System, apparatus, and method for casting bleed out detection

Abstract

Provided herein is a system, apparatus, and method for detecting bleed out in continuous casting, and to detecting bleed out using a pneumo-electric sensor loop. Methods include: receiving casting gas at a manifold of a mold table for distribution to at least one continuous casting mold; dispersing the casting gas from the manifold to the at least one continuous casting mold; diverting at least a portion of the casting gas to a sensor loop disposed proximate a bottom of the at least one continuous casting mold; detecting at least one of a pressure loss or a step change in mass air flow from the sensor loop disposed proximate the bottom of the at least one continuous casting mold; and identifying the at least one continuous casting mold as having a bleed out condition.

Description

TECHNOLOGICAL FIELD

[0001] The present disclosure relates to a system, apparatus, and method for detecting bleed out in continuous casting, and more particularly, to detecting bleed out using a pneumo-electric sensor loop.BACKGROUND

[0002] Metal products may be formed in a variety of ways; however numerous forming methods first require an ingot, billet, or other cast part that can serve as the raw material from which a metal end product can be manufactured, such as through rolling, extrusion, or machining, for example. One method of manufacturing an ingot or billet is through a continuous casting process known as continuous casting, whereby a vertically oriented mold cavity is situated above a platform that translates vertically down into a casting pit. A starter block may be situated on the platform and form a bottom of the mold cavity, at least initially, to begin the casting process. Molten metal is poured into the mold cavity whereupon the molten metal cools, typically using a cooling fluid. The platform with the starter block thereon may descend into the casting pit at a predefined speed to allow the metal exiting the mold cavity and descending with the starter block to solidify. The platform continues to be lowered as more molten metal enters the mold cavity, and solid metal exits the mold cavity. This continuous casting process allows metal ingots and billets to be formed according to the profile of the mold cavity and having a length limited only by the casting pit depth and the hydraulically actuated platform moving therein.BRIEF SUMMARY

[0003] The present disclosure relates to a system, apparatus, and method for detecting bleed out in continuous casting, and more particularly, to detecting bleed out using a pneumo-electric sensor loop. Embodiments provided herein include a method including: receiving casting gas at a manifold of a mold table for distribution to at least one continuous casting mold; dispersing the casting gas from the manifold to the at least one continuous casting mold; diverting at least a portion of the casting gas to a sensor loop disposed proximate a bottom of the at least one continuous casting mold; detecting at least one of a pressure loss or a step change in mass air flow from the sensor loop disposed proximate the bottom of the at least one continuous casting mold; and identifying the at least one continuous casting mold as having a bleed out condition.

[0004] The method of certain embodiments includes ceasing molten metal flow to the at least one continuous casting mold in response to identifying the at least one continuous casting mold as having the bleed out condition. According to some embodiments detecting a pressure loss from the sensor loop disposed proximate the bottom of the at least one continuous casting mold includes: detecting the pressure loss at the manifold with a pressure sensor in response to the pressure loss satisfying a predetermined threshold. According to some embodiments the pressure loss from the sensor loop is caused by molten metal melting a material forming the sensor loop.

[0005] According to certain embodiments diverting at least a portion of the casting gas to the sensor loop disposed proximate the bottom of the at least one continuous casting mold includes diverting at least a portion of the casting gas to a fitting attached to the sensor loop to pressurize the casting gas within the sensor loop. The method of some embodiments further includes limiting pressure loss from the sensor loop using a reducing orifice to retain casting gas pressure and flow to at least one other continuous casting mold. According to certain embodiments dispersing the casting gas from the manifold to the at least one continuous casting mold includes dispersing the casting gas to a casting surface of the at least one continuous casting mold.

[0006] Embodiments provided herein include an apparatus for detecting continuous casting bleed out including: a manifold, where the manifold receives casting gas from a casting gas source wherein the manifold disperses the casting gas to a continuous casting mold; at least one of a pressure sensor or a mass air flow sensor within the manifold associated with the continuous casting mold; a sensor loop attached proximate a bottom of the continuous casting mold; a conduit to convey the casting gas from the manifold to the continuous casting mold; and a passage to convey at least a portion of the casting gas from the conduit to the sensor loop to pressurize the sensor loop, where in response to molten metal from a bleed out condition of the continuous casting mold contacting the sensor loop, the sensor loop is punctured and casting gas escapes the sensor loop, where in response to the casting gas escaping the sensor loop, the pressure sensor or the mass air flow sensor within the manifold detects the bleed out condition.

[0007] According to some embodiments the manifold receives casting gas from the casting gas source at a pressure of around 60 psi (pounds-per-square-inch). According to certain embodiments the pressure sensor or the mass air flow sensor within the manifold detects the bleed out condition in response to a pressure within the sensor loop being reduced by a predefined threshold or the mass air flow sensor detecting a step change in mass air flow through the sensor loop. The apparatus of some embodiments further includes an orifice within the manifold between the pressure sensor and the casting gas source, wherein the orifice defines a diameter of about 0.01 inches.

[0008] According to certain embodiments the manifold disperses the casting gas to at least one other continuous casting mold, where the orifice enables a casting operation of the at least one other continuous casting mold to continue after the pressure sensor within the manifold detects the bleed out condition of the continuous casting mold. According to some embodiments the sensor loop is formed of a polymer tube. The sensor loop of an example embodiment is attached at opposing ends to a fitting, wherein the fitting is in fluid communication with the passage. According to some embodiments the fitting is a T-fitting, and wherein the T-fitting is held within the continuous casting mold with a fastener.

[0009] Embodiments provided herein include a system for continuous casting including: a plurality of continuous casting molds; a casting gas supply; a manifold, where the manifold is configured to receive casting gas from the casting gas supply and distribute the casting gas to the plurality of continuous casting molds; a plurality of conduits, where each conduit conducts the casting gas from a respective channel of the manifold to a respective continuous casting mold of the plurality of continuous casting molds; a plurality of sensor loops, where each sensor loop is attached to a respective continuous casting mold of the plurality of continuous casting molds, where the casting gas from the respective continuous casting mold is conducted to a respective sensor loop for the respective continuous casting mold; a plurality of pressure sensors each associated with a respective continuous casting mold, where a pressure sensor of the plurality of pressure sensors is configured to detect a bleed out condition at the respective continuous casting mold based on a pressure loss satisfying a predetermined threshold.

[0010] According to some embodiments each sensor loop includes a polymer tube encircling a bottom of the respective continuous casting mold. According to certain embodiments the polymer tube encircling the bottom of the respective continuous casting mold is punctured in response to the bleed out condition at the respective continuous casting mold. According to some embodiments the casting gas from the respective continuous casting mold is conducted to the respective sensor loop for the respective continuous casting mold via a passage within the respective continuous casting mold. According to certain embodiments each sensor loop is attached at either end to a fitting, where the fitting is in fluid communication with the passage.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0012] FIG. 1 illustrates an example embodiment of a continuous casting mold according to the prior art;

[0013] FIG. 2 illustrates an example of the initial stages of continuous casting or continuous casting according to an example embodiment of the present disclosure;

[0014] FIG. 3 illustrates an example embodiment following the initial stages of continuous casting according to an example embodiment of the present disclosure;

[0015] FIG. 4 illustrates an example embodiment of steady-state continuous casting according to an example embodiment of the present disclosure;

[0016] FIG. 5 illustrates a sensor loop of a continuous casting mold according to an example embodiment of the present disclosure;

[0017] FIG. 6 illustrates a bottom view of a continuous casting mold including a sensor loop according to an example embodiment of the present disclosure;

[0018] FIG. 7 illustrates sectioned detail view of a passage for providing casting gas to a fitting and to the sensor loop of a continuous casting mold according to an example embodiment of the present disclosure;

[0019] FIG. 8 is a schematic of a manifold for detecting bleed out from a sensor loop of a continuous casting mold according to an example embodiment of the present disclosure;

[0020] FIG. 9 is a diagram of a manifold for detecting bleed out from a sensor loop of a continuous casting mold according to an example embodiment of the present disclosure;

[0021] FIG. 10 is a chart of backpressure distribution during various stages of continuous casting according to an example embodiment of the present disclosure; and

[0022] FIG. 11 is a flowchart of a method for detecting a bleed out condition of a continuous casting mold according to an example embodiment of the present disclosure.DETAILED DESCRIPTION

[0023] Example embodiments of the present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the disclosure are shown. Indeed, embodiments may take many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0024] Vertical direct chill casting or continuous casting is a process used to produce ingots or billets that may have a variety of cross-sectional shapes and sizes for use in a variety of manufacturing applications. The process of continuous casting begins with a horizontal mold table or mold frame containing one or more vertically oriented molds disposed therein. Each of the molds defines a mold cavity, where the mold cavities are initially closed at the bottom with a starter block to seal the bottom of the mold cavity. Molten metal is introduced to each mold cavity through a metal distribution system to fill the mold cavities. As the molten metal proximate the bottom of the mold, adjacent to the starter block solidifies, the starter block is moved vertically downward along a linear path into a casting pit. The movement of the starter block may be caused by a hydraulically lowered platform to which the starter block is attached. The movement of the starter block vertically downward draws the solidified metal from the mold cavity while additional molten metal is introduced into the mold cavity. Once started, this process moves at a relatively steady state for a continuous casting process that forms a metal ingot having a profile defined by the mold cavity, and a height defined by the depth to which the platform and starter block are moved.

[0025] During the casting process, the mold itself is cooled to encourage solidification of the metal prior to the metal exiting the mold cavity as the starter block is advanced downwardly, and a cooling fluid is introduced to the surface of the metal proximate the exit of the mold cavity as the metal is cast to draw heat from the cast metal ingot and to solidify the molten metal within the now-solidified shell of the ingot. As the starter block is advanced downward, the cooling fluid may be sprayed directly on the ingot to cool the surface and to draw heat from within the core of the ingot.

[0026] FIG. 1 depicts a general illustration of a cross-section of a continuous casting mold 100 during the continuous casting process. The illustrated mold could be for a round billet or a substantially rectangular ingot, for example. The cooling water spray pattern as described herein is primarily directed to round billet casting. However, embodiments could potentially be used for a substantially rectangular ingot, particularly when the corners of said ingot have some degree of curvature. As shown, the continuous casting mold 105 forms a mold cavity from which the cast part 110 is formed. The casting process begins with the starter block 115 sealing or substantially filling the bottom of the mold cavity against mold walls of the continuous casting mold 105. As the platform 120 moves down along arrow 145 into a casting pit and the cast part begins to solidify at its edges within the mold walls of the continuous casting mold 105, the cast part 110 exits the mold cavity. Metal flows from a pouring trough 125, which may be a heated reservoir or a reservoir fed from a furnace, for example, through thimble 130 into the mold cavity. As shown, the thimble 130 is partially submerged within a molten pool of metal 135 to avoid the oxidation of metal that would occur if fed from above the molten metal pool 135. The solidified metal constitutes the formed cast part 140, such as a billet. Flow through the thimble 130 may be controlled within the pouring trough 125, such as by a tapered plug fitting within an orifice connecting a cavity of the pouring trough 125 with a flow channel through the thimble 130. Conventionally, the pouring trough 125, thimble 130, and mold cavity / mold walls of the continuous casting mold 105 are held in a fixed relationship from the beginning of the casting operation through the end of the casting operation. Flow of metal through the thimble 130 continues as the platform 120 continues to descend along arrow 145 into the casting pit. When the casting operation is to end, either by the platform being at the bottom of its travel, the metal supply running low, or the cast part reaching the completed size, the flow of metal through the thimble 130 stops, and the thimble assembled on the trough is removed from the molten pool of metal 135 to allow the molten pool to solidify and complete the cast part.

[0027] FIG. 2 illustrates an example embodiment of a hot top casting method of the continuous casting process according to the present disclosure including a continuous casting mold 105, trough 125, and thimble 130 for supplying molten metal from the trough to the cavity of the mold. The illustrated embodiment of FIG. 2 includes a starting position where the tip of the thimble 130 or thimble is positioned proximate the starter block 115 which is supported by the platform 120. The starter block 115 is positioned atop platform 120 and aligned to cooperate with the mold 105 to seal the mold cavity and preclude molten metal 107 from leaking from between the continuous casting mold 105 and the starter block 115. The thimble 130 or thimble is received into a transition plate 200 that is securely attached to the top of the mold 105, such as by threaded engagement. The transition plate 200 may be secured to the mold 105 by a metal ring that is threaded into a round opening atop the billet mold 105 to hold the transition plate securely to the mold. The mold 105 may be of a metal such as aluminum, while the thimble 130 and transition plate 200 are generally formed of a refractory material that is resilient to heat.

[0028] FIG. 2 illustrates the start of a cast with the starter block 115 aligned with the continuous casting mold 105. As the cast starts shown in FIG. 3, the platform 120 descends with the starter block 115 as molten metal flows through the thimble 130 from the trough 125 and solidifies on the starter block 115 and at the bottom of the mold cavity forming the cast part 140. In this manner, as the starter block 115 descends away from the continuous casting mold 105, the cast part, shown in FIG. 4 as 140, is formed. FIG. 4 illustrates the run-state phase of the casting process or the steady-state portion where the platform 120 descends at a near constant rate with the cast part 140 growing accordingly. FIG. 2 also illustrates spray jets 150 that will be described in greater detail below, where the spray jets provide a coolant or cooling fluid to the surface of the casting.

[0029] FIG. 5 illustrates a detail view of mold components for an example embodiment of continuous casting. As shown, the continuous casting mold 105 includes a graphite casting surface 210 upon which the initial solidification of the billet being cast occurs. The permeable graphite material allows for flowing both casting gas and casting lubricant to the casting surface that produces an air-slip casting condition including air gap 220 between the molten metal 107 that is solidifying in the mold cavity and the graphite casting surface 210. The casting lubricant reduces the friction on the casting surface 210 to prevent sticking and tearing of the freshly solidifying shell of the cast part 140. The casting gas flow further aids in reducing this friction while at the same time provides a thin film of gas between the casting surface and the billet shell which reduces the thermal heat transfer from the molten aluminum to the casting surface. When properly balanced, the introduction of gas and oil produces an as-cast billet with a very smooth surface and very narrow shell thickness as compared to conventionally cast billets. Water or coolant flowing to spray jets 150 from the coolant chamber 155 impinges upon the shell of the cast part 140 and proceeds to flow down the sides of the cast part as shown at 145 to further cool the casting.

[0030] Various failures and issues can arise during the casting process. One such failure is bleed out, where the solidified metal leaving the mold is compromised and the casting loses molten metal containment. The molten metal escapes the casting and begins to spill into the casting pit. Bleed out can be dangerous, as there is inherent danger in the use of water or cooling fluid to directly quench and cool the molten aluminum. Molten aluminum and water when mixed in an uncontrolled manner can lead to large molten metal explosions. The loss of containment of the molten metal or bleed out can have varying magnitudes of containment loss with varying durations that indicate these failures.

[0031] Issues relating to bleed out can be mitigated most effectively if the bleed out is detected early, close to when the bleed out failure begins. Early detection of bleed out can provide improved response time minimizing the chance of a catastrophic explosion and / or damage to personnel or equipment. Various iterations of bleed out detection have been proposed with numerous design challenges and use constraints that has rendered adoption in the industry difficult.

[0032] Embodiments described herein include a pressurized pneumatic tube as a sensor loop with a low melting point, typically polyurethane tubing, that melts when damaged by a bleed out. The damage to the pressurized tube results in a loss of pressure within the tube. The pressure loss can be on the order of a 3:1 ratio of prior-to-post bleed out condition in an example embodiment. The ratio of pressure between pre and post detection can vary and is influenced by the orifice and its size if implemented. As such, the pressure ratio can be selected by a user based on casting gas operating pressure and orifice size. The sensor loop is pressurized by a pressure supply that has nominally no flow. To introduce pressure to the system described herein, an interconnection with the independent supply gas line used for casting gas to the mold body is employed. The pressure is then monitored continually for drops in the back pressure of each individual mold position.

[0033] Referring back to FIG. 5, a sensor loop 270 is illustrated in the section view as a tube having a relatively low melting point. The sensor loop 270 is removable and replaceable within the continuous casting mold 105, particularly as the sensor ring is a consumable element and is not re-used after it has been compromised with a detected bleed out. The sensor loop 270 is held in position within the mold using retainers attached to the continuous casting mold 105, and can be removed when the mold is heated during maintenance (e.g., for graphite liner changes)

[0034] FIG. 6 is a bottom view of a continuous casting mold 105 without the other components of the continuous casting mold system. As shown, the continuous casting mold 105 includes an inner wall 207 with ribs 209. The continuous casting mold 105 defines a mold cavity 202 bounded by the casting surface 210. The cooling fluid spray jets 150 surround the mold cavity at a bottom of the mold cavity to cool the casting as the starting head (not shown) descends into the casting pit. Also shown in the embodiment of FIG. 6 is the sensor loop 270 which is attached to the continuous casting mold 105 at the ribs 209 and suspended around a bottom of the continuous casting mold 105. The attachment mechanism can include a variety of mechanical attachment techniques such as a frame or attachment points attached to the bottom of the continuous casting mold 105 or integrated into the ribs 209 of the mold as shown.

[0035] The sensor loop 270 includes a fitting or coupling positioned along the sensor ring whereby the air pressure is introduced to the sensor ring. In the illustrated embodiment, that coupling is a T-fitting positioned at a rib 209, with the T-fitting coupling together opposing ends of the sensor loop 270 and a mating hole in the continuous casting mold 105 body. The mating hole in the mold body includes a passage to connect the mating hole to the casting gas source for the continuous casting mold 105. The sensor loop 270 and the fitting are held in place with fastener 272.

[0036] FIG. 7 illustrates a section view through the continuous casting mold 105 body at the fitting 280 with the fastener 272 holding the fitting in the mold and in contact with the mating hole and passage 284. The fitting 282 can include a barbed end 286 as depicted and may include O-ring 288 to provide an airtight seal between the sensor loop 270 and the passage 284.

[0037] Embodiments are integrated into the casting gas supply line that supplies air to a given mold position, which flows into the passage 284 to provide casting gas pressure to the sensor loop 270. The casting gas is supplied to a plurality of continuous casting molds from a casting gas supply manifold. At the gas supply manifold end of the line, pressure transducers monitor the mold back pressure. With the pneumatic sensor loop 270 in parallel with the casting gas circuit, a drop in mold back pressure triggers the alarm. This architecture allows for retrofit onto existing tables and importantly, decreases the overall system cost to a fraction of previous systems. The pressure transducers can be implemented into the gas control manifold with a bolt-on addition to any table either from the manufacturer or readily retrofitted. Mold systems that include back pressure monitoring capability is ready-made to operate with this bleed out detection configuration with updated code blocks.

[0038] The sensor loop 270 is described and illustrated as a loop, where each end of the sensor loop is connected to a fitting to be in fluid communication with the casting gas received at the continuous casting mold 105. According to some embodiments, the sensor loop may be connected to the fitting at only one end of the loop and function in a manner similar to that described above. However, forming the sensor loop with both ends in fluid communication with the fitting provides a more reliable and robust sensing system as, while unlikely, it is possible for molten metal to melt a polymer tube such as that of the sensor loop and fuse an end of the polymer tube. With only a single source of casting gas pressure into the sensor loop, this possibility increases. However, with the casting gas pressure introduced on both ends of the loop, the likelihood of such a scenario is substantially reduced.

[0039] The sensor loop 270 of example embodiments is also easily replaced in the event of damage to the sensor loop or after detection of bleed out. In the illustrated embodiment of FIG. 6, the fastener 272 is removed, the sensor loop 270 and fitting 282 are removed from the passage 284, and the sensor loop 270 is detached from the ribs 209 of the continuous casting mold 105. The reverse of this removal operation installs a new sensor loop 270 quickly and easily.

[0040] The manifold of example embodiments described herein is compact to be compatible with existing mold systems to fit along a side of the bottom plate of a mold table in the dead space of even the tightest table layouts. A standalone manifold design is compatible with most tables. The manifold houses all cross drilling and supply pressure routing such that there is a single pressure port supplied to the manifold, the pressure port supplies orifices for each individual mold position independently of one another. A branch orifice may be, for example, 0.010 inches in diameter. With a supply pressure of 60 psi (pounds-per-square-inch) to a maximum supply rate of three standard liters per minute during a bleed out condition. The casting gas can be provided at various pressures, where an example embodiment includes a supply of casting gas at 60 psi. However, casting gas can be provided at a variety of pressures including substantially higher pressures such as 150psi in some embodiments. Embodiments described herein can determine bleed out conditions regardless of the supplied pressure of casting gas as would be apparent to one of ordinary skill in the art.

[0041] FIG. 8 illustrates the pneumatic configuration of an example embodiment. As shown, casting gas is provided at 305. Alternatively, a separate compressed air source may be used to achieve similar results. However, using the casting gas already available at the table reduces complexity and cost to more efficiently and effectively implement embodiments of the bleed out detection system. A pressurized feedback system is illustrated at 310. The pressurized gas is supplied to manifold 320, where for each position in the manifold, such as in a twelve-position manifold, an orifice 325 may be positioned (e.g., with a diameter of 0.010 inches) ahead of a pressure switch 330. The pressure switch 330 may be, for example, a 0.4 mPa (megapascal) switch which may include a 0.04 mPa hysteresis. The pressurized gas is provided from the manifold outlet 340 for each position the sensor loop 170.

[0042] If a leak exists in the sensor loop 270 (e.g., where the sensor loop is compromised through a melt caused by a bleed out) then the pressure downstream of the orifice 325 drops below a threshold pressure of the pressure switch 330 indicating a pressure loss (bleed out) condition. The pressure switch 330 may be configured in the normally open position, where pressure must be applied to close the switch. The normally open configuration paired with pull down resistors on the digital inputs to the control system of the continuous casting mold system ensure the pressure must be present for the proper active state and not in alarm indicating pressure loss.

[0043] The orifice 325 is an optional addition that offers the ability to mitigate a magnitude of the pressure drop in the event of a bleed out. The orifice 325 can be implemented in the manifold, integrated as part of the mold body, or directly integrated into the t-fitting of the sensor loop. The air delivery at 305 could be via a pressure or mass flow control system and retain effectively the same function.

[0044] While FIG. 8 depicts a pressure switch 330, embodiments can employ a mass air flow sensor that measures mass air flow to each mold. The mass air flow sensor can be employed in a similar way as the pressure switch 300, whereby a step change of the mass air flow during a casting operation can indicate that the sensor loop has been punctured and indicating that a bleed out event has occurred.

[0045] An alarm or alert indicating a bleed out event can be a visual alarm (e.g., a light, a message at a control interface, a mechanical flag, etc.), an audible alarm, or any combination thereof. The alarm can alert an operator of the bleed out condition who can then take action in response. In some embodiments, the alarm can trigger a shut down of the mold in which the bleed out condition has occurred automatically.

[0046] According to an example embodiment, the manifold assembly includes three primary components: the manifold / housing, pressure switches, and electrical distribution PCB (printed circuit board). The manifold can double as the housing for electrical components to protect them from moisture and mechanical damage. The manifold may be sealed to satisfy Ingress Protection (IP) standards such as IP66 or better with an IP69K breather that can allow air pressure to normalize inside the manifold and allow proper pressure gauge venting while preventing moisture intrusion. Each pressure switch may be mounted into the manifold by use of O-rings and a push connect stem that can be part of the pressure switch assembly. The pressure switches can include a standard pressure switch which can be configurable from the factory with appropriate switching pressure and hysteresis.

[0047] The PCB of an example embodiment may be housed and mounted within the manifold and can route power to each pressure switch while routing all signals back to a main connector. The PCB can include basic power and short circuit protection and may include LEDs tied in parallel to each output signal independently for individual position visual indication without the need for PLC (programmable logic controller) feedback when performing mold maintenance. When pressure is above a threshold pressure, and power is applied to the manifold the pressure circuit is closed and the light will illuminate. The light may be connected to a light guide or light tunnel to direct light to an external surface of the manifold or the lights may be visible based on their position within the manifold.

[0048] FIG. 9 illustrates an example embodiment of a manifold 400 as described herein including supply port 410, pressure switches 420, pressure line connections 430, and PCB distribution 440. When installed on the table all pneumatic connections are made at the table interface via O-rings. The electrical connections can be made via flex conduit. The Flex conduit can house a single cable with 15 conductors in some examples, where 14 are used with one as a spare. Two of the 14 conductors can include power and ground, while the remaining conductors are for signals from each individual position. According to an example embodiment, a main rigid conduit can run a length of the mold table with a T-body conduit junction place near each manifold location. From the t-body conduit junction a short flex conduit could connect to the manifold keeping a liquid tight electrical connection and protecting the casting from the environment.

[0049] Plumbing from the manifold to the mold position can be done using conventional copper tubing and fittings. For example, 4 mm copper may be sufficient for transmitting pressure to each mold position while allowing ample venting capacity in the event of a bleed out and sensor loop rupture. If smaller lines to the individual positions are used, smaller orifices in the manifold may be required to ensure sufficient pressure loss on rupture as smaller lines will have increased flow restriction and thus increased back pressure.

[0050] An example continuous casting system operates casting gas to each continuous casting mold with a needle valve that feeds the mold position. All positions operate with a needle valve that feeds the mold position. During calibration the table pressure may be 55 psi. Based on a 55 psi supply and a back pressure of 24 psi, the needle valve has a pressure differential of ~31 psi. In a bleed out the needle valve will be unchanged, but the casting gas would vent to atmosphere taking the pressure differential across the needle valve from ~31 psi to ~55 psi. The increased in differential pressure would cause an increase in flow rate of the casting gas from the nominal 3 slpm to ~5.3 slpm at most.

[0051] Even with a supply flow through the bleed out detection system of 6 slpm the trip pressure drops to less than 7 psi in virtually all instances. Thus, if the existing casting gas supply system can handle a small percent increase in flow during bleed outs without dropping pressure on the supply, the casting gas supply can be used to monitor for bleed outs using the pneumatic sensor loop design without impacting subsequent billet positions. Put another way this can be seen visually by inspecting the normal distributions shown in FIG. 10. The run flow pressure distribution and trip pressure distribution do not overlap with any statistical significance.

[0052] FIG. 10 illustrates that a start flow of casting gas produces a back pressure in a normal distribution of around 52 psi, while the casting gas run flow back pressure includes a normal distribution centered at around 24 psi. These are merely examples of pressures at which the casting gas may be operating and may vary depending on mold size among other factors. FIG. 10 thus illustrates the differences between casting gas back pressure during different operating scenarios including start flow, run flow, and as a bleed out is detected. These differences can be greater or less than shown, and the specific pressures of each operating phase may vary depending on the specific implementation.

[0053] While pressure changes are depicted in FIG. 10, embodiments described herein may alternatively or additionally employ mass flow measures to determine when the sensor loop has been compromised. Mass flow of casting gas may be relatively high during startup and may then lower to a relatively steady state mass flow during run flow. However, when the sensor loop is punctured, the mass flow would experience a step up in the mass flow. This step up can be used to identify a bleed out in a similar manner to the use of pressure described above. As pressure feedback on a per-mold basis may not be available, mass flow of casting gas can be used in the alternative. Bleed out can thus be indicated by a step change in flow rate or the proportional valve command as compared to prior to the bleed out. This is in direct relation to the reduction in back pressure as lower back pressure requires a proportionally lower command for a proportional valve.

[0054] Advantages for using the casting gas to pressurize the sensor loop include that for installation, no additional plumbing in the mold table is required. On large, tight tables the plumbing can become extremely tight and difficult to route such that use of the existing casting gas does not require additional plumbing. Further, the ability to tie into the casting gas supply after the needle valves renders embodiments well-suited for retrofitting of existing mold tables.

[0055] Embodiments described herein are configured to detect bleed out relatively quickly with improved reliability and configurability. The disclosed system is also relatively inexpensive and can be retrofit to existing mold system, while also being compatible with new mold tables.

[0056] Once bleed out is detected for a continuous casting mold of the plurality of continuous casting molds within a mold table, metal flow to that continuous casting mold can be ceased to stem the molten aluminum spilling from the casting and thus reduce the likelihood of molten metal explosion and to reduce fouling to the casting pit. This system improves efficiency of continuous casting as the remainder of the continuous casting molds can continue to produce castings and the mold operation does not need to cease. Further, the efficiency of the casting operation is improved as the amount of molten metal spilled into the casting pit is reduced substantially requiring less clearing of the casting pit. These efficiencies and improvements can be gained at relatively low expense, particularly when the sensor loop of example embodiments is supplied with pressurized casting gas through the manifold as described above, as such a configuration requires minimal modification to the mold table and the continuous casting molds themselves.

[0057] FIG. 11 is a flowchart of a method for detecting a bleed out condition at a continuous casting mold. Casting gas is received at a manifold of a mold table for distribution to at least one continuous casting mold as shown at 510. The casting gas is dispersed at 520 from the manifold to the at least one continuous casting mold. At least a portion of the gas is diverted at 530 to a sensor loop disposed proximate a bottom of the at least one continuous casting mold. A pressure loss is detected from the sensor loop disposed proximate the bottom of the at least one continuous casting mold as shown at 540. The at least one continuous casting mold is identified at 550 as having a bleed out condition.

[0058] Blocks of the flowchart support combinations of means for performing the specified functions and combinations of operations for performing the specified functions for performing the specified functions. It will also be understood that one or more blocks of the flowcharts, and combinations of blocks in the flowcharts, can be implemented by various aspects of the system for detecting a bleed out condition as described above.

[0059] In some embodiments, certain ones of the operations above may be modified or further amplified. Furthermore, in some embodiments, additional optional operations may be included. Modifications, additions, or amplifications to the operations above may be performed in any order and in any combination that facilitates the detection of a bleed out condition as described herein.

[0060] Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Examples

Embodiment Construction

[0023]Example embodiments of the present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the disclosure are shown. Indeed, embodiments may take many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0024]Vertical direct chill casting or continuous casting is a process used to produce ingots or billets that may have a variety of cross-sectional shapes and sizes for use in a variety of manufacturing applications. The process of continuous casting begins with a horizontal mold table or mold frame containing one or more vertically oriented molds disposed therein. Each of the molds defines a mold cavity, where the mold cavities are initially closed at the bottom with a starter block to seal the bottom...

TECHNOLOGICAL FIELD

[0001] The present disclosure relates to a system, apparatus, and method for detecting bleed out in continuous casting, and more particularly, to detecting bleed out using a pneumo-electric sensor loop.BACKGROUND

[0002] Metal products may be formed in a variety of ways; however numerous forming methods first require an ingot, billet, or other cast part that can serve as the raw material from which a metal end product can be manufactured, such as through rolling, extrusion, or machining, for example. One method of manufacturing an ingot or billet is through a continuous casting process known as continuous casting, whereby a vertically oriented mold cavity is situated above a platform that translates vertically down into a casting pit. A starter block may be situated on the platform and form a bottom of the mold cavity, at least initially, to begin the casting process. Molten metal is poured into the mold cavity whereupon the molten metal cools, typically using a cooling fluid. The platform with the starter block thereon may descend into the casting pit at a predefined speed to allow the metal exiting the mold cavity and descending with the starter block to solidify. The platform continues to be lowered as more molten metal enters the mold cavity, and solid metal exits the mold cavity. This continuous casting process allows metal ingots and billets to be formed according to the profile of the mold cavity and having a length limited only by the casting pit depth and the hydraulically actuated platform moving therein.BRIEF SUMMARY

[0003] The present disclosure relates to a system, apparatus, and method for detecting bleed out in continuous casting, and more particularly, to detecting bleed out using a pneumo-electric sensor loop. Embodiments provided herein include a method including: receiving casting gas at a manifold of a mold table for distribution to at least one continuous casting mold; dispersing the casting gas from the manifold to the at least one continuous casting mold; diverting at least a portion of the casting gas to a sensor loop disposed proximate a bottom of the at least one continuous casting mold; detecting at least one of a pressure loss or a step change in mass air flow from the sensor loop disposed proximate the bottom of the at least one continuous casting mold; and identifying the at least one continuous casting mold as having a bleed out condition.

[0004] The method of certain embodiments includes ceasing molten metal flow to the at least one continuous casting mold in response to identifying the at least one continuous casting mold as having the bleed out condition. According to some embodiments detecting a pressure loss from the sensor loop disposed proximate the bottom of the at least one continuous casting mold includes: detecting the pressure loss at the manifold with a pressure sensor in response to the pressure loss satisfying a predetermined threshold. According to some embodiments the pressure loss from the sensor loop is caused by molten metal melting a material forming the sensor loop.

[0005] According to certain embodiments diverting at least a portion of the casting gas to the sensor loop disposed proximate the bottom of the at least one continuous casting mold includes diverting at least a portion of the casting gas to a fitting attached to the sensor loop to pressurize the casting gas within the sensor loop. The method of some embodiments further includes limiting pressure loss from the sensor loop using a reducing orifice to retain casting gas pressure and flow to at least one other continuous casting mold. According to certain embodiments dispersing the casting gas from the manifold to the at least one continuous casting mold includes dispersing the casting gas to a casting surface of the at least one continuous casting mold.

[0006] Embodiments provided herein include an apparatus for detecting continuous casting bleed out including: a manifold, where the manifold receives casting gas from a casting gas source wherein the manifold disperses the casting gas to a continuous casting mold; at least one of a pressure sensor or a mass air flow sensor within the manifold associated with the continuous casting mold; a sensor loop attached proximate a bottom of the continuous casting mold; a conduit to convey the casting gas from the manifold to the continuous casting mold; and a passage to convey at least a portion of the casting gas from the conduit to the sensor loop to pressurize the sensor loop, where in response to molten metal from a bleed out condition of the continuous casting mold contacting the sensor loop, the sensor loop is punctured and casting gas escapes the sensor loop, where in response to the casting gas escaping the sensor loop, the pressure sensor or the mass air flow sensor within the manifold detects the bleed out condition.

[0007] According to some embodiments the manifold receives casting gas from the casting gas source at a pressure of around 60 psi (pounds-per-square-inch). According to certain embodiments the pressure sensor or the mass air flow sensor within the manifold detects the bleed out condition in response to a pressure within the sensor loop being reduced by a predefined threshold or the mass air flow sensor detecting a step change in mass air flow through the sensor loop. The apparatus of some embodiments further includes an orifice within the manifold between the pressure sensor and the casting gas source, wherein the orifice defines a diameter of about 0.01 inches.

[0008] According to certain embodiments the manifold disperses the casting gas to at least one other continuous casting mold, where the orifice enables a casting operation of the at least one other continuous casting mold to continue after the pressure sensor within the manifold detects the bleed out condition of the continuous casting mold. According to some embodiments the sensor loop is formed of a polymer tube. The sensor loop of an example embodiment is attached at opposing ends to a fitting, wherein the fitting is in fluid communication with the passage. According to some embodiments the fitting is a T-fitting, and wherein the T-fitting is held within the continuous casting mold with a fastener.

[0009] Embodiments provided herein include a system for continuous casting including: a plurality of continuous casting molds; a casting gas supply; a manifold, where the manifold is configured to receive casting gas from the casting gas supply and distribute the casting gas to the plurality of continuous casting molds; a plurality of conduits, where each conduit conducts the casting gas from a respective channel of the manifold to a respective continuous casting mold of the plurality of continuous casting molds; a plurality of sensor loops, where each sensor loop is attached to a respective continuous casting mold of the plurality of continuous casting molds, where the casting gas from the respective continuous casting mold is conducted to a respective sensor loop for the respective continuous casting mold; a plurality of pressure sensors each associated with a respective continuous casting mold, where a pressure sensor of the plurality of pressure sensors is configured to detect a bleed out condition at the respective continuous casting mold based on a pressure loss satisfying a predetermined threshold.

[0010] According to some embodiments each sensor loop includes a polymer tube encircling a bottom of the respective continuous casting mold. According to certain embodiments the polymer tube encircling the bottom of the respective continuous casting mold is punctured in response to the bleed out condition at the respective continuous casting mold. According to some embodiments the casting gas from the respective continuous casting mold is conducted to the respective sensor loop for the respective continuous casting mold via a passage within the respective continuous casting mold. According to certain embodiments each sensor loop is attached at either end to a fitting, where the fitting is in fluid communication with the passage.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0012] FIG. 1 illustrates an example embodiment of a continuous casting mold according to the prior art;

[0013] FIG. 2 illustrates an example of the initial stages of continuous casting or continuous casting according to an example embodiment of the present disclosure;

[0014] FIG. 3 illustrates an example embodiment following the initial stages of continuous casting according to an example embodiment of the present disclosure;

[0015] FIG. 4 illustrates an example embodiment of steady-state continuous casting according to an example embodiment of the present disclosure;

[0016] FIG. 5 illustrates a sensor loop of a continuous casting mold according to an example embodiment of the present disclosure;

[0017] FIG. 6 illustrates a bottom view of a continuous casting mold including a sensor loop according to an example embodiment of the present disclosure;

[0018] FIG. 7 illustrates sectioned detail view of a passage for providing casting gas to a fitting and to the sensor loop of a continuous casting mold according to an example embodiment of the present disclosure;

[0019] FIG. 8 is a schematic of a manifold for detecting bleed out from a sensor loop of a continuous casting mold according to an example embodiment of the present disclosure;

[0020] FIG. 9 is a diagram of a manifold for detecting bleed out from a sensor loop of a continuous casting mold according to an example embodiment of the present disclosure;

[0021] FIG. 10 is a chart of backpressure distribution during various stages of continuous casting according to an example embodiment of the present disclosure; and

[0022] FIG. 11 is a flowchart of a method for detecting a bleed out condition of a continuous casting mold according to an example embodiment of the present disclosure.DETAILED DESCRIPTION

[0023] Example embodiments of the present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the disclosure are shown. Indeed, embodiments may take many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0024] Vertical direct chill casting or continuous casting is a process used to produce ingots or billets that may have a variety of cross-sectional shapes and sizes for use in a variety of manufacturing applications. The process of continuous casting begins with a horizontal mold table or mold frame containing one or more vertically oriented molds disposed therein. Each of the molds defines a mold cavity, where the mold cavities are initially closed at the bottom with a starter block to seal the bottom of the mold cavity. Molten metal is introduced to each mold cavity through a metal distribution system to fill the mold cavities. As the molten metal proximate the bottom of the mold, adjacent to the starter block solidifies, the starter block is moved vertically downward along a linear path into a casting pit. The movement of the starter block may be caused by a hydraulically lowered platform to which the starter block is attached. The movement of the starter block vertically downward draws the solidified metal from the mold cavity while additional molten metal is introduced into the mold cavity. Once started, this process moves at a relatively steady state for a continuous casting process that forms a metal ingot having a profile defined by the mold cavity, and a height defined by the depth to which the platform and starter block are moved.

[0025] During the casting process, the mold itself is cooled to encourage solidification of the metal prior to the metal exiting the mold cavity as the starter block is advanced downwardly, and a cooling fluid is introduced to the surface of the metal proximate the exit of the mold cavity as the metal is cast to draw heat from the cast metal ingot and to solidify the molten metal within the now-solidified shell of the ingot. As the starter block is advanced downward, the cooling fluid may be sprayed directly on the ingot to cool the surface and to draw heat from within the core of the ingot.

[0026] FIG. 1 depicts a general illustration of a cross-section of a continuous casting mold 100 during the continuous casting process. The illustrated mold could be for a round billet or a substantially rectangular ingot, for example. The cooling water spray pattern as described herein is primarily directed to round billet casting. However, embodiments could potentially be used for a substantially rectangular ingot, particularly when the corners of said ingot have some degree of curvature. As shown, the continuous casting mold 105 forms a mold cavity from which the cast part 110 is formed. The casting process begins with the starter block 115 sealing or substantially filling the bottom of the mold cavity against mold walls of the continuous casting mold 105. As the platform 120 moves down along arrow 145 into a casting pit and the cast part begins to solidify at its edges within the mold walls of the continuous casting mold 105, the cast part 110 exits the mold cavity. Metal flows from a pouring trough 125, which may be a heated reservoir or a reservoir fed from a furnace, for example, through thimble 130 into the mold cavity. As shown, the thimble 130 is partially submerged within a molten pool of metal 135 to avoid the oxidation of metal that would occur if fed from above the molten metal pool 135. The solidified metal constitutes the formed cast part 140, such as a billet. Flow through the thimble 130 may be controlled within the pouring trough 125, such as by a tapered plug fitting within an orifice connecting a cavity of the pouring trough 125 with a flow channel through the thimble 130. Conventionally, the pouring trough 125, thimble 130, and mold cavity / mold walls of the continuous casting mold 105 are held in a fixed relationship from the beginning of the casting operation through the end of the casting operation. Flow of metal through the thimble 130 continues as the platform 120 continues to descend along arrow 145 into the casting pit. When the casting operation is to end, either by the platform being at the bottom of its travel, the metal supply running low, or the cast part reaching the completed size, the flow of metal through the thimble 130 stops, and the thimble assembled on the trough is removed from the molten pool of metal 135 to allow the molten pool to solidify and complete the cast part.

[0027] FIG. 2 illustrates an example embodiment of a hot top casting method of the continuous casting process according to the present disclosure including a continuous casting mold 105, trough 125, and thimble 130 for supplying molten metal from the trough to the cavity of the mold. The illustrated embodiment of FIG. 2 includes a starting position where the tip of the thimble 130 or thimble is positioned proximate the starter block 115 which is supported by the platform 120. The starter block 115 is positioned atop platform 120 and aligned to cooperate with the mold 105 to seal the mold cavity and preclude molten metal 107 from leaking from between the continuous casting mold 105 and the starter block 115. The thimble 130 or thimble is received into a transition plate 200 that is securely attached to the top of the mold 105, such as by threaded engagement. The transition plate 200 may be secured to the mold 105 by a metal ring that is threaded into a round opening atop the billet mold 105 to hold the transition plate securely to the mold. The mold 105 may be of a metal such as aluminum, while the thimble 130 and transition plate 200 are generally formed of a refractory material that is resilient to heat.

[0028] FIG. 2 illustrates the start of a cast with the starter block 115 aligned with the continuous casting mold 105. As the cast starts shown in FIG. 3, the platform 120 descends with the starter block 115 as molten metal flows through the thimble 130 from the trough 125 and solidifies on the starter block 115 and at the bottom of the mold cavity forming the cast part 140. In this manner, as the starter block 115 descends away from the continuous casting mold 105, the cast part, shown in FIG. 4 as 140, is formed. FIG. 4 illustrates the run-state phase of the casting process or the steady-state portion where the platform 120 descends at a near constant rate with the cast part 140 growing accordingly. FIG. 2 also illustrates spray jets 150 that will be described in greater detail below, where the spray jets provide a coolant or cooling fluid to the surface of the casting.

[0029] FIG. 5 illustrates a detail view of mold components for an example embodiment of continuous casting. As shown, the continuous casting mold 105 includes a graphite casting surface 210 upon which the initial solidification of the billet being cast occurs. The permeable graphite material allows for flowing both casting gas and casting lubricant to the casting surface that produces an air-slip casting condition including air gap 220 between the molten metal 107 that is solidifying in the mold cavity and the graphite casting surface 210. The casting lubricant reduces the friction on the casting surface 210 to prevent sticking and tearing of the freshly solidifying shell of the cast part 140. The casting gas flow further aids in reducing this friction while at the same time provides a thin film of gas between the casting surface and the billet shell which reduces the thermal heat transfer from the molten aluminum to the casting surface. When properly balanced, the introduction of gas and oil produces an as-cast billet with a very smooth surface and very narrow shell thickness as compared to conventionally cast billets. Water or coolant flowing to spray jets 150 from the coolant chamber 155 impinges upon the shell of the cast part 140 and proceeds to flow down the sides of the cast part as shown at 145 to further cool the casting.

[0030] Various failures and issues can arise during the casting process. One such failure is bleed out, where the solidified metal leaving the mold is compromised and the casting loses molten metal containment. The molten metal escapes the casting and begins to spill into the casting pit. Bleed out can be dangerous, as there is inherent danger in the use of water or cooling fluid to directly quench and cool the molten aluminum. Molten aluminum and water when mixed in an uncontrolled manner can lead to large molten metal explosions. The loss of containment of the molten metal or bleed out can have varying magnitudes of containment loss with varying durations that indicate these failures.

[0031] Issues relating to bleed out can be mitigated most effectively if the bleed out is detected early, close to when the bleed out failure begins. Early detection of bleed out can provide improved response time minimizing the chance of a catastrophic explosion and / or damage to personnel or equipment. Various iterations of bleed out detection have been proposed with numerous design challenges and use constraints that has rendered adoption in the industry difficult.

[0032] Embodiments described herein include a pressurized pneumatic tube as a sensor loop with a low melting point, typically polyurethane tubing, that melts when damaged by a bleed out. The damage to the pressurized tube results in a loss of pressure within the tube. The pressure loss can be on the order of a 3:1 ratio of prior-to-post bleed out condition in an example embodiment. The ratio of pressure between pre and post detection can vary and is influenced by the orifice and its size if implemented. As such, the pressure ratio can be selected by a user based on casting gas operating pressure and orifice size. The sensor loop is pressurized by a pressure supply that has nominally no flow. To introduce pressure to the system described herein, an interconnection with the independent supply gas line used for casting gas to the mold body is employed. The pressure is then monitored continually for drops in the back pressure of each individual mold position.

[0033] Referring back to FIG. 5, a sensor loop 270 is illustrated in the section view as a tube having a relatively low melting point. The sensor loop 270 is removable and replaceable within the continuous casting mold 105, particularly as the sensor ring is a consumable element and is not re-used after it has been compromised with a detected bleed out. The sensor loop 270 is held in position within the mold using retainers attached to the continuous casting mold 105, and can be removed when the mold is heated during maintenance (e.g., for graphite liner changes)

[0034] FIG. 6 is a bottom view of a continuous casting mold 105 without the other components of the continuous casting mold system. As shown, the continuous casting mold 105 includes an inner wall 207 with ribs 209. The continuous casting mold 105 defines a mold cavity 202 bounded by the casting surface 210. The cooling fluid spray jets 150 surround the mold cavity at a bottom of the mold cavity to cool the casting as the starting head (not shown) descends into the casting pit. Also shown in the embodiment of FIG. 6 is the sensor loop 270 which is attached to the continuous casting mold 105 at the ribs 209 and suspended around a bottom of the continuous casting mold 105. The attachment mechanism can include a variety of mechanical attachment techniques such as a frame or attachment points attached to the bottom of the continuous casting mold 105 or integrated into the ribs 209 of the mold as shown.

[0035] The sensor loop 270 includes a fitting or coupling positioned along the sensor ring whereby the air pressure is introduced to the sensor ring. In the illustrated embodiment, that coupling is a T-fitting positioned at a rib 209, with the T-fitting coupling together opposing ends of the sensor loop 270 and a mating hole in the continuous casting mold 105 body. The mating hole in the mold body includes a passage to connect the mating hole to the casting gas source for the continuous casting mold 105. The sensor loop 270 and the fitting are held in place with fastener 272.

[0036] FIG. 7 illustrates a section view through the continuous casting mold 105 body at the fitting 280 with the fastener 272 holding the fitting in the mold and in contact with the mating hole and passage 284. The fitting 282 can include a barbed end 286 as depicted and may include O-ring 288 to provide an airtight seal between the sensor loop 270 and the passage 284.

[0037] Embodiments are integrated into the casting gas supply line that supplies air to a given mold position, which flows into the passage 284 to provide casting gas pressure to the sensor loop 270. The casting gas is supplied to a plurality of continuous casting molds from a casting gas supply manifold. At the gas supply manifold end of the line, pressure transducers monitor the mold back pressure. With the pneumatic sensor loop 270 in parallel with the casting gas circuit, a drop in mold back pressure triggers the alarm. This architecture allows for retrofit onto existing tables and importantly, decreases the overall system cost to a fraction of previous systems. The pressure transducers can be implemented into the gas control manifold with a bolt-on addition to any table either from the manufacturer or readily retrofitted. Mold systems that include back pressure monitoring capability is ready-made to operate with this bleed out detection configuration with updated code blocks.

[0038] The sensor loop 270 is described and illustrated as a loop, where each end of the sensor loop is connected to a fitting to be in fluid communication with the casting gas received at the continuous casting mold 105. According to some embodiments, the sensor loop may be connected to the fitting at only one end of the loop and function in a manner similar to that described above. However, forming the sensor loop with both ends in fluid communication with the fitting provides a more reliable and robust sensing system as, while unlikely, it is possible for molten metal to melt a polymer tube such as that of the sensor loop and fuse an end of the polymer tube. With only a single source of casting gas pressure into the sensor loop, this possibility increases. However, with the casting gas pressure introduced on both ends of the loop, the likelihood of such a scenario is substantially reduced.

[0039] The sensor loop 270 of example embodiments is also easily replaced in the event of damage to the sensor loop or after detection of bleed out. In the illustrated embodiment of FIG. 6, the fastener 272 is removed, the sensor loop 270 and fitting 282 are removed from the passage 284, and the sensor loop 270 is detached from the ribs 209 of the continuous casting mold 105. The reverse of this removal operation installs a new sensor loop 270 quickly and easily.

[0040] The manifold of example embodiments described herein is compact to be compatible with existing mold systems to fit along a side of the bottom plate of a mold table in the dead space of even the tightest table layouts. A standalone manifold design is compatible with most tables. The manifold houses all cross drilling and supply pressure routing such that there is a single pressure port supplied to the manifold, the pressure port supplies orifices for each individual mold position independently of one another. A branch orifice may be, for example, 0.010 inches in diameter. With a supply pressure of 60 psi (pounds-per-square-inch) to a maximum supply rate of three standard liters per minute during a bleed out condition. The casting gas can be provided at various pressures, where an example embodiment includes a supply of casting gas at 60 psi. However, casting gas can be provided at a variety of pressures including substantially higher pressures such as 150psi in some embodiments. Embodiments described herein can determine bleed out conditions regardless of the supplied pressure of casting gas as would be apparent to one of ordinary skill in the art.

[0041] FIG. 8 illustrates the pneumatic configuration of an example embodiment. As shown, casting gas is provided at 305. Alternatively, a separate compressed air source may be used to achieve similar results. However, using the casting gas already available at the table reduces complexity and cost to more efficiently and effectively implement embodiments of the bleed out detection system. A pressurized feedback system is illustrated at 310. The pressurized gas is supplied to manifold 320, where for each position in the manifold, such as in a twelve-position manifold, an orifice 325 may be positioned (e.g., with a diameter of 0.010 inches) ahead of a pressure switch 330. The pressure switch 330 may be, for example, a 0.4 mPa (megapascal) switch which may include a 0.04 mPa hysteresis. The pressurized gas is provided from the manifold outlet 340 for each position the sensor loop 170.

[0042] If a leak exists in the sensor loop 270 (e.g., where the sensor loop is compromised through a melt caused by a bleed out) then the pressure downstream of the orifice 325 drops below a threshold pressure of the pressure switch 330 indicating a pressure loss (bleed out) condition. The pressure switch 330 may be configured in the normally open position, where pressure must be applied to close the switch. The normally open configuration paired with pull down resistors on the digital inputs to the control system of the continuous casting mold system ensure the pressure must be present for the proper active state and not in alarm indicating pressure loss.

[0043] The orifice 325 is an optional addition that offers the ability to mitigate a magnitude of the pressure drop in the event of a bleed out. The orifice 325 can be implemented in the manifold, integrated as part of the mold body, or directly integrated into the t-fitting of the sensor loop. The air delivery at 305 could be via a pressure or mass flow control system and retain effectively the same function.

[0044] While FIG. 8 depicts a pressure switch 330, embodiments can employ a mass air flow sensor that measures mass air flow to each mold. The mass air flow sensor can be employed in a similar way as the pressure switch 300, whereby a step change of the mass air flow during a casting operation can indicate that the sensor loop has been punctured and indicating that a bleed out event has occurred.

[0045] An alarm or alert indicating a bleed out event can be a visual alarm (e.g., a light, a message at a control interface, a mechanical flag, etc.), an audible alarm, or any combination thereof. The alarm can alert an operator of the bleed out condition who can then take action in response. In some embodiments, the alarm can trigger a shut down of the mold in which the bleed out condition has occurred automatically.

[0046] According to an example embodiment, the manifold assembly includes three primary components: the manifold / housing, pressure switches, and electrical distribution PCB (printed circuit board). The manifold can double as the housing for electrical components to protect them from moisture and mechanical damage. The manifold may be sealed to satisfy Ingress Protection (IP) standards such as IP66 or better with an IP69K breather that can allow air pressure to normalize inside the manifold and allow proper pressure gauge venting while preventing moisture intrusion. Each pressure switch may be mounted into the manifold by use of O-rings and a push connect stem that can be part of the pressure switch assembly. The pressure switches can include a standard pressure switch which can be configurable from the factory with appropriate switching pressure and hysteresis.

[0047] The PCB of an example embodiment may be housed and mounted within the manifold and can route power to each pressure switch while routing all signals back to a main connector. The PCB can include basic power and short circuit protection and may include LEDs tied in parallel to each output signal independently for individual position visual indication without the need for PLC (programmable logic controller) feedback when performing mold maintenance. When pressure is above a threshold pressure, and power is applied to the manifold the pressure circuit is closed and the light will illuminate. The light may be connected to a light guide or light tunnel to direct light to an external surface of the manifold or the lights may be visible based on their position within the manifold.

[0048] FIG. 9 illustrates an example embodiment of a manifold 400 as described herein including supply port 410, pressure switches 420, pressure line connections 430, and PCB distribution 440. When installed on the table all pneumatic connections are made at the table interface via O-rings. The electrical connections can be made via flex conduit. The Flex conduit can house a single cable with 15 conductors in some examples, where 14 are used with one as a spare. Two of the 14 conductors can include power and ground, while the remaining conductors are for signals from each individual position. According to an example embodiment, a main rigid conduit can run a length of the mold table with a T-body conduit junction place near each manifold location. From the t-body conduit junction a short flex conduit could connect to the manifold keeping a liquid tight electrical connection and protecting the casting from the environment.

[0049] Plumbing from the manifold to the mold position can be done using conventional copper tubing and fittings. For example, 4 mm copper may be sufficient for transmitting pressure to each mold position while allowing ample venting capacity in the event of a bleed out and sensor loop rupture. If smaller lines to the individual positions are used, smaller orifices in the manifold may be required to ensure sufficient pressure loss on rupture as smaller lines will have increased flow restriction and thus increased back pressure.

[0050] An example continuous casting system operates casting gas to each continuous casting mold with a needle valve that feeds the mold position. All positions operate with a needle valve that feeds the mold position. During calibration the table pressure may be 55 psi. Based on a 55 psi supply and a back pressure of 24 psi, the needle valve has a pressure differential of ~31 psi. In a bleed out the needle valve will be unchanged, but the casting gas would vent to atmosphere taking the pressure differential across the needle valve from ~31 psi to ~55 psi. The increased in differential pressure would cause an increase in flow rate of the casting gas from the nominal 3 slpm to ~5.3 slpm at most.

[0051] Even with a supply flow through the bleed out detection system of 6 slpm the trip pressure drops to less than 7 psi in virtually all instances. Thus, if the existing casting gas supply system can handle a small percent increase in flow during bleed outs without dropping pressure on the supply, the casting gas supply can be used to monitor for bleed outs using the pneumatic sensor loop design without impacting subsequent billet positions. Put another way this can be seen visually by inspecting the normal distributions shown in FIG. 10. The run flow pressure distribution and trip pressure distribution do not overlap with any statistical significance.

[0052] FIG. 10 illustrates that a start flow of casting gas produces a back pressure in a normal distribution of around 52 psi, while the casting gas run flow back pressure includes a normal distribution centered at around 24 psi. These are merely examples of pressures at which the casting gas may be operating and may vary depending on mold size among other factors. FIG. 10 thus illustrates the differences between casting gas back pressure during different operating scenarios including start flow, run flow, and as a bleed out is detected. These differences can be greater or less than shown, and the specific pressures of each operating phase may vary depending on the specific implementation.

[0053] While pressure changes are depicted in FIG. 10, embodiments described herein may alternatively or additionally employ mass flow measures to determine when the sensor loop has been compromised. Mass flow of casting gas may be relatively high during startup and may then lower to a relatively steady state mass flow during run flow. However, when the sensor loop is punctured, the mass flow would experience a step up in the mass flow. This step up can be used to identify a bleed out in a similar manner to the use of pressure described above. As pressure feedback on a per-mold basis may not be available, mass flow of casting gas can be used in the alternative. Bleed out can thus be indicated by a step change in flow rate or the proportional valve command as compared to prior to the bleed out. This is in direct relation to the reduction in back pressure as lower back pressure requires a proportionally lower command for a proportional valve.

[0054] Advantages for using the casting gas to pressurize the sensor loop include that for installation, no additional plumbing in the mold table is required. On large, tight tables the plumbing can become extremely tight and difficult to route such that use of the existing casting gas does not require additional plumbing. Further, the ability to tie into the casting gas supply after the needle valves renders embodiments well-suited for retrofitting of existing mold tables.

[0055] Embodiments described herein are configured to detect bleed out relatively quickly with improved reliability and configurability. The disclosed system is also relatively inexpensive and can be retrofit to existing mold system, while also being compatible with new mold tables.

[0056] Once bleed out is detected for a continuous casting mold of the plurality of continuous casting molds within a mold table, metal flow to that continuous casting mold can be ceased to stem the molten aluminum spilling from the casting and thus reduce the likelihood of molten metal explosion and to reduce fouling to the casting pit. This system improves efficiency of continuous casting as the remainder of the continuous casting molds can continue to produce castings and the mold operation does not need to cease. Further, the efficiency of the casting operation is improved as the amount of molten metal spilled into the casting pit is reduced substantially requiring less clearing of the casting pit. These efficiencies and improvements can be gained at relatively low expense, particularly when the sensor loop of example embodiments is supplied with pressurized casting gas through the manifold as described above, as such a configuration requires minimal modification to the mold table and the continuous casting molds themselves.

[0057] FIG. 11 is a flowchart of a method for detecting a bleed out condition at a continuous casting mold. Casting gas is received at a manifold of a mold table for distribution to at least one continuous casting mold as shown at 510. The casting gas is dispersed at 520 from the manifold to the at least one continuous casting mold. At least a portion of the gas is diverted at 530 to a sensor loop disposed proximate a bottom of the at least one continuous casting mold. A pressure loss is detected from the sensor loop disposed proximate the bottom of the at least one continuous casting mold as shown at 540. The at least one continuous casting mold is identified at 550 as having a bleed out condition.

[0058] Blocks of the flowchart support combinations of means for performing the specified functions and combinations of operations for performing the specified functions for performing the specified functions. It will also be understood that one or more blocks of the flowcharts, and combinations of blocks in the flowcharts, can be implemented by various aspects of the system for detecting a bleed out condition as described above.

[0059] In some embodiments, certain ones of the operations above may be modified or further amplified. Furthermore, in some embodiments, additional optional operations may be included. Modifications, additions, or amplifications to the operations above may be performed in any order and in any combination that facilitates the detection of a bleed out condition as described herein.

[0060] Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Examples

Embodiment Construction

[0023]Example embodiments of the present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the disclosure are shown. Indeed, embodiments may take many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0024]Vertical direct chill casting or continuous casting is a process used to produce ingots or billets that may have a variety of cross-sectional shapes and sizes for use in a variety of manufacturing applications. The process of continuous casting begins with a horizontal mold table or mold frame containing one or more vertically oriented molds disposed therein. Each of the molds defines a mold cavity, where the mold cavities are initially closed at the bottom with a starter block to seal the bottom...

Claims

1. A method for detecting continuous casting bleed out comprising:receiving casting gas at a manifold of a mold table for distribution to at least one continuous casting mold;dispersing the casting gas from the manifold to the at least one continuous casting mold;diverting at least a portion of the casting gas to a sensor loop disposed proximate a bottom of the at least one continuous casting mold;detecting at least one of pressure loss or a step change in mass air flow from the sensor loop disposed proximate the bottom of the at least one continuous casting mold; andidentifying the at least one continuous casting mold as having a bleed out condition.

2. The method of claim 1, further comprising:ceasing molten metal flow to the at least one continuous casting mold in response to identifying the at least one continuous casting mold as having the bleed out condition.

3. The method of claim 1, wherein detecting the at least one of the pressure loss or the step change in mass air flow from the sensor loop disposed proximate the bottom of the at least one continuous casting mold comprises:detecting the pressure loss at the manifold with a pressure sensor in response to the pressure loss satisfying a predetermined threshold.

4. The method of claim 3, wherein the pressure loss from the sensor loop is caused by molten metal melting a material forming the sensor loop.

5. The method of claim 1, wherein diverting at least a portion of the casting gas to the sensor loop disposed proximate the bottom of the at least one continuous casting mold comprises diverting at least a portion of the casting gas to a fitting attached to the sensor loop to pressurize the casting gas within the sensor loop.

6. The method of claim 1, further comprising:limiting pressure loss from the sensor loop using a reducing orifice to retain casting gas pressure and flow to at least one other continuous casting mold.

7. The method of claim 1, wherein dispersing the casting gas from the manifold to the at least one continuous casting mold comprises dispersing the casting gas to a casting surface of the at least one continuous casting mold.

8. An apparatus for detecting continuous casting bleed out comprising:a manifold, wherein the manifold receives casting gas from a casting gas source wherein the manifold disperses the casting gas to a continuous casting mold;at least one of a pressure sensor or a mass air flow sensor within the manifold and associated with the continuous casting mold;a sensor loop attached proximate a bottom of the continuous casting mold;a conduit to convey the casting gas from the manifold to the continuous casting mold; anda passage to convey at least a portion of the casting gas from the conduit to the sensor loop to pressurize the sensor loop,wherein in response to molten metal from a bleed out condition of the continuous casting mold contacting the sensor loop, the sensor loop is punctured, and casting gas escapes the sensor loop, wherein in response to the casting gas escaping the sensor loop, the pressure sensor or the mass air flow sensor within the manifold detects the bleed out condition.

9. The apparatus of claim 8, wherein the manifold receives casting gas from the casting gas source at a pressure of around 60 psi (pounds-per-square-inch).

10. The apparatus of claim 8, wherein the pressure sensor or the mass air flow sensor within the manifold detects the bleed out condition in response to a pressure within the sensor loop being reduced by a predefined threshold or the mass air flow sensor detecting a step change in mass air flow through the sensor loop.

11. The apparatus of claim 8, further comprising an orifice within the manifold between the pressure sensor and the casting gas source, wherein the orifice defines a diameter of about 0.01 inches.

12. The apparatus of claim 11, wherein the manifold disperses the casting gas to at least one other continuous casting mold, wherein the orifice enables a casting operation of the at least one other continuous casting mold to continue after the pressure sensor within the manifold detects the bleed out condition of the continuous casting mold.

13. The apparatus of claim 8, wherein the sensor loop is formed of a polymer tube.

14. The apparatus of claim 13, wherein the sensor loop is attached at opposing ends to a fitting, wherein the fitting is in fluid communication with the passage.

15. The apparatus of claim 14, wherein the fitting is a T-fitting, and wherein the T-fitting is held within the continuous casting mold with a fastener.

16. A system for continuous casting comprising:a plurality of continuous casting molds;a casting gas supply;a manifold, wherein the manifold is configured to receive casting gas from the casting gas supply and distribute the casting gas to the plurality of continuous casting molds;a plurality of conduits, wherein each conduit conducts the casting gas from a respective channel of the manifold to a respective continuous casting mold of the plurality of continuous casting molds;a plurality of sensor loops, wherein each sensor loop is attached to a respective continuous casting mold of the plurality of continuous casting molds, wherein the casting gas from the respective continuous casting mold is conducted to a respective sensor loop for the respective continuous casting mold;at least one of a plurality of pressure sensors or a plurality of mass air flow sensors, each associated with a respective continuous casting mold, wherein a pressure sensor of the plurality of pressure sensors or a mass air flow sensor of the plurality of mass air flow sensors is configured to detect a bleed out condition at the respective continuous casting mold based on a pressure loss satisfying a predetermined threshold or a step change in mass air flow.

17. The system of claim 16, wherein each sensor loop comprises a polymer tube encircling a bottom of the respective continuous casting mold.

18. The system of claim 17, wherein the polymer tube encircling the bottom of the respective continuous casting mold is punctured in response to the bleed out condition at the respective continuous casting mold.

19. The system of claim 16, wherein the casting gas from the respective continuous casting mold is conducted to the respective sensor loop for the respective continuous casting mold via a passage within the respective continuous casting mold.

20. The system of claim 19, wherein each sensor loop is attached at either end to a fitting, wherein the fitting is in fluid communication with the passage.

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