The present invention relates to automated processes that dynamically control rate of delivery of molten metal to a mold during a casting process.
At the beginning of an ingot cast, such as in an aluminum casting process, it is common in the first 300 mm of the cast for metal meniscus to contract and pull away from the mold on the short faces and corners. This phenomenon can occur for various reasons.
First, there can be inadequate metal flow into the corner and short face, which allows the metal to cool and pull away from the mold surface. Typically this inadequate flow is rectified by designing metal distribution systems which preferentially redistribute metal into these areas or by minimizing butt curl, which has in a roundabout way the tendency to restrict metal flow to the corner and short face.
Second, there can be excessive liquid molten-to-mold interface surface tension, which is typically an aspect of the alloy being cast. Alloys which can experience this problem include Aluminum alloys of Magnesium and/or Lithium. In some cases these alloys can be modified by surface active elements, such as, for example, Strontium, Calcium and Beryllium.
Third, there can be excessively tight corner radii. This problem can sometimes be resolved by using more liberal radii, but with a compromise of ingot scalping and hot line edge recovery. Generally, compromises made for start of the cast dynamics and recovery affect the total ingot recovery negatively in the hotline, where millions and millions of pounds are lost each year.
If such compromises are not made, overall ingot recovery is affected along with the inherent EHS aspect of metal dribbling into the mold to meniscus gap that can potentially create a butt hang-up, which can in turn cause a severe ingot explosion.
In some conventional processes, during curl, 150-250 mm into the cast, operators are continually on the casting table to make sure that the mold to meniscus gap is continually filled. From time to time they intervene and mechanically pull the metal control pin, or shake the pin-bag, to allow a sudden disruption to the metal level system to statically overcome the surface tension effect and “fill in” the corner or short face gap.
The following presents a simplified summary of some embodiments of the invention in order to provide a basic understanding of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some embodiments of the invention in a simplified form as a prelude to the more detailed description that is presented later.
Certain embodiments of the invention solve some or all of these problems by using dynamic metal level variation or oscillation (such as by, for example, pulsing the pin or by variation of the metal-level control setpoint) during the mold fill and transient portion of the cast. It has been found that the resulting oscillating metal level, among other things, keeps metal flowing, thus overcoming the “cold corner” effect described above. Among other advantages of certain embodiments, operators no longer need to be on the table in order to overcome such effects, and corner radii compromises are less necessary or obviated.
For a filler understanding of the nature and advantages of the present invention, reference should be made to the ensuing detailed description and accompanying drawing.
Various embodiments in accordance with the present disclosure will be described with reference to the drawings, in which:
In the following description, various embodiments will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the embodiments may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described.
The following description will serve to illustrate certain embodiments of the present invention further without, at the same time, however, constituting any limitation thereof. On the contrary, it is to be clearly understood that resort may be had to various embodiments, modifications, and equivalents thereof which, after reading the description herein, may suggest themselves to those skilled in the art without departing from the spirit of the invention.
The spout 18 encircles a lower end of a control pin 21 that regulates and can terminate the flow of molten metal through the spout. In one embodiment, a plug such as a ceramic plug forming a distal end of the pin 21 is received within a tapered interior channel of the spout 18 such that when the pin 21 is raised, the area between the plug and open end of the spout 18 increases, thus allowing molten metal to flow around the plug and out the lower tip 17 of the spout 18. Thus, flow and rate of flow of molten metal may be controlled precisely by appropriately raising or lowering the control pin 21. In addition to the structures shown in Anderson, spout 18 and pin 21 combinations that accomplish such purposes are also disclosed in U.S. Pub. No. 2010/0032455 published Feb. 11, 2010 to James, which publication is incorporated herein by this reference. Any desirable structure or mechanism may be used for control of flow of molten metal in to the mold. For convenience, the terms “conduit,” “control pin” and “command signals” that control position of the control pin relative to the conduit are utilized in this document to refer to any mechanism or structure that is capable of regulating flow or flow rate of molten metal into the mold by virtue of command signals from a controller; accordingly, reference in this document (including the claims) to providing command signals to a control pin positioner to regulate molten metal flow or flow rate into a mold will be understood to mean providing command signals to an actuator of whatever type to control flow or flow rate of molten metal into the mold in whatever manner and using whatever structure or mechanism.
In the structure shown in
Apparatus 10 can include a metal level sensor 50 whose structure and operation is conventional (unlike the sensor 50 described in Anderson, which is connected to an actuator 51 to allow the Anderson sensor to operate in a particular way in order to perform particular processes disclosed and claimed in Anderson. For example, sensor 50 can be structured and operate in the manner in which the float and transducer are structured and operate as disclosed, for example, in Takeda FIG. 1 and column 6, lines 21-52, among other places in Takeda. Alternatively, sensor 50 could be a laser sensor or another type of fixed or movable fluid level sensor having desired properties for accommodating molten metal. During the cavity filling operations, the information from sensor 50 can be fed to the controller 52. The controller 52 can use that data among other data to determine when the control pin 21 is to be raised and/or lowered by actuator 54 so that metal may flow into the mold 11 to fill a partial cavity, i.e. when the depth of the predetermined cavity reaches a predetermined limit. Thus, the sensor 50 and actuator 54 are coupled with controller 52, as shown in
Examples of the processor 212 include any desired processing circuitry, an application-specific integrated circuit (ASIC), programmable logic, a state machine, or other suitable circuitry. The processor 212 may include one processor or any number of processors. The processor 212 can access code stored in the memory 218 via a bus 214. The memory 218 may be any non-transitory computer-readable medium configured for tangibly embodying code and can include electronic, magnetic, or optical devices. Examples of the memory 218 include random access memory (RAM), read-only memory (ROM), flash memory, a floppy disk, compact disc, digital video device, magnetic disk, an ASIC, a configured processor, or other storage device.
Instructions can be stored in the memory 218 or in processor 212 as executable code. The instructions can include processor-specific instructions generated by a compiler and/or an interpreter from code written in any suitable computer-programming language. The instructions can take the form of an application that includes a series of setpoints, parameters for the casting process, and programmed steps which, when executed by processor 212, allow controller 210 to control flow of metal into a mold, such as by using the molten metal level feedback information from sensor 50 in combination with metal level setpoints and other casting-related parameters which may be entered into controller 210 to control actuator 54 and thereby position of pin 21 in spout 18 in the apparatus shown in
The controller 210 includes an input/output (I/O) interface 216 through which the controller 210 can communicate with devices and systems external to the controller 210, including sensor 50, actuator 54 and/or other mold apparatus components. Interface 216 can also if desired receive input data from other external sources. Such sources can include control panels, other human/machine interfaces, computers, servers or other equipment that can, for example, send instructions and parameters to controller 210 to control its performance and operation; store and facilitate programming of applications that allow controller 210 to execute instructions in those applications to control flow of metal into a mold such as in connection with the processes of certain embodiments of the invention; and other sources of data necessary or useful for controller 210 in carrying out its functions to control operation of the mold, such as mold 11 of
In the embodiment shown in
In the particular embodiment charted in
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1. In some embodiments, control pin pulsing occurs in a manner that modulates flow or flow rate of molten metal through the conduit such that the level of molten metal in the mold remains in a molten metal level range of between 5 mm above and 3 mm below, inclusive, the metal level setpoint, and preferably in a molten metal level range of between 3 mm above and 1 mm below, inclusive, the metal level setpoint. Preferably, in the preferred molten metal level range, the metal level will rise to about 3 mm above setpoint as a result of each pulse, and between pulses (prior to the next pulse) will typically drop to about learn below setpoint under the control of the PID algorithm as a result of undershoot.
2. In some embodiments, pulsing occurs at a frequency of 3-4 pulses/min, inclusive, or a minimum of 15-20 seconds between pulses, inclusive.
3. In some embodiments, pulsing will be allowed to occur only if the actual metal level is at or below the metal level setpoint AND the command signal to the pin positioner is above a predetermined value (for example greater than 5% open pin position, such that the hangup alarm logic will not be adversely affected).
4. In some embodiments, during pulsing, the actual command signal to the pin positioner is preferably set to 100% open pin position for a duration of preferably about 3 seconds, which period may be larger or smaller, after which it will return to control under the PID algorithm. The pin positioner takes time to open/close and thus can only open to between 30% and 50% open in 3 seconds. In some embodiments, depending on characteristics of the particular control pin positioner at issue, the command signal to the pin positioner is set to open pin position for a longer or shorter period that is at least partially a function of how quickly the pin positioner can open and/or close.
5. In some embodiments, pulsing will begin at a cast length of 50 mm.
6. In some embodiments, pulsing will end when the cast length reaches, preferably, between 400 and 500 mm.
Pin pulsing can be accomplished in any number of alternative ways according to various embodiments of the invention. For instance, pulsing could be accomplished by time-varying the metal level setpoint, or by time-varying sinusoidally the pin positioner command signal about the PID control value (by adding a sinusoidal signal to the PID output control value).
Other variations are within the spirit of the present invention. Thus, while the invention is susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof are shown in the drawings and have been described above in detail. It should be understood, however, that there is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
This application claims the benefit of U.S. Provisional Patent Application No. 61/777,574, filed Mar. 12, 2013, entitled “INTERMITTENT MOLTEN METAL DELIVERY”, which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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61777574 | Mar 2013 | US |