BACKGROUND OF THE INVENTION
Traditionally, in conventional processes for forming metal castings, a mold, such as a metal die or sand mold having an interior chamber with the exterior features of a desired casting defined therein, is filled with a molten metal. A sand core that defines interior features of the castings is received and/or positioned within the mold to form the interior detail of the casting as the molten metal solidifies about the core. After the molten metal of the castings has solidified, the castings generally are moved to a treatment furnace(s) for heat treatment of the castings, removal of sand from the sand cores and/or molds, and other processing as required. The heat treatment processes condition the metal or metal alloys of the castings to achieve the desired physical characteristics for a given application.
FIG. 1A illustrates one type of a conventional heat treatment apparatus in which a series of castings can be placed within a basket and passed along a roller health or similar conveying mechanism through one or more heating chambers of the heat treatment apparatus. As the castings are passed through the chambers of the heat treatment apparatus, the castings are heated to a solution heat treatment temperature. Additionally, as the castings move along the chambers of the heat treating furnace, the sand cores or molds of the castings also can be broken down as their binder materials are combusted, such that the castings can be de-cored and their molds broken down and removed, with the sand falling beneath the roller hearth for collection. After the castings have been heat treated, they can be removed from the heat treatment unit or furnace and directed to a quench station or tank.
During the transfer of the castings from the pouring station to the heat treatment station, and especially if the castings are allowed to sit for any appreciable amount of time, however, the castings may be exposed to the ambient environment of the foundry or metal processing facility. As a result, the castings tend to rapidly cool down from a molten or semi-molten temperature. While some cooling of the castings is necessary to allow the castings to solidify, the more the temperature of the castings drops, and the longer the castings remain below a process critical temperature (also referred to herein as the “process control temperature”) of the castings, the more time is required to heat the castings up to a desired heat treatment temperature and to heat treat the castings. For example, as illustrated in FIG. 1B, it has been found that for certain types of metals, for every minute of time that the castings drops below its process control temperature, at least about four minutes or more of extra heat treatment time will be required to achieve the desired solution heat treatment results in the castings. Thus, even dropping below the process control temperature for the metal of the castings for as few as 10 minutes may require at least about 40 minutes of additional heat treatment time to achieve the desired physical properties. As a consequence, therefore, castings typically are heat treated for 2 to 6 hours, in some cases longer, to ensure the desired heat treatment effects are achieved in all the castings of a batch or series. This results in greater utilization of energy and, therefore, greater heat treatment costs.
Accordingly, it can be seen that a need exists for a system and method of heat treating castings that addresses the foregoing and other related and unrelated problems in the art.
SUMMARY OF THE INVENTION
Briefly described, the present invention generally comprises a system for enabling the pouring, forming, heat treating, and further processing of castings formed from metal and/or metal alloys at enhanced rates and efficiency. The castings are formed at a pouring station at which a molten metal such as aluminum, iron, or a metal alloy, is poured into a mold or die, such as a permanent metal mold, semi permanent mold, or a sand mold. The molds then are moved from the pouring or casting position to a transfer position, where the castings can be removed from their molds or transferred directly to a vertical heat treatment unit according to the present invention. The transfer mechanism typically includes a robotic arm, crane, overhead hoist or lift, pusher, conveyor, or similar conveying mechanism. The same mechanism also may be used to remove the castings from their molds and to transfer the castings to the vertical heat treatment unit(s). During this transition from the pouring station to the vertical heat treatment unit(s), the molten metal of the castings generally is permitted to cool to an extent sufficient to form the castings, while generally being monitored and heat applied thereto as needed to maintain the castings at or above a process control temperature for the metal thereof.
The vertical heat treatment unit according to the present invention comprises a vertically aligned heat treatment or “cell unit” having a reduced footprint such that it typically can be arranged adjacent or in close proximity to a loading carousel for one or more pouring stations, which carousels can be positioned adjacent their associated pouring stations. The castings also can he received on a transfer line or monorail from their pouring stations and then transferred directly to a vertical heat treatment unit or to a loading carrousel for each vertical heat treatment unit. Each vertical heat treatment unit or cell unit generally can include a vertically extending furnace chamber having heat sources, such as blowers, fans, radiant heaters, infrared, inductive, convection, conductive, or other types of heating elements. The ceiling and walls of the furnace chamber further generally will include a radiant material that radiates or directs heat toward the castings and/or molds with the castings therein, as they are moved through the furnace chamber. The castings are received and maintained within their cell unit or vertical heat treatment system for a time and at temperatures sufficient to heat treat the castings as needed to achieve desired mechanical properties thereof.
The heat sources further can include a variety of heating systems including conduction, convection, and other sources. In one embodiment, the heat sources can comprise high velocity forced air heating sources that direct turbulent, high velocity flows of heated air or other fluid media at velocities flows of approximately 2,500-4,000, up to approximately 40,000 feet per minute generally at distances of about 21-26 inches or less, and as short as 2-10 inches, from the castings. The velocity of the heated air flows and the distance of the applicator nozzles from the castings and their molds generally can be determined based upon the diameter and the configuration(s) of the nozzles being used (i.e., use of a series of spaced large, medium, or small diameter circular nozzles, slotted nozzles, or other configurations) and the positions/locations of the nozzles with respect to the centerlines of the castings as they are conveyed through the furnace chamber of the vertical heat treatment unit, which can be adjusted depending on sizes of the castings and the volume and velocity of the flames. The air flows further generally are at temperatures sufficient to promote heat treatment of the castings and additionally can assist with mold breakdown and core removal as the castings are moved through their vertical heat treatment units.
The vertical heat treatment unit further can include a conveying mechanism such as a rotary carousel that extends upwardly through the furnace chamber and includes a series of platforms, trays or racks on which a series of castings, i.e., 1-4 or more castings, are received. The castings typically will remain within in their molds, although they also can be previously removed from their molds prior to introduction into the vertical heat treatment unit. The castings generally will be fed into the furnace chamber by a manipulator, which can include a crane, forklift, or similar mechanism or can comprise the transfer robot of an associated loading carousel. As the castings are fed into the furnace chamber, the rotary carousel generally is operated in a up and down stepping motion, for example moving up one step to receive the castings and then downwardly two steps so as to ensure that a desired separation between incoming (colder) castings and outgoing (fully heated) castings is as large as possible. The vertical heat treatment unit can further include features that assist in removal and reclamation of the sand from the molds of the castings, which generally will be collected and reclaimed for reuse.
Alternatively, the castings can be received within the vertical heat treatment unit on a gantry or elevator type conveying mechanism and placed within one or more compartments or chambers of a grid unit for heat treatment. Each of the compartments are insulated along their side walls as to prevent heat transfer between castings through the side walls, while the floors and ceilings thereof can have slots or openings to enable sand removed from the sand cores and/or molds of the castings to pass therethrough for collection at the bottom of the vertical heat treatment unit. In another alternative embodiment, the vertical heat treatment unit can include a series of conveyors in a vertically stacked arrangement with heat sources such as high velocity fluid media nozzles mounted therealong for directing heated fluid flows toward the castings.
The vertical heat treatment unit of the present invention thus provides a significantly smaller footprint within the casting facility, which enables the vertical heat treatment unit to be placed in as close proximity as possible to the pouring stations. The vertical heat treatment unit of the present invention additionally can utilize existing robotic transfer mechanisms, lifts, or cranes for receiving the castings substantially directly from the pouring stations or from a loading carousel, with the time that the castings are exposed to the ambient environment of the metal processing facility thus being substantially minimized. As a result, the castings can be maintained at or above their process control temperature, as they are transferred from the pouring station to the vertical heat treatment unit of the present invention. In addition, the castings further can be monitored as they are removed from their pouring stations and transfered to their vertical heat treatment units, and additional heat added, such as by additional heating sources such as infrared lamps, heated fluid flows, inductive heaters, and/or other heat sources, as needed to substantially arrest cooling and/or maintain the temperature of the castings substantially at or above the process control temperature for the metal of the castings. Accordingly, the time required to heat treat the castings can be significantly reduced from approximately 2-6 hours down to as low as about 40 minutes to an hour.
Various objects, features and advantages of the present invention will become apparent to those skilled in the art upon review of the following detailed description when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a schematic illustration of an exemplary conventional heat treatment unit.
FIG. 1B is a graphical representation of a heat treatment cycle, illustrating the increase in heat treatment time required for each minute of time the temperature of the casting is below its process control temperature.
FIG. 2A is a schematic illustration of an exemplary metal casting processing system according to various aspects of the present invention.
FIG. 2B is a schematic illustration of another exemplary metal casting processing system illustrating the collection and transfer of castings from multiple pouring stations to vertical heat treatment units according to various aspects of the present invention.
FIG. 3 is a perspective view of a casting and mold.
FIG. 4 is a perspective illustration of the vertical heat treatment according to one embodiment of the vertical heat treatment unit of the present invention.
FIGS. 5A and 5B are perspective views of the vertical heat treatment unit of FIG. 4, with parts broken away to illustrate the internal portions of the unit.
FIGS. 6A is a top plan view of the vertical heat treatment unit of FIG. 4.
FIG. 6B is a cross-sectional view of the vertical heat treatment unit of FIG. 4 illustrating the operation of the carousel.
FIG. 6C is a side elevational view of the vertical heat treatment unit of FIG. 4 illustrating the forced air flow therethrough.
FIGS. 7A-7C are perspective views of example embodiments of nozzle configurations for use in the vertical heat treatment units.
FIGS. 8A and 8B are side elevational views of yet another embodiment of the vertical heat treatment unit of the present invention in which the castings are conveyed along stacked, laterally extending conveyor mechanisms.
FIG. 9A is a top plan view of yet another embodiment of a vertical heat treatment unit according to the principles of the present invention.
FIG. 9B is a side elevational view, with parts broken away, of the embodiment of the vertical heat treatment unit of FIG. 9A.
FIG. 9C is a side elevational view of the embodiment of the vertical heat treatment unit of FIG. 9A, taken in cross section along lines B-B of FIG. 9A.
FIG. 9D is a side elevational view schematically illustrating an alternative embodiment of the loader of the vertical heat treatment unit of FIGS. 9A-9B.
FIG. 10A-10B are top plan views of a further embodiment of a vertical heat treatment unit according to the principles of the present invention.
FIGS. 11A-11B are side elevational views illustrating the vertical heat treatment unit of FIGS. 10A-10B.
FIG. 12 is a graphical comparison of the processing of a casting utilizing a conventional heat treatment process and system versus the system and process of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now in greater detail to the drawings in which like numerals refer to like parts throughout the several views, FIGS. 2A-2B schematically illustrates an exemplary integrated metal processing facility or system 5 including the vertical heat treatment unit or “cell unit” 10 according to the present invention for processing metallurgical castings. Metal casting processes generally are known to those skilled in the art and a traditional casting process will be described only briefly for reference purposes. It will be understood by those skilled in the art that the present invention can be used in any type of casting process, including metal casting processes for forming aluminum, iron, steel, and/or other types of metal and metal alloy castings. The present invention thus is not and should not be limited solely for use with a particular casting process or a particular type or types of metals or metal alloys.
As illustrated in FIG. 2A, a molten metal or metallic alloy M typically is poured into a die or mold 11 at a pouring or casting station 12 for forming a casting 13, such as a cylinder head, engine block, or similar cast part as illustrated in FIG. 3. A casting core 14 formed from sand and binder, such as a phenolic resin or other known binder materials, can be received or placed within the mold 11 to create hollow cavities and/or casting details or core prints within the casting. Each of the molds alternatively can be a permanent mold or die, typically formed from a metal such as steel, cast iron, or other material as is known in the art. Such molds may have a clam-shell style design for ease of opening and removal of the casting therefrom. Alternatively still, the molds can be “precision sand mold” type molds and/or “green sand molds”, which generally are formed from a sand material such as silica sand or zircon sand mixed with a binder such as a phenolic resin or other binder as is known in the art, similar to the sand casting cores 14. The molds further may be semi-permanent sand molds, which typically have an outer mold wall formed form sand and a binder material, a metal such as steel, or a combination of both types of material.
Additionally, the molds may be provided with one or more user openings (not shown) to serve as reservoirs for molten metal. These reservoirs supply extra metal to fill the voids formed by shrinkage as the metal cools and passes from the liquid to the solid state. When the cast article is removed from its mold, the solidified metal in the opening remains attached to the casting as a projection or “riser” (not shown). These risers generally are non-functional and are subsequently removed, typically by mechanical means.
It will be understood that the term “mold” will be used hereafter to refer generally to all types of molds, including, without limitation, those discussed above, including permanent or metal dies, semi-permanent and precision sand mold types, and other metal casting molds, except where a particular type mold is indicated. It further will be understood that in the various embodiments discussed below, unless a particular type of mold and/or heat treatment process is indicated, the present invention can be used for heat treating castings that have been removed from their permanent molds, or that remain within a sand mold for the combined heat treatment and sand mold break-down, removal, and sand reclamation.
A heating source or element, such as a heated air blower, gas-fired heater mechanism, electric heater mechanism, fluidized bed, or any combination thereof also may be provided adjacent the pouring station for preheating the molds. Typically, the molds are preheated to a desired temperature depending upon the metal or alloy used to form the castings. For example, for aluminum, the mold may be preheated to a temperature of from about 400° C. to about 600° C. The varying preheating temperatures required for preheating the various metallic alloys and other metals for forming castings are well known to those skilled in the art and can include a wide range of temperatures above and below from about 400° C. to about 600° C. Additionally, some mold types require lower process temperatures to prevent mold deterioration during pouring and solidification. In such cases, and where the metal process temperature should be higher, a suitable metal temperature control method, such as induction heating, may be employed.
Alternatively, the molds may be provided with internal heating sources or elements for heating the molds. For example, where a casting is formed in a permanent type metal die, the die may include one or more cavities or passages formed adjacent the casting and in which a heated medium such as a thermal oil or other fluid material is received and/or circulated through the dies for heating the dies. Thereafter, thermal oils or other suitable media may be introduced or circulated through the die, with the oil being of a lower temperature, for example, from about 250° C. to about 300° C., to cool the casting and cause the casting to solidify. A high temperature thermal oil, for example, heated to from about 500° C. to about 550° C., then may be introduced and/or circulated through the die to arrest cooling and raise the temperature of the casting back to a soak temperature for heat treating. The pre-heating of the die and/or introduction of heated media into the die may be used to initiate heat treatment of the casting. Further, preheating helps maintain the metal of the casting at or near a heat treatment temperature to minimize heat loss as the molten metal is poured into the die, solidified, and transferred to a subsequent processing station for heat treatment. If additionally desired, the casting also may be moved through a radiant chamber or zone to prevent or minimize cooling of the casting.
As shown in FIG. 3, each of the molds 11 generally includes side walls 16, an upper wall or top 17, a lower wall or bottom 18, which collectively define an internal cavity 19 in which the molten metal is received and formed into the casting 13. A pour opening 21 generally is formed in the upper wall or top 17 of each mold and communicates with an internal cavity for passage 22 of the molten metal through each mold and into its internal cavity 19 at the pouring station. As indicated in FIG. 2A, the pouring station 12 generally includes a ladle or similar mechanism 23 for pouring the molten metal M into the molds 11. The pouring station 12 further can include a conveyor, carousel, or similar conveying mechanism, that moves one or more molds from a pouring or casting position, indicated by 24 in FIG. 2A, where the molten metal is poured into the molds, to a transfer point or position 26 (FIG. 2B), at which the castings can be removed from their molds or transferred while remaining in their molds from the pouring station to the vertical heat treatment unit 10 for heat treatment. Prior to and/or during such transfer, the molten metal is allowed to cool to a desired extent or temperature within the molds as needed for the metal to sufficiently solidify into the castings. The castings then are heat treated at a desired heat treatment temperature for a time sufficient to achieve desired mechanical properties thereof. Thereafter, the castings generally will be removed and transferred to a quench unit or station 28, which can be part of or can be a separate station positioned adjacent or downstream from the vertical heat treatment unit 10 as illustrated in FIG. 2A.
As indicated in FIG. 2B, the castings can be transferred from their pouring stations 12, either within their molds or after removal and placed on a transfer line 31, such as a monorail or similar conveying mechanism, that transfers or conveys the castings in series or in batches to one or more loading carousels 32. The carousels 32 generally can include a series of receiving bins or trays 33 and a transfer mechanism 34 such as a robot, crane, boom, or other similar device. The transfer mechanism 34 then feeds the castings, or the molds with the castings therein, into one or more vertical heat treatment units 10 for solution heat treatment of the castings.
It has been discovered that as the metal of the casting is cooled down, it reaches a temperature or range of temperatures referred to herein as the “process control temperature” or “process critical temperature.” Below such process control temperature(s), the time required to both raise the castings to the heat treating temperature and perform the heat treatment is significantly increased. It will be understood by those skilled in the art that the process control temperature for the castings being processed by the present invention will vary depending upon the particular metal and/or metal alloys being used for the castings, the size and shape of the castings, and numerous other factors.
In one aspect, the process control temperature may be about 380° C.-480° C. and as low as about 300° C.-325° C. or less for some alloys or metals. In another aspect, the process control temperature may be from about 400° C. to about 600° C. In another aspect, the process control temperature maybe from abut 800° C. to about 1100° C. In still another aspect, the process control temperature may be from about 1000° C. to about 1300° C. or more for some alloys or metals, for example, iron. In one particular example, an aluminum/copper alloy may have a process control temperature ranging from about 300° C. to about 480° C. In this example, the process control temperature generally is below the solution heat treatment temperature for most aluminum/copper alloys, which typically is from about 427° C. to about 495° C. While particular examples are provided herein, it will be understood that the process control temperature will vary depending upon the particular metal and/or metal alloys being used for the castings, the size and shape of the castings, and numerous other factors.
When the metal of the castings is within the desired process control temperature range, the casting typically will be cooled to sufficiently solidify as needed or desired. For example, depending on the alloy formation or metal composition of the castings, castings made from aluminum alloys generally will need to cool to about 460° C.-425° C. to enable sufficient solidification so that the castings can be gripped and manipulated, i.e., removed from their molds/dies and/or transferred to the vertical heat treatment unit or line as needed. This solidification temperature will be understood as varying and can be determined as understood by those skilled in the art based on the formulation(s) of the metals or metal alloys being cast. However, if the metal of the castings is permitted to cool below its process control temperature, it has been found that the heat treatment time for the casting is meaningfully impacted. For example, for some metals or metal alloys, the castings may need to be heat treated for at least about one to four additional minutes of heat treatment time for each minute that the temperature of the metal of the castings is cooled below the process control temperature, for example, from about 475° C. to about 495° C. for aluminum/copper alloys, or from about 510° C. to about 570° C. for aluminum/magnesium alloys, to achieve the desired heat treatment properties for the castings. Thus, if the castings cool below their process control temperature for even a short time, the time required to heat treat the castings properly and completely may be increased significantly.
In addition, it should be recognized that in a batch processing system, where several castings are processed through the heat treatment station in a single batch, the heat treatment time for the entire batch of castings generally is based on the heat treatment time required for the casting(s) with the lowest temperature in the batch. As a result, if one of the castings in the batch being processed has cooled to a temperature below its process control temperature, for example, for about ten minutes, the entire batch typically will need to be heat treated, for example, for as much as at least an additional forty minutes or more to ensure that all of the castings are heat treated properly and completely.
Various aspects of the present invention therefore, are directed to an integrated processing facility or system 5 (FIG. 2A-2B) and methods of processing metal castings. The various systems are designed to move and/or transition the castings (within or apart from their molds) from the pouring station 12 to the vertical heat treatment system or cell unit 10, while arresting cooling of the molten metal to a temperature at or above the process control temperature of the metal, but below or approximately equal to the desired heat treatment temperatures thereof to allow the castings to solidify. Accordingly, various aspects of the present invention include systems for monitoring the temperature of the castings to ensure that the castings are maintained substantially at or above the process control temperature.
For example, thermocouples or other similar temperature sensing devices 36 (FIG. 2A) or systems can be placed on or adjacent the castings at spaced locations along the path of travel of the castings from the pouring station to a vertical heat treatment unit or cell unit 10 to provide substantially continuous monitoring as indicated in FIG. 2A. Alternatively, periodic monitoring of the castings along their path of travel at selected intervals determined to be sufficiently frequent, may be used. Such sensing devices may be in communication with a controller 37 that can be linked to and in control of one or more heat sources 38 positioned at desired or predetermined locations along the path of the castings from the pouring station 11 to the vertical heat treatment unit 10. For example, the heat sources could be positioned at desired locations such as along the transfer line 31 (FIG. 2B). A heat source also can be positioned on or adjacent the robot or other transfer mechanism 34 for the loading carousel(s) 32 for applying heat to the castings during transfer to the vertical heat treatment unit.
The temperature measuring or sensing device(s) 36 and the operation of the heat source(s) 38 can be controlled or coordinated to substantially arrest cooling of the castings and apply heat as needed to maintain the temperature of the castings substantially at or above the process control temperature for the metal of the castings. It also will be understood that the temperature of the castings can be measured at one particular location on or within the castings, can be an average temperature calculated by measuring the temperature at a plurality of locations on or within the castings, or may be measured in any other manner as needed or desired for a particular application. Thus, for example, the temperature of the castings may be measured at multiple locations on or in the casting and/or mold therefore, and an overall temperature value may be calculated or determined to be the lowest temperature detected, the highest temperature detected, the median temperature detected, an average of the detected temperatures, or any combination or variation thereof.
A first embodiment of the integrated facility 5 and vertical heat treatment system or cell unit 10 for processing metal castings therethrough is illustrated in FIGS. 1, 2A, 2B, and 4-6C. FIGS. 8A-11C illustrate additional, alternative embodiments of the vertical heat treatment unit 110, 150, and 200, respectively, for heat treating castings. Still further, FIGS. 7A-7C illustrate various nozzle configurations for fluid media nozzles/applicators for applying heat to the castings in the vertical heat treatment units according to the present invention. It also will be understood by those skilled in the art that the principles of the present invention can be applied equally to batch type and continuous processing type facilities for castings. The embodiments described hereinafter therefore are not and should not be limited only to continuous or batch-type processing facilities. The present invention also can be utilized for facilities in which the castings are to be removed from their dies before heat treatment, as well as for “2-in-1,” 3-in-1,” and/or “6-in-1” or other, similar processes wherein the castings are placed in the vertical heat treatment unit while still inside their sand molds for breakdown, removal and/or reclamation of the molds and sand cores in conjunction with heat treatment of the castings. In addition, it further will be understood by those skilled in the art that various features of the embodiments discussed hereafter and illustrated in the drawings can be combined to form additional embodiments of the present invention.
In an exemplary system as illustrated in FIGS. 2A and 2B, the castings are transferred, either remaining within their molds or after removal therefrom, from the transfer positions 26 (FIG. 2A) of their pouring stations 12 to the transfer line 31 or directly to an adjacent vertical heat treatment unit 10 by a transfer mechanism 34. The transfer system or mechanism 34 typically includes a robotic arm 39 or crane, although it will be understood by those skilled in the art that various other systems and devices for moving the castings and/or molds, such as an overhead boom or hoist, conveyor, pushing rods, or other similar material handing mechanisms also can be used. As indicated in FIG. 2A, the robotic arm 39 or other transfer mechanism generally includes an engaging or gripping portion or clamp 41 for engaging and holding the molds or castings, and a base 42 on which the robotic arm is pivotally mounted so as to be moveable between the transfer point 26 (FIG. 2B) of the pouring station and the transfer line indicated by 31. In addition, as shown in FIG. 2B, the transfer line 31 also can be used to transfer molds and/or castings from multiple pouring stations 12 to multiple vertical heat treatment units 10.
The castings can be transferred from their pouring station(s) 12 to a loading carousel 32, where an additional transfer mechanism 34 such as a robotic arm, crane, boom, or similar mechanism, such as already in use at the facility, generally will pick up the molds with their castings contained therein, or can remove the castings 13 (FIG. 3) from their molds 11 and feed the castings to an associated vertical heat treatment unit 10. Thus, the same manipulator or transfer mechanism can be used for removing the castings from the pouring station and for introducing the castings into the vertical heat treatment unit 10. Additionally, one or more heat sources or heating elements 38 (FIG. 2A) can be positioned adjacent the transfer point (not shown) and/or along the transfer path for the castings to apply heat to the castings as needed to maintain the castings at or above their process control temperatures. These heat sources typically can include any type of heating element or source such as conductive, radiant, infrared, convective, and direct impingement types of heat sources. As illustrated in FIG. 2A, multiple heat sources also can be used, positioned to most effectively apply heat to the castings during a transfer operation from the pouring station to the heat treatment line.
Typically, in the case of permanent or metal dies or molds, the molds will be opened at the transfer point and the castings removed by the transfer mechanism. The same transfer mechanism then can transfer the castings to the transfer line 31 or directly to one or more vertical heat treatment units or systems 10 of the integrated processing facility 5. As the molds are opened and the castings removed, the heat sources can apply heat directly to the castings to arrest or otherwise control the cooling of the castings during their exposure to the ambient environment of the foundry or plant, as the castings are being transferred to the heat treatment unit, to maintain the castings substantially at or above the process control temperature of the metal of the castings.
For the processing of castings that are being formed in semi-permanent or sand molds, in which the castings typically remain within their molds during heat treatment, during which the molds are broken down by the thermal degradation of the binder material holding the sand of the mold, the transfer mechanism may transfer the entire mold with the casting contained therein, from the transfer point to the inlet conveyor. The heat source thus may continue to apply heat to the mold itself with the amount of heat applied being controlled to maintain the temperature of the castings inside the mold at levels substantially at or above the process control temperature of the metal of the castings without causing excessive or premature degradation of the molds.
A first embodiment of the vertical heat treatment unit or cell unit of the present invention generally is illustrated in FIGS. 4-6C. As shown, the vertical heat treatment unit 10 generally can be a vertically oriented, free-standing “cell unit,” according to the invention, having a significantly reduced footprint such that the amount of plant floor space required is minimized, while still accommodating a desired amount of castings to be processed. The vertical heat treatment unit thus also can be positioned in close proximity to the pouring station(s) supplying castings thereto. In the present embodiment shown, the vertical heat treatment unit can be approximately 20-30 feet in height, although each vertical heat treatment unit also can be constructed with greater or lesser heights depending upon the required capacity and/or sizes of the castings being processed.
The vertical heat treatment unit 10 includes an upstanding furnace 50 supported by a surrounding frame 51. As previously noted, the furnace can be formed with varying heights and typically can be approximately 20-30 feet in height, with the height and width of the furnace chamber being varied as needed and generally being designed to accommodate a desired number of castings, i.e., 10-20 or more rows of 1-5 castings generally received in each row or batch for batch processing, although the castings also can be processed individually or in larger batch sizes as needed or desired. The vertical orientation and ability to vary the height of the furnace chamber of the vertical heat treatment unit 10 of the present invention depending upon the application and/or facility/setting for its use, thus can enable up to an approximately a 75% smaller footprint over many conventional heat treatment units.
As shown in FIGS. 4-5A and 6B, the furnace 50 includes a top portion 52, substantially flat side walls 53, the interior surfaces 54 (FIGS. 5A and 6B-6C) of which typically will be formed from or lined or coated with a radiant material so as to reflect direct heat inwardly toward the castings. The radiant material of the radiant interior walls or surfaces 54 may be metal, telefilm, ceramic, composite or other similar high temperature enduring material capable of radiating heat. These radiant coatings or materials generally form a non-stick surface on the walls and ceiling of the furnace, and as the walls and ceiling of the radiant chamber are heated, the heat tends to radiate inwardly toward the castings, while at the same time, the surfaces of the walls and ceiling generally can be heated to a temperature sufficient to burn off waste gases and residue such as soot, etc., resulting from the combustion of the binders of the sand molds and/or sand cores to prevent collection and buildup thereof on the walls and ceiling of the radiant furnace. The furnace 50 further includes a lower or bottom portion 56 having inwardly sloped side walls 57 that terminate at a substantially flat bottom 58. As indicated in FIG. 6B, the lower portion 56 also can include a fluidizer 59 positioned therealong for fluidizing and assisting in substantially completing the breakdown of the remaining binder materials from the sand being collected from the sand cores and sand molds of the castings, and a conveying mechanism 61 (FIG. 6C) for thereafter transporting the reclaimed sand away for reuse.
As also indicated in FIG. 6B, the furnace 50 further can include upper and lower sections 62 and 63 that serve to help define a radiant furnace chamber 64 through which the castings 13 are conveyed for heat treatment and/or de-coring and mold removal. As further indicated in FIG. 6B, the upper and lower portions 62 and 63 taper or slope inwardly, with the upper sections 62 defining a narrowed upper air passage 66 for the passage of heated air flows directly therethrough, while the lower section 63 defines a narrow outlet passage 67 through which sand from the sand cores and/or sand molds of the castings is directed into the bottom or lower portion 56 of the furnace 50. Still further, as indicated in FIGS. 5A-5B, and 6B, an inlet/outlet port or opening 69 generally is formed through one of the side walls 53 (FIG. 6B) and radiant walls 54 for ingress and egress of the castings into and out of the furnace chamber 50. A door or other cover mechanism 71 is provided for controlling access to the furnace.
As additionally indicated in FIGS. 4, 6A, and 6B, a manipulator 75 will be mounted along one side of the vertical heat treatment unit 10 in a position for receiving the castings from their associated loading carousel 32 (FIG. 2B) or directly from the transfer line 31. The manipulator 75 generally is moveable horizontally and vertically as needed to lift, move, insert, and withdraw the castings into and out of the furnace. As indicated in FIGS. 4 and 6B, the manipulator 75 typically includes one or more lift plates or forks 76 mounted to a motorized carriage 77 that can ride on guide rails 78 for picking up and moving the castings into the port or opening 69 (FIG. 6B) of the furnace chamber 50.
As indicated in FIGS. 5A-5B and 6B, within the radiant chamber 64 of the furnace 50 of the vertical heat treatment unit 10 is a vertically oriented carousel or “ferris wheel” type conveying mechanism 81 having a series of platforms, racks, or trays 82 (hereinafter, collectively, the “tray”) mounted on chains 83 that are rotated around large drive sprockets 84/84′ driven by variable speed, reversible motors (not shown) for driving the conveying mechanism 81 at varying speeds and in a stepped fashion. Typically, for loading/unloading operations, as the castings 13 are received within the furnace 50, and/or after removal of a group or set of heat treated castings, the conveying mechanism 81 generally will be operated in a controlled stepping, up and down type motion, i.e., moving the rocks of the conveying mechanism (in direction of arrow 86′ of FIG. 6B) to load a next casting or series of castings therein, up one position and after the castings are received therein, rotating the conveying mechanism downwardly so a to move the racks or sets of racks two positions up from the just-loaded rack(s) into a position for unloading, as needed, heat treated castings therein, (in the direction of arrow 86, FIG. 6B) during loading and unloading operations. Thereafter during normal operation, the castings will be conveyed in a substantially elliptical path down and around the lower sprocket 84′ and upwardly and over the upper sprocket 84 for heat treatment. The stepping up one, down two, motion of the conveying mechanism helps ensure a sufficient separation between the incoming (“colder”) castings and the hottest castings within the furnace to help substantially reduce or prevent heat transfer/loss between the hottest and “colder” castings to enable completion of the heat treatment of such hotter castings.
As further illustrated in FIGS. 4-6C, the furnace 50 generally includes one or more heat sources 90, here illustrated as fans or blowers 91 positioned adjacent the upper end of the furnace 50. The blowers 91 direct a heated media such as air or other gases or fluids into the furnace so as to create a turbulent heated fluid flow that passes about the castings as the castings are conveyed along their heat treatment path by the conveying mechanism 81 (FIGS. 5A, 5B, and 6B). The blowers or fans 91 further can be utilized in conjunction with other heat sources such as radiant or infrared heaters, gas fired burners or other types of heat sources to create a heated environment within the furnace for heating the castings to their solution heat treatment temperature. In addition, where the castings are processed in their sand molds, the application of heat and the turbulent heated fluid flow about the castings and downwardly to the bottom of the furnace 50, as indicated in FIGS. 6B and 6C, helps facilitate the decomposition and combustion of the binder materials of such sand cores and sand molds so as to cause them to combust, pyrolize or otherwise be driven off and the sand removed from the castings and directed downwardly to the lower portion 56 of the furnace for collection and removal as indicated in FIG. 6C.
In another aspect, additional or alternative heat sources 90 can be mounted within the radiant walls 54, positioned at desired intervals therealong for directing high pressure fluid flows at the castings within the trays of the conveying mechanism, as illustrated in FIG. 6B, or as conveyed individually or in discrete groups, such as illustrated in FIGS. 9A-11B. These heat sources 90 can include high velocity blowers or nozzle assemblies 92 positioned at desired distances with respect to the known center-lines of the castings, including high pressure blowers or nozzles positioned at desired distances with respect to the known center-lines of the castings as they are conveyed within the trays 82 of the conveying mechanism 81, through the radiant chamber of the furnace. The location and design of the nozzle or blower assemblies 92 along the radiant walls 54 of the furnace 50, as well as the actual distance that the pressurized fluid media directed from such blowers needs to travel to impinge the castings and/or the sand cores within the castings, such as passing through core openings therein, the design of the flow pattern, the fluid media, and other flow parameters of the fluid media directed from the nozzle openings or ports 93 (FIGS. 7A-7C) generally will depend on the type and size of the work piece, as well as the size of the nozzles themselves.
According to one aspect of the invention, at least one of the nozzles 92, blowers or other impingement devices can have a nozzle opening or port 93 in the range of about ⅛ inch to about 6 inches in diameter or width, and in particular, the nozzles can have one or more openings or ports 93 having a diameters of less than about 1-1.5 inches to about 4 inches and can extend a length of approximately 10″-26″ depending on the distances from the nozzles to the castings. The diameters of the nozzle openings or ports 93 can be fixed, although variable size nozzles also can be used, and further will be dependent upon the desired or needed velocities of the fluid media flows striking or impinging the castings and their sand cores as desired or needed, as well as the size of the core openings at which and through which the fluid flows are directed. Alternatively, as indicated in FIGS. 7A and 7B, the nozzles 92 also can include an elongated slotted opening or port 94 for applying a broader or extended fluid flow along an expanded area or over a series of locations rather than more localized applications to specific points or areas of the castings. Accordingly, while certain nozzle opening configurations, widths and/or ranges of widths or diameters are set forth herein, it will be understood by those skilled in the art that any suitable impingement device or nozzle diameter and/or configurations can be used in accordance with the present invention to achieve the desired results. Thus, other nozzle opening diameters and/or configurations are also contemplated hereby.
FIGS. 7A-7C illustrate various nozzle configurations or arrangements for applying the heated fluid media to the castings. In one embodiment shown in FIG. 7A, an upper nozzle assembly 92A is formed with a series of large, medium or small nozzle openings or ports 93 arranged at selected locations along the plenum 95. Typically, the nozzle ports of the upper nozzle generally will be arranged at locations approximately corresponding to the core openings or other desired locations formed along the upper surface of the casting, so as to apply a heated fluid media, such as heated air or other fluids, primarily directed at selected locations and/or providing fluid velocity flows across the remainder of the upper surface of the castings. As also indicated in FIG. 7A, a lower nozzle assembly 92B generally will be positioned beneath the casting for applying heated fluid media flow at the bottom or lower portion of the casting. In the embodiment illustrated in FIG. 7A, the lower nozzle assembly 92B generally comprises a slotted nozzle port 97 having an elongated slotted opening. The slotted nozzle port 97 can extend substantially along the length of its plenum 95, typically for a length approximately equivalent to the largest or longest casting to be treated. For example, the slotted opening 94 can extend approximately 10-15 inches in length (although greater or lesser lengths also can be used), and generally can be approximately 0.5 inch to 1 inch wide, although greater or lesser widths also can be utilized depending upon the penetration velocities desired or needed by the fluid media flow being applied by the nozzle assembly 92B.
FIG. 7B illustrates a further example embodiment of a nozzle configuration arrangement 92 that can be utilized in the vertical heat treatment unit according to the principles of the present invention. In this embodiment, a series of four nozzle assemblies 92A-92D are indicated, although greater or lesser numbers of nozzle assemblies also can be used. The upper or top nozzle assembly 92A is shown with a series of varying size nozzle ports or openings 93/93′, which further can be arranged as singles for directing fluid flows towards specific locations or openings along the upper top surface of the casting. The remaining nozzle assemblies 92B-92D are illustrated at having slotted openings 94, and are arranged or positioned along the bottom and side surfaces, respectively, of the casting. Such a nozzle assembly can be provided in a chamber or along a conveyor or other guiding mechanism, along which the castings are conveyed through various embodiments of the vertical heat treatment unit such as discussed more fully below with respect to the embodiments of the vertical heat treatment unit as illustrated in FIGS. 8A-11D. The nozzle assemblies 92B-92D (FIG. 7B) are illustrated with a slotted nozzle openings 94, although it will be understood that one or more of the additional nozzle assemblies can be provided with individual, localized ports or openings, and similar configurations to that of the upper nozzle assembly 92A.
FIG. 7C illustrates yet another example embodiment of a nozzle arrangement in which an upper nozzle assembly 92A is positioned above the upper surface of a casting, while a lower nozzle assembly 92B applies a heated fluid media flow across desired locations along a bottom surface of the casting. In this embodiment, the upper nozzle assembly includes ports or openings 93/93′ and can comprise small, medium, or large diameter openings or ports and are generally spaced along or across the upper surface of the castings for applying heated fluid media at varying velocities across or at differing locations along the upper surface of the casting. For example, smaller diameter nozzle ports 93′ can be oriented or focused at core openings or recesses so as to provide a high velocity, heated fluid flow at such core openings for breaking up and dislodging sand cores, while the larger diameter ports or openings 93 can provide heated media fluid flow over a larger area or wider location along the upper surface of the casting. Additionally, the lower nozzle assembly 92B is shown with a series of small or medium diameter nozzle ports or openings 93′ (although larger diameter nozzle ports or openings also can be used) in which nozzle ports are arranged at angles. Such nozzle ports can be of varied lengths and be oriented at an angle with respect to the bottom surface of the casting and can apply a high velocity fluid flow across a larger area, or can be specifically directed to certain locations, such as core openings in the castings, as needed.
According to another aspect of the present invention, the nozzle ports or openings 93/93′/94 generally can be positioned from about 1-1.5 inches to about 10 inches or more away from the castings, and more typically, can be located about 1 inch to about 6-8 inches from the casting in order to impinge and or blast fluid into and around the molds, castings, and/or sand cores of the castings so as to direct substantially full velocity or pressure of the fluid media exiting the nozzle openings being substantially maintained. Typically, it has been found that substantially the full speed or velocity and/or pressure of the fluid media being applied by the nozzles can be maintained at a distance from the nozzle opening that is approximately five-seven times the diameter of the nozzle. For example, if the nozzle opening is approximately one inch in width or diameter, the full velocity of the fluid flow generally will be substantially maintained for approximately five-seven inches, after which the velocity will begin to significantly dissipate or decrease. Thus, the nozzles generally are positioned at locations spaced from known or projected center-lines of the castings as the castings are conveyed within the trays 82 (FIG. 5B) of the conveying mechanism 81 by a distance of approximately five-seven times the nozzle opening diameter. It will, however, be understood that while various distances and ranges of distances are provided herein, each nozzle or impingement device may be positioned at varying distances with respect to the center-lines of the castings being processed or from a desired point or area of effect of the fluid flow as needed to achieve the desired results. Thus, numerous other possible positions or separation distances between the castings and the nozzle are contemplated hereby.
The fluid media applied by the nozzles 92 generally is delivered at a high discharge flow velocity of approximately 4,000-40,000 feet per minute (ft/min), for example, in a range of about 5,000-9,000 ft/min (approximately 50 m/sec) so as to impinge against the castings and/or create a turbulent high temperature, high velocity fluid flow through the furnace chamber. It also will be understood that while there are velocities and ranges of velocities provided above, other velocities also can be used in accordance with the present invention, depending, for example, upon the size and type of casting, to achieve the desired results. The fluid media thus generally can be delivered to the castings and/or the core contained therein at a rate of approximately 50-500 standard cubic feet per minute per foot from the nozzles, although other flow rates also can be utilized or provided.
As a result, the fluid media is delivered to the castings, and more particularly to the core openings at a substantially high velocities so as to create significant turbulence and to enhance the burnout of the binder materials for the sand cores and/or sand molds of the castings to enhance the rapid breakdown thereof. The velocities of the fluid flows also can be varied by the pressure and volume of the fluid flow as well as the configurations and sizes of the nozzle ports or openings. In addition, the fluid media flow may be directed to specific portions of the castings and/or sand molds to localize the fluid flows where needed. For example, the fluid media may be directed at one or more faces of the castings to enhance the effect of the impinging fluid media, including being directed at the core openings to enhance the breakdown and removal of the sand cores from the castings.
The following Table 1 illustrates a comparison of various options or examples of different nozzle configurations. The fluid media flow is applied in volumes of approximately 10.86 pounds per minute of heated air from the upper or top nozzle assembly, and similarly, approximately 10.86 pounds per minute of heated air through the bottom or lower nozzle assembly, with the nozzles arranged in configurations similar to those illustrated in FIGS. 7A and 7C. The temperature of the heated air being applied was approximately 1000° F. or more.
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Example 1
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(4) 1.5″ diameter round nozzles at the top of the casting
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(4) 1.5″ diameter round nozzles at the bottom of the casting
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(8) 0.5″ diameter round nozzles along the bottom of the casting
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The 1.5″ bottom nozzles were placed under the fire place of the casting to get better air
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penetration. The 0.5″ bottom nozzles are placed below the intake ports which are around the
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fireplace of the casting.
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Example 2
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(1) 0.5″ wide × 15″ long slot along the top of the casting
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(1) 0.5″ wide × 15″ long slot along the bottom of the casting
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Example 3
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(8) 1″ diameter round nozzles at 2″ spacing along the top of the casting
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(8) 1″ diameter round nozzles at 2″ spacing along the bottom of the casting
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The bottom nozzles were generally centered on the fireplace of the casting
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Example 4
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(8) 1″ diameter inclined round nozzles along the top of the casting
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(1) 0.5″ wide × 15″ long slot along the bottom of the casting
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Example 5
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(1) 0.5″ wide × 15″ long inclined slot along the top of the casting
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(1) 0.5″ wide × 15″ long slot along the bottom of the casting
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Air Velocity through Casting Cavities (fpm)
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Example 1
Example 2
Example 3
Example 4
Example 5
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Velocity of impingement
6000
4000-4500
4500-5500
3000-3800
3000-4500
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on upper side (under
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nozzle)
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Velocity of impingement
3000-4000
N/A
2000-2300
2000-3000
3000-4500
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on upper side (between
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nozzles)
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Velocity of impingement
N/A
1000-2000
N/A
N/A
N/A
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on upper side (under riser)
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Air Velocity in upper area
4000-4800
3000-3500
2800-3200
1000-2500
900-1800
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opposite the nozzles
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Velocity in the vertical
2000-4000
2000-4000
2300-4000
800-1000
1000-1300
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passages connecting top
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and bottom
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Best case velocity in
8500
6800
4000-5500
4000-5800
3500-5400
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exhaust ports
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Worst case velocity in
8500
6800
2100-3400
N/A
N/A
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intake ports
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Best case velocity in intake
8500
6800
3000-4900
2000-4800
2000-5000
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ports
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Worst case velocity in
8500
6800
1800-2200
N/A
N/A
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intake ports
|
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According to the velocities measured in the table, the highest fluid flow velocities were achieved with the nozzle configurations of Examples 1 and 2. However, given the general configuration of most conventional types of castings that typically will be treated in the vertical heat treatment units of the present invention, it has been found that a combination of nozzle configurations as disclosed in Options or Examples 1 and 2, including the use of a slotted nozzle assembly along the bottom or lower side of the casting and an upper nozzle assembly generally having a series of nozzle openings or ports ranging from approximately 0.5 to about 1.5 inches or larger in diameter and arranged at desired locations across the upper surface for providing localized and higher velocities across the upper surface of the castings, generally can provide preferred heating coverage. It will be understood by those skilled in the art, however, that such nozzle configurations can be further varied, as needed, depending on the design or configuration of the castings being treated, and can provide additional heat treatment to certain desired areas or locations of the castings as needed.
Still further, as indicated by arrows 98 and 98′ in FIGS. 7A and 7B, the castings, or the nozzles themselves, or both, also can be oscillated, rotated, or otherwise moved at predetermined intervals or through predetermined motions based upon the known positioning of the castings, including the known center-line positions thereof. Such oscillation of the nozzles and/or the castings during application of the heated fluid flows has been found to provide expanded fluid media impingement across the castings and thereby achieve enhanced efficiency of the process. Depending upon the sizes of the nozzles and the castings themselves, the nozzles or the castings can be moved or oscillated at rates ranging from about 5 feet per minute to upwards of approximately 40 feet per minute, although other rates of movement also can be used in accordance with the present invention to achieve the desired results. Still further, the oscillation of the castings and/or nozzles can be limited from about 3 inches to about 15 inches, up to about 36 inches in either direction, and can be done relatively quickly, i.e., in about 2 seconds per revolution to about 1 minute or at more controlled rates from about 1 minute to about 10 minutes. However, it also will be understood that the oscillation distances and cycle times can be varied as needed to achieve the desired results.
Additionally, the temperatures of the fluid media being directed at the castings by the nozzle assemblies or blowers 92 generally will be at elevated temperatures, typically from about 400° C. to about 600° C., or more depending upon the metal or metal alloy being treated. The temperatures of the fluid media being applied generally will be sufficient to promote and/or cause the combustion (for example where air or oxygenated gas flows are used for the fluid media) or pyrolyzing of the binder materials of the sand cores and/or sand molds of the castings and to help assist in heat treatment, but generally will be less than the temperature at which the castings might be softened or substantially raised above their solution heat treatment temperature so as to potentially cause damage thereto. It also will be understood that while a particular temperature range is discussed herein, other temperatures also may be used to achieve the desired results.
As further shown in FIG. 6C, a separator 96 also can be provided adjacent the furnace 50. The separator 96 can be a cyclonic separator that is in flow communication with the lower portion or bottom 56 of the furnace 50, so as to draw off excess air therefrom. As this waste air is passed through the separator 96, it will be filtered and thus substantially cleaned of particulate matter such as sand, dust, and other debris. Thereafter, the cleaned air can be re-circulated back to the fans or blowers 91 at the top of the furnace 50 where it can be cleaned and reused/redirected into the furnace or can be exhausted or otherwise vented therefrom.
As shown in FIGS. 4 and 6B, the vertical heat treatment unit additionally can be provided with a quench unit 28 mounted adjacent or in front of the door 71 to the furnace 50 along the path of movement of the castings into and out of the furnace by the manipulator 75. The manipulator 75, after removal of the castings from the furnace chamber of the vertical heat treatment unit, can lower the castings into the quench unit 28 for quenching the castings, and thereafter can remove the castings and deposit them on the transfer line 31 (FIG. 2B) or other conveyance for removal.
In an alternative embodiment of the vertical heat treatment unit 110 shown in FIGS. 8A-8B, the vertical heat treatment unit 110 includes a furnace 111 having walls 112, ceiling 113, and a lower portion 114, that includes downwardly sloping sections or walls 116 that terminate at a bottom or floor 117. The walls, ceiling, and lower portion of the furnace 111 generally are formed from or coated with a radiant material as discussed above with respect to the embodiment of FIGS. 4-6C, and define a radiant furnace chamber 118 therein. A series of longitudinally extending conveyors 119, which can include chain or slotted/belted conveyors having a series of openings or slots 121 (FIG. 8B) defined therein will be positioned in a vertically stacked arrangement. Each of the conveyors 119 will extend longitudinally along the radiant chamber 118 of the furnace 111 as indicated in FIG. 8B and will be operated at a desired rate as needed to complete the heat treatment of the castings as they are passed through the radiant furnace chamber 118. It will be understood by those skilled in the art that while only 2-3 conveyors 119 are illustrated in FIGS. 8B and 8A, respectively, additional conveyors also can be provided in a vertically stacked arrangement, with the furnace 111 of the vertical heat treatment unit 110 being extended or increased in size vertically to enable the loading of additional castings and castings of varying sizes therein.
As shown in FIG. 8A, a series of heat sources 122 generally are provided above and between the conveyors 119. The heat sources can include conduction, convection, infrared or other radiant heat sources, such as gas fired burners, and/or can include nozzles or blowers that direct a flow of heated fluid media to the castings as the castings are passed therebeneath on the conveyors 119 so as to heat the castings to a solution heat treatment temperature for heat treatment of the castings. The fluid media further can be applied at substantially higher velocities from the nozzles as discussed above, with the nozzles or heat sources being placed at pre-determined distances with respect to the centerlines castings, so as to direct fluid flows at desired portions of the castings, for example, at and into core openings thereof to facilitate the breakdown and pyrolization of any binder materials for the sand cores and/or sand molds of the castings.
As further illustrated in FIG. 8A, any sand dislodged from the sand cores and/or sand molds of the castings can be collected and directed downwardly into the bottom portion 114 of the furnace or along the downwardly sloping sections of the walls 116 thereof. A fluidizer 123 also can be provided adjacent the floor 117 of the bottom or lower portion 114 of the furnace 111 so as to fluidize any collected sand and help further promote the substantially complete breakdown and burnoff of any remaining binder materials so that the sand materials can be substantially cleaned and reclaimed for further use.
FIGS. 9A-9D illustrate yet another embodiment of the vertical heat treatment unit 150 according to the principles of the present invention. As illustrated FIGS. 9A-9D, the vertical heat treatment unit 150 generally includes a furnace 151 mounted in the vertically extending, upstanding arrangement and can extend between 10-30 feet in height, although greater or lesser heights also can be used as needed or desired, depending on the application. The furnace 151 generally includes a ceiling 152, vertically extending side walls 153, and a lower portion 154 (FIG. 9B), including downwardly sloping sections or walls 156 that extend inwardly and downwardly toward a floor or bottom 157. The ceiling 152, side walls 153, and lower portion 154 of the furnace 151 are generally formed form or have applied thereto a radiant material, such as discussed above with respect to the embodiment of FIGS. 4-6C, so as to radiate heat inwardly therefrom toward the castings, and define a radiant chamber 158 (FIGS. 9B and 9D) within the furnace 151. Heat sources 159, such as one or more blowers 161 or fans, or other heat sources such as convection or conduction heat sources, including infrared or other radiant heat sources and/or gas fired burners, etc. also can be used to introduce heat into the radiant chamber and raise the temperature of the castings therein to their solution heat treatment temperature.
As additionally shown in FIGS. 9B and 9C, a grid system 162, having a series of chambers 163 formed therein, will be mounted within the radiant chamber 158 of the furnace 151. The chambers of the grid system 162 generally will be spaced apart or separated by walls 164, typically including insulating and radiant materials to prevent heat transfer or loss from hotter castings to cooler castings that are in adjacent chambers or compartments on the same row of the grid system 162. The floors and ceilings 166 and 167 of each of the chambers or compartments 163 typically can have a slotted construction, with a plurality of openings formed therein, or can be substantially open, with the castings being received and contained on rails 168 (FIG. 9C) or similar supports so as to allow free flow of air, heat, and dislodged sand from the sand cores and/or sand molds of the castings to pass therethrough and fall through the entire grid system 162 for collection in the lower portion 154 of the furnace 151. Additional heat sources also can be provided along the floor and ceiling portions 166, 167 of each of the chambers 163 to help provide additional, directed heat to the castings. For example, such heat sources can include nozzles that apply high velocity fluid media flows directed at desired portions or sections of the castings, such as at core openings, thereof to help facilitate the breakdown and dislodging of the sand from the sand cores and sand molds of the castings.
As additionally illustrated in FIG. 9B and 9D, in this embodiment of the vertical heat treatment unit 150, a gantry or elevator type loader 175, which can include a crane, boom, or robotic arm, generally is provided in the radiant chamber 158 of the furnace 151. The loader 175 generally includes a platform or support 176 on which one or more castings or molds, here shown as four castings or molds 11/13, are received and will be moved vertically and horizontally for introduction and removal of the castings or batches of castings from the compartments or chambers 163 of the grid system 162, as illustrated in FIG. 9B. Typically, the support platform 176 of the loader 175 will include a slot or central opening in which the rails or supports of the chambers 163 can be received for removal of the castings from the support platform of the loader after the loader has inserted the castings into their assigned chamber. As further illustrated in FIG. 9B, where the castings include risers or supports, the support platform of the loader can include a rail or skid adapted to be inserted within such openings in the castings and insert the castings on the rails for a particular assigned chamber.
Alternatively, as illustrated in FIG. 9D, the loader 175 can be positioned outside of the furnace 151. In this embodiment, the loader 175 will be moveable into and out of the chambers or compartments 163 of the grid 162 through associated compartment openings 180. Each compartment opening or passage 180 will include a door or cover 181 that is moveable between an open position (as shown in FIG. 9D) for receiving the castings therein and a closed position for sealing the compartment openings. The doors 181 can be automatically engaged by sensors that activate a motor or hydraulic or pneumatic lift mechanism, or could be engaged and opened by the loader itself via a lift/positioner mechanism or extension on the loader, which contacts and causes the door to open, after which the doors can be allowed to close by gravity.
FIGS. 10A-11B illustrate still a further embodiment of the vertical heat treatment system or cell unit 200 according to the principles of the present invention. In this embodiment, the vertical heat treatment unit 200 generally is illustrated as including a substantially circular or octagonally-shaped configuration, although other similar configurations also can be provided, and generally includes a furnace 201 having a series of chambers 202A-202D. The furnace 201 can extend to approximately 10-20 feet in height although it also can be formed at greater or lesser heights as needed or desired, depending upon the application, including the types of casting to be processed, as well as the environment in which the vertical heat treatment unit or cell unit is to be placed, while providing a reduced footprint and the ability to place the cell unit in close proximity to the pouring station(s).
As indicated in FIG. 10A, each of the chambers 202A-202D can be formed with a substantially C or U-shaped configuration including angled or curved walls 203 having inner surfaces 204 generally formed from or coated with a radiant material, such as a ceramic material or other, similar heat resistant and heat radiating material capable of withstanding high temperatures. The walls 203 further can be hollow so as to define flow passages, indicated by arrows 206, through which heated fluid flows, such as heated air flows or other similar heated fluid media, are passed.
As further illustrated in FIGS. 10A, 10B and 11B, a series of heat sources 207, such as one or more blowers or forced air fans 208, generally are mounted along outer side walls 209 of the furnace 201 of this embodiment of the vertical heat treatment 200, with at least one heat source 207 being provided for each of the chambers 202A-202D as indicated in FIGS. 10A and 10B. The heat sources 207, which also can include sources such as convection or conduction heaters, infrared or other radiant sources and/or gas fired burners, etc., introduce heat into each of the radiant chambers 202A-202D, such as via heated fluid media flows passing along the passages, as indicated by 206, through the walls 203 of each chamber and through openings 211 (FIG. 10A) formed in the chamber walls 203.
It is further shown in FIGS. 10A, 11A, and 11B, each of the furnace chambers 202A-202D generally includes a series of racks or grid storage units 212 on which the castings 13 are received and retained for heat treatment. The racks or grids 212 further can be formed with or be positioned in a series of compartments or heating chambers 213 in which one or more castings are received. The compartments 213 typically include side walls 214 (FIGS. 10A and 11B) generally being formed from or coated with insulating and/or radiant materials to prevent heat transfer or loss from hotter castings to cooler castings in adjacent compartments on the same row of racks or grids 212. The floors and ceilings of the compartments 213 typically can have a slotted or substantially open construction having a plurality of openings formed therein, with the castings being supported on rails or tracks, or similar supports. As a result, a substantially free flow of air, heat, and dislodged sand from the sand cores and/or sand molds of the castings is enabled through the entire rack or grid system 212 of each furnace chamber and/or compartment for collection. The compartments 213 in each of the furnace chambers further can include additional heat sources 215, such as nozzles, blowers, or other similar heaters for applying heated fluid flows into the compartment, or can include conduction, radiant or other, similar heat sources for applying heat both above and below the castings within each of the compartments.
As indicated in FIGS. 11A and 11B, the furnace 201 farther generally includes a lower or bottom portion 216 below each of the furnace chambers. The bottom portions can have sloped walls to facilitate collection of the dislodged mold/core sand and other materials, such as is shown in FIGS. 11A, for reclamation and recovery. Additional heat sources also can be provided in the lower portion of each of the chambers, including fluidizers or nozzles that apply high velocity fluid flows through the bed of the collected sand to help facilitate the further combustion of the binder materials of the sand cores and sand molds to help with the further breakdown and recovery of the sand. Such reclaimed sand then can be discharged via a discharge chute 217 and conveying system 218. Still further, while each of the chambers can be provided with a lower portion collection area 216, such as shown in FIG. 11B, the furnace 201 also can be configured so as to have a central collection area 216 at a lower point thereof, whereby the sand from all the furnace compartments is directed to and collected at such a central location.
As additionally illustrated in FIGS. 11A and 11B, in this embodiment of the vertical heat treatment unit 200, a gantry or elevator type loader 225, which can include a crane, boom, robotic arm or other similar lifting mechanism, is located approximately within the center of the furnace. The loader is moveable vertically and horizontally, as well as being rotatable or pivotable about a centrally extending axis, for delivering and removing the castings 13 from the compartments 213 of each of the racks or grid systems 212 of the furnace chambers. The loader 225 generally can include a platform or support 226 on which one or more castings or molds with castings therein 13/11 are received and carried for introduction and removal of the castings or batches of castings in to/from each of the compartments 213 of each furnace chamber. The support platform 226 further can include clamping rails or similar supports that can engage and clamp the castings from the sides thereof or can engage the castings through one or more core openings. Additionally, a heat source can be mounted so as to apply heat through or along the support platform 226 as needed or desired for helping speed the heating of the castings to their heat treatment temperatures for treatment, and mold and/or sand core removal and reclamation. Still further, if the castings include risers or other supports, the support platform of the loader can include rails or skids adapted to be inserted within such openings or for engaging the risers or supports for loading and unloading operations.
As illustrated in FIGS. 10B and 11A, the loader 225 generally can receive the castings from an inlet mechanism 230. The inlet mechanism 230 can include a reversible conveyor or series of conveyors 231 in which the castings are fed individually or in batches into the furnace 201, into a position where they can be engaged by the loader 225, as indicated in FIG. 11A. Still further, it is also possible to utilize more than one loader within the furnace to further enhance or increase the efficiency of loading and unloading the castings within the compartments of the furnace chambers for heat treatment and/or sand mold removal and reclamation.
As illustrated in FIG. 12, utilizing the vertical heat treatment unit of the present invention, the heat treatment units can be placed immediately adjacent or in close proximity to the pouring stations for the castings, which thus enables more efficient processing and heat treatment of the castings. Through the use of the vertical heat treatment unit according to the present invention, the castings can be removed from their pouring stations and transferred substantially directly to a heat treatment unit without the castings being unduly exposed to the ambient environment that would allow the castings to cool substantially below the process control temperature for the metal or metal alloy from which the castings are being formed.
It can be understood by those skilled in the art that for any given casting, the desired dendrite arm spacing is substantially constant, with the interdiffusion coefficients of various metals or metal alloys generally being known values. For example, the interdiffusion coefficient (D) of copper and aluminum is on the order of about 6×10−11cm2s−1 at 450° C. and about 7×10−12 cm2s−1 at 400° C. As will be understood by those skilled in the art, the ratios of the interdiffusion coefficients can be evaluated to estimate the differences in diffusion and thus corresponding heat treatment times required for castings that are held at varying temperatures. It is further understood that the diffusion distances (which can be correlated to the desired dendrite arm spacings used for certain metal alloys after heat treatment) can be expressed as L=√{square root over (Dt)}, wherein D=interdiffusion coefficient of a metal alloy at a desired temperature, while t=Time. Accordingly, for a casting for which the metal thereof has a process control temperature of approximately 450° C. (for example) if the casting is allowed to drop below this predetermined process control temperature, and to a temperature of approximately 400° C., it theoretically can take approximately three (3) times longer to heat treat the castings to achieve the desired properties (such as a desired dendrite arm spacing) than if the casting is maintained at or above its process control temperature of approximately 450° C.
FIG. 12 is a graphical illustration of a comparison of a process for forming a metal casting, including pouring, maintaining the casting at or above its process control temperature from pouring to heat treatment, then heat treating, quenching, and aging the casting, which can be carried out utilizing a vertical heat treatment unit according to the present invention, as compared to a conventional type casting formation process in which the castings are poured, and then heat treated, while the core and sand molds of the castings are removed and broken down/reclaimed at substantially the same time within the heat treatment furnace, and thereafter quenched and later aged. The dark solid line indicates a process utilizing the present invention, while the lighter colored line illustrates the time required to process a casting according to conventional casting processing methods.
As illustrated in FIG. 12, with the present invention, by maintaining the casting substantially at or above its process control temperature (PCT) and placing the casting into heat treatment as quickly as possible via transfer to the “cell unit” or vertical heat treatment unit formed according to the present invention, which, due to its size and configuration can be positioned adjacent or substantially in time with one or more pouring stations, heat treatment of the casting can be accomplished in approximately 98 minutes or less, as compared to over two hours for the conventional process. It also can be seen that the casting is generally able to be raised back up to a solution heat treatment temperature more rapidly as compared to a conventional process. Thus, while the conventional process may take upwards of 13-14 hours to finish pouring, solidifying, heat treating, quenching, and aging a casting, the present invention enables a casting to be formed and processed in about less than half that amount of time.
Accordingly, as part of a casting process system in which the temperature of the castings is monitored and controlled during transition of the castings from pouring to heat treatment so as to maintain the castings at or above a process control temperature for the metal/metal alloys thereof up to heat treatment, the vertical heat treatment system or cell unit of the present invention can not only provide a substantially shorter heat treatment cycle, but also will provide easier maintenance and labor savings and can support increased casting complexity, while at the same time taking up a much smaller footprint within the facility space of the metal processing and thus enabling more diversification of the casting being produced. The vertical heat treatment system or cell unit of the present invention further can allow for the use of high velocity treatment processes for enhancing the de-coring and mold removal from the castings, in addition to enhancing and further speeding of the heat treatment thereof. For example, with the present invention, time for de-coring a casting can be reduced from approximately 2-4 hours to approximately 40-75 minutes, with the entire cycle time required for de-coring and heat treatment of a casting up until quench being reduced to about an hour and a half or less.
It will be readily understood by those persons skilled in the art that, in view of the above detailed description of the invention, the present invention is susceptible of broad utility and application. Many adaptations of the present invention other than those herein described, as well as many variations, modifications, and equivalent arrangements will be apparent from or reasonably suggested by the present invention and the above detailed description thereof, without departing from the substance or scope of the present invention.
Additionally, while the present invention is described herein in detail in relation to specific aspects, it is to be understood that this detailed description is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the present invention. The detailed description set forth herein is not intended nor is to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications, and equivalent arrangements of the present invention, the present invention being limited solely by the claims appended hereto and the equivalents thereof.
Patent Application
20080236779
