cross-section in a direction perpendicular to a main length axis of the cylinder.

[0026] In the specification, the term ram is used generically to describe electric cylinders, electro cylinders or linear actuators which extend and contract linearly, typically but not essentially along a straight line axis, and which are powered by an electric motor and/ or with an electric control unit.

[0027] In the specification, the term “tube changer” or “nozzle changer” is used to refer to the more general outlet changer apparatus, which is capable of changing even shroud tube, a nozzle plate, or a blanking plate underneath an outlet nozzle of a tundish.

[0028] Figures 3 to 13 herein show various views and component views of the first automatic tube changer. In figures 3 to 13 herein, like components are identified with like reference numerals.

[0029] Referring to figure 3A herein, there is shown a first embodiment automatic tundish outlet changing apparatus 300 in various operating positions during a casting process.

[0030] The automatic tundish outlet changer 300 comprises a mounting plate or main body 301 for mounting a lower refractory tundish tube 302 underneath an upper refractory tundish nozzle 303, said tundish nozzle comprising a base portion of a tundish.

[0031] In figure 3A, there is shown a shroud tube 302 in a casting position, in which an upper flange of the shroud tube has been slid along a channel in the main body 301 position directly underneath the tundish nozzle 303 so that liquid metal can flow through the tundish nozzle 303, through the shroud tube 302 and into a casting. As casting proceeds, the shroud tube 302 becomes worn to the point where it needs to be replaced to avoid failure. Shown in a ready position, is a blank refractory plate 309 which lies in the channel adjacent the shroud tube 302 ready to be pushed underneath the nozzle outlet by a pusher arm 310, which is pushed by a ram 305.

[0032] Referring to figure 3B, there is shown the automatic outlet changer in a closed position. If there is a need during casting to shut off the flow of metal to the casting mould, casting process, for example in an emergency, the pusher arm 310 pushes the refractory blank plate 309 along the channel, displacing the shroud tube 302 and positioning the refractory plate underneath the outlet of the nozzle 303.

[0033] Referring to figure 3C herein, there is shown the automatic outlet changer in an end of cast position, in which the blank refractory plate 309 has closed off the end of the nozzle 303, and the spent shroud tube 302 has been removed.

[0034] Referring to figure 3D herein, there is illustrated the automatic outlet changer in a ready position, in which the current shroud tube 302 in use is in position under the nozzle 303, and a replacement shroud tube 306 has been inserted ready to displace the currently in use shroud tube 302. The pusher arm 310 is ready to push the replacement shroud tube 306 along the channel in the main body, displacing the currently in use shroud tube 302.

[0035] Referring to figure 3E herein, there is illustrated schematically the automatic outlet changer in a “fire position” in which the pusher arm 310 has pushed the replacement tube 306 along the channel, and the replacement tube is now aligned with the outlet of the nozzle 303, replacing the previously in use shroud tube 302. The previously in use shroud tube 302 is in a position where it can be removed from the channel in the main body 301, at which point the casting process will revert to the situation shown in figure 3A above, where a single shroud tube is aligned with the nozzle 303, and a blanking plate 309 is kept ready to shut off the metal flow through the nozzle 303 in case there is a problem emergency requiring shut-off of the metal flow.

[0036] The shroud tube exchange operation between figures 3D and 3E herein takes around 1.2 seconds to implement, as the pusher arm 310 pushes the shroud tube is along the channel of the automatic outlet changer.

[0037] Referring to figure 3F herein, there is shown the same automatic outlet changer apparatus in a ready position, but this time using a second type of shroud tube 314, 315, which has an extended flange portion 316 instead of the substantially square shaped flange of the first tube type 302, 306. The extended flange portion 316 has an upper surface area greater than the cross-sectional area of the channel of the nozzle 303, so that if that flange portion is moved directly underneath the channel of the nozzle 303, it will blank off the channel and prevent metal flow.

[0038] In figure 3F, and in use shroud tube 314 is in position with liquid metal flowing through the nozzle 303, and through the shroud tube 314 into the mould underneath. A replacement shroud tube 315 is located in the channel of the main body 301 ready to displace the use shroud tube.

[0039] Referring to figure 3G herein, there is shown the automatic outlet changer in a firing position, after which the previously in use shroud tube 314 has been displaced by a replacement shroud tube 315. The main central bore of the replacement shroud tube 315 aligns with the main central bore or channel the tundish nozzle 303, so that the replacement shroud tube 315 has now replaced the previously in use shroud tube 314.

[0040] Referring to figure 3H herein there is illustrated schematically the automatic outlet changer showing the spent tube removed, and the new replacement tube in a casting position.

[0041] Referring to figure 3I herein, there is shown the automatic outlet changer with the shroud tube 314 at a closed position in which the extended flange portion is positioned directly underneath the outlet of the tundish nozzle 303, thereby blocking its outlet. By use of the second type of shroud tube 314,315 there is no need for a separate blanking plate to be kept in the channel adjacent the in use shroud tube, because the shroud tube itself can be pushed over using the electric ram and pusher arm 317 to block off the flow of metal. To achieve this close off position, the electric ram would not move a full flange distance, as with the shroud tube and blank plate arrangement shown in figures 3A a to 3E herein. Rather, the pusher arm 316 needs to move only a short distance, enough to move the shroud tube off centre so that the extended flange portion aligns with the outlet of the nozzle 303.

[0042] At an end of casting, when the spent shroud tube is to be removed altogether, a refractory blanking plate as shown in figures 3B and 3C herein can be moved into position underneath the nozzle outlet, similarly as described herein with reference to figures 3A to 3C.

[0043] Figure 4 herein shows schematically the first automatic outlet changer 300 in perspective view from above and one side. The first outlet changer 300 comprises: a rigid robust base plate 307 which is attachable to the underside of a tundish, a pivotable frame or gate assembly 308, onto which is mounted a ram holding flange 309 and an electric ram 305; electric and control cables to the electric ram 310, 311 respectively are attached to the electric ram via a set of conduit type connectors 312, 313 respectively.

[0044] Figure 5 herein shows the first embodiment automatic outlet changer of figures 3 and 4 herein from underneath. As shown in figure 5, there are provided two sets of retaining arms 501, 502 each comprising one or a plurality of individual spring mounted substantially horizontally extending arms, extending underneath a pair of opposing walls forming a central channel 503 therebetween. The retaining arms are pivotable with respect to the wall members, and each has an end portion which overlaps the central channel 503, so that as an upper flange of a tundish tube enters the channel, and is moved to a position directly underneath a tundish aperture, the spring mounted retaining arms urge the underside of the flange of the tundish tube upwardly, so as to make contact with a lower surface of an upper tundish nozzle.

Operation of the First Outlet Changer [0045] Figure 6 herein shows the first automatic outlet changer in a loading position in which a replacement shroud tube 306 is inserted into the under hanging channel of the outlet changer, in readiness for replacing an existing in use shroud tube 302. Whilst the tube 302 is in use transferring molten liquid metal from a tundish to a mould, the end gate 308 is unlatched from the end of the base plate 307, by operating a latch mechanism 601 and swinging the gate 308 open on a pivot 602. The electric ram 305 which is rigidly attached to the gate mechanism also swings away from the first end of the channel. A human operator, or a mechanical handling equipment then inserts the upper flanged end of a replacement shroud tube 306 into the first end of the channel. The gate is then swung shut, and the latch mechanism 601 engages with the base plate, rigidly securing the gate to the base plate as shown in figure 7 herein.

[0046] Figure 8 shows the first automatic outlet changer with an operative tube 302 in position underneath a tundish nozzle, in perspective view from underneath, with a replacement tube 306 ready to be swapped for the operative tube.

[0047] Figure 9 herein shows the first automatic outlet changer positioned underneath a tundish, in perspective view from underneath, where the replacement tube 306 has been swapped for the previously in use tube 302, and has displaced the previously used tube 302. The replacement tube 306 is now under the tundish nozzle, and the previous tube 302 is in a removal position along the channel, from which it can be removed from the outlet changer [0048] As shown in figures 8 and 9 herein, the first outlet changer is shown firstly in figure 8, in a first stage of operation for changing a refractory shroud tube underneath a tundish. A first tube 302 is in use under the outlet of the tundish and is to be replaced by sliding a second tube 306 horizontally into an outlet position under the tundish by pushing the upper end of the second tube along the channel, using the electric ram 305, and thereby pushing the in use tube to an extraction position in the channel on the other side of the in use position underneath the outlet, as shown in figure 9 [0049] To repeat the tube replacement process with a further replacement tube involves repeating the stages set out above with reference to figures 6 to 9 herein.

[0050] Referring to figure 10 herein, there is shown further detail of the electric cylinder 305 and gate assembly 308 which secures and attaches the end of the electric ram to the end gate 308.

[0051] A piston 1100 of the electric ram pushes through an aperture 1001 in the end gate. The ram 305 comprises a robust rigid end case 1001 containing at one end an electric motor, and another case part 1002 within which is provided a worm gear type mechanism for extending or retracting a ram into and out of the casing part 1002.

[0052] Referring to figure 11 herein, there is illustrated schematically in another perspective view, the gate assembly 308 and electric ram 305 of the first outlet changer apparatus, showing the piston 1100 of the electric ram in an extended position. The piston has at a distal end, a substantially rectangular or brick shaped head 1101, which forms a “T” shape on the end of the piston 1100.

Underneath the space in which the piston 1100 extends and retracts, there is provided an underside guard 1102 for safety. The underside guard 1102 is connected to the movable head 1101 and moves backwards and forwards as the piston moves backwards and forwards.

[0053] Referring to figure 12 herein, there is shown in a further perspective view, the gate 308 and the electric ram 305 with the piston 1100 in a partially extended position, and also showing an underside guard or housing 1200 which protects the underside of the electric ram 305.

[0054] Referring to figure 13 herein, there is shown in a further perspective view the gate assembly 308 and electric ram 305, showing the electric ram fully enclosed in the underside guard 1200, and an upper guard member 1300 which protects the electric cylinder from above.

Tests Results - First Outlet Changer [0055] Test results for a prototype first outlet changer described herein fitted with an electric cylinder having a 200 mm stroke were as follows.

[0056] It was found that in fitting an electric ram to the gate mechanism of the outlet changer, the outer housing of the ram must be rigidly mounted with a mounting bracket strong enough to resist twisting of the ram relative to the end gate/ latch mechanism due to the torque exerted by the electric ram. The central piston of the electric cylinder needs to be held in a fixed orientation rotationally, to prevent the piston simply spinning around instead of moving axially to extend or contract. By fitting an anti-rotation housing to the end of the housing of the electric cylinder, where it meets the gate assembly 308 this not only prevents rotation, but also prevents the distal end of the thread of the electric cylinder being exposed. The anti-rotation housing comprises an outer housing having a substantially circular cylindrical perimeter, intersected by two opposing flat sides, to prevent the housing rotating. This housing fits into a corresponding shaped aperture in the gate assembly 308.

[0057] Lateral forces acting on the central piston of the cylinder could potentially damage the cylinder. However by providing a rigid and robust end gate component, to which the end of the ram robustly and rigidly fits, this prevents misalignment of the cylinder, and keeps the piston acting in an axial direction.

[0058] With the outlet changer set up to replicate actual use, with the spring tension on the retaining arms set to a value suitable for actual use in a steel plant, the electric cylinder was found to perform well.

[0059] The outlet changer was subjected to a shear test, to test the force of the electric cylinder pushing a tube along the channel. The shear test involved fitting a plate to the end of the piston of the cylinder, and fitting a conventional steel bolt to project from the roof of the channel into the cavity of the channel, obstructing the path of the end pusher for pushing the upper part of the shroud. The purpose of this test is to compare performance of the electric cylinder with a hydraulic equivalent.

[0060] Various bolts of grade 8.8 steel including M6, M8, M10 and M12 sizes were tested. For a comparable hydraulic cylinder, the maximum bolt size which can be sheared is M10. The hydraulic cylinder bends an M12 bolt but will not achieve a shear for that bolt size. The comparable performance for the electric cylinder tested was that the maximum bolt size sheared was an M10 size, and an M12 bolt is bent, but the shear is not achieved. This result was for a 28kN force electric cylinder, compared to a 30kN hydraulic cylinder.

[0061] The capacity of the electric cylinder was 30kN maximum force and 10kN continuous force at a speed of 340mm/s. Different embodiment electric cylinders can be used which increase the amount of continuous force available, but at lower speeds. With a first embodiment electric cylinder, the maximum continuous force which could be achieved was 17kN, giving the ability to change a shroud tube in 1.2 seconds.

[0062] Using a second embodiment electric cylinder having a maximum force of 60kN and an available continuous force of 27kN, at a speed of 195mm/s also gives acceptable performance.

[0063] Figure 14 herein shows schematically in perspective view from above and one side a second automatic outlet changer mechanism 1400 for holding and changing a refractory tube 1415 under a tundish or a ladle nozzle 1416, in a continuous casting operation. The second automatic outlet changer comprises a base plate 1401; underneath the base plate, first and second opposing walls 1402, 1403 either side of a central channel such that the channel is formed between the first and second opposing walls 1402, 1403, and an underside of the base plate 1401; the opposing walls each having a lower elongate ledge 1404, 1405 respectively upon which an upper flanged part of a tundish tube can be placed to support the tundish tube in the channel, such that the tundish tube can slide along the channel; a crank arm 1406 pivotally attached to the base plate at a pivot 1417; an electric ram 1407 mounted at a side of the base plate, the electric ram having an outer casing 1408 and a central piston 1409. The electric ram is mounted via a vertical or upright pivotal mounting 1410 to the base plate 1401 such that a main length axis of the ram is movable in the horizontal plane, with respect to a main length axis of the central channel of the base plate.

[0064] In use, the base plate is secured to the underside of a tundish by bolting the base plate 1401 to the underside of the tundish.

[0065] An end of the piston of the electric ram is pivotally mounted to a first end 1411 of the crank arm 1406, by a shear pin 1412, so that as the piston extends, the second end of the crank arm moves towards and along the channel, and as the piston of the electric ram retracts into the ram, the first end of the crank arm is pulled so that the second end of the crank arm swings away from the open end of the channel, as shown in figure 14 herein. On the second end 1413 of the crank arm there is provided a pivotable head 1414 having a flat surface suitable for pushing a flat face of a flange of a shroud tube.

[0066] In figure 14, the crank arm 1406 is in a parked position, with the electric ram fully contracted and in a ready position.

[0067] Figure 15 herein shows schematically in perspective view from above and one side, the second automatic outlet changer of figure 14 showing a tube changing arm being operated to effect a tube change in a position where the piston 1409 is pushing the crank arm 1406 so that the second end of the crank arm passes along the channel.

[0068] Figure 16 herein shows the second automatic outlet changer showing the tube changing arm further extended along the channel for pushing a refractory tube out of an operating position. In this position, the piston 1409 of the electric ram 1407 is fully extended, pushing the first end of the arm beyond a pivot position 1417 about which the crank arm 1406 pivots about the base plate. In this position, the crank arm has pushed a shroud tube underneath an upper nozzle 1416 in the centre of the base plate.

[0069] Figure 17 herein shows schematically the second automatic outlet changer showing additional guard components 1700 around and electric ram, and additional electric cabling and shielding components 1701 which protect the electric power and control cables to the electric ram.

[0070] There is also shown a quick fitting connector 1702 suitable for fast change-over of the electric ram. The quick fitting connector 1702 comprises upper and lower arms extending outwardly from a side of the base plate 1401, each arm having a substantially “V" shaped slot having at its apex a part-cylindrical inner surface into which respective upper 1703 and lower vertical cylindrical pins may be fitted in a horizontal direction, and each secured therein by a respective upper 1704 and lower cotter pin to prevent the vertical pin sliding out of the “V” shaped housing. The casing of the electric ram is also fitted with a triangular shaped upward projecting lifting bracket 1705 having a lifting ring 1706, for lifting the electric ram when it is swung away from the mounting bracket.

Operation of the Second Outlet Changer [0071] Operation of the second outlet changer is as follows. In the first operating position as shown in figure 14 herein, hot liquid metal passes through an intermediate refractory nozzle 1416 and through a shroud tube 1415 into a tundish or a mould. The lower end of the shroud tube 1415 is immersed in liquid metal, so that the shroud tube prevents atmospheric air from coming into contact with the liquid molten metal as it is being poured. The shroud tube 1415 erodes over time and requires replacement.

[0072] With the crank arm 1406 in the open position as shown in figure 14, a further shroud tube is inserted with its upper end in the open channel, resting the underside of a square or rectangular flange of the shroud tube on the ledges 1403,1404 either side of the channel. The replacement shroud tube is inserted manually, using a long holding tool to protect manual operators from the heat in the vicinity of the shroud tube, or using mechanical handling equipment. Once in place adjacent the in use shroud tube 1415, the replacement should shroud tube occupies a first position in the channel from which it can be pushed into a second position, being the position of the in use shroud tube 1415, using the crank arm 1406. At this time, liquid metal continues to pour through the intermediate nozzle 1416 and the shroud tube 1415.

[0073] Referring to figure 15 herein, the electric ram 1407 pushes the first end 1411 of the crank arm 1406, so that the crank arm pivots about the pivot 1417, causing the second end 1413 of the crank arm to swing round and push the upper flanged portion of the second (replacement) shroud tube along the channel into the second position, pushing the original shroud tube 1415 to a third position on the opposite side of the second position, from where it can be removed either by human operators using a holding tool, or by a mechanical handling equipment.

[0074] Figure 16 shows the position of the piston 1409 of the electric ram and the crank arm 1406 after having pushed the replacement shroud tube 1600 into the second position under the intermediate nozzle 1416.

[0075] The changeover operation in which the crank arm pushes the replacement nozzle along the channel into the second position, thereby pushing the original worn shroud tube to the ejection position (third position), typically takes 1 to 2 seconds. The force exerted by the electric ram and the crank arm is sufficient to overcome the friction between the upper end of the tundish tube and the lower end of the upper nozzle and between the retaining arms and the upper end of the tundish tube, so that the replacement shroud tube can be pushed into position, and at the same time moving the worn shroud tube along the channel to the removal position (third position) as shown in figure 16.

[0076] A further shroud tube replacement involves a repetition of the process described above, as the replacement model nozzle itself becomes worn and requires replacement. In this manner, shroud tubes can be indefinitely replaced allowing continuous casting to continue.

Electric Ram Component [0077] The rams described herein, also termed an electric cylinder, or an electric actuator (applicable to all embodiment nozzle or tube changers) comprises an outer tube or casing; and inner tubular piston; an electric motor drive; a gearbox between the electric motor and the piston; a worm gear drive inside the outer tube for driving the piston horizontally between an extended position and a retracted position. There may also be provided a set of control electronics within the outer tube or casing. In the general case, the outer tube / casing and the piston may be circular cylindrical, or may be of square cross-section.

[0078] A distal end of the piston may be provided with a rectangular substantially brick shaped block for pushing the flange of the shroud tube directly in some embodiments, or alternatively as shown in the second shroud tube change embodiment, a distal end of the piston may be fitted with a “C” shaped pivotable eye connector so that the end of the piston can be used to either push or pull a crank arm component to which the end of the electric cylinder is connected.

[0079] Similarly, an eye connector can be connected to a plunger or pusher for pushing nozzles or shroud tubes along a channel of a nozzle or tube changer apparatus. Alternatively, a plunger or pusher component can be screwed directly into the end of the cylindrical piston rod of the electric cylinder.

[0080] In various embodiments of the electric ram, an electric motor may be fitted coaxially with a rotating worm gear along a main length axis of the ram, or in other embodiments, a rotary axis of the electric motor may lie at 90° to the main length axis of the ram, with electric motor being connected to the worm drive of the electric ram via a gearbox. In some embodiments, the electric motor may be fitted in parallel with a main body of the electric ram, and side-by-side or above the ram, such that the drivetrain from the motor to the worm drive needs to travel through 180°, via a gearbox on the end of the ram.

[0081] The electric rams disclosed herein may comprise a set of position sensors which detect the position of the inner piston rod relative to the outer cylinder, and thereby provide information on the extent of contraction or extension of the inner rod relative to the outer cylinder, in other words, to detect the amount of extension or contraction of the electric cylinder itself. Further, with known hydraulic systems, positional sensors need to be provided to check the position of the cylinder piston and/or other components. Use of an electric ram avoids the need for these prior art external sensors, since the position of the piston of the electric ram can be determined from the control electronics of the electric motor of the ram and/or from sensors within the electric ram unit itself.

[0082] The electric ram operates by electric power being supplied to the electric motor which rotates either clockwise or anticlockwise for extending or retracting the electric cylinder. The motor drives the worm gear via the gearbox. The worm drive which extends for a distance inside the outer cylinder and may protrude a short distance beyond the end of the outer cylinder causes the tubular inner cylinder to extend or retract into the outer cylinder and to move forwards and backwards along a main axial length of the outer cylinder. The outer cylinder, inner cylinder and worm drive are coaxially located with each other.

[0083] A separate power supply and control unit may be located away from the electric cylinder, and therefore away from the tundish tube changing unit, out of the way of high temperatures and other hazards present in the immediate vicinity of the base of the tundish. Power feeds and connections to the electric ram are by way of electric cables (including armoured electric cables), and therefore the need for complex prior art hydraulic feed and return lines with their inherent complexity is avoided.

[0084] In the embodiment electric rams herein, the screw thread may be either of the multiple speed trapezoidal thread spindle type, or a ball screw type with profile geometry optimized for the application and torque requirements imposed by forces needed to move the refractory nozzles along the channels.

[0085] The embodiment electric cylinders are capable of operating under extreme operating conditions such as heat, dust, vibration, humidity, and are capable of operating in modified atmospheres, for example in inert gas atmospheres.

[0086] In the embodiments described herein, the electric ram may have the following characteristics, in comparison with known pneumatic or hydraulic rams:

[0087] Two separate embodiment tube changers have been described herein, the first type being of a linear tundish tube changing type in which the nozzle moves in a same direction of action as an electric ram, and a second embodiment in which an electric ram is used to push a shroud tube via an intermediate crank arm. In each case, an electric cylinder is used to move a tundish tube between various positions along a linear channel, being a first holding position, and a second operating position in which the nozzle or shroud tube is used for casting metal, and further, to a third position in which the nozzle or shroud tube can be removed from the channel.

[0088] Referring to figure 18 herein, there is illustrated schematically two types of known nozzle outlet 1800, 1804.

[0089] A first type of nozzle outlet 1800 comprises an upper tubular portion 1801, and a lower flange portion 1802. At the base of the lower flange portion, there is a flat annular surface, having an argon sealing ring 1803. The base of the flange seals against an upper flange of a shroud tube, when the shroud tube is urged upwardly against the underside of the nozzle.

[0090] A second type of nozzle tube 1804 comprises an upper tubular part 1805; and a lower flange 1806. The second nozzle having a 0.5 mm argon sealing ring. In use, the lower part of the nozzle flange, urges against an upper flange part of a shroud tube to make a gas tight seal.

[0091] Referring to figure 19 herein, there is illustrated schematically a known refractory blanking plate 1900 as described in the operation of the first automatic tube changer in figures 3B and 3C herein. The blanking plate comprises a flat substantially square or rectangular plate 1901 made of refractory material, and a substantially circular cylindrical portion 1902 extending from the base of the plate.

[0092] Referring to figure 20 herein, there is illustrated schematically a known shroud tube which can be used in the embodiment automatic outlet changer described herein. The shroud tube 2000 comprises an upper flange plate 2001; and an elongate tube 2002 extending downwardly from the flange plate, to an outlet 2003 which acts to distribute molten liquid metal in a direction substantially transverse to the main length axis of the shroud tube. Typically the area dimension of the upper flange are around 209 mm x 199 mm.

[0093] Although detailed descriptions have been made for electric tube changing devices, the same principles apply for electric nozzle changing devices, whereby the refractory used in the casting process is a known nozzle used primarily for unshrouded casting of steel.

[0094] Further, the changing devices disclosed herein can also incorporate push a refractory blanking plate as shown in fig in 19 herein underneath the tundish nozzle, for use in stopping the flow of metal.

[0095] Advantages of electric cylinders compared to conventional hydraulic or pneumatic cylinders include: • Improved safety due to the absence of hydraulic fluid • Avoids the need for bulky and technically complex hydraulic or pneumatic controls • Reduced maintenance requirement. • A reduced level of spare parts need to be available on site compared to hydraulic or pneumatic cylinders. • High reliability under extreme operating conditions • Easy replacement without the need to connect, disconnect or recharge hydraulic or pneumatic lines • Actuator control using a force limiter or a limit switch • Electric cylinders may provide completely enclosed pushing/pulling systems with special sealing and corrosion protection for hazardous environments. • Service life of up to 25 years. • The use of electric cylinders may enable a faster nozzle or tube changer than is currently available with hydraulic or pneumatic alternatives. • A piston extension / retraction speed in the range 50 mm/s to 425mm/s

Claims (13)

Claims

1. A changer apparatus for changing a refractory component in a casting apparatus, said changer apparatus comprising: a changing mechanism for moving a said refractory component between a first position in which said refractory component is located fully offset from a path of a flow channel through which molten metal may pass, and a second position in which said refractory component lies in said path of said flow channel; said changing mechanism characterised by comprising an electric ram operable to move a said refractory component between said first and second positions.

2. The changer apparatus as claimed in any one of the preceding claims wherein said changing mechanism comprises a channel capable of holding a said refractory component in said first position and in said second position, and a pusher component for pushing said refractory component between said first and second positions.

3. The changer apparatus as claimed in any one of the preceding claims, wherein said electric ram comprises: an outer casing; a movable piston which extends from and retracts into said outer casing along an axial direction of said outer casing; a drive mechanism for driving said movable piston relative to said outer casing; and an electric motor which powers said drive mechanism for moving said movable piston relative to said outer casing.

4. The changer apparatus as claimed in any one of the preceding claims, wherein said movable mounting is operable to move said refractory component in a substantially straight line.

5. The changer apparatus as claimed in any one of the preceding claims 1 to 3, wherein said changing mechanism is operable to move said refractory component in a substantially circular path.

6. The changer apparatus device as claimed in claim 4, wherein said electric ram has a maximum push force in the range 500N to 100kN

7. The changer apparatus as claimed in any one of the preceding claims, wherein said electric ram comprises a rotary position encoder.

8. The changer apparatus as claimed in any one of the preceding claims, wherein a piston of said electric ram is connected relative to said holding plate such that said piston is free to move in an axial direction along its main axial length, but is constrained such that it cannot rotate about its main axial length.

9. The changer apparatus as claimed in any one of the preceding claims comprising a guard substantially surrounding said electric ram, for protecting said ram from debris and/ or heat.

10. The changer apparatus as claimed in any one of the preceding claims wherein said electric ram has a stroke in the range 90mm to 250mm.

11. The changer apparatus as claimed in any one of the preceding claims wherein said electric ram has an overall length in a contracted state in the range 300mm to 800mm.

12. The changer apparatus as claimed in any one of the preceding claims wherein said electric ram has a speed of extension / contraction in the range 50mm/s to 425mm/s.

13. A changer device for changing a refractory nozzle or a shroud tube under a tundish, said changer comprising; a frame adapted to be mounted under a said tundish; a horizontally extending channel member able to hold a plurality of said tubes or nozzles simultaneously; a pusher for pushing said tube or nozzle along said channel. said pusher operable to push one or more said tubes or nozzles along said channel such that said tubes or nozzles are pushed successively between a holding position in which a said tube or nozzle is held ready to be pushed into an operating position; said operating position, in which said tube or nozzle is positioned underneath a liquid metal outlet; and a removal position in which said tube or nozzle can be removed from said changer device; wherein said pusher comprises an electric ram operable to move said tube or nozzle between said positions.