The present invention relates to a robotized loading station for preparing a fresh ladle loaded on a rotating turret before being brought to a casting station over a tundish. In particular, the present invention concerns a robotized installation for loading a ladle shroud to a ladle sliding gate coupled to an outlet of the ladle, and for coupling a driving device to both ladle and ladle sliding gate for actuating the ladle sliding gate. The robotized loading station is also configured for de-coupling the driving device and unloading a spent ladle shroud off an emptied ladle recently removed from the casting station over the tundish. The robotization of these operations saves the operators from a strenuous task and enhances reproducibility of the operations. A specific ladle sliding gate comprising a collector nozzle positioned next to the ladle shroud allows a swift unclogging of the outlet, should the latter become clogged.
In continuous metal forming processes, metal melt (2) is transferred from one metallurgical vessel to another, to a mould or to a tool. For example, as shown in
Since casting of metal into a mould or tool is to run continuously, the tundish plays the role of a buffer and the level of molten metal in the tundish must remain substantially constant during the whole casting operation. Maintaining the level of molten metal in the tundish substantially constant requires a rapid swap of a new ladle filled with molten metal with an old ladle after it has been emptied, to ensure a quasi-continuous feed of molten metal to the tundish, such that metal is poured into the tundish at substantially the same rate as it flows out thereof into the mould or the tool. This operation is rendered more complex by the following constraints.
First, since for safety reasons and to avoid any collision, a ladle (11,12) cannot be carried over a workshop from the furnace to a corresponding tundish with a ladle shroud (13a-13c) coupled to a bottom floor of the ladle and extending 1 m or more below the bottom floor, the ladle shroud must be coupled to the bottom floor of the ladle at a loading station located close to the tundish.
Second, to prevent metal contained in the second ladle (12) from freezing in contact with ‘cold’ moving parts of the ladle sliding gate (15) maintained in sealed position thus avoiding gripping the mechanism and preventing the opening of the ladle sliding gate, the inner bore of the inner nozzle is generally filled with a plugging material (19), usually sand or other particulate materials, to prevent any metal melt from reaching the gate mechanism, such that metal freezing and clogging of the nozzle and gate system are prevented. Upon opening the ladle sliding gate to a casting position with the ladle located at the casting station, the sand flows out followed by molten metal which can flow through the ladle shroud into the tundish. Sometimes, however, the plugging material is locally bound with frozen metal forming a solid plug preventing the plugging material from flowing out. The inner nozzle is therefore clogged, and no metal can flow out of the ladle into the tundish in spite of the ladle sliding gate being in the casting position. This problem can easily be solved with an unclogging tool (19r) inserted into or close to the bore of the inner nozzle. The unclogging tool (19r) can be a pressurized gas lance or an elongated rod, as illustrated in
For this reason, in most installations, the ladle shroud is not coupled to the sliding gate in an autonomous way at the loading station, but it is inserted over a collector nozzle and held in place by a robot at the casting station instead. This allows the ladle shroud to be removed from the collector nozzle by the robot in case of clogging of the ladle outlet, for easier access thereto from the bottom with an unclogging tool (19r). Once the clogged passage is unclogged, the ladle sliding gate can move into the sealing position while the robot reintroduces the ladle shroud over the collector nozzle. At this point the ladle sliding gate moves back into the casting position to start casting molten metal into the tundish.
A newly filled ladle is transported from the furnace to a casing installation with a ladle sliding gate fixed to a bottom floor of the ladle, but without a driving device to actuate the relative movements of the plates forming the ladle sliding gate. For this reason, many metallurgic installations use a turret (30) comprising a first holding device for holding a first ladle (11) at a casting station over the tundish (1) and a second holding device for holding a second ladle (12) full of molten metal at a loading station. While the first ladle discharges the molten metal contained therein into the tundish, the second ladle can be prepared for performing the same operation once the first ladle is emptied. In particular, a driving device, such as a hydraulic piston can be coupled to the bottom floor of the ladle and to the ladle sliding gate, to allow actuation thereof.
US2006/0118268 describes a ladle sliding gate configured for autonomously holding a ladle shroud as well as a collector nozzle, set side by side. One or more driving devices, such as hydraulic pistons, can be used to actuate the ladle sliding gate by moving plates thereof between a sealed position wherein the opening is sealed, a casting position wherein the opening is in fluid communication with the ladle shroud, and an unclogging position wherein the opening is in fluid communication with the collector nozzle. This way, in case of clogging of the inner bore, the ladle sliding gate moves to the unclogging position, so that the unclogging tool (19r) can easily be introduced through the short collector nozzle bore to break the solidified metal bonded plugging material. Once the plugging material can flow again, the ladle sliding gate moves the collector nozzle out of registry from the ladle outlet and brings the ladle shroud into casting position to allow molten metal to flow through the ladle shroud into the tundish. Handling of the unclogging tool (19r) can advantageously be performed by a robot located adjacent to the casting station. A clear advantage over the holding of the ladle shroud by a robot described above, is that with this ladle sliding gate, no robot is required to hold the ladle shroud and it can be used instead to the unclogging tool (19r). Else, this operation must be performed manually by a human operator or a second robot must be installed adjacent to the casting station to unclog the inner bore. Manual handling is generally more laborious and takes longer time than when a robot performs this operation. This is disadvantageous because the longer time the tundish is not fed with fresh molten metal by the ladle, lower is the level of molten metal in the tundish, and/or the longer time the casting operation must be run at lower flow rate which is disruptive of the quality of the beam thus produced. Examples of ladle sliding gates of this type holding a collector nozzle and a ladle shroud side-by-side are illustrated in
U.S. Pat. No. 8,215,375 describes a continuous casting plant having at least one multifunction robot for implementing a plurality of different process-controlled or automated interventions at the continuous casting plant. The multifunction robot arranged on a pivotable arm at a rotary column fastened to the pouring platform of the continuous casting plant and the robot can be pivoted with the pivot arm between a retraction position and a working position. The robot is also movable with respect to its arm.
The operation of swift swapping an emptied first ladle with a filled second ladle at the casting station remains a delicate operation. This operation is rendered even more critical in case of clogging of the inner bore, which can increase the time during which the tundish is not replenished with fresh molten metal. A need for a reproducible and shorter ladle swapping operation is sought in the metal casting industry. The present invention proposes a metal casting installation with fully automated ladle changing operations, including in case of clogging of the outlet of a ladle by frozen plugging material (19) allowing a reproducible and in all cases shorter swapping operation. These and other advantages of the present invention are explained more in detail in the following sections.
The objectives of the present invention have been reached with a metal casting installation comprising,
The robot is preferably also configured for removing off the emptied first or second ladle which is held at the loading station after being moved from the casting station,
It is preferred that the loading platform comprises a tool storage rack containing one or more spare ladle shrouds within reaching distance of the robot. The spare ladle shroud can be pre-heated in the storage rack or in a separate oven. The storage rack preferably comprises one or more driving devices and/or additional spare collector nozzles, and/or tools.
In a preferred embodiment, the robot is movingly mounted on the loading platform such that the robot can translate parallel to a first axis (X) and/or second axis (Y) normal to the first axis (X), or combination thereof, and/or rotate about a vertical axis (Z) normal to the first and second axes (X, Y), in order to reach and retrieve any tool or component from the storage rack and to reach the ladle sliding gate of the first or second ladle which is held at the loading station for carrying out the operations of loading/unloading a ladle shroud and of coupling/removing a driving device.
The ladle sliding gate is important for the present invention. In a first embodiment, the ladle sliding gate comprises,
wherein the driving device is coupled to the lower plate and comprises a cylinder rigidly and reversibly coupled to the bottom portion of the corresponding first or second ladle, and a piston rigidly and reversibly fixed to the lower plate, the driving device being configured for moving the lower plate to bring the lower bore in and out of registry with the upper bore, and
wherein the drawer driving device is coupled to the drawer and comprises a cylinder rigidly and reversibly coupled to the bottom portion of the corresponding first or second ladle, and a piston rigidly and reversibly fixed to the drawer, the drawer driving device being configured for moving the drawer to bring the shroud bore and the collector bore in and out of registry with the lower bore.
In an alternative embodiment, the ladle sliding gate comprises,
The driving device can be actuated hydraulically or pneumatically or electrically. Each of the at least first holding device and second holding device of the ladle turret can be provided with,
In a preferred embodiment, a pre-heating oven is provided for bringing and maintaining at a pre-heating temperature the new ladle shroud loaded on the ladle sliding gate of the first or second ladle located at the loading station. This pre-heating oven can be provided instead of, or additionally to a heating storage rack or a separate oven for pre-heating a new ladle shroud before it is coupled to the ladle.
In a preferred embodiment, the robot is also configured,
The present invention also concerns a method for casting a molten metal comprising the following steps,
In a preferred embodiment, the method comprises the following steps during step (f),
In many instances, the opening of the first ladle is filled with a plugging material to prevent metal from solidifying in contact with cold surfaces of the upper plate of the ladle sliding gate. The plugging material is generally in a particulate form. In some cases, some molten metal percolates through the particulate plugging material and solidifies forming a solid mass which clogs the opening, preventing any molten metal from flowing out of the opening upon bringing the ladle sliding gate of the first ladle into casting station in step (b). When such clogging occurs, the following steps can be carried out to unclog the opening.
Step (e) of swapping positions of the first and second ladles preferably comprises the following steps,
In a preferred embodiment, the robot also,
On these figures,
As illustrated in
A ladle (11,12) comprises, a floor provided with an opening (11o, 12o). An inner nozzle (18) provided with an inner bore brings an inner volume of the tundish in fluid communication with the opening (11o, 12o). The ladle (11,12) also comprises a ladle sliding gate (15) configured for reversibly receiving and supporting the ladle shroud, and for being coupled to a driving device (17) for actuating the ladle sliding gate between a sealed position wherein the opening is sealed, and a casting position wherein the opening is in fluid communication with the ladle shroud (13a-13c).
The ladle sliding gate (15) of a ladle according to the present invention is also configured for reversibly receiving and supporting a collector nozzle (14a, 14b). The driving device (17) or drawer driving device (17w) is further configured for actuating the ladle sliding device (15) to an unclogging position wherein the opening is in fluid communication with the collector nozzle (14). As explained more in detail below, the unclogging position is used in case no molten metal flows out of the ladle when the ladle sliding gate is in the casting position due to clogging.
To accelerate the swap between an emptied first ladle (11) with a full second ladle (12), the first and second ladles are supported by corresponding first and second holding devices of a rotating turret (30) (cf.
Because the ladle shroud (13a-13c) is partly inserted in the tundish (1), the turret (30) must first lift the first and second ladles to drive the ladle shroud (13a) of the first ladle (11) out and above the tundish (1) prior to rotating about the central rotating axis (Z) to avoid the ladle shrouds of the first and second ladles to collide with the tundish.
The loading is provided with a loading platform (20) comprising tools and spare parts, such as new ladle shrouds (13b, 13c), new collector nozzles (14), or spare driving devices (17). As explained supra, a ladle cannot be transported across a workshop between a furnace and a casting installation with a long ladle shroud (13a-13c) protruding out of the bottom floor thereof. Consequently, a fresh ladle, full of molten metal, reaches the casting station devoid of a ladle shroud (13a-13c). The fresh ladle (11, 12) full of molten metal (2) reaches the turret (30) with a ladle sliding gate (15) fixed to the bottom floor of the ladle but without an operational driving device (17), and with a collector nozzle (14) coupled to the ladle sliding gate. The collector nozzle is very short and can travel across the workshop attached to the ladle without any risk of collision. A new ladle shroud (13a-13c) can therefore be coupled to the fresh ladle (12) when the latter is docked on the turret (30) at the loading station. At the same time, a driving device (17) must be coupled to the ladle (11, 12) and the ladle sliding gate (15) and must be activated by connecting it to a source of pressurized fluid for hydraulic or pneumatic driving devices (17), or to a source of electric power for electric driving devices (17).
Rather than carrying out these operations manually by a human operator, the present invention proposes to provide a robot (21) on or adjacent to the loading platform (20). The robot (21) is configured for loading a new ladle shroud (13b) onto the ladle slide gate (15), and for coupling a driving device (17) to the ladle slide gate (15).
A second ladle (12) full of molten metal, coming straight from a furnace, is held at the loading station by the second holding device of the turret (30), at the loading station, within robot reach of the loading platform (20). The ladle sliding gate (15) of the second ladle (12) is in the sealed position. Unlike the first ladle (11), the second ladle (12) is not ready for casting molten metal because it is devoid of any ladle shroud (13b) and of any driving device (17). It is possible to bring a second ladle (12) already equipped with a driving device (17), but not in an operational state, since it would not be connected to any source of pressurized fluid for hydraulic and pneumatic driving devices, nor to any source of electric power for electric driving devices. Generally, the second ladle (12) when reaching the turret is devoid of any driving device (17), and in the few instances where it is provided with a driving device, the latter is not operational.
The loading platform (20) comprises a storage rack (29) with various tools (not shown) required for preparing the second ladle (12) for casting, and with spare ladle shrouds (13b, 13c). The ladle shroud (13a, 13c) first in line for being coupled to a ladle is preferably preheated in the storage rack (29) or in a separate oven within reach of the robot, to avoid any brutal thermal shock when molten metal flows through the ladle shroud upon starting of the casting operation at the casting station. In some instances, the platform can comprise spare driving devices (17), and possibly spare collector nozzles (14), although a collector nozzle (14) is preferably coupled to the second ladle in a separate, refurbishing station, prior to filling the ladle with molten metal from the furnace.
The driving device (17) and optionally the drawer driving device (17w) (defined below with respect to the first embodiment illustrated in
The robot (21) can preferably move along a horizontal plane (X, Y) and has several degrees of liberty, preferably at least five or at least seven degrees of liberty. The robot must be able to reach both the storage rack (29) to collect or deposit tools and or casting components, and also to reach the ladle sliding gate (15) of the ladle stationed at the loading station. It must have enough degrees of liberty for carrying out all the connections and de-connection and couplings and de-coupling required for ensuring a continuous casting operation of the casting installation.
In particular, as shown in
With this configuration, all the robot (21) needs to do is to collect the driving device (17) from its storing station at the second holding device and couple it to the ladle and ladle sliding gate (15). In case the driving device is stored in the storage rack (29) or in case the driving device stored in the storing station must be changed with a new one stored in the storage rack (29), additionally to coupling the one or more (drawer) driving devices (17, 17w) to the ladle and ladle sliding gate (15), the robot (21) must also connect one or more hoses (17t) to corresponding (drawer) driving devices to render the driving device operational for actuating the ladle sliding gate.
As shown in
The movements of the turret and of the ladle sliding gates (15) of both first and second ladles must be perfectly synchronized to prevent any undesired dripping or flow of molten metal from any of the first and second ladles.
The robot (21) must also be configured for removing from the emptied first ladle (11) located at the loading station, the ladle shroud (13a) and the driving device (17). The spent ladle shroud (13a) can be cleaned and stored for further use or it can be disposed of into a disposal bin (27). The driving device (17) can be stored in the storing station on the first holding device of the turret (30) without having to disconnect it from the source of pressurized fluid, or into the storage rack (29) of the loading platform, after having disconnected the source of pressurized fluid therefrom. The emptied first ladle (11) stripped of both ladle shroud (13a) and driving device (17) can now be removed to a service station for being refurbished. A new ladle full of molten metal can be brought from the furnace and loaded onto the now empty first holding device of the turret, for starting the whole operations as illustrated in
The robot (21) can have at least five, preferably at least six or seven degrees of liberty. The robot is preferably movingly mounted on the loading platform (20) such that the robot can translate parallel to a first axis (X) and/or second axis (Y) normal to the first axis (X), or combination thereof. The robot (21) can preferably rotate about a vertical axis (Z) normal to the first and second axes (X, Y). With these combinations of movements, the robot must be able to reach and retrieve any tool or component from the storage rack (29) and to reach the ladle sliding gate (15) of the first or second ladle (11, 12) which is held at the loading station for carrying out the operations described below. Excellent results were obtained using a Kuka Foundry type Robot KR480.
The robot is configured for coupling a ladle shroud (13a-13c) and a driving device (17) to a ladle (11, 12) full of molten metal and to the ladle sliding gate (15) thereof. It is also configured for removing off the emptied first or second ladle (11, 12) which is held at the loading station after being moved from the casting station the spent ladle shroud (13a-13c) and the driving device (17). To avoid brutal thermal shocks, the ladle shroud (13b) is preferably enclosed in a pre-heating station prior to being coupled to the ladle sliding gate (15) of the ladle at the loading station. The robot can handle the ladle shroud from the storage rack (29) to the pre-heating station (not shown) and thence to be coupled to the ladle sliding gate (15). Similarly, for removing the ladle shroud off an emptied first ladle (11), the robot can remove it, bring it to a pressurized gas (e.g. oxygen) cleaning station (not shown) and to the pre-heating station or to the storage rack (29) for further use. Alternatively, the robot can dump the ladle shroud into a disposal bin (27) in case it is too worn out for further use.
The robot is also configured for checking the state of a spent ladle shroud (13a-13c) after removal from an emptied ladle. In a preferred embodiment, the robot is configured for assessing whether the spent ladle shroud can be re-used after cleaning or whether it must be disposed of. This can be achieved with an artificial intelligence programming of the robot which can “learn” to distinguish between spent ladle shrouds which can be re-used or must be disposed of. The robot is also preferably configured for cleaning a spent ladle shroud, advantageously with an oxygen shower, to remove any residue clinging to walls of the spent ladle shroud.
A ladle sliding gate (15) suitable for the present invention comprises an upper plate (15u) and a lower plate (15d). The upper plate comprises a fixing surface and a bottom sliding surface separated from one another by a thickness of the upper plate, and an upper bore extending from the fixing surface to the bottom sliding surface. The fixing surface of the upper plate is rigidly fixed to a lower portion of the corresponding first or second ladle (11, 12) with the upper bore in fluid communication with the opening (11o, 12o). The opening is generally formed by a downstream end of an inner bore of an inner nozzle (18), as illustrated in
The lower plate (15d) comprises a nozzle sliding surface and a top sliding surface separated from one another by a thickness of the lower plate, as well as one or two lower bores extending from the top sliding surface to the nozzle sliding surface. The lower plate (15d) is slidingly mounted such that the top sliding surface can slide in translation along the bottom sliding surface to bring the one or two lower bores in and out of fluid communication with the upper bore. The lower plate can be moved in translation by activating a driving device (17). The driving device can comprise a cylinder (17c) rigidly and reversibly coupled to the bottom portion of the first or second ladle (11, 12), and a piston (17p) reversibly fixed to the lower plate (15d). For example, the driving device (17) can be a hydraulic piston or a pneumatic piston.
In a first embodiment illustrated in
The sealed position of the drawer (15w) is preferred but not essential, since flow from the ladle can be stopped by moving the lower bore of the lower plate out of registry with the upper bore of the upper plate. Like the lower plate, the drawer (15w) can be moved in translation by activating a drawer driving device (17w). The drawer driving device can comprise a cylinder (17c) rigidly and reversibly coupled to the bottom portion of the first or second ladle (11, 12), and a piston (17p) reversibly fixed to the drawer (15w). For example, the drawer driving device (17w) can be a hydraulic piston or a pneumatic piston. Actuating the drawer driving device (17w) allows moving the drawer (15w) to bring the shroud bore and the collector bore in and out of registry with the lower bore.
As shown in
As illustrated in
As soon as the solid mass is disrupted, the particles of plugging material (19) start flowing out through the collector nozzle and, as shown in
In a second embodiment illustrated in
As shown in
As shown in
As soon as the solid mass is disrupted, the particles of plugging material (19) start flowing out through the collector nozzle and, as shown in
In all embodiments of ladle sliding gates (15), the driving device (17) can be actuated hydraulically or pneumatically or electrically. Each of the at least first holding device and second holding device of the ladle turret is preferably provided with a source of pressurized fluid for actuating the driving device (17) and, if it comprises a drawer (15w), for actuating the drawer driving device (17w), via a hose (17t). In a preferred embodiment, each of the at least first holding device and second holding device of the ladle turret also comprises a storing unit for storing the driving device (17) and the drawer driving device (17w) if there is a drawer (15w), when the (drawer) driving device(s) (17) is (are) not coupled to the ladle sliding gate (15), as shown in
The present invention also concerns a method for casting molten metal (2) from a ladle (11, 12) into a tundish (1) in a casting installation as discussed supra, with the first ladle (11) being full of molten metal and being located at the casting station and the second ladle (12) being full of molten metal and being at the loading station. As illustrated in
In order to start casting molten metal from the first ladle (11) through the ladle shroud (13a) into the tundish (2), the ladle sliding gate (15) of the first ladle (11) is brought into casting position. This operation is performed by actuating the driving device (17). The first ladle (11) discharges the molten metal (2) contained therein into the tundish (1) until the first ladle is considered emptied.
As the first ladle (11) is discharging its content into the tundish, the robot (21) loads a new ladle shroud (13b) onto the ladle sliding gate (15) of the second ladle (12) (cf.
As shown in
The ladle sliding gate (15) of the second ladle (12) can be brought into casting position such that molten metal can flow from the second ladle (12) through the ladle shroud (13b) into the tundish (2). The whole swapping operation from closing the ladle sliding gate of the first ladle (11) to opening the ladle sliding gate of the second ladle (12) can last less than 2 min, preferably less than 1 min more preferably less than 30 s, and the level of molten metal in the tundish can easily be restored to a stationary casting level.
The emptied first ladle (11) parked at the loading station can now be stripped of the ladle shroud to allow the removal and transportation thereof across the workshop to a refurbishing station (not shown). The spent ladle shroud (11a) can be removed from the ladle sliding gate (15) of the emptied first ladle (11) with the robot (21). The spent ladle shroud (13a) can be stored for refurbishing and cleaning (not shown) or as waste in a disposal bin (27) as shown in
As illustrated in
The emptied first ladle, stripped of the ladle shroud (13a) and of the one or more (drawer) driving means (17, 17w) can be removed from the first holding device by a crane to a refurbishing station (not shown), where the ladle can be cleaned, repaired, and made ready for being filled with a new load of molten metal from a furnace. A new ladle full of molten metal can be loaded onto the now empty first holding device of the ladle turret (30) at the loading station wherein, like the second ladle (12) in step (a), the new ladle comprises a ladle sliding gate (15) in the sealed position and comprising no ladle shroud (13a-13c) and no (drawer) driving device (17, 17w).The cycle depicted in
In case step (e) of swapping positions of the first and second ladles does not proceed optimally, because the inner and/or upper bores are clogged with solidified plugging material, the use of ladle sliding gate (15) comprising both ladle shroud (13a-13c) and collector nozzle (14) side-by-side allows a rapid and efficient un-clogging of the inner and/or upper bores by using an appropriate unclogging tool (19r) through the collector bore, as described supra in the section entitled “LADLE SLIDING GATE (15).” This way, the interruption of metal flow into the tundish is reduced to a minimum. Absent this option of rapid un-clogging through the collector bore, many operators would be reluctant to fix a ladle shroud (13a-13c) to a bottom of a ladle at the loading station, with or without a robot (21), because unclogging the inner and upper bores with a ladle shroud fixed to the ladle sliding gate would require returning the clogged ladle to the loading station and replacing the ladle shroud by a collector nozzle to allow un-clogging with an unclogging tool (19r), then coupling again the ladle shroud and bringing the ladle back to the casting station. All these operations would take too long, with a risk of metal freezing, which was to be prevented by the use of a plugging material. Furthermore, a long period without feeding the tundish with molten metal could provoke the interruption of the casing operation, which must be avoided by all means.
In a preferred embodiment, the loading operations of a second ladle (12) stationed at the loading station are carried out in the following order: (1) coupling of the (drawer) driving device(s) to the ladle sliding gate (15), followed by the coupling of a new ladle shroud (13b). The unloading operations of an emptied first ladle (11) stationed at the loading station are preferably carried out in the following order: (1) uncoupling of the spent ladle shroud (13b), followed by uncoupling of the (drawer) driving device(s) from the ladle sliding gate (15).
The present invention offers an automated metal casting installation, wherein a fresh ladle can be made ready for casting by a robot (21) at the loading station, without any additional risk of casting disruption into the tool compared with conventional metal casting installations.
Number | Date | Country | Kind |
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20157812.7 | Feb 2020 | WO | international |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2021/053854 | 2/17/2021 | WO |